Dissertations / Theses on the topic 'Multi-LED'
To see the other types of publications on this topic, follow the link: Multi-LED.
Create a spot-on reference in APA, MLA, Chicago, Harvard, and other styles
Consult the top 50 dissertations / theses for your research on the topic 'Multi-LED.'
Next to every source in the list of references, there is an 'Add to bibliography' button. Press on it, and we will generate automatically the bibliographic reference to the chosen work in the citation style you need: APA, MLA, Harvard, Chicago, Vancouver, etc.
You can also download the full text of the academic publication as pdf and read online its abstract whenever available in the metadata.
Browse dissertations / theses on a wide variety of disciplines and organise your bibliography correctly.
1
Wu, Haoran. "Multi-Channel Constant Current (MC3) LED Driver for Indoor LED Luminaries." Thesis, Virginia Tech, 2011. http://hdl.handle.net/10919/35727.
Full textAbstract:
Recently, as a promising lighting source, light-emitting diodes (LEDs) have become more and more attractive and have great opportunity to replace traditional lighting sources - incandescent, fluorescent and HID because of the advantages such as high luminous efficacy, long lifetime, quick on/off time, wide color gamut, eco-friendly etc.
Based on the research from U.S. Department of Energy, over 30% of total electric consumption in U.S. each year is for lighting, 75% of which are for indoor lighting (including both residential and commercial buildings). In the indoor LED lighting application, to provide multiple current source outputs for multiple LED strings, traditional solutions usually adopt a two-stage structure, which is complicated and cost-ineffective. How to design a simple, low-cost and efficient LED driver with multiple current source outputs is in great demand and really challenging.
In this thesis, a single-stage multi-channel constant current (MC3) LED driver structure has been proposed. Multiple transformer structure is utilized to provide multiple current source outputs. The current control scheme is also simple - only one LED string current is sensed and controlled; other strings' currents are cross regulated.
Firstly, a PWM half bridge topology is chosen to implement the proposed single-stage MC3 LED driver concept. In order to analyze the current cross regulation, a general model is derived. The circuit has been simulated under various LED load conditions to verify its good current sharing capability.
In order to further improve efficiency, simplify the driver's complexity and reduce cost, a LLC resonant topology is also investigated. LLC current gain characteristic has been derived by considering LED's i-v character and a design procedure is developed. A 100 kHz, 200 W, 4-string MC3 LLC LED driver is designed and tested. The experimental results show that the driver can maintain constant current output within the whole input and output variations, achieve good efficiency and realize current sharing under both balanced and unbalanced LED conditions. The dimming function can also be realized through frequency modulation method and burst mode control method.
As a conclusion, a single-stage MC3 LED driver concept is proposed and implemented with two topologies. The proposed idea provides a simple, low-cost and efficient solution for indoor LED lighting application with multiple LED string configuration. It also has good current sharing capability and robustness to LED forward voltage variations or short failures.Master of Science
2
Ayub, Suleman [Verfasser], and Oliver [Akademischer Betreuer] Paul. "Implantable multi-LED devices for optogenetic studies." Freiburg : Universität, 2021. http://d-nb.info/1236845943/34.
Full text
3
Chen, Xuebing. "Two-Stage Multi-Channel LED Driver with CLL Resonant Converter." Thesis, Virginia Tech, 2014. http://hdl.handle.net/10919/50484.
Full textAbstract:
LED is widely used in many applications, such as indoor lighting, backlighting and street lighting, etc. For these application, multiple LED strings structure is adopted for reasons of cost-effectiveness, reliability and safety concerns. Several methods and topologies have been proposed to drive multiple LED strings. However, the output current balance and efficiency are always the two major concerns for LED driver.
A simple two-stage multi-channel LED driver is proposed. It is composed of a buck converter as the first stage and a multi-channel constant current (MC3) CLL resonant converter as the second stage. For the CLL resonant converter, the magnetizing inductance of the transformer can be as large as possible. Therefore, the magnetizing current of the transformer has little influence on the output currents. In addition, the currents of two LED strings driven by the same transformer is balanced by a DC blocking capacitor. As a result, the current balance among LED strings is very good, even if the load is severely unbalanced. Meanwhile, the current flowing through the external inductance Lr1, instead of the magnetizing current is used to help the primary-side switches to achieve ZVS. Therefore, large magnetizing inductance is good for current balance and properly designed Lr1 is helpful for ZVS achievement. These properties of MC3 CLL are preferred to drive multi-channel LED strings.
In the design procedure of MC3 CLL resonant converter, the parasitic junction capacitor of the secondary-side rectifier is taken into account. It influences the operation during dead time significantly when the voltage step-up transformer is applied. The junction capacitors of the secondary-side rectifiers, and the output capacitors of the primary-side switches will resonate with the inductor Le2 during the dead time. Finally, this resonance impact the ZVS achievement of the primary-side switches. Therefore, the inductors Lr1 and Le2 should be designed according the charge needed to achieve ZVS with considering the resonance.
Additionally, the control strategy for this two-stage structure is simple. Only the current of one specific LED string is sensed for feedback control to regulate the bus voltage, and the currents of other LED strings are cross-regulated. Furthermore, the MC3 CLL is unregulated and always working around the resonant frequency point to achieve best efficiency. The compensator is designed based on the derived small signal model of this two-stage LED driver. Due to the special electrical characteristics of LED, the soft start-up process with a delayed dimming signal is adopted and investigated. With the soft start-up, there is no overshoot for the output current.
Finally, a prototype of the two-stage LED driver is built. The current balance capability of the LED driver is verified with the experiment. Good current balance is achieved under balanced and severely unbalanced load condition. In addition, the efficiency of the LED driver is also presented. High efficiency is guaranteed within a wide load range. Therefore, this two-stage structure is a very promising candidate for multi-channel LED driving applications.Master of Science
4
Gilliom, Michael B. "Use of SIMO Converstion for Optimizing LED Light Drivers." Thesis, Virginia Tech, 2012. http://hdl.handle.net/10919/76876.
Full textAbstract:
As a growth industry, tremendous cost pressures are pushing the LED lighting market away from traditional power electronics converters and towards solutions that are more unconventional. Lower quality LED lights use simple low-cost converters, whereas high end product may add complexity in order to achieve a more dramatic energy savings.
SIMO technology represents an opportunity in LED lighting to combine the low cost of single-stage converters with the energy saving capability of a two-stage, multiple string solution. This paper describes the modeling, analysis, design, and testing of a Multiple Independently Regulated Output Flyback (MIROF) converter, used in LED lighting for the purpose of multiple string control. This converter is based upon SIMO technology applied to a PFC Flyback converter.
The result was the development of a novel control method and an operational demonstration unit. A cost comparison of the MIROF and a conventional two-stage driver shows a promising cost reduction benefit for the former, and comparative testing shows favorable performance of the MIROF converter compared to the two-stage approach.Master of Science
5
Llenas, Farràs Aleix. "Spectral control methods and applications for multi-channel LED light engines." Doctoral thesis, Universitat Politècnica de Catalunya, 2019. http://hdl.handle.net/10803/672450.
Full textAbstract:
Lighting installations are usually static and based on long-standing visual indicators such as colour temperature, colour rendering, and illuminance values. However, we now know that spectral variations in light elicit non-visual effects via a distinct pathway in our brain, and it is important for designers and architects to take these into account: light influences our mood, modulates our attention, can suppress the production of melatonin and can shift our circadian rhythms. Considering all the spectral aspects of light is the initial step towards designing healthier environments that are both pleasant and respectful to our biology.
Multi-channel LED light engines can provide the core technology for a truly spectral lighting design, thereby enabling wider applications of light with different purposes.
This dissertation aims at facilitating this transition by delivering cost-effective multi-channel LED light engines capable of generating arbitrary spectral shapes. In the first part of this work, we develop a light engine for a research-oriented market and explore novel designs and solutions for an advanced industrial device aimed at tackling a more general lighting market. These two efforts led to the development of two optically and spectrally different devices: the SPECTRA TUNE LAB light engine (with an on-board spectrometer and ten different LED channels), and the VEGA 07 light engine (equipped with a colour sensor and seven different LED channels).
