Дисертації: "LED lighting diodes"

1

Freymiller, Aaron Troy. "LED shipboard lighting a comparative analysis." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FFreymiller.pdf.

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Thesis (Master of Business Administration)--Naval Postgraduate School, December 2009.
Thesis Advisor(s): Dew, Nicholas. Second Reader: Hudgens, Bryan. "December 2009." Description based on title screen as viewed on January 28, 2010. Author(s) subject terms: Lighting, LEDs, shipboard lighting. Includes bibliographical references (p. 31-32). Also available in print.

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2

Chan, Ho-kan, and 陳可芹. "Life cycle assessment of LED road lighting." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2012. http://hub.hku.hk/bib/B48542611.

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It is observed that the power consumption of road lighting is increased with the length of trafficable road in Hong Kong. The energy used in road lighting is increasing, which means that the greenhouse gases (GHGs) emitted from power plant for generating electricity for road lighting is at the same time increasing. To compare the performance of light emitted diode (LED) road lighting with road lighting of other lamp sources, literature review, life cycle assessment (LCA) and technical assessment are adopted to give an overall comparison. This research focuses more on the environmental impacts of road lighting. LCA is adopted in order to give a comprehensive view on the environmental impact of road lighting. A total of 3 different lamp sources are compared: high pressure sodium (HPS) lamp, induction lamp and light emitted diode (LED) lamp. From the model result, it is found that due to the low power consumption and long life time, LED and induction lamp road lighting gives generally less environmental impact than HPS road lighting. As induction lamp has a longer life span than LED, the environmental impact of induction lamp road lighting is found slightly less than that of LED road lighting. Taking account the future development in LED technology, leading to longer life time, higher efficacy and lower production cost, LED road lighting is expected to be a replacement for road lighting in Hong Kong for the future.
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Environmental Management
Master
Master of Science in Environmental Management

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3

Cizek, Christopher J. "Shipboard LED lighting a business case analysis." Thesis, Monterey, California : Naval Postgraduate School, 2009. http://edocs.nps.edu/npspubs/scholarly/theses/2009/Dec/09Dec%5FCizek.pdf.

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Thesis (Master of Business Administration)--Naval Postgraduate School, December 2009.
Thesis Advisors: Dew, Nicholas ; Mutty, John. "December 2009." Description based on title screen as viewed on January 26, 2010. Author(s) subject terms: LED lighting, solid state lighting, business case analysis. Includes bibliographical references (p. 81-83). Also available in print.

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4

Li, Sinan, and 李思南. "Several reliability issues and solutions for LED lighting system." Thesis, The University of Hong Kong (Pokfulam, Hong Kong), 2013. http://hdl.handle.net/10722/197552.

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This thesis presents a study on several reliability issues for LED lighting systems. Firstly, a full survey on exsiting LED ballast has been conducted, and critical design challenges are classified on power level basis (low/ middle/ high power). Specifically, reliability issues have been highlighted, and three major factors have been stipulated: issue of electrolytic capacitor; issue of current imbalance in parallel LED strings; issue of LED junction temperature. The information revealed in the whole survey provide important design criteria for existing LED system designs and guidance for further research directions by pointing out the critical design problems. Two possible solutions for Electrolytic-Capacitor-Less LED Ballasts are proposed regarding the first reliability issue. A series of novel passive LED ballasts are proposed. They are found to be suitable for outdoor applications, such as street lighting applications, where the ability to withstand extreme weather conditions are of major concern. When compared with those in switched mode power supplies, these passive ballasts have good power factor performance and comparatively high efficiency. In addition, an active solution has been developed for indoor applications. Its circuit topology is derived from existing differential inverter topologies and inherits same merits such as simple structure, reduced size, and low cost. Self-configurable current-mirror techniques have been derived and developed afterwards to cope with the current imbalance issue for system with parallel LED strings. In contrast with traditional current sharing methods (either linear type or switched type), the proposed techniques offer a simple solution without the need of independent current references, complicated controllers and auxiliary power supplies. These features are favored by outdoor applications and such re-configurable mirror circuits are originally designed for passive LED ballast as post-current regulators. The techniques are further extended with the ability to tolerate possible circuit failure, such as short circuit and open circuit fault. Then, a new non-contact method for the measurement of both junction-to-case thermal resistance and junction temperature in a LED device has been proposed, with respect to the third reliability issue. Traditionally the direct measurement of junction temperature in LED is not easy without the help of sophisticated methods such as laser or expensive equipment like TeraLED Transient Thermal Tester system. In contrast, the proposed method requires only the external LED power, luminous flux, and heatsink temperature information. The method can be further adopted as a simple tool by engineers to check the internal temperature states in a practical LED system for regulation and evaluation purpose. Finally, a thermal design methodology has been developedfor an LED street lamp system powered by a weakly regulated renewable small power grid. It has been successfully incorporated in the proposed passive LED ballast, such that the LED system can provide the least output luminous fluctuation against line voltage variation. It is envisaged that, with the proposed design methodology, such lighting system will not only provide high reliability, with potential lifetime exceeding 10 years, but with a proven feature of reduced light fluctuation, furthermore, it is found that the passive LED system can act as a smart load and has the potential of reducing the energy storage requirement for smart grids. These merits are attractive to public lighting systems powered by future renewable power grids.
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Electrical and Electronic Engineering
Doctoral
Doctor of Philosophy

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5

Tuladhar, Looja R. "Resonant power MOSFET drivers for LED lighting /." Connect to resource online, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ysu1264709029.

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6

Solomon, Ramzi, P. Pillay, and A. B. Sebitosi. "An automotive interior lighting application using white light-emitting diodes." Thesis, Cape Town : Cape Town University, 2008. http://hdl.handle.net/10019.1/357.

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Thesis (MScEng (Department of Electrical Engineering))--University of Cape Town, 2008.
Energy drives technological societies. Developing countries such as South Africa are caught between the desperate need for economic growth and the emerging obligations to the environment. Efficient technologies can be used to mitigate the impact of these seemingly conflicting requirements in urban and rural environments. In this thesis the commercially available white light-emitting diode (LED) with its inherent efficiency, longevity and mechanical strength, is used to show, that success in energy efficiency can be obtained. Two cases are used to illustrate the need for efficient demand-side technology: the electricity shortages of the Western Cape Province in South Africa and a white LED pilot project in Namulonge, Uganda. The Namulonge Solar-Home System (SHS) is analyzed with the intention of creating a more acceptable general lighting solution. The concept of appropriateness through self-determination is discussed within the context of location-specific information integrated into a design procedure. The major thrust and contribution of this thesis, however, is the design of an interior luminaire for Golden Arrow Bus Services (GABS). This is in part based on the hypothesis that application-specific information will lead to implementation and human-needs success, and is researched, designed, fabricated and then laboratory tested. The biggest challenge to be overcome was the spatial light distribution of the LED array. Thus non-imaging optical lens design became the main focus of this project as it held the key to utilizing available light while conserving the light-systems energy. Circular Fresnel and Linear Fresnel (an adaptation of the concentric design) lenses were designed. Electrical, mechanical and thermal aspects of design are also detailed. Far-field, horizontal plane detection over the specified area is used to best gain the uniformity of distribution. The four criteria namely luminance, illuminance, intensity and étendue (collection efficiency), against which each design and focal length iv configuration is compared to, are extensively explored and eventually lead to a final design. In the first designs, the area of the spatial distribution between 50% and 80% of its relative intensity is collimated. The Hybrid Circular Fresnel and Hybrid Linear Fresnel lenses now redirects the relative intensity in two areas, from 50% to 70% (creating parallel rays) and then from 70% to 100% (away from the central axis), renders a distinct difference is spatial uniformity and a reduction in the peak and offaxis located intensity. All four criteria are met, with a minor adjustment of configuration within the bus internal luminaire spacing, with the hybrid designs. It is proposed that GABS employ polished designs of the Hybrid Circular Fresnel, in any of the configurations, which have collection efficiencies ranging between 64.8% and 78.3%.
Sponsored by the Centre for Renewable and Sustainable Energy Studies, Stellenbosch University

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7

Krigel, Arthur. "Ocular toxicity evaluation of LED lighting systems." Thesis, Sorbonne Paris Cité, 2015. http://www.theses.fr/2015USPCB167.

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Pas de résumé
The aim of the study was to evaluate in controlled retinal risk LED lighting conditions compared to other common household lighting such as CCFL or CFL, in standard lighting conditions, on different animal species pigmented and non-pigmented. At first, we characterized the conditions of adaptation before enlightenment. We found that housing conditions before the light exposure is a source of artifact. Indeed, the location of the cages in a ventilated cabinet and the period before stalling before illumination generates a variable response to retinal light toxicity. Then, we tested the relative sensitivity of the albino strains and pigmented. After 3 weeks of stabulation, the animals were exposed for 24 hours to cold white LED at a luminance of 6000 lux, with dilation of pupils, and the retinas were examined in a week. In these extreme illumination conditions, retinas showed a significant loss of photoreceptors in superior retina, not only in albino animals, but also in pigmented animals. In another experiment, we tested different luminance in cages provided for this purpose. We have used as control a compact fluorescent lighting at 500 lux, with a homogeneous on the floor of the cage. An illumination of 24 hours dilation was performed after the time of dark adaptation. A luminance of 500 lux is a classic condition of a good visual quality domestic lighting. Unlike a compact fluorescent lighting at 500 lux, white LEDs result in a significant loss of photoreceptor nuclei of retinal pigmented rats (LE) 500 lux with an increasing toxicity in function of the luminance of the LED lighting. Finally, to assess the effects prolonged exposure we exposed the rats for one week or one month, but in alternating illumination only during the day, and without dilated pupils (day / night cycle 12h / 12h, no dilated pupils) with LED different spectra. We have compared these lighting conditions to a compact fluorescent lighting at 500 lux and non-illuminated rats. After one week, only albino rats showed a loss of photoreceptors and only after exposure to blue LEDs. These results show that the blue LEDs are more toxic than the white LEDs confirming the effects of short wavelengths. After 1 month of illumination, a significant loss of photoreceptors is observed in the retinas of non-pigmented rats, not only with the blue LEDs, but also with green LEDs and cool white LEDs. An increase of the exposure time under standard conditions leads to a loss of photoreceptors accumulated suggesting a potentially toxic effect of LED light, not observed with a compact fluorescent lighting even luminance

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8

Deng, Wenpeng. "A solar PV-LED lighting system with bidirectional grid ballasting." Thesis, University of Cambridge, 2015. https://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.709190.

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9

Leng, Sovannarith. "Identifying and evaluating aging signatures in light emitting diode lighting systems." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30035/document.

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Dans ce travail, les dégradations des diodes électroluminescentes (DEL) ont été étudiées en identifiant et en évaluant leurs signatures électriques et photométriques en vieillissement accéléré sous stress thermique et électrique. Un prototype de banc de test expérimental a été développé et construit spécifiquement pour cette étude ce qui nous a permis de tester 128 échantillons en appliquant différentes conditions de stress thermiques et électriques. Quatre types différents de DEL ont été étudié avec des caractéristiques techniques similaires (température de couleur, courant nominal, mono-puce,...) mais avec des technologies différentes couvrant les principaux acteurs du marché (Cree, Osram, Philips et Seoul Semiconductor). Les échantillons ont d'abord été caractérisés à leur état initial, puis soumis à des conditions de stress électrique (à 350mA ou 1050mA) et thermique (fixé à 50°C). Les mécanismes de défaillance ont été analysés en étudiant l'évolution des signatures électriques et photométriques. Ces caractérisations ont permis d'évaluer et de déterminer l'origine des dégradations à différents niveaux : puce semi-conductrice, interconnexions, phosphore ou encapsulation du dispositif. Les caractérisations électriques nous ont permis d'identifier les mécanismes de dégradation de la puce semi-conductrice et de déterminer la nature des dégradations au niveau du contact ohmique du dispositif (sous fort courant injecté). Les caractérisations photométriques complètent cette étude en évaluant les dégradations associées à l'optique (encapsulation et packaging)
In this work, the degradation of light emitting diodes (LEDs) is studied by identifying and evaluating their aging signature during the stress time. The custom-made experimental test bench is built for realization of the test measurement. Through this experimental test bench, it allows to test a large amount of LED samples and enable to select different temperature condition and different current stress level. There are four different types of LED with similar characteristic in term of their color temperature, IF, VF, power (1W) and as monochip, but different technology coming from Cree, Osram, Philips and Seoul Semiconductor. The devices are firstly characterized their electrical and photometrical characteristic at their initial state, then they are submitted to different current stress condition at low current stress (350mA) and high current stress (1000mA) while the thermal stress is fixed at one temperature (50°C). The study of these devices failure mechanism is archived by using the primary method based on the electrical and photometrical characterization of the devices that allows to evaluate their degradation at different locations of the device components such as semiconductor chip, interconnection and device's package. The electrical characteristic of the device's I-V curve: at low injected current level and reverse bias allow us to identify the degradation characteristic of device's semiconductor chip, at high injected current level allows us to determine the degradation of device's ohmic contact and photometric characteristic allows us to evaluate the degradation of device's package system

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10

Li, Nola. "GaN on ZnO: a new approach to solid state lighting." Diss., Georgia Institute of Technology, 2009. http://hdl.handle.net/1853/33840.

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The objective of the research was to develop high quality GaN epitaxial growth on alternative substrates that could result in higher external quantum efficiency devices. Typical GaN growth on sapphire results in high defect materials, typically 10⁸⁻¹⁰cm⁻², due to a large difference in lattice mismatch and thermal expansion coefficient. Therefore, it is useful to study epitaxial growth on alternative substrates to sapphire such as ZnO which offers the possibility of lattice matched growth. High-quality metalorganic chemical vapor deposition (MOCVD) of GaN on ZnO substrate is hard to grow due to the thermal stability of ZnO, out-diffusion of Zn, and H₂back etching into the sample. Preliminary growths of GaN on bare ZnO substrates showed multiple cracks and peeling of the surface. A multi-buffer layer of LT-AlN/GaN was found to solve the cracking and peeling-off issues and demonstrated the first successful GaN growth on ZnO substrates. Good quality InGaN films were also grown showing indium compositions of 17-27% with no indium droplets or phase separation. ZnO was found to to sustain a higher strain state than sapphire, and thereby incorporating higher indium concentrations, as high as 43%, without phase separation, compared to the same growth on sapphire with only 32%. Si doping of InGaN layers, a known inducer for phase separation, did induce phase separation on sapphire growths, but not for growths on ZnO. This higher strain state for ZnO substrates was correlated to its perfect lattice match with InGaN at 18% indium concentration. Transmission electron microscopy results revealed reduction of threading dislocation and perfectly matched crystals at the GaN buffer/ZnO interface showing coherent growth of GaN on ZnO. However, Zn diffusion into the epilayer was an issue. Therefore, an atomic layer deposition of Al₂O₃was grown as a transition layer prior to GaN and InGaN growth by MOCVD. X-ray and PL showed distinct GaN peaks on Al₂O₃/ZnO layers demonstrating the first GaN films grown on Al₂O₃/ZnO. X-ray photoelectron spectroscopy showed a decrese in Zn diffusion into the epilayer, demonstrating that an ALD Al₂O₃layer was a promising transition layer for GaN growth on ZnO substrates by MOCVD.