Second, to generate arbitrary spectral shapes, we perform an extensive study on different heuristic algorithms implemented directly in the microcontroller of the light engine as well as in its control software. We show that the simulated annealing algorithm provides fast computation times with excellent spectral fidelity.
Third, we develop two types of optical feedback controllers with different light sensors to prevent temperature-driven colour and spectral shifts, and the wear-out of the LEDs. Both these sensors, i.e. the spectrometer in the SPECTRA TUNE LAB and the colour sensor in the VEGA 07, are used to ensure high precision and accuracy of the emitted light at all times and for any kind of target spectrum.
Finally, we demonstrate the ways in which these devices can be used for different applications, thereby verifying the huge advantages and added value of this technology as compared to traditional lighting systems. Our developed light engines were installed in the intensive care units of two hospitals (Hospital Vall d'Hebron and Hospital Clínic in Barcelona), in office settings (ARUP's office in London), and 24/7 control rooms (Repsol's refinery control room in Tarragona), among others.Les instal·lacions dil·luminació solen ser estàtiques i basades en indicadors visuals clàssics com la temperatura de color, la representació dels colors o els nivells d'il·luminació. Tanmateix, avui sabem que la llum també té una funció que no és propiament visual i que els arquitectes i dissenyadors haurien de començar a tenir en compte: la llum pot influir en el nostre estat d'ànim, modular la nostra atenció, regular la producció de melatonina o modificar els ritmes circadiaris. Tenir en compte totes les propietats espectrals de la llum és el primer pas per dissenyar entorns més sans i respectuosos amb la nostra biologia. Així, el disseny i desenvolupament de noves fonts de llum LED multicanal assequibles serà la tecnologia que permetrà un autentic canvi de paradigma espectral i començar a utilitzar la llum per a múltiples aplicacions. Aquest treball té com a objectiu facilitar aquesta transició proporcionant fonts de llum LED amb capacitat per generar qualsevol tipus de forma espectral. En una primera part, hem desenvolupat un sistema d'il·luminació multicanal orientat a un mercat d'investigació i recerca, i hem explorat nous dissenys i solucions per a un dispositiu més industrial amb l'objectiu de penetrar al mercat d'il·luminació general. Els dos esforços s'han materialitzat en dos dispositius òpticament i espectralment diferents: el sistema de llum SPECTRA TUNE LAB (amb un espectròmetre a l'interior i 10 canals LED diferents) i el sistema de llum VEGA 07 (amb un colorímetre i 7 canals LED diferents). En segon lloc, per poder crear qualsevol tipus de forma espectral, hem estudiat diferents algorismes heurístics implementats directament al micro-controlador de la lluminària o en un programari extern. L'algorisme desenvolupat de simulated annealing ha resultat ser el més ràpid amb una fidelitat espectral excel·lent. En tercer lloc, hem desenvolupat dos tipus de controladors òptics de llaç tancat amb dos sensors de llum diferents per evitar canvis de color i canvis espectrals degut a increments de la temperatura o degradació dels LEDs. Ambdós sensors, l'espectròmetre per l'SPECTRA TUNE LAB i el colorímetre pel VEGA 07, s'utilitzen per assegurar que la llum emesa romangui precisa i estable en tot moment, per a qualsevol espectre que vulguem generar. Finalment, demostrem com aquests dispositius es poden utilitzar per a diferents aplicacions oferint grans avantatges en comparació amb sistemes tradicionals. El nostre sistema d'il·luminació s'ha instal·lat a la unitat de cures intensives dhospitals (a l'Hospital Vall d'Hebron i a l'Hospital Clínic, a Barcelona), en entorns d'oficina (a ARUP, a Londres) o en sales de control 24 hores (a la sala de control de la refineria de Repsol, a Tarragona), entre d'altres
Enginyeria òptica
6
Gilbertson, Matthew (Matthew W. ). "Measuring cycling kinematics using a low-cost, flashing LED, multi-camera approach." Thesis, Massachusetts Institute of Technology, 2008. http://hdl.handle.net/1721.1/45845.
Full textAbstract:
Thesis (S.B.)--Massachusetts Institute of Technology, Dept. of Mechanical Engineering, 2008.Includes bibliographical references (p. 60).
In this thesis a low cost motion capture approach is presented and applied to measure cyclists' kinematics. The motion capture system consists of low cost hardware and custom developed software. Based on still-frame, off-the-shelf digital cameras, the method represents a solution which is accessible to the average athlete. With the exception of off-the-shelf digital cameras the total cost of the hardware is less than $100. The motion capture system is applied to study cyclist kinematics for three different types of bicycles: road bikes, triathlon bikes, and mountain bikes. Coupled with power output measurement and wind tunnel drag measurements, the investigation of several different standard cycling positions is performed. The results indicate a significant component of out-of- plane joint motions, especially in the knee, with an average knee excursion between 0.15" and 0.21". The system was also used to measure cycling cadence, with a range between 1.06Hz and 1.63Hz. Joint angle analysis suggested a positive correlation between ankle angle range and power output. Further in-depth analyses of these data or similar data collected using these motion capture approaches may give deeper insight into which motions correlate with higher power outputs. Wind tunnel and power data were used to calculate position transition velocities for different exertion levels and hill angles. This low-cost system was demonstrated to be a useful and effective tool for measuring and analyzing cycling kinematics.
by Matthew Gilbertson.
S.B.
7
Sereda, Alexandra. "Imagerie multi-spectrale par résonance des plasmons de surface : développement et applications." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112321/document.
Full textAbstract:
Dépistage du VIH, test de grossesse, mais également surveillance des eaux, détection de contaminants agro-alimentaires : la biodétection est au coeur des problématiques de santé actuelles. Dans ce contexte, les biocapteurs plasmoniques connaissent depuis quelques années un essor particulièrement important : de plus en plus de sociétés, telles que HORIBA Scientific, proposent des prototypes commerciaux, destinés tant à des utilisateurs du domaine de la recherche que de l'industrie. Basée sur le phénomène de résonance des plasmons de surface (communément appelé SPR) la biodétection plasmonique repose sur l'extrême sensibilité d’une onde évanescente se propageant à l’interface entre un film d’or, la biopuce, et le milieu diélectrique couvrant, siège des interactions biomoléculaires étudiées. De manière plus concrète, toute adsorption de matériel biologique se produisant à cette interface entraîne une modification importante des propriétés optiques d’un faisceau de lumière réfléchi par la biopuce : le principe de transduction par SPR consiste alors à mesurer directement ces variations. A l'heure actuelle, différents modes d'interrogation, offrant des performances intéressantes, mais également des limitations propres à chaque configuration. Pour répondre aux exigences de précision et de dynamique de mesure posées par de nombreuses applications, un développement théorique et instrumental, présenté dans ce document, a été initié dans le but de proposer un nouveau un nouveau mode d'interrogation des biopuces plasmoniques : l'interrogation multi-spectrale. Les résultats obtenus par cette technique ont été exploités pour concevoir et réaliser une source multi-spectrale à base de LEDs, particulièrement avantageuse vis-à-vis des configurations existant à l'heure actuelle. La caractérisation du système développé dans le cadre du diagnostic génétique (mucoviscidose) et celui du cancer, ouvre la voie à une nouvelle génération de biocapteurs performants, compacts et de coût relativement raisonnable, présentant un potentiel industriel certainBiodetection is at the core of the current health concerns, as shown through the variety of applications to HIV screening, food contaminant analysis or water quality monitoring. In this field, plasmonic biosensing is a well-established label-free technique on the market: commercial systems from HORIBA Scientific are currently available for both research and industrial users.Based on the surface plasmon resonance (SPR) phenomenon, plasmonic biodetection uses the high sensitivity of an evanescent wave propagating along a metallic film (forming the biochip) and the surrounding dielectric medium interface. More specifically, the adsorption of biomolecules onto the metal surface induces a strong change in the optical properties of a light beam reflected by the biochip: the main principle of plasmonic transduction consists in measuring these physical changes. Several interrogation techniques have therefore been developed to access such optical information, but they fail in meeting the most demanding user requirements for precise, real-time, high-throughput measurement.Initiated by these issues, the instrumentation work presented in this document has led to the development of a novel SPR interrogation technique, referred to as multi-spectral interrogation. Moreover, the promising results obtained have been pushed forward to propose a multi-spectral illumination system based on LEDs, providing attractive performances compared to existing configurations. The biosensing potential of the developed system, demonstrated through applications to genetic diagnosis and cancer detection, opens the door to a new generation of compact, high-performance, low-cost SPR sensors
8
Souza, Ana Maria de. "Efeito de diferentes doses de energia de unidades LED uni- e multi-ondas nas propriedades mecânicas de Resinas Compostas." Universidade Nove de Julho, 2013. http://bibliotecadigital.uninove.br/handle/tede/1139.
Full textAbstract:
Submitted by Nadir Basilio (nadirsb@uninove.br) on 2015-07-21T15:07:51Z
No. of bitstreams: 1
Ana Maria de Souza.pdf: 717565 bytes, checksum: 0b6ad0f4adba71695d0147808fdc405c (MD5)Made available in DSpace on 2015-07-21T15:07:51Z (GMT). No. of bitstreams: 1 Ana Maria de Souza.pdf: 717565 bytes, checksum: 0b6ad0f4adba71695d0147808fdc405c (MD5) Previous issue date: 2013-12-10
The aim of the present study was to evaluate the influence of different doses of energy and uni- or multi-wave LED units on mechanical properties of composite resins. Thereunto, six experimental groups were established for each assessed resin (IPS Empress Direct - Ivoclar Vivadent , Venus - Heraeus - Kulzer , SDR - Dentsply) according to the different different amounts of energy (5J , 10J and 20J) and LED unit (bluephase 16i and bluephase G2 - Ivoclar Vivadent) . Thirty six specimens were prepared (7mm long x 2mm wide x 1mm height) from silicon matrices and were used for evaluation of mechanical properties (flexural strength and modulus of elasticity) using the three points bending test, in a universal testing machine at a speed of 0.5 mm/min until the specimens fracture. Data were tested for normality and then the two-way analysis of variance was applied and Tukey's test was used to point out differences among means, with significance level set at 5%. Thus, the results showed that the resins presented different performance by energy amounts and by the difference of the spectra of light emitted by different sources. It appears from the data presented that the factors studied in this work are directly related to the mechanical properties of resin composites.
O objetivo do presente estudo foi avaliar a influência de diferentes doses de energia e unidades LED fotoativadoras de banda estreita e com amplo espectro nas propriedades mecânicas de resinas compostas. Para isso, 6 grupos experimentais foram estabelecidos para cada resina avaliada (IPS Empress Direct – Ivoclar Vivadent, Venus – Heraeus-Kulzer, SDR - Dentsply), de acordo com as diferentes doses de energia (5J; 10J e 20J) e unidades fotoativadoras (Bluephase 16i e Bluephase G2 – Ivoclar Vivadent). Trinta e seis corpos-de-prova foram confeccionados (7mm comprimento X 2mm largura X 1mm de altura) a partir de matrizes de silicone e foram utilizados para avaliação das propriedades mecânicas (resistência à flexão e módulo de elasticidade) utilizando o teste de flexão de três pontos, em máquina de ensaio universal a uma velocidade de 0,5 mm/min até que ocorresse a fratura do corpo-de-prova. Os dados foram avaliados quanto à sua normalidade e então, aplicado a Análise de Variância a dois critérios e teste de Tukey, com nível de significância fixado em 5%. Os resultados mostraram que as resinas apresentaram comportamentos diferentes entre si tanto pelas doses de energia utilizadas quanto pela diferença dos espectros de luz emitidos pelas diferentes fontes. Conclui-se dos dados apresentados que os fatores estudados neste trabalho têm relação direta com as propriedades mecânicas dos compósitos resinosos.
9
Naqvi, Asjad, and Irene Monasterolo. "Natural Disasters, Cascading Losses, and Economic Complexity: A Multi-layer Behavioral Network Approach." WU Vienna University of Economics and Business, 2019. http://epub.wu.ac.at/6914/1/WP_24.pdf.
Full textAbstract:
Assessing the short-term socio-economic impacts of climate-led disasters on food trade networks requires new bottom-up models and vulnerability metrics rooted in complexity theory. Indeed, such shocks could generate cascading socio-economic losses across the networks layers where emerging agents¿ responses could trigger tipping points. We contribute to address this research gap by developing a multi-layer behavioral network methodology composed of multiple spatially-explicit layers populated by heterogeneous interacting agents. Then, by introducing a new multi-layer risk measure called vulnerability rank, or VRank, we quantify the stress in the aftermath of a
shock. Our approach allows us to analyze both the supply- and the demand-side dimensions of the shock by quantifying short-term behavioral responses, the transmission channels across the layers, the conditions for reaching tipping points, and the feedback on macroeconomic indicators. By simulating a stylized two-layer supply-side production and demand-side household network model we find that, (i) socio-economic vulnerability to climate-led disasters is cyclical, (ii) the distribution of shocks depends critically on the network structure, and on the speed of supply-side and demand-side responses. Our results suggest that such a multi-layer framework could provide a comprehensive picture of how climate-led shocks cascade and how indirect losses can be measured. This is crucial to inform effective post-disaster policies aimed to build food trade network resilience to climate-led shocks, in particular in more agriculture-dependent bread-basket regions.Series: Ecological Economic Papers
10
Adolfsson, Tobias, and Axel Dellenby. "Pre-study of optical LED units for shunting signals." Thesis, KTH, Hälsoinformatik och logistik, 2021. http://urn.kb.se/resolve?urn=urn:nbn:se:kth:diva-296561.
Full textAbstract:
Alstom wanted to investigate the possibility of adapting its light emitting diode (LED) technology for shunting signals in train traffic. The LED technology uses 50V, but Alstom wants to adapt it for 12V. The LED technology is energy efficient but needs to be adapted for existing signal interlocking by drawing a higher current. This meant that the possibility of reactive power compensation was investigated to obtain lower thermal dissipation in dwarf signal. The essay presents a couple of possible solutions. One of the solutions is to raise the voltage by using a booster converter to use the existing 50V LED unit. Capacitors were reviewed to be used in reactive power compensation to increase current supply. One of the solutions then became a capacitor bank. Simulations indicated that a booster converter and a capacitor bank can be used to adapt the circuit. However, some modifications must be made.Alstom ville undersöka möjligheten att anpassa sin lysdiodsteknik för dvärgsignaler i tågtrafiken. Lysdiodstekniken använder 50V men Alstom vill anpassa den för 12V. Lysdiodtekniken är strömsnål och behöver anpassas för befintliga signalställverk genom att dra en högre ström. Detta innebar att möjligheten för reaktiv kompensering undersöktes för att få en låg värmeutvecklingen i dvärgsignalen. I uppsatsen presenteras ett par möjliga lösningar. En av lösningarna för spänningen är en step-up omvandlare för att nyttja 50Vs enheten. Det gjordes också en genomgång av kondensatorer för att nyttjas i reaktivkompensering för att öka strömförbrukningen. En av lösningarna blev då ett kondensatorbatteri. Det kunde konstateras med matematisk simulering att step-up omvandlare och ett kondensatorbatteri kan användas för att anpassa kretsen dock måste vissa modifieringar utföras.
11
Chambion, Bertrand. "Etude de la fiabilité de modules à base de LEDs blanches pour applications automobile." Thesis, Bordeaux, 2014. http://www.theses.fr/2014BORD0163/document.