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11

Bavencove, Anne-Laure. "Réalisation de diodes électroluminescentes à base de nanofils GaN." Thesis, Grenoble, 2012. http://www.theses.fr/2012GRENY037/document.

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Ces travaux de thèse portent sur l'évaluation des propriétés de nanofils InGaN/GaN en vue de la réalisation de diodes électroluminescentes (LEDs). Deux types d'architecture, obtenus par des techniques de croissance différentes, ont été étudiés. La technique MBE a conduit à la réalisation de LEDs en structure axiale émettant du domaine spectral bleu au rouge. Les émetteurs uniques présentent dans ce cas des diamètres typiquement inférieurs à 100 nm. La technique MOCVD a conduit quant à elle la fabrication de LEDs émettant des longueurs d'onde plus courtes à partir d'hétérostructures InGaN/GaN en Coeur/Coquille présentant des dimensions micrométriques. Dans les deux cas, la croissance est réalisée de manière spontanée sur un substrat Silicium (111) de conductivité élevée permettant l'injection verticale du courant dans les dispositifs intégrés à l'échelle macroscopique. L'ensemble des briques technologiques nécessaires à la fabrication de LEDs a été évalué par un panel important de techniques expérimentales adaptées aux structures à fort rapport de forme. Ainsi, l'effet de l'incorporation d'espèces dopantes de type n (Silicium) et de type p (Magnésium) a été caractérisé par des expériences de spectroscopie optique couplées à des mesures électriques sur fils uniques. De plus, la cathodoluminescence basse température a été largement utilisée afin d'étudier les propriétés optiques de la zone active à base d'InGaN dans les deux architectures considérées. Après intégration technologique, des caractérisations électro-optiques résolues à l'échelle du fil unique ont montré que les performances des LEDs à nanofils restent principalement limitées par la fluctuation des propriétés électriques et optiques entre émetteurs uniques
This thesis aims at studying the intrinsic properties of InGaN/GaN nanowires (NWs) in order to fabricate efficient light emitting diodes (LEDs). Two active region designs, obtained through different growth techniques, have been extensively investigated. Axial NW-based LEDs emitting from the blue to the red spectral range have been grown by MBE. In this case, single emitters present diameters typically smaller than 100 nm. MOCVD allowed the fabrication of LEDs emitting shorter wavelengths from Core/Shell heterostructures with typical dimensions in the micrometre range. In both cases, the spontaneous growth has been conducted on Silicon (111) highly conductive substrates in order to inject the current vertically into macroscopically contacted devices. Technological building blocks needed to fabricate LEDs have been investigated using a wide range of characterization techniques adapted for high aspect ratio structures. Thus, n-type (Silicon) and p-type (Magnesium) dopings have been assessed thanks to optical spectroscopy techniques, and these results have been confirmed by electrical measurements carried out on single wires. Furthermore, low temperature cathodoluminescence has been widely used to study the optical properties of InGaN-based active regions. After technological integration, electro-optical characterizations with spatial resolution down to the single wire level have revealed that device performances are mainly limited by the fluctuation of electrical and optical properties between single emitters

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12

Baillot, Raphaël. "METHODOLOGIE D'ANALYSE DE DEFAILLANCE POUR L'EVALUATION DE LA FIABILITE DE DIODES ELECTROLUMINESCENTES GaN." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2011. http://tel.archives-ouvertes.fr/tel-00673985.

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Ce mémoire s'inscrit dans la construction d'une méthodologie d'analyse de défaillance pour l'évaluation de la fiabilité de diodes électroluminescentes, par une approche basée sur l'analyse physique de dégradation et l'extraction de signatures électriques de défaillance et optiques pour localiser les zones dégradées. L'ajout d'analyses physico-chimiques réduit le nombre de composants et peut confirmer les mécanismes de dégradation induits par les vieillissements en stockage actif. Un projet, en collaboration avec le CNES, a permis la mise en évidence des zones sensibles de DELs à MPQ InGaN/GaN à faible puissance (30mW) soumises à un vieillissement en conditions opérationnelles (1500h/85°C/Inominal). L'analyse de défaillance de ces DELs a permis d'expliquer une perte de 65% de puissance optique par la modification de la structure moléculaire de l'huile silicone activée photothermiquement induisant une perte de fluorescence de 69% et une très forte diminution de l'absorption de la lumière de la DEL (90%). Nous avons également démontré (projet CEA-LETI - éclairage public) que le même mécanisme est présent dans le mélange gel silicone/phosphore YAG:Ce de DELs blanches à MPQ InGaN/GaN soumises à un vieillissement similaire (85°C/550mA/500h). A 450nm, le rendement de fluorescence a augmenté de 1,2% malgré des pertes en absorption (> 94%) et en réémission de fluorescence (> 85%). La modification de la structure moléculaire du gel a induit une perte de puissance optique des DELs de 45% et une dérive de la couleur blanche vers le jaune (≈ 3,6%). Cette dérive est due à un décalage spectral de la fluorescence de l'UV (5nm) vers le bleu entraînant un décalage vers le rouge (2nm) de la lumière de la DEL.

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13

Cantarano, Alexandra. "Nanocristaux de grenat pour l'éclairage blanc par LED et pour la nanothermométrie." Thesis, Université Grenoble Alpes, 2020. http://www.theses.fr/2020GRALI050.

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La génération de lumière blanche par LED est généralement obtenue par la combinaison d’une diode bleue et d’une couche de luminophores convertissant une partie de la lumière bleue en lumière jaune. La couche de luminophores est constituée de cristaux microniques de YAG:Ce3+ encapsulés dans une résine organique dont le vieillissement détériore les performances lumineuses des LED blanches. La taille des cristaux, supérieure aux longueurs d’onde impliquées, conduit à de la diffusion aléatoire entraînant des pertes d’énergie. Afin de diminuer ces pertes, de s’affranchir de la résine et de permettre le couplage des luminophores avec des LED nanostructurées, nous avons développé des nanocristaux de YAG:Ce3+ et proposé leur mise en forme sans liant.Le développement d’une voie de synthèse solvothermale modifiée nous a permis, grâce à l’apport d’une pression externe initiale, d’élaborer de nanocristaux individuels, stables dans l’éthanol. La cristallinité de ces nanocristaux a été optimisée en modifiant le solvant de synthèse et en utilisant un protocole de bullage au sein de la solution de précurseurs qui, en déclenchant une étape de germination hétérogène, permet une phase de croissance plus longue et donc l’obtention de nanocristaux hautement cristallins. Cette stratégie a conduit à l’élaboration de nanocristaux à haut rendement interne : 52% pour des nanocristaux de 60 nm et 66% pour des cristaux de 200 nm. Ces nanocristaux ont été mis sous forme de couches d’une épaisseur contrôlée (dans la gamme 10 - 100 µm), sans ajout de liant, puis combinés à des LED bleues nanostructurées pour l’élaboration de diodes blanches.De plus, en utilisant la voie de synthèse développée pour les nanocristaux de YAG :Ce3+, très versatile, nous avons développé des nanocristaux de YAG:Nd3+ et de GSAG:Nd3+, de très bonne qualité cristalline. Ces nanocristaux peuvent être stabilisés dans un milieu biologique grâce à un couplage avec des copolymères à blocs doublement hydrophiles et présentent une photoluminescence étroite dans les fenêtres de transparence des tissus biologiques, parfaitement adaptée à leur utilisation comme nanosondes pour l’imagerie in vivo. Enfin, ces nanocristaux nous ont permis d’effectuer des mesures de température à l’échelle nanométrique avec une sensibilité thermique relative de l’ordre de 0,2% K-1
White LED lighting is usually achievable through the combination of a blue LED and a phosphor powder which converts part of the blue light into yellow light. The phosphor layer is typically made of micron-sized YAG:Ce3+ crystals encapsulated in an organic resin that does not age well in operating LEDs. The size of the crystals, much larger than the wavelengths involved, leads to uncontrolled scattering resulting in energy losses. In order to reduce these losses, to get rid of the organic resin and to allow the coupling of phosphors with nanostructured LEDs, we developed YAG:Ce3+ nanocrystals and proposed their binder-free shaping.We developed a modified solvothermal synthesis route that, by applying an initial external pressure, allows the elaboration of individual nanocrystals, stable in ethanol. Their crystallinity was optimized by modifying the solvent and by the use of an original bubbling protocol which, by triggering a heterogeneous nucleation step, allows a longer growth step and thus an increased crystallinity. The resulting nanocrystals present high internal quantum yield: 52% for 60 nm nanocrystals and 66% for 200 nm nanocrystals. These nanocrystals were shaped as binder-free layers with a controlled thickness between 10 and 100 µm and coupled with blue nanostructured LEDs.In addition, thanks to the versatility of this modified solvothermal route, we developed YAG:Nd3+ and GSAG:Nd3+ nanocrystals, with high crystal quality. Thanks to a stabilization with block copolymers, we obtained stable colloidal solutions in aqueous medium and showed their ability to be used as luminescent nanoprobes for in vivo bio-imaging. In addition, these nanocrystals can be used for nanothermometry, with a relative thermal sensibility of 0,2%.K-1

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14

Hamon, Benoit. "Fiabilité des LED : mécanismes et modélisation." Thesis, Grenoble, 2014. http://www.theses.fr/2014GRENI058.

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Ces dernières années, les diodes électroluminescentes (ou LED) blanches ont connu une forte augmentation de leurs performances ainsi qu'une baisse de coût, faisant de cette technologie la source d'éclairage incontournable des années à venir. Tout comme leur faible consommation en énergie, leur forte durée de vie est un argument de poids pour leur adoption massive dans les solutions d'éclairage. Cependant, cette même durée de vie est l'un des paramètres qui rend l'évaluation de leur fiabilité longue et coûteuse. La multitude de produits proposés, tant au niveau de la puce que du packaging, multiplie les mécanismes de défaillance potentiels et rend donc les études de fiabilité plus difficiles. Ce travail de thèse se concentre l'étude de la fiabilité de ces composants dans son ensemble, depuis les défaillances précoces jusqu'aux défaillances de fin de vie. Dans un premier temps, nous verrons que la mise en place d'un nouveau test de qualification en fin de chaîne de production a permis la caractérisation ainsi que l'amélioration de la détection des défaillances précoces. Le suivi croisé de caractéristiques optiques et électriques au cours de tests accélérés en température et en courant a permis, dans un second temps, d'étudier les défauts aléatoires et les défauts de fin de vie des échantillons. Les résultats statistiques de cette étude ont abouti à la mise en place d'un modèle de variations électro-optiques, permettant une prédiction de la durée de vie plus précise que l'état de l'art actuel. Finalement, l'analyse des échantillons présentant une défaillance durant les tests accélérés a permis la mise en évidence des mécanismes de dégradation majoritairement responsables de la dégradation des échantillons étudiés. Les résultats obtenus permettent une meilleure compréhension de la fiabilité des LED au travers de la modélisation de leur comportement dans le temps et de l'identification de leurs principaux mécanismes de défaillance. La fiabilité des produits étant un élément différenciateur critique, ce travail de thèse est particulièrement utile pour l'industrie des LED
In the past years, white light emitting diodes (LEDs) have faced an increase of their performances combined with a decrease of their cost. In the present situation, LEDs are considered to be the light source of the future. As well as their low energy consumption, their long lifetime is one argument for a massive adoption of this technology. However, due to their long lifetime and the multitude of existing failure mechanisms (at die and package levels), the study of their reliability still remains challenging. This thesis proposes a wild range study of LED reliability, from early life failures to end of life failures. First, a new qualification test has been implemented in production to characterize and detect early failures of LED. Second, the cross study of electrical and optical variations during accelerated lifetime has been conducted. Results allowed modeling those variations and using this model for more precise lifetime estimations. Finally, failure analyses of aged samples have been conducted highlighting the failures mechanisms responsible for the measured degradations. The obtain results allow a better understanding of LED reliability through the modeling of their behavior during time and the analysis of the most critical failure mechanisms. Because lighting device reliability is a key factor, these results are useful for the LED industry

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15

Baillot, Raphaël. "Méthodologie d'analyse de défaillance pour l'évaluation de la fiabilité de diodes électroluminescentes GaN." Thesis, Bordeaux 1, 2011. http://www.theses.fr/2011BOR14364/document.