Full textAbstract:
Les composants dédiés et actuellement disponibles pour le marché automobileprésentent une grande diversité technologique tant au niveau puce que stratégie de packaging ouencore architecture module (mono-puce ou multi-puce) pour des performances équivalentes. Cetteétude s’est attachée à développer une méthodologie d’évaluation de la fiabilité de deux filièrestechnologiques particulières de modules de LEDs multi-puce : l’une intègre une technologie verticale(VTF pour Vertical Thin Film) tandis que la seconde est focalisée sur une structure par puce montéeretournée(TFFC pour Thin Film Flip Chip). La méthodologie s’articule autour de trois principaux axes:· La connaissance des structures et le développement de modèles électro-optiques et thermiquesmulti-puce permettant d’extraire les paramètres clés à suivre au travers d’un panel varié detechniques d’analyse physique et non-destructives incluant les aspects électriques, optiques,thermiques….· Une analyse comportementale de robustesse par paliers afin de dégager les margesopérationnelles de fonctionnement ainsi que les modes et les signatures caractéristiques dedéfaillance.· Une étude de fiabilité conduite à partir de différents régimes de contraintes accélérées pourestimer les durées de vie moyennes de ces nouveaux composants en environnement automobileet l’impact au niveau système.Les résultats mettent en évidence une durée de vie très dépendante de la filière technologique(facteur 6 entre les deux filières étudiées). Les analyses de défaillance ont permis d’identifierprécisément les comportements de ces nouvelles sources d’éclairage pour dégager des indicateursprécoces de défaillance. Enfin, des préconisations ont été extraites afin de fiabiliser les futursprojecteurs à sources LEDs de puissance pour les applications en automobileWith rapid development of Lighting Emitting Diode (LED) market, LED performancesare now suitable for automotive high beam / low beam lighting applications. Due to the need of UltraHigh Brightness (UHB-LEDs), LEDs are packaged on high thermal conductivity materials to obtainmultichip module (4 chips in series), which deliver up to 1000 lumens at 1A. Currently, several LEDtechnologies are commercially offered for the same performances, and different packaging strategieshave been implemented in terms of chip configuration, bonding, down conversion phosphor layerand mechanical protection to optimize performances. This study addresses a dedicated methodologyfor reliability analysis, applied on two LED chip packaging technologies: On the one hand, a VerticalThin Film (VTF) technology; on the other hand a Thin Film Flip Chip (TFFC). Our methodology is basedon 3 main items: Packaging technology structure, materials analysis and electro-optical and thermal multichipmodels for both technologies to understand and extract the key parameters to monitor duringageing tests. Robustness assessment tests to define operating margins, adjust accelerated life-testingconditions, and identify failures signatures. Reliability study through a 6 000 hours High Temperature Operating Life (HTOL) acceleratedtests, to predict the Mean Time To Failure (MTTF) of these new light source technologiesregarding the automotive mission profile. Linked to failure analysis, convincing failuremechanisms are proposed.Based on these results, parametric variations are compared to failure analysis results topropose failure mechanisms. The HTOL tests reveal that both LED technologies have their specificreliability behavior and failure modes: catastrophic failure and gradual failure. Predictive lifetimeestimations (L70B50) of these multichip modules give a factor 6 between both technologies.Beyond these reliability results, the multichip architecture brings new issues for Solid StateLighting (SSL) sources in automotive, as well as partial failure or unbalanced behavior after stress.These new issues are discussed through the behavior modeling of a 10 LED modules batch for bothfailure modes. Modeling results demonstrate that the predictive lifetime of a LED multichiparchitecture is directly related with the LED technology failure mode
12
Arexis, Boisson Lydie. "Étude et optimisation d'un système d'éclairage efficace énergétiquement et adapté aux besoins de ses utilisateurs (santé, sécurité et qualité de vie)." Toulouse 3, 2014. http://thesesups.ups-tlse.fr/2332/.
Full textAbstract:
La perception visuelle de la lumière est un sujet qui interroge depuis des années. Dans cette recherche, nous nous attachons plus particulièrement au confort visuel des êtres humains soumis à une lumière scintillante ou flickering, pouvant présenter des impacts sanitaires non négligeables. Mais comprendre la perception visuelle du flickering, aussi dit contraste de luminance ou chromatique temporel, implique de multiples pré requis. C'est pourquoi, tout au long de ce travail de recherche nous avons une approche pluridisciplinaire, et faisons appel à des connaissances relatives aux êtres humains : physiologie de l'œil humain et ses mécanismes de perception, neurophysiologie, psychologie cognitive, sociologie; mais également relatives à la physique: les sources de lumière, leurs photométrie et colorimétrie, notions d'optique géométrique et modélisation optique, etc. Le terme " confort " étant souvent utilisé à mauvais escient, nous avons tout d'abord réfléchi à définir avec exactitude les notions de confort en le distinguant des termes " qualité de vie " et " bien être ", trop souvent pris pour synonymes. Afin d'y parvenir, nous avons basé notre étude sur une approche cognitive, et nous sommes particulièrement intéressés au cas du confort visuel, en relation avec notre thématique de recherche. Ensuite, une campagne d'expérimentations sur le flickering a été menée. Elle a consisté en l'étude phénoménologique de la perception visuelle du flickering dans différents contextes : couleur de l'environnement et axes de perception visuelle et pour différentes configurations expérimentales. Pour cela, un dispositif expérimental et interactif a été réalisé. Afin de générer le flickering, des diodes électroluminescentes (LEDs) ont été utilisées, et un boîtier de commande a permis la variation de deux paramètres particuliers : la fréquence et le rapport cyclique. Nous avons ainsi créé un signal MLI, et avons fait en sorte que le stimulus soit une lumière indirecte à champ large. De part le logiciel associé aux boîtiers de commande, de nombreux scenarii ont pu être présentés à des observateurs volontaires qui ont donné leur ressenti quand à leur perception du flickering. Les observateurs ont des caractéristiques visuelles similaires (vision emmétrope) et âgés entre 20 et 39 ans. Une approche des résultats pour yeux amétropes a également été débutée. Afin d'analyser plus en détail les réponses expérimentales, une méthode d'optimisation a été utilisée et a mis en évidence des couples optimaux de solutions (fréquence et rapport cyclique) quelle que soit la couleur de l'environnement et quel que soit l'axe de perception visuelle. Nous nous sommes ensuite basés sur ces résultats pour mettre en place des graphes de paramètres physiques de confort visuel du flickering. Enfin, une étude applicative du flickering a été menée. Elle a consisté en la comparaison de la dégradation colorimétrique de tableaux de musées, via échantillons normalisés, éclairés par une lumière continue et une lumière pulsée, à éclairement moyen constant. Les dégradations se sont révélées être du même ordre de grandeur au bout de 635000 lux. H mais l'effet Broca Sulzer ayant été vérifié dans le cadre de nos expériences (la brillance ressentie est plus grande que la brillance réelle) a ainsi permis d'envisager des économies d'énergieLight visual perception is a topic that interrogates since many years. In this research, we focus particularly on visual comfort of Humans subjected to light flickering, which may have significant health impacts. But in order to understand the visual perception of flickering, also known as luminance or chromatic temporal contrast, multiple prerequisites are required. That is why, throughout this research we have a multidisciplinary approach, and make use of knowledge about Humans: physiology of the human eye and its mechanisms of perception, neurophysiology, cognitive psychology, sociology, but also on the physics of light sources, their photometry and colorimetry, geometrical optic and optical modeling concepts, etc. The term "comfort" is often misused, that's why we first thought to accurately define the notions of comfort and distinguish terms "quality of life" and "well being" too often taken to be synonymous. To achieve this, we based our study on a cognitive approach, and oriented it in the particulary case of visual comfort, in relation to our research topic. Then, an experimental campaign on the flickering was conducted. It consisted in phenomenological study of the visual perception of flickering in different contexts: color of the environment, areas of visual perception for different experimental configurations. For this purpose, an experimental and interactive box was created. To generate the flickering, light emitting diodes ( LEDs) have been used, and a control module were used to change the two particular parameters : frequency and duty cycle. We have created a PWM signal, and have made an indirect light stimulus with a wide field. Due to the associated control module, many scenarii of flicker light have been presented to volunteers who have given their felt. The observers were selected with similar visual characteristics (emmetropic vision) and aged between 20 and 39 years. Some studies on ametropic eyes were also started. To further analyze the experimental results, an optimization method was used. It showed optimal solutions couples (frequency and duty cycle) regardless of the color of the environment and whatever axis of visual perception. We then based on these results to develop graphs of physical parameters of flickering visual comfort. Finally, a flickering application study was conducted. It consisted of comparing the color degradation of museums artworks using standard samples lit with LED power supplied with continuous mode comparing to pulse mode, and creating a constant average illumination. The damage proved to be of the same order at the end of 635000 lux. H. But as we could check the Broca Sulzer effect in our experiments (brightness felt is greater than the physical brightness), we could expect energy savings with flickering
13
Atkinson, D., and M. Ingle. "A multi-dimensional analysis of local economic development in Graaff-Reinet, Eastern Cape." Journal for New Generation Sciences, Vol 8, Issue 1: Central University of Technology, Free State, Bloemfontein, 2010. http://hdl.handle.net/11462/547.
Full textAbstract:
Published ArticleThis article presents the results of a business survey conducted in the Great Karoo town of Graaff-Reinet. The survey solicited the views of business owners on a range of economic issues. The findings also draw on a number of in-depth Midlands-Karoo studies, carried out in the early 1970s, in order to add nuance to the prevailing understanding of the factors that influence local economic development (LED) in small towns. It is argued that LED is a multi-facetted phenomenon. It requires a holistic approach that recognises its inherent complexity, involving factors such as local leadership, diversification, the local skills base, in-migration, corporate investment, and entrepreneurship.
14
Marzaduri, Luca. "WINDOWS 10 IoT SU RASPBERRY PI 2: MULTI-PARADIGM PROGRAMMING TRA JAVA E C#." Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2016. http://amslaurea.unibo.it/10299/.
Full textAbstract:
Questa tesi ha come obiettivo la sperimentazione del nuovo sistema operativo Windows 10 IoT Core su tecnologia Raspberry Pi 2, verificandone la compatibilita con alcuni sensori in commercio. Tale studio viene poi applicato in un contesto di Home Intelligence al fine di creare un agente per la gestione di luci LED, in prospettiva della sua integrazione nel sistema prototipale Home Manager.
15
Verban, Alison Jane. "A porous field : immersive inter-media installation and blurring the boundaries of perception." Thesis, Queensland University of Technology, 2007. http://eprints.qut.edu.au/19237/.
Full textAbstract:
Through creative and theoretical research, this practice-led PhD project investigates the conditions that facilitate embodied sensory awareness within digital inter-media installation. Central to this exploration are questions concerning ‘immersion.’ The research uses this term to describe a transformation in perception that allows us to shake off representational and symbolic meaning in favour of embodied, sensory and intuitive awareness within an installation space. Drawing from embodied memories of immersion in natural and spiritual environments, I consider the elements that contributed to these experiences and ask whether it is possible to create this sense of immersion in art. I then consider the elements that produce immersive, inter-media environments including space, sound, light, and projected moving images. Drawing on theoretical and artistic precedents, I propose a set of principles for producing a sense of embodied sensory immersion. The practical outcomes of the research - three digital inter-media installations included in the exhibition, in an other light - incorporate different combinations and treatments of these material elements to investigate and test the proposed principles.
16
Verban, Alison Jane. "A porous field: immersive inter-media installation and blurring the boundaries of perception." Queensland University of Technology, 2007. http://eprints.qut.edu.au/19237/.
Full textAbstract:
Through creative and theoretical research, this practice-led PhD project investigates the conditions that facilitate embodied sensory awareness within digital inter-media installation. Central to this exploration are questions concerning ‘immersion.’ The research uses this term to describe a transformation in perception that allows us to shake off representational and symbolic meaning in favour of embodied, sensory and intuitive awareness within an installation space. Drawing from embodied memories of immersion in natural and spiritual environments, I consider the elements that contributed to these experiences and ask whether it is possible to create this sense of immersion in art. I then consider the elements that produce immersive, inter-media environments including space, sound, light, and projected moving images. Drawing on theoretical and artistic precedents, I propose a set of principles for producing a sense of embodied sensory immersion. The practical outcomes of the research - three digital inter-media installations included in the exhibition, in an other light - incorporate different combinations and treatments of these material elements to investigate and test the proposed principles.
17
Shao, Kuei-Yu, and 邵桂裕. "Multi-Channel LED Driver Circuit." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/4mxxhr.
Full textAbstract:
碩士崑山科技大學
電子工程研究所
96
Displayer has become the inportant part of Electronical prudoct, and it also requires light source by Back light module. High brightness White Emitting Diode(LED) has become the important back light source. The profites of White light Led are cheep price、long life、and low power etc. The White light led is going to replace the traditional Sunlight bulb in the future. Therefore,driver IC will reveal its is important. In this paper, three LED drivers with uniform current adjustment mechanism were designed by the H-Spice tool. The first chip uses a high-gain OPA, an NMOS transistor and a resistor to implement a current source that can be controlled by an external voltage. It would drive sixteen high-brightness white-light LEDs through sixteen current mirrors. The second chip is trying to add a bandgap reference voltage circuit and to use a cascode mirror circuit construction. Because the chip will produce heat by itself, in order to promote the precision and yield of the whole circuit, we need a steady reference voltage. which will not change a lot when the input voltage and temperature change. The cascode mirror circuit construction is designed to reduce the effects of drain-source voltage drop on the mirrored current because the turn-on voltage of LED is process-dependent. The third chip is designed to improve the bandgap reference construction of the second chip in order to make LED driving current adjustable. These LED drivers use the full-custom-design methodology of the 0.35μm 2P4M CMOS technology provided by Taiwan Semiconductor Manufacturing Company (TSMC) as the design and simulation platform in this paper.
18
Lan, Yu-Chin, and 蘭瑜瑾. "Multi-step Linear LED Driver." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/01286011901178857769.
Full textAbstract:
碩士國立交通大學
電機學院電機與控制學程
101
Global warming and energy shortage in recent years have led the world countries to propose energy saving plan, energy efficiency improving plan, and greenhouse gas inhibiting plan. Energy saving of lighting is an important part. Countries of world have made safety certifications, EMI certifications, energy saving certifications, and incandescent replacement schedules. LED bulbs can replace incandescent bulbs with low energy efficiency. LED bulbs for replacing conventional incandescent bulbs often have many problems in the design of the LED drivers. For example, the linear LED driver circuit has inefficient problem while the switching LED driver circuit has the EMI problem. Besides, dimming flicker problem and power loss problem in bleeding circuit also deteriorate the LED performance. To solve these problems, designer often needs to increase the cost. As a result, it caused the replacement of conventional incandescent bulbs by LED encounters many difficulties. Conventional linear LED driver structure is very simple. Linear LED diver features to remove the EMI problem. The proposed multi-step linear LED driver circuit is a modification of conventional linear LED driver circuit. Multi-step linear LED driver not only has no EMI problem but also improves the power conversion efficiency. Simultaneously, it solves the flicker issue and energy loss in TRIAC dimmer applications. This paper realized the theory of multi-step linear LED driver, and proved that the theory of multi-step linear LED driver can meet safety and energy saving certifications. This paper also proposed and verified the optimized design method to enhance LED bulbs luminous efficiency.
19
Bautista, Meriam Gay, and 梅利安. "Dimmable Multi-Channel RGB LED Driver." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/41938135831591875664.
Full textAbstract:
碩士國立臺北大學
電機工程學系
101
This paper proposes a dimmable multi-channel Red-Green-Blue (RGB) LED Driver for backlighting and display and applies variable control technique to regulate color mixing. A linear Control DC-DC converter is used to provide the needed constant current for the RGB LEDs. It is designed to provide greater than 25mA constant output current with high accuracy. A PWM control method is used, of which the variable external voltage determines the available brightness levels and has a dimming frequency of 2 kHz. The proposed LED driver system is also able to dim each individual LED color through the dimming controller circuit; for each of the 3 channel per color around 90%, 93% 93% efficiencies for the red, green and blue channels respectively. A digital port was provided for the option of Digital dimming using a microcontroller. A linear current regulator is presented and this can be extended and applied to multiple strings. The temperature coefficient for the red channel is 75.43 ppm/°C and 89.46 ppm/°C for both green and blue channel. This was designed and simulated using 0.35micron TSMC 2P4M 5V technology and the chip area is 2.31x1.48 (mm2).
20
Shia, Yung-Fu, and 夏永富. "Multi-purpose Energy-saving LED Lighting System." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/27754114499385688000.