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Ce mémoire s'inscrit dans la construction d'une méthodologie d'analyse de défaillance pour l'évaluation de la fiabilité de diodes électroluminescentes, par une approche basée sur l'analyse physique de dégradation et l'extraction de signatures de défaillance électriques et optiques pour localiser les zones dégradées. L'ajout d'analyses physico-chimiques réduit le nombre de composants et peut confirmer les mécanismes de dégradation induits par les vieillissements en stockage actif. Un projet, en collaboration avec le CNES, a permis la mise en évidence des zones sensibles de DELs à MPQ InGaN/GaN à faible puissance (30mW) soumises à un vieillissement en conditions opérationnelles (1500h/85°C/Inominal). L'analyse de défaillance de ces DELs a permis d'expliquer une perte de 65% de puissance optique par la polymérisation de l'huile silicone activée photothermiquement induisant une perte de fluorescence de 69% et une très forte diminution de l'absorption de la lumière de la DEL (90%). Nous avons également démontré (projet CEA-LETI  éclairage public) que le même mécanisme est présent dans le mélange gel silicone/phosphore YAG:Ce de DELs blanches à MPQ InGaN/GaN soumises à un vieillissement similaire (85°C/550mA/500h). A 450nm, le rendement de fluorescence a augmenté de 1,2% malgré des pertes en absorption (> 94%) et en réémission de fluorescence (> 85%). La polymérisation de l'huile silicone a induit une perte de puissance optique des DELs de 45% et une dérive de la couleur blanche vers le jaune (≈ 3,6%). Cette dérive est due à un décalage spectral de la fluorescence de l'UV (5nm) vers le bleu entraînant un décalage vers le rouge (2nm) de la lumière de la DEL
GaN-based LEDs are currently used in a wide range of applications as solid-state lighting, backlighting or full-color displays. Up to date, polymer-based packaging degradation mechanisms are not fully understood. The purpose of this thesis is to work out a methodology of failure analysis contributing towards reliability estimation of GaN-based LEDs under active storage ageing tests. The methodology consists in extracting electro-optical failure signatures to locate degraded zones. A second step is based on physico-chemical analyses used to both confirm failure mechanisms and reduce the number of components to study. Environmental ageing tests (1500h/85°C/Inominal) have been performed on low power InGaN/GaN MQW LEDs (30mW) through a project in collaboration with the French Space Agency (CNES). A 65% loss of optical power has been reported after ageing. Through the methodology, we have found out that optical loss is due to the silicone oil (i.e. chip coating) polymerization activated by photothermal mechanism thereby involving both a 69% fluorescence emission loss and a strong decrease of LED light absorption (90%). A similar failure mechanism has been reported on YAG:Ce/silicone oil mixture located in phosphor converted high power white InGaN/GaN MQW LEDs (CEA-LETI collaboration - Solid-State Lighting project). Fluorescence efficiency has increased (1,2% at 450 nm) despite both strong absorption (94%) and fluorescence emission (85%) losses. Actually, silicone oil polymerization has induced a 45% loss of optical power and a 3,6% yellow shift of white light. Such drift has been linked to both a 5nm blue shift of UV fluorescence involving a 2nm red shift of LED light

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16

Barroso, Angel. "Optimisation des systèmes d'éclairage des bâtiments de l'Université Paul Sabatier basé sur un réseau novateur de type bus continu/basse tension." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30345/document.

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Les diodes électroluminescentes (LEDs) constituent de nouvelles solutions pour créer des luminaires plus robustes, ayant un meilleur rendement de conversion et plus respectueuses de l'environnement. Malgré les avantages indiscutables déjà obtenus aujourd'hui, ce type de luminaire présente encore quelques optimisations possibles et offre des possibilités de fonctionnalités multiples. A travers plusieurs campagnes de tests, l'auteur montre sur des LEDs du commerce, que les points d'optimisation non encore exploités dans les luminaires commerciaux. Ces LEDs ont ainsi été testés sur de larges plages de fonctionnement du point de vue photométrique, électrique mais aussi thermique pour connaitre la reproductibilité des résultats obtenus. Ainsi les influences des conditions d'utilisation notamment en température de fonctionnement et niveaux de courant d'alimentation ont été étudiées. Pour dimensionner au mieux une alimentation électrique spécifique, une recherche de modèles de LED élémentaires a été effectuée. L'objectif est que les modèles tiennent compte des principaux paramètres mais soit suffisamment simple pour être inséré dans un environnement système afin de simuler le luminaire dans son environnement complet. Ainsi, l'étude comparative de plusieurs associations de LEDs a été effectuée permettant d'en déduire des compromis pour proposer de nouvelles solutions faibles consommatrices d'énergie à coût réduit incluant de nouveaux types d'alimentation
Light emitting diodes (LEDs) bring new possibilities to get luminaires more robust with an improved efficiency and more environmentally respectfull. Despite the benefits already achieved today, this type of luminaire still presents some possible optimizations and provides opportunities for multiple features. Through several tests, the author shows on LEDs in market that optimization points are not operated in commercial luminaires. These LEDs have been tested over a wide range of operation in photometric, electrical but also thermal to know the reproducibility of the results. Thus the influences of operating conditions including operating temperature and supply current levels were studied. To design a specific power supply for each LED type, a search of elementary LED models was performed. The objective is to take into account the main parameters of the models but also to be enough simple to be inserted into a system environment to simulate the luminaire in whole environment. Thus, the comparative study of several associations of LEDs was conducted to deduce the best compromise and propose new solutions to reduce energy consumptions and production costs, including new types of power supply

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17

Benmamas, Arezki Lotfi. "Valorisation des systèmes d’éclairage à LED en fin de cycle de vie." Thesis, Troyes, 2021. http://www.theses.fr/2021TROY0044.

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Si l’éclairage solide permet une réduction conséquente de la consommation d’électricité, reste posé la problématique des dispositifs à base de LED. Cette thèse associée au projet RECYLED a consisté à identifier puis à développer des méthodes et des procédés en fonction des typologies des dispositifs (lampes, tubes et luminaires) et ce en vue d’une valorisation et d’une réutilisation de certains composants élémentaires. L’objectif, par une approche globale, incluant à la fois les aspects techniques, économiques et environnementaux était d’aboutir à un taux de recyclage de 80%. Trois scénarii ont été identifiés pour le recyclage des lampes et des tubes à LED, la réutilisation, le broyage et le désassemblage des lampes et des tubes à LED. Des études des déchets et des produits commercialisés, ont été menées afin de caractériser le gisement et de dimensionner les solutions de traitement proposées et estimer le potentiel de valorisation global. Concernant le désassemblage identifié comme le point bloquant, la technologie des puissances pulsées reposant sur la fragmentation est proposée. En ce qui concerne les tubes des solutions purement mécaniques ont été validées. Les méthodes proposées permettent d'obtenir un taux de valorisation matière de 74% pour les lampes et 94% pour les tubes. Ces taux sont à relier avec les prévisions estimées pour 2030 dans le cadre de ce travail qui aboutissent à un gisement annuel maximal évalué pour les lampes à LED à 2600 tonnes et pour les tubes et dalles à LED à 1600 tonnes
While solid-state lighting allows for a significant reduction in electricity consumption, the problem of the end-of-life of the LED-based devices remains. This thesis associated with the RECYLED project consisted in identifying and then developing methods and processes according to the typologies of the devices (lamps, tubes and luminaires) with a view to recovery and reuse of certain elementary components. The objective, through a comprehensive approach, including both technical, economic and environmental aspects, was to achieve a recycling rate of 80%. Three scenarios have been identified for the recycling of LED lamps and tubes, reuse, shredding and disassembly. Studies of waste and marketed products have been carried out in order to characterize the deposit and size the proposed treatment solutions and estimate the overall recovery potential. Regarding the disassembly identified as the blocking point, the technology of pulsed powers based on fragmentation is proposed. With regard to the tubes, purely mechanical solutions have been validated. The proposed methods make it possible to obtain a material recovery rate of 74% for the lamps and 94% for the tubes. These rates are to be linked with the forecasts estimated for 2030 as part of this work, which lead to a maximum annual deposit estimated for LED lamps at 2600 tons and for LED tubes and panels at 1600 tons

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18

Girard, Joffrey. "Modélisation de l'éblouissement d'inconfort dans des situations dynamiques." Thesis, Paris Est, 2019. http://www.theses.fr/2019PESC2058.

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L’éblouissement d’inconfort est défini comme la sensation de gêne ressentie par un observateur en présence de sources lumineuses, sans nécessairement impacter ses performances visuelles. Ce doctorat s’intéresse à ce phénomène dans le cadre d’une situation d’éclairage extérieur. Bien que beaucoup de modèles de prédiction de l’éblouissement d’inconfort aient été établis dans la littérature, aucun d’entre eux ne fait consensus en éclairage extérieur. De plus, la majorité de ces modèles ont été conçus pour prédire l’éblouissement d’inconfort quand une seule source immobile est présente dans le champ visuel de l’observateur. Or, en éclairage extérieur, l’usager est généralement en mouvement par rapport aux nombreuses sources qui l’entourent. Pour étudier ce phénomène dans des situations dynamiques à sources multiples, plusieurs expérimentations psychovisuelles ont été conduites en laboratoire sur des panels de participants, en proposant des stimuli multi-sources et dont les caractéristiques (luminance, taille apparente, position) varient périodiquement. Grâce aux données collectées, un modèle de prédiction de probabilité de quatre niveaux de gêne a été établi. Il dépend des caractéristiques photométriques et géométriques de la scène visuelle
The discomfort glare is defined as the sensation of discomfort felt by an observer in presence of light sources, without necessary impacting his visual performance. This PhD investigates this phenomen on in the context of outdoor lighting. Although many models of discomfort glare have been proposed in the literature, there is no consensus in outdoor lighting. Moreover, most of these models have been developed to predict the discomfort glare level from one static light source in the visual field. In outdoor lighting, the road user is usually moving with multiple sources around him. To study this phenomenon in dynamic multi-source situations, seven psychovisual experimentations were carried out in the laboratory with panels of participants. These experimentations proposed multi-source stimuli having their characteristics (luminance, apparent size, position) that periodically varied. From the experimental data, a model was developed which predict the probability of four discomfort glare levels. It depends on the photometric and geometric characteristics of the visual scene

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19

Wang, Dongxue Michael. "Optoelectronic device simulation optical modeling for semiconductor optical amplifiers and solid state lighting /." Diss., Available online, Georgia Institute of Technology, 2006, 2006. http://etd.gatech.edu/theses/available/etd-03292006-132611/.

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Thesis (Ph. D.)--Electrical and Computer Engineering, Georgia Institute of Technology, 2006.
Buck, John, Committee Co-Chair ; Ferguson, Ian, Committee Chair ; Krishnamurthy,Vikram, Committee Member ; Chang, Gee-Kung, Committee Member ; Callen, W. Russell Jr., Committee Member ; Summers, Christopher, Committee Member.

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20

Niangoran, N'goran Urbain Florent. "Optimisation de la culture de la spiruline en milieu contrôlé : éclairage et estimation de la biomasse." Thesis, Toulouse 3, 2017. http://www.theses.fr/2017TOU30378/document.

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L'agriculture en milieu contrôlé, et notamment la culture sous serre, est une des réponses possibles aux besoins alimentaires d'une population mondiale en constante croissance. Elle permet aussi d'optimiser les terres cultivables et d'éviter les pesticides néfastes à l'Homme. Afin de s'affranchir des cycles des saisons et d'avoir une production annuelle continue, l'éclairage artificiel a été introduit dans les serres. L'éclairage horticole a suivi l'évolution des technologies d'éclairage pour arriver aujourd'hui jusqu'à la LED. Cet éclairage donne certes des résultats corrects mais il peut être amélioré tant au niveau de la quantité que de la qualité spectrale de lumière. De ce point de vue, les LEDs présentent deux grands avantages : la possibilité de recomposer un spectre idéal à partir de différentes longueurs d'ondes et de moduler l'intensité de la lumière. Ainsi, elles permettent de fournir un éclairage adapté aux besoins de la plante et ce, en fonction du stade de sa croissance. L'objectif de ce travail de thèse est de proposer un système d'éclairage optimal pour la croissance des plantes en milieu contrôlé. A partir du rendement photosynthétique moyen des plantes, nous avons donc établi des modèles de systèmes d'éclairage à LEDs optimisés pour les plantes. Ces modèles sont basés sur la combinaison de plusieurs LEDs monochromes obtenues à partir de la décomposition de la courbe RQE par des fonctions de Pearson VII. Nous avons appliqué ces résultats théoriques à la culture d'une algue bleue-verte : la Spiruline Platensis. Le choix de cette plante-bactérie repose sur plusieurs critères : cycle de culture court, applications en cosmétique, en médecine et forte valeur nutritionnelle. Ainsi, nous avons pu étudier l'influence de paramètres de culture tels que l'intensité lumineuse, la photopériode, la température sur sa croissance. Par ailleurs, nous avons mis en œuvre deux méthodes basées sur la réflectance optique pour quantifier la biomasse produite par la spiruline
Agriculture in a controlled environment, and in particular greenhouse cultivation, is one of the responses to the food needs of a growing population. It also makes it possible to optimize the surface of arable land and avoid pesticide and fertilizer releases harmful to man. In order to free of the cycles of the seasons and annual production, artificial lighting was introduced greenhouses since decades. Horticultural lighting followed the evolution of lighting technologies to arrive today up to LED. This lighting gives correct results, but it can be improved both in terms of quantity and spectral quality of light. From this point of view, LEDs have two main advantages : the possibility of recompose an ideal spectrum from different wavelengths and modulate the intensity of the light. Thus, they provide adapted lighting to the needs of the plant and this, in depending on the stage of its growth. The objective of this thesis is to propose an optimal lighting system for the growth of plants in a controlled environment. From the yield photosynthesis of plants, we established models of LED lighting systems optimized. These models are based on the combination of several monochrome LEDs obtained from the decomposition of the curve RQE by Pearson VII functions. We applied these theoretical results to the cultivation of a blue-green algae, the Spirulina Platensis. The choice of this plant-bacterium is based on several criteria : short crop cycle, applications in cosmetics, medicine and high nutritional value. Thus, we were able to study the influence of culture parameters such as light intensity, photoperiod, temperature on its growth. In addition, we have implemented two methods based on optical reflectance to quantify the biomass produced by spirulina

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Souza, Ithalo Hespanhol de. "Sistema de iluminação pública baseado em drivers modulares para lâmpadas de LED." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2427.

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A utilização de luminárias baseadas em diodos emissores de luz (LED) é uma tendência para iluminação de interiores e para iluminação pública devido a sua alta durabilidade e eficiência. Apesar destas características desejáveis impulsionarem a utilização de LEDs na iluminação, a vida útil dos drivers utilizados para o acionamento de LEDs de potência, baseados em topologias tradicionais, pode ser inferior a vida útil do próprio LED. Estes drivers são, geralmente, constituídos de topologias que utilizam capacitores eletrolíticos, que tem baixa vida útil, principalmente, em altas temperaturas de operação. Assim, este trabalho propõe uma luminária LED para iluminação pública que seja baseada em drivers modulares. Esta metodologia, visa o aumento da vida útil dos drivers, bem como a manutenção do funcionamento da lâmpada mesmo quando um dos módulos falhar. O projeto dos drivers eletrônicos e a modelagem matemática dos conversores é apresentada. Além disso, são apresentados resultados experimentais obtidos através de um protótipo com 50W (dois módulos com potência média de 25W, cada um).
The use of LED based luminaires is a tendency for both indoor and street lighting, due to its high durability and efficiency. Despite these desirable features propel the use of LEDs on lighting systems, the lifespan of its drivers can be lower than the LED itself. Such drivers are usually based on topologies that make use of electrolytic capacitors, which present low durability, mainly in high temperatures. Therefore, this work proposes a LED luminaire for street lighting based on modular drivers. This approach intends to increase the lifetime of the drivers, as well as maintain the luminaire in operation even with one or more modules failure. The design of the electronic drivers and the technique used for the mathematical modeling of the converters are presented. Furthermore, the obtained experimental results from a prototype with rated power of 50W (two modules with rated power of 25W each one) are presented.

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Barros, Anthony. "Luminophores inorganiques sans terre rare pour l'éclairage LEDs : synthèse, caractérisations et évaluation des performances." Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22708.

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Ce travail de thèse porte la synthèse et la caractérisation d’un luminophore rouge inorganique sans terres rares de formulation Na2SiF6 : Mn4+. Un protocole de synthèse originale des matrices fluorures A2MF6 : Mn4+ (A = Na, K ; M = Si, Ti) par un procédé sol-gel a ainsi été mis au point. Cette synthèse brevetée et industrialisable permet d’obtenir des composés avec un rendement quantique absolu supérieur à 50% sous excitation LED bleue. Plusieurs analyses structurales, microstructurales, et à sondes locales ont permis de caractériser précisément les composés synthétisés. Le deuxième volet important de ce travail a été la construction d’une enceinte de vieillissement permettant de suivre l’évolution des propriétés de luminescence des luminophores en fonction du temps sous l’effet combiné d’un stress hydrique, thermique et photonique. Les mesures, entièrement automatisées, nous ont permis d’établir des lois cinétiques de dégradation du flux lumineux à partir desquels des facteurs de maintenance (L90, L70, L50, etc…) ont pu être déterminés. De plus, un mécanisme de dégradation de cette famille de luminophores a été proposé. Finalement, un prototype d’éclairage à base de LEDs bleues intégrant une couche de conversion constituée des luminophores Na2SiF6 : Mn4+ et YAG : Ce3+, Gd3+ a conduit à des caractéristiques très prometteuses
This PhD work deals with the synthesis and characterization of a rare earth-free inorganic red phosphor of Na2SiF6: Mn4+ formulation. An original synthesis protocol of fluoride matrices A2MF6: Mn4+ (A = Na, K, M = Si, Ti) by a sol-gel process has been developed. This patented and industrializable synthesis allows to obtain compounds with an absolute quantum yield greater than 50% under blue LED excitation. Several structural, microstructural and local probe analyzes have made it possible to precisely characterize the synthesized compounds. The second important part of this work was the design of an aging chamber to follow the evolution of phosphor luminescence properties as a function of time under the combined effect of hydrous, thermal and photonic stress. Measurements, fully automated, allowed us to establish kinetic laws of luminous flux degradation from which maintenance factors (L90, L70, L50, etc. ...) could be determined. Moreover, a degradation mechanism of this family of phosphors has been proposed. Finally, a blue LED lighting prototype incorporating a conversion layer consisting of Na2SiF6: Mn4+ and YAG: Ce3+, Gd3+ phosphors led to very promising characteristics

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Legentil, Paul. "Développement de poudres hybrides "Hydroxydes Doubles Lamellaires-luminosphores" sans terres rares. Intégration dans des revêtements composites compatibles avec des sources d'excitation LED." Thesis, Université Clermont Auvergne‎ (2017-2020), 2020. http://www.theses.fr/2020CLFAC013.

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Ces travaux de thèse ont pour ambition de proposer des solutions alternatives, aux luminophores avec terres rares, offrant des performances convenables pour des applications dans des dispositifs à LED comme l’éclairage mais également la visualisation ou encore le marquage ou la signalétique. Nous nous sommes intéressés à des luminophores organiques mais également inorganiques tels que les quantum dots (QD). Le problème majeur de ces familles de luminophores est leur instabilité sous contrainte thermique et/ou photonique. Aussi, afin de pallier ce problème nous avons choisi d’utiliser des matériaux inorganiques plaquettaires de type « hydroxyde doubles lamellaires » (HDL) comme matrice hôte du luminophore. Les luminophores étudiés sont la fluorescéine, la sulforhodamine B et des quantum dots InP/ZnS. Plusieurs techniques expérimentales ont été utilisées afin de caractériser leurs propriétés structurales et morphologiques (DRX, SAXS, IR, MEB, MET…). Les propriétés optiques ont également été enregistrées (émission, excitation, rendement quantique de photoluminescence, déclins…). Ces travaux ont mis en évidence la plus-value de la matrice HDL qui permet de reproduire un effet de solvatation pour le luminophore organique ou QD dans une matrice solide et de retrouver des propriétés d’émission semblables à celles de ces luminophores en solution diluée. La dispersion dans une matrice silicone est également favorisée et la stabilité de ces revêtements composites (HDL-Luminophore/silicone) sous différentes contraintes est nettement améliorée
These works have the ambition to offer alternative solutions to phosphors with rare-earth elements, displaying suitable performance for LED devices applications as well as signage or display applications. We have been interested in organic as well as inorganic phosphors such as quantum dots (QD). The main problem encountered with these compounds is their relative instability under thermal and/or photonic stresses. Thus, in order to overcome this issue, we decided to use inorganic materials called layered double hydroxide (LDH) as host matrix to protect these phosphors. Several experimental techniques (XRD, SAXS, IR, SEM, TEM…) have been used to characterize structural and morphological properties. Optical properties have also been recorded (emission and excitation spectra, photoluminescence quantum yields, fluorescence decay…). Using extremely small amounts of phosphors, it is demonstrated here that Zn2Al cation-based LDH tethering acts as a «solid solvent» for the dye, enabling its luminescence even in powder form. Additionally, LDH platelets are found to help the dispersion of the dye or QD in silicone to obtain homogeneous composite films, which exhibit luminescent properties. Finally, the stability of composite coatings (LDH-phosphor/silicone) under different stresses (thermal and photonic) is most often improved

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Lu, Shuxian. "Modélisation et validation expérimentale de concept de Détection Vidéo Coopérative destiné à un système stéréo anticollision inter-véhicule." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112154/document.

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Le travail de cette thèse a été consacré au développement d’une nouvelle méthode de détection pour un système anticollision par la mesure de trajectographie, ce qui pourrait contribuer aux systèmes d’aide à la conduite. Pour obtenir une haute probabilité de détection, nous avons choisi la solution de vidéo stéréoscopique coopérative : la coopération entre véhicules rend la détection plus facile et fiable. Il y a deux participants dans le système : les véhicules « porteurs du système » aussi bien que les « suiveurs », sont équipés de caméras stéréoscopiques, c’est à dire de deux capteurs d’image, appartenant à des familles technologique à haute cadence; les véhicules « cibles » sont équipés des feux à Leds modulés, dont la fréquence de modulation est déjà connue par les véhicules « suiveurs ». Après filtrage dans l’espace temporel, le système ne détecte que des signaux issus des feux modulés, ce qui réduit fortement l’information à traiter par rapport aux calculs de trajectographie traditionnels. La détection de feux modulés est donc réalisée par le filtrage par traitement numérique des images, qui est adapté à la fréquence de modulation recherchée. Pour cela, nous avons proposé 3 types de filtres adaptés à la fréquence de modulation et conçus de façon à rejeter au mieux les signaux de fond.Pour évaluer les performances tant en détection qu’en réjection des fausses alarmes, nous avons d’abord effectué des simulations numériques en prenant en compte des signaux artificiels, puis des calculs sur vrais signaux obtenus dans les expérimentations avec véhicule d’essai statique, puis roulant. Les roulages étaient de différentes vitesses, de 30km/h jusqu’à 100km/h, ce qui nous a permis d’analyser le signal issu du feu ainsi que le comportement de nos filtres à des vitesses angulaires de feu nulles, faibles ou élevées. Le résultat de ces expérimentations montre que le filtrage permet de détecter les feux à Leds de type DRL jusqu’à 140m sans aucune fausse détection sur le fond. Ces expérimentations sont une étape essentielle pour définir de façon plus précise un tel système, en particulier dans le choix du seuil. Nous avons aussi évalué des technologies qui peuvent améliorer la performance du système, mais qui ne sont pas encore prêtes à industrialiser. Par exemple, les « rétines » artificielles nous permettent d’utiliser les filtres analogiques intégrés, et ainsi de réduire leurs bandes passantes
This thesis was devoted to the development of a new detection method for vehicular collision avoidance system based on trajectory measurement, which could contribute to driver assistance systems.In order to obtain high detection probability, we have chosen the cooperative stereoscopic video solution: the cooperation between vehicles makes it easier and more reliable when they aim to detect each other. There are two participants in the system: the “system carriers" vehicles, or the " followers" are equipped with stereoscopic cameras (two image sensors), who belong to high speed technology families; the "targets" vehicles are equipped with modulated LED lights, with the modulation frequency being already known by the "followers". After space-time filtering, the system detects the signals emitted bymodulated lights sources, which greatly reduces the amount of information to be processed comparing to traditional trajectory calculations methods. The detection of modulated light is achieved by filtering based on digital image processing, which is adapted to the desired modulation frequency. We have proposed three types of filters suitable for detecting the modulation at this frequency and at the same time for rejecting the background as well as possible.In order to be able to evaluate the performances of both detecting signals and rejecting false alarms, we first performed numerical simulations based on the model signals, then calculations on real signals acquired in static and driving experiments. The tested speeds were from 30km/h up to 100km/h, which allowed us to analyze the signals emitted from vehicle lights as well as the behavior of our filters under different angular velocities of the lights (zero, low and high). The result of these experiments showed that our method of filtering could detect LED-type DRL lights up to 140m without any false alarm. This is essential to define more precisely the values of thresholds of such systems. We have also evaluated technologies that are possible to improve system performance in the future, which are not yet ready to be used in industry productions. For example, artificial "retinas" could allow us to integrate analog filters in the chips, and thus to reduce bandwidth of the filters

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25

Gaffuri, Pierre. "Nouveaux matériaux pour des LED blanches éco-efficientes : hétérostructures à base de nanofils de ZnO et luminophores d'aluminoborates sans terres rares." Thesis, Université Grenoble Alpes, 2021. http://www.theses.fr/2021GRALI004.

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L’implémentation généralisée de diodes électroluminescentes blanches (wLED), basées sur l’électroluminescence bleue d’une LED et la photoluminescence jaune d’un luminophore, représente une opportunité majeure de réduction de la consommation énergétique mondiale. Les performances des wLED reposent sur des matériaux considérés comme critiques par les mondes politiques et scientifiques, comme les nitrures de gallium et de gallium/indium pour la LED bleue, et le grenat d'yttrium et d'aluminium dopé au cérium pour le luminophore. La synthèse de ces matériaux nécessite des techniques de dépôt physique et chimique coûteuses et à haute température. C’est dans ce contexte qu’ont été étudiés deux matériaux non critiques et fabriqués par des méthodes de chimie douce : les réseaux de nanofils de ZnO comme semi-conducteurs de type n, et les poudres d’aluminoborate comme luminophore. D’une part, les mécanismes de dopage extrinsèque et la modification associée de la croissance des nanofils de ZnO par dépôt en bain chimique ont été examinés, montrant les rôles dominants du pH et de la concentration en précurseurs. Les défauts et complexes de défauts incorporés au sein des nanofils de ZnO, cruciaux du point de vue applicatif, modifient largement leurs propriétés optiques et électriques. Leur croissance épitaxiale sur des couches minces de GaN de type p forme des hétérojonctions dont les propriétés d’électroluminescence sont évaluées. D’autre part, les poudres luminophores à base d’aluminoborate ont été synthétisées par la méthode Pechini, en substituant l’yttrium habituellement présent dans les particules amorphes. L’optimisation des nouvelles compositions chimiques et des traitements thermiques offre une émission spectrale large, dont le rendement quantique interne de luminescence dépasse 60 %. Cette étude permet une meilleure compréhension du piégeage d’espèces carbonées, et de leur rôle dans la luminescence. Finalement, l’intérêt des consommateurs pour de telles structures sans matériaux critiques et à basse énergie grise est mesuré et offre des perspectives optimistes pour leur développement
The widespread implementation of white light-emitting diodes (wLEDs), based on the blue electroluminescence of an LED and the yellow photoluminescence of a phosphor, represents a major opportunity to reduce global energy consumption. The performances of wLEDs are based on materials considered as critical, such as gallium and gallium/indium nitrides for the blue LED, and cerium doped yttrium aluminium garnet for the phosphor. The synthesis of these materials require costly and high-temperature physical and chemical deposition techniques. In this context, new non-critical materials have been studied and manufactured by soft chemistry methods: ZnO nanowires array as n-type semiconductor, and aluminoborate powders as phosphor. On the one hand, the mechanisms of the extrinsic doping and related modification of the growth of ZnO nanowires deposited by chemical bath deposition were investigated, showing the dominant roles of pH and precursor concentrations. Defects and complex defects incorporated in ZnO nanowires, crucial from an application point of view, greatly modify their optical and electrical proprieties. Their epitaxial growth on p-type GaN thin films forms heterojunctions whose electroluminescence properties are evaluated. On the other hand, aluminoborate-based phosphors powders were synthesized by the Pechini method, by substituting yttrium, usually present in the amorphous particles. The optimization of the new chemical compositions and thermal annealing offers a broad emission whose internal quantum luminescence efficiency exceeds 60 %. This study provides a better understanding of the trapping of carbon species, and their role in the luminescence. Eventually, consumer interest in such structures without critical materials and with low embodied energy is measured and offers optimistic prospects for their development

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Fernandes, Ricardo Liz de Castilho. "Green emitting diodes for solid state lighting." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/17763.