Full textAbstract:
碩士國立高雄應用科技大學
電子工程系
98
ABSTRACT Most of the current use of low luminous efficiency, low power factor of the luminous efficiency of conventional lighting fixtures not only low, but also the power consumption of a waste of limited resources, according to statistics from Taiwan Power Company and the Industrial Technology Research Institute that if Taiwan into existing traditional lighting replacement high efficiency energy saving lamps, then Taiwan will be able to save energy consumption by 20%, and 12.6 billion NT dollars a year can save the electricity bills and reduce 3.7 million tons of carbon emissions, 1171 million barrels of crude oil consumption and the equivalent of a nuclear power plant's annual capacity, energy savings is considerable. In this thesis, energy saving, environmental protection as the main appeal, to improve the current use of low luminous efficiency, low power factor, the conventional mercury lighting equipment, the use of high luminous efficiency, no radiation, low environmental pollution, longer service life of white LED light module group, combined with PFC control circuit, LED constant voltage, constant current drive circuit to produce high luminous efficiency, high power factor (> 0.95), wide voltage input range (90 ~ 265 VAC), to improve lighting device efficiency and service life, and can also facilitate the combination of different lighting environments demand a variety of LED light module to meet the high efficiency, energy saving, environmental protection and multi-purpose lighting needs. Keyword: energy saving, environmental protection, PFC control circuit, White light LED.
21
Ko, Pei-Wei, and 柯佩瑋. "A Multi-Channel LED Driver with Accurate Current Control and Adjustable LED Numbers." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/14696022789126987397.
Full textAbstract:
碩士國立中興大學
電機工程學系所
99
In recent years, we have gradually accepted the concept of the energy conservation and reducing carbon dioxide emission, and the mainstream of the design and manufacturing idea for daily supplies will follow it. Therefore, it is very important for increasing the efficiency when we make use of energy. It is possible to conserve electricity energy by using some suitable components, LED especially. Long life of LED is its merit, and LED can be widely applied in many products, such as the lighting and lamps, large-scale electronic monitors, back lights, vehicles electronic parts, portable electronic devices and so on. In this thesis, it is mainly aimed at the LED driver to have a discussion about reducing the electricity energy loss and enhancing the accuracy of lower error driving current, and looking forward to more practical applications for automobile equipments that are necessary, for instance, the rear light, the turn signal, the head light, the brake light, the lighting, the indicator, the back light signal, the head light, the brake light, the lighting, the indicator, the back light panel, etc. When the battery power is unstable, or insufficient battery charge by the problems of charging circuit, engine or generator, it can assure the reliability of driving safety. In addition to the system clock generator and the function control circuits, the circuit designed in this thesis makes use of a method of Automatic Pulse Frequency Modulation Control Output to design the boost converter circuits. It can supply a power source with preset and regulated voltage, offer a number of independent circuits for current balance which could preset different current in demand, and also control the lowest loading voltage automatically. In the experimental model, boost converter output voltage will rise to the preset value of 15.6V. The three current balance circuits provide the three LED strings with stable regulated current, respectively. Each LED string can serially connect from 1 up to 3 LEDs at will. The total loading current achieves approximately 150mA. Although the LED string has replaced the different number of LEDs, it can still maintain the same current, and the current error coefficient is just only 0.054%. The circuit was designed by using TSMC 0.35μm 2P4M 3.3V/5V Mixed Signal CMOS fabrication process. The chip size is 1.328×1.328 mm2 .The chip was built in multi-function control circuit with pin out so that, it is so easy to be used for automobile electronic equipments.
22
Chen-YiFang and 方貞懿. "The production plan for multi-site and multi-stage in LED industry." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/88820871365419456348.
Full textAbstract:
碩士國立成功大學
工業與資訊管理學系碩士在職專班
104
The thesis uses actual data from the LED industry to do the analysis. The purpose of the research is to allocate capacity efficiently and minimize cost. The production plan is mainly intended to solve the allocation problem for multi-site and multi-stage production plans. According to the mathematical programming characteristics, such as MPS demand, the limitation of each production site, the upper and lower capacity bounds, production variable costs, transportation costs, and limits to the target production time, are formulated in the MP model for the case firm. A GA (genetic algorithm) is implemented to solve the proposed model and the near-optimal of the problem can be acquired using the GA. Furthermore, a sensitivity analysis is conducted to verify the parameters of the GA and it is found that the value set of the parameters can facilitate reaching the near-optimal solution.
23
Hsu, Chen-Jung, and 許佳蓉. "Multi-Plant Capacity Planning for LED Product Manufacturing." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/65813481278187314863.
Full textAbstract:
碩士元智大學
工業工程與管理學系
98
Recently green energy issue is getting more and more concerns in the world. In the meanwhile, this green twister blooms LED (Light Emitting Diode) industry tremendously. Therefore, many LED enterprises have expansion plan for production capacity to meet their customers’ requirement. However, they will face some issues such as diverse product allocation, various processes, and intricate multi-plant capacity planning. Normally, different plants are with different features and restriction conditions.So when working on capacity planning, planner shall take into account production resource arrangement and allocation so as to meet high efficiency and low cost output. In this research, the main objective is to develop a Multi-Plant Capacity Planning model of LED package industry under different constraints. In this research, linear programming is used as methodology for Multi-Plant Capacity Planning in LED package industry. The main target is to reach minimum production cost, delay cost, transportation cost, and storage cost. The model conditions include maximum production utilization, maximum input limit, yield rate, BIN degree rate, production output unit exchange rate, input output rate, minimum LED package consideration….etc, and then allocate and control production between plants to reach optimistic output. This model will be implemented in some cases to verify the feasibility and usefulness. The outcome could be the reference for the management and production control staff in real production planning. Finally, this research uses four real examples to verify the feasibility of the model. The result could help a company to enhance the decision support of derail production scheduling.
24
Chiu, Ming-Lei, and 邱明磊. "Study of high CRI multi-wavelength LED Source." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/5tj9m2.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
98
PWM dimming technology driven mainly by tuning the pulse width of the average change in forward current, and thus achieve the purpose of regulating the amount of light output, we can adjust the output stability of the amount of light, it can avoid the main wavelength drift phenomenon is. The resistance and the current control circuit is used to directly control the forward current is designed pulse width modulation of the function is completed by the series an electronic switch, so as long as the adjustment of the optical signal transfer width, we can adjust the forward current pulse, then the amount of light reaching the purpose of adjusting the output. The advantage of this design may with high rapid response, 5 groups respectively LM555 LED light source thread dimming switch mode LED driver architecture. With 9 pieces LED wavelength chips comprising adjustable light source, adjusted to change the current of LED light mixed light of this ratio, we can assemble any number of sources is multiplied with the color of the spectral distribution function, and therefore a variety of adjustable mixture under different color temperature light effect, color rendering standard for comparison because the reflectivity under color blocks, we can use LED on characteristics of the narrow FWHM(Full Width at Half Maximum) out of CRI are more than 98%. Since the LED can be used as artificial light source, but with multi-wavelength LED light source device as limited to three kinds of different wavelengths of light changes, light duration, light modulation of the working ratio, frequency or amplitude changes. As the LED’s characteristics, and different LED wavelengths can be formed, the development of artificial multi-wavelength LED light source modulation. Study of multi-wavelength light source may generate a new research field.
25
Hu, I.-Ling, and 胡伊伶. "Achieving Color Consistency between Multi-color LED and Monitor." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/35886616235140952000.
Full textAbstract:
碩士國立臺灣大學
資訊工程學研究所
98
Monitor-based LED light casting has a large color variation. As designers design a lighting space, they cannot employ monitor color palette to choose the LED color due to color definition varies between monitors and multi-color LEDs. To address this problem, we use a low cost camera as measurement device to achieve color consistency of monitor based light casting. Our method contains three calibration steps: Firstly, we perform a gamma correction in the monitor and the LEDs. Secondary, the color matching between the monitor and the LEDs is found automatically. Finally, the linear transformation function of the LEDs and the monitor color space is constructed by using a linear operation. Experimental results show the proposed calibration algorithm successfully make the color variation becomes slighter. Moreover, we evaluate the calibration result with a chroma meter, which shows the color differences of three primary colors between the monitor and the LED become much lesser. To the best of our knowledge, this is the first effort to achieve color consistency between the monitor and the LEDs by using a commodity off-the-shelf product like an inexpensive digital camera. Our method has a great potential for many applications that requires the multi-color LED light such as emotional light system.