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Mestrado em Engenharia Física
Nos anos recentes a iluminação de estado sólido impulsionou alternativas de iluminação efí cientes e ecológicas. Os desafi os correntes envolvem o desenvolvimento de materiais emissores de luz que convertem radiação de uma determinada energia para radiação de energia mais baixa, na gama do visível. Esta tese estuda um complexo novo, Tb(NaI)3(H2O)2 onde NaI é o ácido nalidíxico, que emite na região do verde e é estável sob iluminação no ultravioleta. Este foi incorporado em materiais híbridos orgânico-inorgânico tripodais com dois pesos moleculares médios (3000 e 5000 g.mol-1, denominados t- U(3000) e t-U(5000) respetivamente) que permitem o processamento de monólitos e fi lmes com forma e espessura controlada. Estes híbridos também aumentam o rendimento quântico absoluto de emissão de 0.11 medidos para o Tb(NaI)3(H2O)2 isolado para ~0.82 após incorporação no t-U(5000). Foi também demonstrado o potencial de usar estes materiais híbridos como emissores na região verde para uso em iluminação de estado sólido através do revestimento do díodo emissor na região ultravioleta (365 nm). Este LED apresenta uma efi cácia de 1.3 lm.W􀀀1.
In the last few years, solid state light-emitting diodes (LEDs) have been driving the lighting industry towards energy e cient and environmental friendly lighting. Current challenges encompass e cient and low-cost downconverting photoluminescent phosphors with emission in the visible region. This thesis will cover a novel UV-photostable green emitting complex, Tb(NaI)3(H2O)2 where NaI is nalidixic acid, was incorporated into organic-inorganic tripodal hybrid materials with two average molecular weights (3000 and 5000 g.mol{1, termed as t- U(5000) and t-U(3000), respectively) which enable the easy shaping of monoliths and lms with controlled thickness. Moreover, the hybrid hosts boost the Tb3+ green absolute emission quantum yield from 0.11 measured for the isolated Tb(NaI)3(H2O)2 complex to 0.82 after incorporation into t-U(5000). The potential use of the hybrid materials as UV-down converting green-emitting phosphors for solid state lighting was demonstrated by means of coating a near-UV LED (365 nm). This LED shows an e cacy of 1.3 lm.W􀀀1.

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Rodrigues, Cláudio Roberto Barbosa Simões. "Contribuições ao uso de diodos emissores de luz em iluminação pública." Universidade Federal de Juiz de Fora, 2012. https://repositorio.ufjf.br/jspui/handle/ufjf/1695.

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No intuito de aportar contribuições ao uso de diodos emissores de luz (ou LEDs, do inglês Light Emmiting Diodes) em sistemas de iluminação pública, cobrindo lacunas existentes no cenário nacional, este trabalho traz uma ampla análise sobre este tema. São apresentados conceitos básicos da fotometria clássica e um estudo sobre adaptações da fotometria para baixos níveis de luminância, que é a condição observada nas vias públicas durante o período noturno. Propõe-se a utilização de métricas escotópicas em sistemas de iluminação pública, uma vez que estas melhor representam a real sensação visual (se comparadas às métricas clássicas – fotópicas) nas condições de iluminamento típicas observadas nestes sistemas. Aspectos gerais da iluminação pública e um histórico da evolução do sistema nacional são brevemente apresentados bem como uma discussão sobre a situação atual deste sistema e das tecnologias utilizadas. O trabalho traz também um estudo sobre características ópticas, elétricas e mecânicas dos LEDs e uma análise dos diferentes tipos de LEDs brancos mais utilizados (HB – High Brightness – e HP – High Power – LEDs). Algumas normas e recomendações aplicáveis à utilização de LEDs em iluminação pública são analisadas e discutidas, com o intuito de se investigar lacunas ainda não cobertas pela normatização existente. Análises de resultados de ensaios de laboratório e de campo, inéditos no país, realizados com alguns modelos de luminárias LED para iluminação pública disponíveis no mercado, são também apresentadas. Um estudo sobre acionamento de LEDs é realizado, abordando técnicas de equalização de corrente entre arranjos série de LEDs associados em paralelo e diferentes tipos de circuitos de acionamento para LEDs. São propostas, analisadas e implementadas uma estrutura inédita de baixo custo para a equalização de corrente e um circuito para o acionamento de LEDs baseado na integração de dois conversores cc cc não isolados. A topologia de dois estágios proposta é composta por um conversor boost no primeiro estágio, utilizado para a correção do fator de potência e por um conversor buck no segundo estágio, utilizado para o controle da corrente nos LEDs. Por fim, o acompanhamento da implantação e do desempenho, ao longo de dez meses, do projeto piloto de iluminação pública empregando LEDs instalado no anel viário da Faculdade de Engenharia da UFJF é apresentado.
In order to present contributions to the use of light emitting diodes (LEDs) in public lighting systems, covering gaps on the national scenario, this work encompasses abroad analysis related to this issue. Basic concepts of classical photometry are presented and so a study of photometry’s adaptations for low luminance levels. It is proposed the use of scotopic metrics for street lighting systems, since they can better represent the actual visual sensation (when compared to the classical one – photopic metrics) on its typical nighty conditions. General aspects of street lighting and the history of the national’s public lighting system are briefly presented as well as a discussion about the current situation of the Brazilian system and technologies adopted. The work also brings a study of mechanical, electrical and optical characteristics of LEDs and an analysis of the two different types of commonly used white LEDs (HB – High Brightness – and HP – High Power - LEDs). Some standards and recommendations related to the use of LEDs in street lighting are analyzed and criticized, with the aim of show some gaps not yet covered by the existent standards. An unprecedented analysis regarding laboratory and field test benchmarking, taken for some luminaires available in commerce, is also presented. A study of LED driving is presented, covering equalization techniques for parallel LEDs strings and different types of LED driving circuits. It was proposed, analyzed and implemented a novel and low cost structure for current equalization and an LED driver, based on the integration of two non-isolated dc dc converters. This proposed two stages topology is composed by a boost converter, on the first stage, employed to the power factor correction and a buck converter, on the second stage, to control the LED’s current. Finally, the process of monitoring the installation and the performance, during ten months, of the LEDs public lighting pilot project, on the roadway belt of Engineering Faculty of UFJF is presented.

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Deram, Paul. "Light-emitting-diode (LED) lighting for greenhouse tomato production." Thesis, McGill University, 2013. http://digitool.Library.McGill.CA:80/R/?func=dbin-jump-full&object_id=116996.

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The cost of artificial lighting is a major expense in the greenhouse production industry, especially during the winter where supplemental lighting is required to maintain production. Current technology uses broad spectrum high pressure sodium lamps (HPS), which, despite being excellent luminous sources, are not the most efficient light source for plant production. Specific light frequencies have been shown to impact photosynthesis more directly than others (especially in the red and blue ranges); focusing on specific wavelengths, light-emitting diodes (LEDs) could diminish lighting costs due to their high efficiency and lower operating temperatures. LEDs can be selected to target the wavelengths absorbed by plants, enabling the growers to customize the wavelengths of light required to maximize production and limit wavelengths that do not significantly impact plant growth. The primary purpose of this experiment was to test tomato plants (Solanum lycopersicum), in a research greenhouse using a full factorial design with three light intensities (High: 135 µmol m-2 s-1, Medium: 115 µmol m-2 s-1 and Low: 100 µmol m-2 s-1) at three red to blue ratio levels (5:1, 10:1 and 19:1) compared to 100% HPS, and a control (no supplemental lighting). The exact wavelengths chosen were 449 nm for the blue and 661 nm for the red. Secondary treatments were also tested using 100% red light supplied from the top, 100% red light supplied from the bottom, a 50%:50% LED:HPS and a replicate of the 10:1 ratio with High light intensity. The experiment was replicated over two different seasons (Summer-Fall 2011 and Winter-Spring 2011-2012). During the experiment, the highest biomass production (excluding fruit) occurred with the 19:1 ratio (red to blue), with increasing intensity resulting in more growth, whereas a higher fruit production was obtained using the 5:1 ratio. The highest marketable fruit production (fruit over 90 g, Savoura internal standard) was the 50%:50% LED:HPS, followed by 5:1 High and 19:1 High. From this research, LEDs have been shown to be superior in fruit production over HPS alone, and LEDs can improve tomato fruit production with HPS and have the ability to become the dominant supplemental greenhouse lighting system.
Le coût de l'éclairage artificiel est une dépense importante dans le secteur de la production en serre, surtout en hiver lorsqu'un éclairage supplémentaire est nécessaire pour maintenir le niveau de production. La technologie actuelle utilise des lampes à haute pression de sodium (HPS), qui en dépit d'être d'excellentes sources lumineuses, ne sont pas les sources lumineuses les plus efficaces pour la production végétale. Certaines fréquences spécifiques de lumière ont montré avoir un impact plus direct sur la photosynthèse que d'autres (en particulier dans les gammes de rouge et de bleu); en mettant l'accent sur certaines longueurs d'onde, les diodes électroluminescentes (LED) pourraient diminuer les coûts d'éclairage, en raison du rendement élevé et des températures plus basses de ce type de lampe. Les LED peuvent cibler les principales fréquences de lumière mieux absorbées par les plantes, ce qui permettrait aux producteurs de créer une lumière aux longueurs d'onde adaptées à la production optimale des plantes. Le principal objectif de cette expérience était de tester les lampes sur des plants de tomate (Solanum lycopersicum) dans une serre de recherche en utilisant un plan factoriel complet avec trois intensités lumineuses (Haute: 135 μmol m-2 s-1, Moyenne: 115 μmol m-2 s-1 et Basse: 100 μmol m-2 s-1) et trois proportions de rouge et bleu (5:1, 10:1 et19: 1), et comparer leur performance à celle de 100% HPS, et d'un contrôle (pas d'éclairage supplémentaire). Les longueurs d'onde choisies sont 449 nm (bleu) et 661 nm (rouge). Certains traitements secondaires ont également été testés, dont 100% rouge (éclairage par le haut ou le bas), un 50%:50% LED:HPS et une reproduction du 10:1 à haute intensité. L'expérience a été menée au cours de deux saisons différentes (été-automne et hiver-printemps). La production végétative la plus importante s'est produite avec le rapport 19:1 (rouge : bleu). La production de fruits était la plus élevé avec le rapport 5:1. La production en fruits commercialisables la plus importante (fruits de 90 g et plus : étalon interne de Savoura) a été pour le 50%:50% LED:HPS, suivi du 5:1 et 19:1 à haute intensité. Les LED se sont montrés supérieures aux HPS quant à la production de tomates.

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Koždoň, Jakub. "Světelný zdroj s nastavitelnou intenzitou osvětlení." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2014. http://www.nusl.cz/ntk/nusl-220973.

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This work is focused on description how the light impact human live, description of light sources and finally design and construction of light source with adjustable colour temperature and luminous flux. In introduction is mentioned the process of vision and how the light impact humans. In next part is characterization of currently used light sources, their construction, properties, benefits and drawback with their main parameters. Important part of this chapter is more extensive description of light emitting diodes with their operational parameters. The last two parts is focused on design and measuring the parameters of created light source with adjustable colour temperature and luminous flux and evaluating the results.

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Fonseca, Zito Palhano da. "Sistemas eletrônicos com elevado fator de potência de estágio único e sem capacitores eletrolíticos para acionar LEDs de potência." Universidade Tecnológica Federal do Paraná, 2014. http://repositorio.utfpr.edu.br/jspui/handle/1/1575.

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Este trabalho propõe a utilização de dois conversores de estágio único e elevado fator de potência para acionar LEDs de potência sem a utilização de capacitores eletrolíticos no barramento CC. Ambas as topologias podem operar com entrada universal, dimerização da corrente de saída e comando auto-oscilante. No entanto o número de dispositivos semicondutores é maior em relação aos conversores estáticos de energia convencionais. A correção do fator de potência do primeiro conversor proposto é obtida através de uma conexão direta realizada por um indutor inserido entre o estágio inversor de saída e dois capacitores conectados antes do estágio retificador de entrada criando um caminho alternativo para a corrente fornecida pela fonte de alimentação CA entre estes estágios. O segundo conversor realiza a correção do fator de potência através de dois indutores acoplados magneticamente conectados na entrada da ponte retificadora. Estes indutores também operam em conjunto com os dois capacitores de entrada e, por possuírem acoplamento subtrativo, processam energia de forma complementar propiciando um volume de núcleo reduzido em relação ao indutor da primeira topologia proposta. Em ambas as topologias apresentadas, a corrente da fonte de alimentação CA fornece energia instantânea com o dobro da frequência de comutação aplicada ao estágio inversor, permitindo a redução do filtro LC necessário na entrada do sistema. As correntes contínuas aplicadas aos LEDs das duas topologias são obtidas através de pontes retificadoras com filtros capacitivos conectados entre os estágios inversores e os pontos centrais de dois capacitores dos barramentos CC. Resultados de simulação e experimentais utilizando 12 LEDs conectados em série com potência total de 45 W, alimentados em 127 V e 220 V são apresentados para validarem as metodologias de projetos propostas.
Two single-stages high-power-factors converters without DC bus electrolytic capacitors for power LEDs applications are proposed in this work. The power factor correction of the first proposed topology is obtained through direct link of one boost inductor connected between the output inverter stage and two capacitors placed before of input bridge rectifier. In the second proposed lighting system, the power factor correction is performed by two magnetically coupled inductors placed at input bridge rectifier that also operate with the two input capacitors and the output inverter stage. In this case, the coupled inductors magnetic fluxes are complementary and their core is reduced when compared with the inductor of the first proposal. In both converters the input voltage provides instantaneous ripple current with twice switching frequency of the output inverter and the input filter inductor is reduced. To obtain continuous current on the LEDs, one output rectifier placed between output inverter stage and a neutron point (NP) of the two DC bus capacitors is used. The LEDS current is limited by a serie inductor. Through steady-state operation the main theorical waveforms as well as the converters design methodologies are presented. To verify the theoretical analysis carried out, simulation and experimental results are also presented. To verify the theoretical analysis, also simulation and experimental results using 12 LEDs connected in series with a power of 45 W, suplied at 127 V and 220 V are presented to validate the methodology proposed projects.

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Pickering, Philip. "Towards a systematic methodology for the design, testing and manufacture of high brightness light emitting diode lighting luminaires." Thesis, University of Manchester, 2013. https://www.research.manchester.ac.uk/portal/en/theses/towards-a-systematic-methodology-for-the-design-testing-and-manufacture-of-high-brightness-light-emitting-diode-lighting-luminaires(e1573c06-9abf-402a-bfa3-13597d60079b).html.

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Reducing the consumption of electricity is one of the principal areas of current research into energy saving technologies. Within this area is the effort to reduce the demand for electricity for lighting purposes. To consider just the domestic requirements, during 2011 domestic electricity consumption in the UK was 30% of a total electricity demand of 374TWh. Of this figure of 112TWh some 13TWh were used for lighting alone. This thesis describes research made in this area, in particular the manufacture of lighting luminaires making use of High Brightness Light Emitting Diodes (HBLEDs). The thesis outlines and demonstrates a methodology for the design, testing and subsequent manufacture of complete luminaires which make suitable, low energy consumption alternatives to conventional lighting using filament lamps and fluorescent fittings. Work has been done in the areas of:Thermal management, Power supply design, Luminaire design, Performance simulation in software, 'Remote phosphor’ luminaires in which LEDs with blue light outputs are used to provide blue light which is converted to usable white light by phosphor laden acrylic plates employed in luminaires for both wavelength conversion and light diffusion, Luminaire performance measurementIt is shown that substantial savings in energy (over 50%) can be made by using HBLEDs in lighting luminaires whilst producing satisfactory lighting for a variety of purposes.

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Stone, Roni. "An investigation into novel red emitting phosphors and their applications." Thesis, Brunel University, 2011. http://bura.brunel.ac.uk/handle/2438/6296.

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New red emitting phosphors, based on the double tungstate/molybdates, were discovered. Some were able to retain their luminous efficacy after substituting Y3+ for Eu3+, reducing the cost of the phosphor. This substitution was attempted for existing commercial red emitting phosphors and proved unsuccessful. Another set of phosphors based on these lattices were discovered and the emitted luminous efficacy was 140% greater than other reported Eu3+ phosphors. The best of these was Na2WO4MoO4Eu0.44Al1.34Sm0.011. The integration of phosphors to the lighting application was also studied, including improvements in light extraction for existing phosphors. ACEL panels are currently applied to many applications and were briefly examined. The more recent OLED technology was investigated and comparisons can be drawn with the ACEL panels. LEDs were also a focus of the work with a new method developed for remote application of phosphors to LEDs, based on a dome shaped encapsulant, and this was adopted commercially by a high brightness LED manufacturer. The studies on the phosphors reported herein were aimed at integrating these into commercial applications. Although this was not achieved as brightness and particles size were problematic, if it is demonstrated that further development of the synthetic methods produce phosphors with suitable attributes, this may lead to the integration in applications.

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Krist, Michael S. "The Design and Manufacture of a Light Emitting Diode Package for General Lighting." DigitalCommons@CalPoly, 2010. https://digitalcommons.calpoly.edu/theses/255.

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Lighting technologies have evolved over the years to become higher quality, more efficient sources of light. LEDs are poised to become the market standard for general lighting because they are the most power efficient form of lighting and do not contain hazardous materials. Unfortunately, LEDs pose unique problems because advanced thermal management is required to remove the high heat fluxes generated by such relatively small devices. These problems have already been overcome with complex packaging and exotic materials, but high costs are preventing this technology from displacing current lighting technologies. The purpose of this study is to develop a low-cost LED lighting package capable of successfully managing heat. Several designs were created and analyzed based on cost, thermal performance, ease of manufacturing, and reliability. A unique design was created which meet these requirements. This design was eventually assembled as a prototype and initial testing was conducted. This thesis reviews the design process and eventual results of the LED package design.

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Mikula, Vladimír. "Aplikace LED pro signalizační a osvětlovací účely v dopravě." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217884.

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Chief topic of a Master’s Thesis is comparing of conventional sources of light with LED diodes, their characteristics. This work deals with utilizing LED diodes in automotive lighting, in railway applications and universal information about principle of lighting. Else this work describes feasibility study of headlight of railway locomotive. Emphasis is laying for clearness of this work.

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Soares, Guilherme Marcio. "Sistema inteligente de iluminação de estado sólido com controle remoto e análise de parâmetros da rede elétrica." Universidade Federal de Juiz de Fora, 2014. https://repositorio.ufjf.br/jspui/handle/ufjf/696.

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Este trabalho propõe um sistema inteligente de iluminação pública utilizando diodos emissores de luz (LEDs). Neste âmbito, é proposta uma topologia para o acionamento dos LEDs com controle de intensidade luminosa. Além disso, funções adicionais são propostas de modo a expandir o conjunto de funcionalidades da luminária. Para o acionamento dos LEDs foi desenvolvido um conversor baseado na topologia Ćuk operando em modo de condução descontínuo (DCM) com um interruptor estático em série com a carga, sendo uma solução para o acionamento de LEDs de estágio único. Deste modo, este conversor foi projetado para desempenhar simultaneamente as funções de correção do fator de potência e controle da potência na carga. Através da análise da resposta fotométrica dos diodos emissores de luz perante ondulações de baixa frequência em sua corrente, foi possível criar uma metodologia de projeto que evita o uso de capacitores eletrolíticos no circuito de acionamento dos LEDs, aumentando assim a confiabilidade do sistema. A modelagem e o controle do conversor também foram feitas e estão mostradas no trabalho. De modo a controlar e gerenciar o sistema eletrônico da luminária, foi proposta uma arquitetura baseada no microcontrolador TM4C123GE6PM. Este sistema digital é responsável ainda por promover outras funcionalidades como controle automático de intensidade luminosa, proteção do circuito e ainda monitoramento de parâmetros de qualidade de energia da tensão de entrada do conversor, tais como afundamentos e elevações. A fim de avaliar experimentalmente o sistema proposto, foram desenvolvidos um programa de computador capaz de gerenciar as funcionalidades da luminária e um protótipo de 70W deste equipamento. Os resultados experimentais obtidos mostraram um bom desempenho tanto do circuito de acionamento dos LEDs, como das funcionalidades da luminária.
This paper proposes a smart lighting system based on light-emitting diodes (LEDs) for street lighting applications. In this context, a power converter with dimming capability was designed. Furthermore, additional functions are proposed in order to expand the feature set of the luminaire. To drive the LEDs, a topology based on Ćuk converter operating in discontinuous conduction mode (DCM) with an electronic switch in series with the load was proposed. This converter was designed to perform simultaneously the functions of power factor correction and power control, being a single-stage LED driver solution. By analyzing the LEDs photometric response due to low-frequency current ripple, a design methodology that avoids the use of electrolytic capacitors in the proposed converter was developed. The modeling and control of the converter were also done in order to ensure that the system is always operating within the desired specifications. To control and manage the electronic system of the luminaire, it was developed an architecture based on the microcontroller TM4C123GE6PM. Beside the aforementioned functions, this digital system was designed aiming the promotion of other features, such as automatic dimming, protection of the driver and even monitoring some power quality parameters related to the input voltage, such as sags and swells. In order to experimentally evaluate the proposed system, a software, able to manage the luminaire functionalities, and a 70W prototype were built. The experimental results demonstrated a good performance of the LED driver as well as the functionalities of the proposed luminaire.

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Hernández, Ricardo. "Growth and Development of Greenhouse Vegetable Seedlings Under Supplemental LED Lighting." Diss., The University of Arizona, 2013. http://hdl.handle.net/10150/306916.

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The greenhouse industry is interested in light emitting diodes (LEDs) as a light source supplement to solar light to improve plant growth and development. Before LEDs can be adopted as supplemental light for greenhouse crops, plant responses to LED spectral quality need to be investigated. Tomato and cucumber seedlings were grown under different supplemental blue and red photon flux ratios (B:R ratios) under high (16-19 mol m⁻² d⁻¹) and low (5-9 mol m⁻² d⁻¹) solar daily light integrals (DLIs). The supplemental daily light integral was 3.6 mol m⁻² d⁻¹. A treatment without supplemental light served as a control. Both tomato and cucumber seedlings had increased growth rate and improved morphology when grown under the supplemental LED light compared to the control. However, no significant differences were observed for any growth and morphological parameters measured in this study between the different B:R ratios for both cucumber and tomato transplants under high DLI conditions. Cucumber seedlings showed a tendency to decrease dry mass, leaf number and leaf area under low DLI conditions with increasing B:R ratio. Tomato seedlings did not show any differences between the different B:R ratios under low DLI conditions. Seedlings growth and morphology under supplemental LED light were compared to those under supplemental high pressure sodium (HPS) light. Cucumber seedlings under supplemental HPS light had greater shoot dry mass than those under the supplemental red LED light. Tomato shoot dry mass showed no differences between the HPS and red LED supplemental light treatments. Cucumber seedlings were also grown under supplemental LED pulsed lighting and supplemental LED continuous lighting. Cucumber seedlings showed no differences in shoot dry mass and net photosynthetic rate between the treatments. Collectively, these studies concluded that red LED is preferred for supplemental lighting and the increase of blue light does not offer any benefits unless the efficiency of blue LEDs largely exceeds the red LEDs. The results of this research can be used for fixture development by LED manufactures and as a decision making tool for the adoption of supplemental LED lighting by greenhouse growers.

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Matlack, Daniel W. "Incorporating new age technology into campus lighting." Manhattan, Kan. : Kansas State University, 2009. http://hdl.handle.net/2097/1391.

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Allen, Steven C. "Illumination for the 21^st Century: High Efficiency Phosphor-Converted Light-Emitting Diodes for Solid-State Lighting." University of Cincinnati / OhioLINK, 2007. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1186160915.

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Zolfaghari, Zahra. "Study of the Effect of Light Emitting Diode (LED) on the Optimum Window-to-Wall Ratio and Whole-Building Energy Consumption in Open Offices." Thesis, Virginia Tech, 2020. http://hdl.handle.net/10919/100642.

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Daylight harvesting is an essential strategy that is often used to enhance both the design and performance of an architectural project. Windows, as crucial architectural elements, not only admit natural light into spaces but also provide the occupants with visual connections. However, the excessive usage of windows brings an uncontrolled amount of solar energy to the spaces and negatively affect the building's energy performance. When utilizing passive design strategies such as daylight harvesting, several parameters, including the electrical lighting system, can impact the outcome. The current study investigates the role of lighting systems on daylight harvesting's effectiveness and their impact on window dimension and total energy consumption. In this study, the optimum window-to-wall ratio of an open office in the presence of two different light sources (LED and fluorescent) is explored through a computer simulation method. A combination of tools including AGi32, ElumTools, OpenStudio, EnergyPlus, Radiance, and MATLAB helps to conduct the simulation and deliver optimal results. In the results and conclusion chapter, the study provides guidelines to specify optimal window percentages considering two lighting systems in each cardinal direction. Importantly, the guideline focuses only on energy performance and not on the spatial quality of the design.
Master of Architecture
Harnessing daylight with the use of windows helps to offset parts of the electric lighting needs, and decrease the total building energy consumption. This is accomplished by using glazed materials to admit daylight and lighting control systems, which can respond to the dynamic light level. However, improper implementation of a passive daylighting strategy may cause increased energy consumption. Sunlight is accompanied by solar heat radiation which can increase the HVAC load of a space and compromise the energy savings achieved by daylighting. Therefore, a balance between solar heat and light gain is required to fully take advantage of solar energy without reverse impacts. Concerning the mentioned balance, recent advancements in lighting technology question the effectiveness of natural light in reducing whole-building energy consumption. Due to the high energy efficiency of LED luminaires, lighting power consumption is rather low, even when the lighting system operates at full capacity. Therefore, it is unclear whether the solar energy coming through glazed materials works to the advantage or disadvantage of total building energy consumption. This study hypothesized that the total energy consumption of an open office with LED luminaires would be less in absence of solar energy compared to a scenario which utilizes the solar energy. A simulation-based methodology, using a combination of photometric computation and building energy simulation tools, was utilized to examine the hypothesis and explore the impacts of lighting systems on the optimum window-to-wall ratio. The results provide a helpful guideline which highlights the impact of lighting systems on window dimensions and their mutual effect on whole-building energy consumption. Although the optimum window-to-wall ratios suggested by this study only concern energy consumption, integration of them with occupants' preferences can propose an acceptable window-to-wall ratio that satisfies both design quality and performance of a building.

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Möttönen, Karin, and Mikael Hedén. "Human Centric Lighting : Automatisk belysningsvariation för hälsa, välbefinnande och elsparande." Thesis, Högskolan Dalarna, Energiteknik, 2019. http://urn.kb.se/resolve?urn=urn:nbn:se:du-31324.