26
Chang, Chien-Kun, and 張建焜. "A multi-channel LED driver for mobile device applications." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/14825855782174477504.
Full textAbstract:
碩士國立臺北大學
資通科技產業碩士專班
101
This research presents a multi-channel LED driver for mobile device applications. With regards to the new trend for backlighting applications in mobile electronics and portable devices; requiring a smaller size, lower cost, lesser noise and more accurate current control LED driver is highly desirable, with this the idea of integrating more than one design features within a single chip is advantageous. The analysis of using a capacitor-less low dropout regulator to power the constant current source has been explored, with the implementation of wide range battery voltage of 2.7V to 4.2V. Possible load current variations were introduced and verified to output a fixed voltage of 2.5V. The design ensure a current matching of less than 1% error current balance and achieve a high accuracy current control of less than 1% error regardless with LED’s forward voltage variation. Moreover, for high end portable device with multimedia applications, dimming frequency can be set to 10 KHz. In addition, a switching output is a better approach for managing LED’s contrast and brightness adjustment as well as maximizing power consumption, ensuring longer life for driving string of LEDs. This design is implemented in 0.35um TSMC 2P4M CMOS process and the chip size is 1.89x1.7 mm2.
27
Chang, Ping-Huang, and 張炳煌. "Multi-Energy Source for the Application of LED Research." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/16409176676906119002.
Full text
28
Liao, Yu-De, and 廖于德. "Design and Fabrication of Multi-Color Modes of LED Products." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/qr8v59.
Full textAbstract:
碩士淡江大學
電機工程學系碩士班
102
Energy saving and environment protection issues have drawn people’s attention these days as the global industrial development prospers; the conventional incandescent lamps in recent years have continuously been faded and instead the LED (light emitting diode) lamps have brought in unlimited business opportunities in the illumination industry. Comparing with other illumination technology LED has many unique characteristics and also with its capability to illuminate many different color patterns makes the applications of LED across many fields. It needs to have direct current and low voltage in LED power supply therefore it is not suitable to design and fabricate LED directly on the same power sources as the conventional incandescent and fluorescent lamps. Consequently in the development of LED products it needs to use fixed voltage transformation and to consider proper electronic circuit technology in its product design. In this thesis many color modes of LED products are designed and fabricated; it utilizes one single light apparatus to generate many different color modes of LED lamps and it also solves the heat dissipation problem. The design of control circuit is for fixed voltage circuit and with it to accomplish the requirements of energy saving, small size anal then to produce many specific color patterns of LED lamps.
29
Yi-Sheng, Chang, and 張義聖. "The Study of Plant Factory by Multi-band LED Technology." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/32249867348053095517.
Full textAbstract:
碩士萬能科技大學
影像顯示技術研究所
101
In recent years, the global climate is unstable usually. Often cause the loss of the crops. In addition, the area of cultivation reduces gradually. Plant factory is a crop production system which is isolated from outside environment. It prevent natural disaster, blight of crops, limited land effectively. In the thesis, the goal was to develop a new light apparatus with LEDs optimized for vegetable production in plant factory. We design a novel LED lamps and lanterns with the structure of curve. The lamps enhance the uniformity of radiation, and reduce the dead area of radiation. Fluorescent lamp is popularly used in the plant factory, however, the spectrum of fluorescent light is broad and some portion of them is not necessary for photosynthesis. Power consumption of LED light source is reduced by useful spectrum. In our study, we split three different light source condition. They are white LED, monochromatic LED (Red 620nm and Blue 460nm), monochromatic LED (Red 660nm and Blue 450nm), respectively. The specific objective was to investigate the effective light quality for growing plant more healthy and rapidly. The effect of light provided by various light qualities provided by the combination of LEDs(blue, green, red) on the photosynthesis rate. The growth of lettuce were evaluated compared with those of plant irradiated by white LED. The experimental result shows, 660nm wavelength is helpful to the leaf. Stem length increased in blue light obviously. And the novel lamps and lanterns that we designed have really improved of radiation uniformity. The power of consumption of light source is effective reduced. The growth parameter of lettuce is optimized by our study.
30
Chi, Tsui Yu, and 崔玉麒. "Variable Frequency Dimmable Multi-Channel LED Driver System IC Design." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/84427500612742637432.
Full textAbstract:
碩士國立臺北大學
電機工程學系
102
This paper presents a variable frequency dimmable multi-channel LED Driver with 12-channels, each channel supplying a stable current of 30mA. This circuit design can be used in indoor plant cultivation for dimming and illumination purposes, simulation of sunlight source and optical inspection system. Operating at a frequency of 133 kHz to 233 kHz using PWM control, this chip is fabricated and simulated by Taiwan Semiconductor Manufacturing Company using the 0.35um 2P4M CMOS 5V process and the chip size is 0.76mm2. External inputs, as well as a multiplexer control with a fixed external input voltage, Use a multi-switch sawtooth generator can be used to control the brightness.
31
Yeh, Lin, and 林曄. "Multi-frequency fluorescence lifetime system based on directly-modulated LED." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/31196299936926708458.
Full textAbstract:
碩士國立交通大學
影像與生醫光電研究所
105
Fluorescence lifetime signals have been widely used in bio-physics and biophotonics research. With the advance of light emitting diode (LED) technology, it has been demonstrated that there are several advantages to apply LEDs as the light source of a fluorescence lifetime system: i.e. cost, size, etc. In this thesis, I’ve developed a dual-color dual-frequencies fluorescence lifetime system based on directly-modulated LED. I modulated different color of LED dice located on the same chip at different radio frequencies, in order to acquire the nanosecond lifetimes of two different fluorescent species simultaneously. I designed a modulation circuit based on a field-programmable gate array (FPGA), which provided dual-frequencies to the high power LEDs with sufficiently high modulation depth to resolve nanosecond fluorescence lifetimes. In addition, as LED has fast switching time, I applied the dual-frequency fluorescence lifetime system to measure chlorophyll a fluorescence signals of green algae cells under different wavelength of illumination in real time. By switching between different color of LED dice, the dynamic decay curve of chlorophyll a fluorescence lifetime and fluorescence intensity were acquired simultaneously. The system developed in this thesis can be applied to measure real time dynamics of fluorescence lifetimes under different excitation wavelengths.
32
Mapula, Nieva Malagum, and 妮爾娃. "Multi-Channel Constant Current LED Driver with PWM Boost Converter." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/59664622080559677617.
Full textAbstract:
碩士國立臺北大學
電機工程研究所
98
This thesis presents an integrated LED driver with boost converter designed with standard CMOS technology considering Lithium-Ion battery used to drive LED strings that provides overall maximum efficiency of 85% and current error accuracy of 0.0046%. The boost converter operates in PWM voltage mode at 600kHz with stable output voltage as a voltage source to LED driver. A dimmable LED driver with a dimming frequency up to 10MHz is implemented for the application of constant current driving capability for LED displays and LCD backlighting that is used in many portable devices with advanced video and image processing operating at low voltage. A current balance circuit is applied having two or three channels that act as a constant current source for the series connection of LED strings and also used to control the amount of driving current for regulating the constant light luminance of LEDs. The design is simulated with TSMC 0.35μm process with an effective layout area of 2.279967 x 2.39105mm2 and a power lower than 1W.
33
Cheng, Ya-Jou, and 程雅柔. "Enhanced Communication Quality Uniformity for Indoor Multi-LED VLC System." Thesis, 2017. http://ndltd.ncl.edu.tw/handle/vjhf79.