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Examensarbetet är en undersökning avseende implementering av Human Centric Lighting (HCL)- system i hemmamiljö. En litteraturstudie har genomförts om HCL, dess effekter på människan och LED-belysningens påverkan både på människan och miljön. För att få en bra praktisk grund gjordes även ett undersökande besök på Lindeborgsskolan i Malmö som i ett pilotprojekt har installerat HCL-system i ett klassrum. HCL handlar bland annat om att anpassa ljuset till människans varierande behov genom att variera intensitet (Lux) och färgtemperatur (Kelvin). Belysning har stor betydelse för människans välmående där en belysning med onaturlig spektralfördelning och flimmer kan leda till stress, sömnproblem samt att ögonen kan försämras. Ett bra varierande ljus kan däremot öka människans välmående, produktivitet och även ge en positivare inställning. En del forskning visar även på att HCL kan minska risken för årstidsbunden depression. Ett blått, mer intensivt ljus har en uppiggande effekt medan ett rött nerdämpat ljus verkar lugnande. Genom att utsätta kroppen för mycket blått ljus på förmiddagen men inte på eftermiddagen/kvällen gynnas kroppens cirkadiska cykel. Även rött ljus har visat sig ha en uppiggande effekt men påverkar inte den cirkadiska cykeln och kan med fördel användas även på kvällstid om en högre ljusintensitet behövs. Tre separata reglerbara belysningssystem har undersökts: Clas Ohlson WiFi Smart Bulb, IKEA trådfri belysning och Philips Hue White Ambiance. Kravet som ställdes för att belysningen skulle tas med i testet var att den skulle finnas tillgänglig i en relativt vanlig butik. Belysningen har testats både med avseende på ljusegenskaper samt energianvändning. En del av mätningarna utfördes med ett Ulbrichtklot på Clas Ohlsons ljuslaboratorium där färgspektrum, lumenvärde samt mycket annan information om ljuskällan kunde tas fram, samt med en handhållen spektrometer för att se flimmeravgivningen ifrån lampan vid olika inställningar. Energianvändningen undersöktes beträffande förändringar vid variation av färgtemperatur, intensitet och även i de fall som separat reglerutrustning krävdes. De tre belysningssystemen visade sig ha olika fördelar och nackdelar där en till slut valdes ut för att installeras i ett sovrum i utbildningsprojektet Dalarnas Villa. Baserat på ett tidigare gjort ljusschema, i en masteruppsats gjord av en ljusdesigner vid KTH, togs ett nytt ljusschema fram för sovrummet som förändrar ljusets intensitet och färgtemperatur för att främja den cirkadiska cykeln. Då författarna ser att detta är ett viktigt ämne så har varje möjlighet till att visa upp det installerade systemet tagits. Vid samtal med bland annat energirådgivare från Dalarna så har ett stort intresse visats. ” Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (WHO 1946). Health should be at the centre of all societal planning because social inequalities in health are costly to the society and counteract sustainable development (Malmö stad 2013). It is one of the main conditions for individual development opportunities through education, work, social relationships and participation in the society (UN 1949). Health is a key to the other human rights and also constitutes a separate right (WHO 2008).” Sustainability issues for SSL (R. Karlsson et al. 2016)
This thesis is a study concerning the implementation of Human Centric Lighting (HCL)-systems in the home environment. A literature study has been conducted on light, its effects on humans and the influence of LED lighting on both humans and the environment. To obtain a good practical foundation, an investigative study visit was also made to Lindeborgsskolan in Malmö, which as a pilot project has installed HCL systems in a classroom. HCL is, among other things, about adapting the light to man's varying needs by varying intensity (Lux) and color temperature (Kelvin). Lighting is of great importance to human well-being where lighting with unnatural spectral distribution and flicker can lead to stress, sleep problems and that the eyes can deteriorate. A good variety of light can, on the other hand, increase human well-being, productivity and give a positive attitude. Some research also shows that HCL can reduce the risk of seasonal depression. A blue, more intense light has a wakeup effect, while a red low intensity light feels soothing. By exposing the body to much blue light in the morning but not in the afternoon / evening, the body's circadian cycle benefits. Even red light has been shown to have a stimulating effect but does not affect the circadian cycle and can be used even in the evening if a higher light intensity is needed. Three separate controllable lighting systems have been investigated: “Clas Ohlson Wi-Fi Smart Bulb”, “IKEA trådfri” and “Philips Hue White Ambiance”. The lighting has been tested both in terms of light quality and energy use. The light quality was examined partly with an “Ulbrichtklot” at Clas Ohlson's light laboratory where color spectrum as well as various other information could be obtained, and with a hand-held spectrometer to see the flicker output from the lamp at different settings. The energy consumption was investigated regarding variation of color temperature, intensity and even in cases where separate control equipment was required. The three lighting systems were shown to have different advantages where eventually the Philips Hue Ambience White was selected to be installed in a bedroom in the project villa Dalarnas Villa. Based on a previous master thesis, a light schedule was developed that changes the intensity and color temperature of light to promote the circadian cycle. As the authors see this as an important topic, every opportunity to show the installed system has been taken. A great deal of interest has been shown during discussions including Dalarna´s energy advisers. ” Health is a state of complete physical, mental and social well-being and not merely the absence of disease or infirmity (WHO 1946). Health should be at the centre of all societal planning because social inequalities in health are costly to the society and counteract sustainable development (Malmö stad 2013). It is one of the main conditions for individual development opportunities through education, work, social relationships and participation in the society (UN 1949). Health is a key to the other human rights and also constitutes a separate right (WHO 2008).” Sustainability issues for SSL (R. Karlsson et al. 2016)

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Motta, Leandro Chelski da. "Conversor de único estágio baseado na integração Charge-Pump Valley-Fill para acionamento de LEDs de potência." Universidade Tecnológica Federal do Paraná, 2017. http://repositorio.utfpr.edu.br/jspui/handle/1/2887.

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Este trabalho propõe um sistema eletrônico de único estágio para acionar LEDs de potência empregando os conceitos Charge-Pump e Valley-Fill. Ambos conceitos estão relacionados a configurações topológicas baseadas na integração de um retificador boost de entrada com um inversor meia onda de saída, caracterizando o sistema de único estágio. A configuração Charge-Pump é utilizada para diminuir a ondulação de corrente dos LEDs. A configuração Valley-Fill é empregada para grampear a tensão de barramento CC em níveis inferiores ao valor de pico da tensão da fonte de entrada durante um longo intervalo de tempo no período da rede de alimentação, mantendo o sistema com elevado fator de potência. Desta forma é possível utilizar capacitores de barramento com valores reduzidos. O princípio de funcionamento do conversor proposto, que em regime permanente inclui três modos de operação, será apresentado e analisado. Uma metodologia de projeto, bem como resultados de simulação também serão apresentados para que se possa verificar as características operacionais do sistema. Neste trabalho será utilizado o comando simétrico em uma frequência de comutação de 67 kHz e 90 kHz. A tensão de alimentação é de 220 V e a carga é composta por 18 LEDs conectados em série com potência total de 47 W.
This work proposes a single stage electronic system to drive power LEDs employing Charge-Pump and Valley-Fill concepts. Both concepts are related to topological configurations based on the integration of an input boost rectifier with an output halfbridge inverter, characterizing the single stage system. The Charge-Pump configuration is used to decrease LEDs' current ripple. The Valley-Fill configuration is used to restrict the DC bus voltage at levels lower than the input source voltage peak value over a long period of time in the source period, keeping a high power-factor system. Thus, it is possible to use bus capacitors with reduced values. The proposed converter operation principle, which in steady-state includes three operation modes, that will be presented and analyzed. A design methodology as well as simulation results will also be presented so that the system operational characteristics can be verified. In this paperwork, the symmetric command will be used at a switching frequency of 67 KHz. The supply voltage is 220 V and the load is composed of 18 LEDs series connected with total power of 47 W.

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Correia, Gonçalo Daniel. "Indoor wireless architecture for smart lighting." Master's thesis, Universidade de Aveiro, 2016. http://hdl.handle.net/10773/18715.

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Mestrado em Engenharia Eletrónica e Telecomunicações
Esta dissertação propõe um sistema de iluminação para espaços interiores com o objetivo de ultrapassar as limitações dos sistemas atuais e melhorar a eficiência energética. Este trabalho enquadra-se no projeto Smartlighting que tem o objetivo de desenvolver um sistema de gestão integrada para o edifício do IT2. Na sua fase inicial, o sistema foca-se principalmente no controlo da iluminação através do uso de sensores e tecnologias da Internet das Coisas. Numa primeira fase, é feita uma análise do problema e das tecnologias envolvidas. Depois os requisitos para o sistema são identificados através da exploração de vários cenários de utilização. Daqui é desenvolvida uma solução conceptual que resulta do trabalho colaborativo do projeto Smartlighting. A solução apresentada é baseada Bluetooth Low Energy e gerida através de técnicas deem Pcroocmeusnsiacmaçeãnot o pdoer Eventos Complexos, constituindo assim uma topologia distinta das usadas atualmente em sistemas iluminação para espaços interiores. A solução é depois analisada numa perspetiva de iluminação através de uma simulação de DIALux que visa validar a implementação no âmbito da norma europeia 12464, referente a sistemas de iluminação para espaços interiores. Desta simulação também resulta uma projeção da eficiência enérgica do edifício em termos de iluminação, considerando as funcionalidades que o sistema idealizado implementará. A solução é concretizada num protótipo que é avaliado de forma a validar a solução numa perspetiva de automação.
building energy consumption problematic and the constrains present in current indoor lighting systems. The work presented results from the Smartlighting project that aims to develop an integrated building management system for the IT2 building. In its initial stage, this system focuses primarily in indoor lighting control, using sensors and IoT technologies. First, the problem and the technologies involved are presented and reviewed. Then the project requirements are identified by exploring a set of use case scenarios. From this, a concept solution is presented that results from the Smartlighting project collaborative work. The proposed solution takes advantage of Bluetooth Low Energy and Complex Event Processing technologies to deliver a topology distinct from the indoor lighting system status quo. The solution is then analysed in terms of a lighting application, via a DIALux simulation that aims to validate the implementation in the European Norm 12464 scope, referring to indoor lighting systems. From this simulation, it was also conducted an energy efficiency study referring to the building lighting, that took in consideration the functionalities implemented by the system. The solution is then materialized into a prototype to be evaluated in an automation perspective.

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Burgardt, Ismael. "Conversor SEPIC empregando um snubber regenerativo associado a um regulador linear de corrente para acionar e controlar LEDs de potência." Universidade Tecnológica Federal do Paraná, 2015. http://repositorio.utfpr.edu.br/jspui/handle/1/1467.

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CAPES
Este trabalho apresenta um sistema eletrônico com entrada universal utilizando um retificador SEPIC não isolado para fornecer e controlar a corrente de LEDs de potência. Um Snubber regenerativo que reduz as perdas de comutação e melhora a eficiência do sistema é proposto. Para realizar a dimerização, bem como reduzir a ondulação da corrente nos LEDs, um regulador linear de corrente é conectado na saída do conversor SEPIC. A utilização do regulador linear também permite que o conversor opere com entrada universal sem a utilização de circuitos adicionais. Para evitar perdas excessivas, o regulador é configurado para operar na região limiar da regulação. O ponto de perda mínimo do regulador é ajustado através de um circuito detector de mínimo com o sistema operando em malha fechada. As etapas de operação, as formas de onda e as principais equações do snubber regenerativo aplicado ao SEPIC são descritas no trabalho. Para verificar e validar a análise teórica são apresentados dois protótipos com potências de saída de 42 W e 145 W, variando de 15% a 100%, para o conversor operando com tensão de entrada de 90 a 240 V e alimentado 35 LEDs conectados em série.
This paper presents a universal-input AC electronic lighting system using a non-isolated SEPIC PFC rectifier to drive and control power LEDs currents. One energy regenerative snubber for reducing the converter switching losses and improve the system efficiency is proposed. The dimmable flicker-free current in the LEDs array is obtained through a linear current regulator placed in the SEPIC’s output terminals. In order to reduce the efficiency impairment, the conditions for achieving minimum energy loss in the current regulator are also detailed. Point of minimum energy loss in the linear regulator is adjusted through valley detector circuit in closed loop system operation. The operation stages as well as the theoretical waveforms and main equations at steady state of the proposed SEPIC rectifier using the regenerative snubber are described. To verify the theoretical analysis carried out, experimental results of two prototypes (42 W and 145 W) operating from 90 to 240 V and output power from 15 to 100% for 35 LEDs are also presented.

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Pinto, Rafael Adaime. "Projeto e implementação de lâmpadas para iluminação de interiores empregando diodos emissores de luz(LEDS)." Universidade Federal de Santa Maria, 2008. http://repositorio.ufsm.br/handle/1/8458.

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Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This work presents an efficient lighting system using high intensity light emitting diodes (LEDs). The goal is to develop a compact and low cost electronic circuit to drive and control the current of LEDs disposed in a single enclosure. The proposal aims energy saving, high luminous efficacy and high useful life when replacing traditional lighting systems, as dichroic, incandescent or compact fluorescent lamps by LEDs without any change in electrical system installation. Furthermore, an emergency lighting system integrated into the lamp is proposed, allowing the use of the same equipment in the daily activities, supplied by mains, and under a possible break in the electrical network. To supply the LEDs through the mains with universal input voltage and charge the battery, a Buck converter was employed. To supply the LEDs with a continuous current through the battery, a Boost converter was used. The converters operate at high frequency and control the current through the LEDs independently. The battery can be composed of three rechargeable Ni-MH batteries (1,2 V) or a Li-ion battery (3,6 V). The design attends the Brazilian standard and international standard for emergency lighting systems. To validate the proposed idea, the circuits were designed and implemented. The experimental results are shown with the intention to prove the satisfactory behavior of the lamps.
Este trabalho apresenta um sistema de iluminação eficiente empregando diodos emissores de luz (LEDs) de alta intensidade. O objetivo é desenvolver um circuito eletrônico, compacto e de baixo custo, para acionamento e controle da corrente dos LEDs contidos em um único invólucro. A proposta visa a racionalização no uso da energia elétrica através de uma elevada eficácia luminosa e longa vida útil na substituição dos sistemas de iluminação tradicionais, como lâmpadas dicróicas, incandescentes ou fluorescentes compactas, por LEDs sem qualquer alteração na instalação elétrica. Além disso, é proposto um sistema de iluminação de emergência integrado a esta lâmpada, permitindo a utilização de um único equipamento para iluminação convencional, alimentada pela rede elétrica, e sob uma possível falha no fornecimento de energia. Para alimentar os LEDs, através da rede elétrica, com tensão de entrada universal e ainda carregar a bateria, um conversor Buck é empregado. Para alimentar os LEDs em corrente contínua através da bateria, um conversor Boost é utilizado. Os conversores operam em alta freqüência e controlam a corrente nos LEDs de forma independente. A bateria pode ser composta por três pilhas recarregáveis de Ni-MH (1,2 V) ou por uma bateria de Li-Ion (3,6 V). O projeto atende às exigências da norma brasileira (NBR 10898) e da norma internacional (IEEE Std 446-1995) para sistemas de iluminação de emergência. Para analisar a idéia proposta, os circuitos são projetados e implementados. Os resultados experimentais são apresentados de forma a comprovar o comportamento satisfatório das lâmpadas.

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Morávek, Petr. "Regulovatelný zdroj pro napájení LED." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2018. http://www.nusl.cz/ntk/nusl-376929.

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This thesis deals with the description of artificial light sources, that use light-emitting diodes for their operation. Further down, the parameters of LEDs and their emissions are detailed. The work follows with the characterization of principles of LED power regulation. In the practical section, an example of one of the possible LED light source topologies, is designed. The offered solution includes the options to manually and automatically regulate the chromaticity of emitted light. Functionality of the solution was verified experimentally.

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Pinto, Rafael Adaime. "Sistemas eletrônicos para iluminação de exteriores empregando diodos emissores de luz (leds) alimentados pela rede elétrica e por baterias." Universidade Federal de Santa Maria, 2012. http://repositorio.ufsm.br/handle/1/3675.

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Анотація:

Coordenação de Aperfeiçoamento de Pessoal de Nível Superior
This work presents a design methodology and analysis of electronic circuits applied to outdoor lighting systems using light emitting diodes (LEDs). The goal of topologies developed here is to supply the LEDs from the mains, with high power factor, and from batteries when it is needed. Thus, some topologies employing integrated DC-DC converters and single stage converters are proposed and analyzed. The main application of these topologies is street lighting systems without energy consumption from the mains during the Peak Load Time, feeding the circuit by batteries. Moreover, the batteries can keep the system working during a possible fault in the main power supply, operating as an emergency lighting system. These applications are justified by the reduction in energy demand from the electric power system and by the increase in the lighting system reliability. Throughout the work, the main characteristics of the LED and batteries applied in lighting systems are presented, as well as the specification of the luminaire and the battery bank employed. The design methodology proposed for each topology aims to help the converter design intended for better utilization of semiconductors and reduce the value of the bus capacitor. A critical analysis of the converters is performed in order to evaluate the efficiency of the circuits, the power factor, the voltage and current characteristics of the main devices, and compliance with the IEC 61000-3-2 Class C standard that limits the harmonic content of the input current. Finally, electronic circuits are proposed for the management and control of the lighting system.
Este trabalho apresenta uma metodologia de projeto e análise de circuitos eletrônicos aplicados à iluminação de exteriores empregando diodos emissores de luz (LEDs). O objetivo das topologias desenvolvidas neste trabalho é proporcionar aos LEDs uma alimentação adequada através da rede elétrica, com alto fator de potência, e através de baterias quando necessário. Para isso, são propostas e analisadas algumas topologias empregando conversores CC-CC integrados e de estágio único. Estas topologias têm como principal aplicação sistemas de iluminação pública sem consumo de energia a partir da rede elétrica durante o Horário de Ponta, alimentando o circuito por baterias. Além disso, as baterias podem manter o funcionamento do sistema durante uma possível falha no fornecimento de energia pela rede elétrica, operando como um sistema de iluminação de emergência. Estas aplicações são justificadas pela redução da demanda de energia do sistema elétrico de potência durante horários críticos e aumento da confiabilidade do sistema de iluminação pública. Ao longo do trabalho, as principais características do LED e de baterias aplicadas em sistemas de iluminação são abordadas, juntamente com a especificação da luminária e do banco de baterias empregados. A metodologia de projeto proposta para cada topologia desenvolvida tem por objetivo auxiliar o projeto do conversor visando melhor aproveitamento dos semicondutores e redução do valor do capacitor de barramento. A análise crítica dos conversores é realizada com o objetivo de avaliar a eficiência dos circuitos, o fator de potência, características de tensão e de corrente nos principais componentes e o atendimento à norma IEC 61000-3-2 Classe C que limita o conteúdo harmônico da corrente de entrada. Por fim, são propostos circuitos eletrônicos para o gerenciamento e controle do sistema de iluminação.

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47

Almeida, Camila do Carmo. "Sistema eletrônico baseado em diodos emissores de luz (LEDs) para aplicação em estudos de fisiologia vegetal." Universidade Federal de Juiz de Fora (UFJF), 2014. https://repositorio.ufjf.br/jspui/handle/ufjf/4167.

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Este trabalho teve por objetivos projetar um sistema eletrônico de controle destinado a fornecer uma alternativa simpliﬁcada e eﬁciente para estudos de ﬁsiologia vegetal envolvendo luz artiﬁcial, bem como para sua utilização em determinados processos de cultivo de plantas em estufas. O trabalho apresenta uma revisão sobre a interação entre a iluminação artiﬁcial e o cultivo de plantas, tanto para o propósito de uma cultura comercial quanto para possibilitar a interpretação do comportamento de plantas em estudos botânicos. Este sistema eletrônico possibilita a determinação das quantidades radiométricas de interesse quando a iluminação artiﬁcial é usada como suplemento ou como única fonte de iluminação em cultivos. Com base em estudos anteriores, é proposto a produção de um sistema autônomo constituído por um aparelho de iluminação composto por LEDs brancos e/ou coloridos. Além disso, foram realizados alguns experimentos radiométricos preliminares utilizando luminárias comerciais de LEDs, visando sua utilização em associação com o sistema de controle proposto. Os parâmetros medidos mais relevantes foram o ﬂuxo de fótons fotossinteticamente ativos, ﬂuxo luminoso e a temperatura de cor correlata. Espera-se que o protótipo desenvolvido apresente características que agreguem ﬂexibilidade e comportamento radiométrico relevante para cultivos controlados.
This work aims to develop an electronic control system with the purpose to drive a simpliﬁed and eﬃcient alternative for vegetal physiology studies involving artiﬁcial light as well as for its utilization in certain plants crop at greenhouses. Additionally, this work presents a brief review regarding the interaction between artiﬁcial lighting and plants, with purposes of commercial crops and the possibility of interpretation of plants behavior in botanic studies. This electronic system enables the determination of the radiometric quantities of interest when the lighting is used as a supplement or as the only lighting source in crops. Using the latest studies, it is proposed an autonomous system consisting basically of white and/or colored LEDs. Besides, it were performed radiometric experiences using commercial luminaires with LEDs aiming the use of them in the proposed control system. The more relevant measured parameters were the photosynthetic photon ﬂux, luminous ﬂux and correlated colour temperature. The proposed system shows ﬂexibility and relevant radiometric behavior, which are particularly useful in Plant Physiology.

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Liu, Tong. "Lighting Evaluation and Design for the Stockholm Metro System Based on Current Models for Non-visual Responses." Thesis, KTH, Ljusdesign, 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-280028.

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Light has a wide and profound non-visual impact on the human body. It is related to the suppression or synthesis of a hormone called melatonin which regulates the human circadian clock. In Nordic countries like Sweden, lack of natural light in winter may lead to negative health effects such as circadian disorders or depression. At the same time, the underground metro system in Stockholm carries more than one million passengers on a weekday. The lighting in the train carriage may have distinct circadian effects on the passengers. The paper takes the metro system in Stockholm as an example, calculates the non-visual effects of the artificial lighting in the train according to Equivalent Melanopic Lux (EML), Circadian Stimulus (CS) and Melanopic Equivalent Daylight Illuminance (M-EDI) Models, compares with current guidance and suggestions, considers the daylighting conditions of Stockholm, and proposes a new design solution with adjustable LEDs to achieve a better healthful circadian lighting result.

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49

Guisso, Ronaldo Antonio. "Uma metodologia de otimização para sistemas de iluminação que empregam LEDs." Universidade Federal de Santa Maria, 2015. http://repositorio.ufsm.br/handle/1/8559.

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Conselho Nacional de Desenvolvimento Científico e Tecnológico
This work presents an optimization methodology for lighting systems that employ LED. Initially, this work brings a calculation methodology capable of obtaining a thermal resistance of heat sink from their dimensions of area, besides enable optimization of the system through reducing their volume by through of change in the number of finned, length and consequently the weight of heat sink. Subsequently, the thesis present a new optimization methodology that has the objective of find the optimal point of operation lighting system taking into consideration the parameters of application current in the device, luminous flux, junction temperature, thermal resistance heat sink, number of LED and lifetime. An example of project is shown, confirming the theory, where the obtained results through of routine calculation coincided with the values found in experimental. The work also present the development of electronic topologies to power a public lighting system employing LED. Therefore, a driver to power of LED based in the integrated two-flyback converters was proposed. One prototype this system was implemented, where the luminaire provide a power of 63W. The experimental results proved the project methodology through of system satisfactory operation, presenting power factor near unit, high efficiency and a low input current distortion was obtained.
Este trabalho apresenta uma metodologia de otimização para sistemas de iluminação que empregam LEDs. Inicialmente, traz-se uma metodologia de cálculos capaz de obter a resistência térmica de dissipadores de calor a partir de suas dimensões de área, além de possibilitar a otimização do sistema através da redução do volume do mesmo por meio da variação do número de aletas, do comprimento e consequentemente da massa do dissipador. Posteriormente o trabalho apresenta uma nova metodologia de otimização que tem o objetivo de encontrar o ponto ótimo de operação do sistema de iluminação, levando-se em conta os parâmetros de corrente direta aplicada no dispositivo, fluxo luminoso, temperatura de junção, resistência térmica do dissipador, número de LEDs e vida útil dos mesmos. Um exemplo de projeto é demonstrado confirmando a teoria apresentada, onde os resultados obtidos através da rotina de cálculos coincidiram com os valores encontrados experimentalmente. O trabalho também apresenta o desenvolvimento de uma topologia eletrônica para alimentar um sistema de iluminação pública empregando LEDs. Dessa maneira, um driver para acionamento de LEDs baseado na integração de dois conversores flyback foi proposto. Um protótipo desse sistema foi implementado, onde a luminária apresenta uma potência de 63W. Resultados experimentais comprovam a metodologia de projeto através da operação satisfatória do sistema, apresentando fator de potência próximo ao unitário, elevada eficiência e o conteúdo harmônico da corrente de entrada do sistema de iluminação atendeu a norma.

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Bartos, Krzysztof Mirosław. "Efficient LED drivers for general illumination applications." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14575.

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Mestrado em Engenharia Eletrónica e Telecomunicações
The ever growing energy consumption trends and its impact on the environment has triggered worldwide attention. This has motivated several measures, such as the Kyoto protocol, or the 20 20 20 European strategy, aiming at the reduction of energy consumption. Globally, these measures defend a better and efficient usage of the available energy. This in turn is strongly linked to public awareness and the introduction of efficient electronic equipment. Public street lighting is a good example of these trends, where both aspects are of the utmost importance. The introduction of power LEDs as future lighting devices has motivated several advances coping with these strategies. On one side, LEDs are able to deliver higher efficiency when compared to conventional lighting devices. This has triggered the replacement of old style luminaires by LED based ones. However, their high cost has prevented full adoption and at the present stage, is acting as a slowing down force against this replacement trend. Better solutions are under research on the framework of several European projects. Power LEDs are solid-state devices able to support fast switching, a feature which was not fully supported by conventional lighting devices. Combining this feature with environmental sensing and intelligent control may lead to better power savings. A simple approach would be to consider the that the actual lighting demands depend on the street usage and surrounding lighting levels. For this purpose, the combination of twilight sensors, motion detectors and intelligent control schemes may provide a suitable approach. This way, the real lighting demands can be effectively taken into consideration, providing luminaires able to consume the least possible energy. For this to become a reality several challenges have to be addressed. One of the most important challenges is the LED driver design. Modern lighting systems based on LEDs, replace the traditional ballasts by LED drivers. When efficiency is a major concern, such as in public street lighting, these drivers have to be designed in order to be the most robust and efficient as possible. Recurring solutions resort to switched mode power supplies, able to support light dimming. One of the major problems with these drivers is the fact that their efficiency decreases for lower dimming levels. This is of the utmost importance for public street lighting, as most of the time during night, the luminaires are on a low lighting level (as changes to high lighting conditions depend on street usage). Thus, in order to promote better power savings, the efficiency of the driver should be high for both lighting conditions. Commercially available drivers, exhibit efficiencies on the 90% range for the high lighting conditions, with only 40% to 60% under the low lighting. On the framework of this master dissertation it was investigated the problem of LED driver design aiming at the highest possible uniformity of the efficiency curve, under different loading and dimming conditions. The selected approach was based on quasi-resonant flyback converter, backed up by an active power factor correcting block. The designed driver supports remote configuration and monitoring as well as sensor integration. The archived results show that this driver achieves a peak efficiency of 93% under maximum load and 100% duty-cycle. The efficiency for low dimming conditions (10% duty-cycle) achieves 75%.
As tendências de consumo de energia cada vez maior e seu impacto sobre o meio ambiente tem captado a atenção a nível mundial. Isso tem motivado várias medidas, tais como o Protocolo de Quioto, ou a estratégia Europeia 20 20 20, visando a redução do consumo de energia. Globalmente, estas medidas defendem um uso melhor e eficiente da energia disponível. Este, por sua vez, está fortemente ligado à consciência pública e à introdução de equipamento eletrónico eficiente. A iluminação pública é um bom exemplo dessas tendências, em que ambos os aspetos são de extrema importância. A introdução de LEDs como dispositivos de iluminação tem motivado vários avanços que lidam com essas estratégias. De um lado, os LEDs são capazes de oferecer uma maior eficiência quando comparados com dispositivos de iluminação convencionais. Isso provocou a substituição de luminárias convencionais por luminárias baseadas em LED. No entanto, o custo elevado destes dispositivos tem impedido a adoção plena e na fase atual, está mesmo a atuar como uma força negativa contra esta tendência de substituição. Melhores soluções estão sob investigação no âmbito de vários projetos europeus. Os LEDs são dispositivos de estado sólido, capazes de suportar a comutação rápida, uma característica que não é totalmente suportada por dispositivos de iluminação convencionais. Combinando esta característica com sensores ambientais e controlo inteligente pode-se ambicionar melhores poupanças energéticas. Uma abordagem simples seria a de considerar o que as exigências de iluminação reais dependem do uso das ruas e os níveis de iluminação circundantes. Para este efeito, a combinação de sensores de crepúsculo, detetores de movimento e regimes de controlo inteligentes podem propiciar uma abordagem adequada. Desta forma, os requisitos reais de iluminação podem ser efetivamente considerados, fornecendo luminárias capazes de consumir apenas a energia necessária. Para que isto se torne uma realidade vários desafios têm de ser vencidos. Um dos desafios mais importantes é o projeto LED driver. Nos sistemas de iluminação modernos baseados em LEDs, substitui-se os balastros convencionais por LED drivers. Quando a eficiência é importante, como no caso da iluminação pública, O LED driver têm de ser concebido de forma a ser o mais robusto e eficiente possível. Soluções recorrentes usam a fontes de alimentação comutadas, capazes de suportar o escurecimento adaptativo do fluxo luminoso. Um dos problemas principais no projeto destes drivers é o facto de a sua eficiência diminuir para níveis de regulação mais baixos. Isto é de extrema importância para a iluminação pública, pois na maioria dos casos durante a noite, as luminárias estão num nível de iluminação de baixo. Assim, com a finalidade de promover uma melhor economia de energia, a eficiência do driver deve ser elevada para ambas as condições de iluminação. Drivers comercialmente disponíveis, exibem eficácias na gama de 90% com elevado fluxo luminoso, e apenas 40% a 60% na condição de baixo fluxo luminoso. No âmbito desta dissertação de mestrado foi investigado o problema do projeto de driver LED visando a maior uniformidade possível da curva de eficiência, sob diferentes condições de carga e de fluxo luminoso. A abordagem escolhida foi baseada no conversor flyback quasi-ressonante, apoiado por um bloco de correção de fator de potência ativa. O driver projetado suporta configuração e monitorização remota, bem como de integração de sensores. Os resultados alcançados mostram que este driver atinge um pico de eficiência de 93% na condição de carga máxima e máximo fluxo luminoso. A eficiência em condições de baixo fluxo luminoso é superior a 75%.

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