Full text
34
Chang, Ming-Li, and 張銘利. "Design and Development of High Power Multi-chip LED package." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/ha84pp.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
99
In recent years, the development of LED light sources was carried out all over the world. Especially for general illumination, backlighting of the monitor or automotive lighting is by far the most popular themes. This paper is primarily a study on lighting design. The common light sources on the market are mostly designed by high power LED chips. However, the external quantum efficiency of the present high power LED chip was poor. Because the operation power is higher than before, such that the generated heat can be easily accumulated and that the temperature of heat source is also higher than before. For the general LED packaging design, the junction temperature can be well controlled less than 70oC if possible. At the same time, more tasks must be used in the back-end heat sink, and its costs are also high. This study focused on the LED light source design and verification, using a base substrate and arranged most of an array type LED chips set onto the substrate. By using the small-size LED chips (between 280~500 microns), the substrate thickness and chip spacing are well controlled. It was found that the space between every two LED chips is twice times above the size of the chip. The thermal resistance will have a slowing down rate. The temperature reduction is less obvious when the additional space was given. In addition, the multi-chip LED submount was verified by the experiment. We found the thermal resistance decreased by increasing the thickness of submount. The reduction of thermal resistance is slowing down while the thickness is increasing over 2mm. However, based on cost effective, current copper and aluminum plate was commercially available with a thickness of 1.0~2.0 mm. Finally based on the thermal simulation results, if the temperature of heat sink can be controlled within 60oC, the reliability can be achieved pass through the United-States-Energy-Star requirements, or 25,000 hours, that is, the optical attenuation of life requirement is less than 30%.
35
Liao, Shih-An, and 廖世安. "The Optimization Design for High Uniformity multi-reflector LED Luminaire." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/q7c4kt.
Full textAbstract:
碩士國立虎尾科技大學
光電與材料科技研究所
99
Since the efficiency of LED continually upgrading and their prices gradually approach with traditional light sources, makes a variety of luminaires began to use LED as a light source, but the LED optical properties different from conventional light sources, creating many of the products is not consistent with the relevant regulations, such as with beam distribution, illumination and glare, etc.. Traditionally, to solve the problem of uniformity of lighting, the way is installation a frosted glass or plastic diffuser, however, it will cause efficiency significantly reduced and adverse effect of uniformity, this paper focuses on the design of reflector, use CAD software to create initial model of reflector, and use TracePro and DiaLux which is the optical simulation software for analysis the lighting quality problems, as the Taguchi method in a shorter time and less number of experiments to complete parameter optimization, so the design with the Taguchi method, the reflector angle, the bend forming R angle and the reflectivity of reflector material as a parameter to Taguchi orthogonal arrays for optical simulation and analysis of variance with the parameters, optimization of the more influential factor. This research proposes a more rules of lighting design process, improve the speed and change the design of non-imaging optical design than the traditional reliance on personal experience of lighting design methods, and compare the control group of commercially available LED lamps, luminaire optimized design uniformity will be increased to 86.3%, UGR glare compared with the commercially luminaires reduced more than 30% , the final mold to produce the finished product and the actual measured value and simulated value of the comparative analysis, to verify the feasibility of this design method. The results showed that the optimization multi-reflector average illumination higher than the two commercially luminaires of 21.9% and 44.84%, and the uniformity improved 54.71% and 30.89%.
36
Chen, Shuan Fu, and 陳宣甫. "Thermal and Optical Analyses and Measurements of Multi-chip LED Package." Thesis, 2009. http://ndltd.ncl.edu.tw/handle/41589017205958552700.
Full textAbstract:
碩士長庚大學
機械工程研究所
97
The purpose of this study is to investigate the thermal behaviors and candela distributions of multi-chip LED package. This package contains three kinds of LEDs colors (red, green and blue chips), which can be combined to generate colored and white light. In experiment the junction temperature (Tj) of the different chips were measured by “LED Junction Temperature Tester” for only one chip heated and all of three chips heated, and the surface temperatures can be found by thermal couple. In simulation the LED model was built by using finite element method. In addition, the linear superposition method and thermal resistance circuit method were used for predicting the Tj. Then the parametric studies were performed by effective FEM model to find out the key factors to Tj. Finally, the relations about chip position on thermal and optical analyses were discussed by using FEM and TracePro. The results of experiments, FEM, linear superposition method and thermal resistance circuit method indicate that the trends on Tj of the different chips are similar under different input powers. Each parts of thermal resistance between FEM and experiment are consistent. So the FEM method, experiment, linear superposition method and thermal resistance circuit method are proved to be valid. Parametric studies by validated FEM model show that the thermal conductivity coefficient of Ag-epoxy, lead frame and PCB substrate have an obviously effect on Tj. And the best efficiency can be achieved by replacing the substrate material of PCB with aluminum. As aspect of geometry, it can’t affect Tj when varying Ag-epoxy overflow, fillet and number of thermal via. In thermal and optical analyses, changing chip position almost have no effect on Tj and candela distributions. This package includes three kinds of chips which Tj are affected by each other. By linear superposition method, a thermal resistance matrix from experiment was applied to thermal resistance circuit method for estimating the Tj. Besides, because of the lead frame has uniform temperature under low power, the thermal resistance matrix can be adjusted and used to do parametric studies for thermal resistance circuit method.
37
Hsu, Yen-Chun, and 許延駿. "Design a LED Modulation Lighting System Using Multi-Objective Genetic Algorithm." Thesis, 2010. http://ndltd.ncl.edu.tw/handle/53275713990250209374.
Full textAbstract:
碩士國立高雄第一科技大學
光電工程研究所
98
In this paper, a real-coded genetic algorithm (RGA) technique is developed for the optimal design of a supplemental lighting system for plant-growth, which is affected by the parameters: wavelength, frequency, duty ratio and amplitude. A light intensity stimulation system of functional is designed that can provide a flexible interface to adjust the parameters for users and researchers. Here, the technique of modulation and synchronizing in multi-wavelength light emitting diodes (LEDs) are employed. Through operations of the personal computer, microprocessor and related interface circuits, the system allows the light quality, light intensity, frequency (0 ~ 10 kHz), duty ratio (0 ~ 100%) and phase shift (0 ~ 360o) to be controlled. The optimal design in height and current of the plant-growth lamp by the RGA shows the improvement in the light uniformity and illumination efficiency. The innovatively designed systems are compared favorably with the typical and expert-designed lighting systems. It is concluded that the system is satisfactorily suitable to the photosynthesis applications. In multi-objective optimization, a describing genetic algorithm (GA) specifically developed for problems with multiple objectives. Control the input voltage distance of the RGB LEDs, the optimal illumination and uniformity can be found with by multi-objective genetic algorithms (MOGA). They primarily differ from traditional GA by using specialized fitness functions and introducing methods to promote solution diversity.
38
Lee, Den-Hua, and 李登華. "Development of A Multi-wavelength LED Modulation System for Biology Study." Thesis, 2005. http://ndltd.ncl.edu.tw/handle/86690182831577390226.
Full textAbstract:
碩士國立高雄第一科技大學
機械與自動化工程所
94
Abstract In recent year, it is increasing and rapidly that the high intensity light emitting diode （ LED ） is applied in the research of biotechnology. LED is provided with characteristic of cooling light、small volume and saving power, and is driven by directed current that is easy to be controlled and modulated, and the life time of LED is 10 multiple of fluorescent lamp. Now, there are many products that used the modulation technique in multiple wavelength of LED. The research we want to do is the invention that uses the technique of modulation and synchronizing in multi-wavelength LED. Also we discuss the design of the phase shift between multi-wavelength LED. The research which we develop is the function of the tuning in wavelength、frequency、duty ratio、intensity and phase shift for modulating light. It is a very powerful instrument in the study of photophysiology for biology.
39
陳家祥. "The Application of Multi-Sided Pyramid Encapsulation on LED Packaging Module." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/14649552380631181636.
Full textAbstract:
碩士逢甲大學
自動控制工程學系
102
This study presents a micro fabrication with high efficiency. By using the processes of bulk micromachining, wafers bonding and photoresist spin coating and heating the encapsulated air., we propose a LED light module with large viewing angle and light uniformity. Bulk micromachining techniques combined with the production method to produce a micro-cavity and connected to the through-hole of the wafer, and then spin-coated and then micro through holes through the photoresist process, the specific volume of air in the sealed chamber, and finally via the external heating mode, the air cavity extrusion resist thermal expansion and further out of the plane to produce non-spherical shape. Through changing heating temperature and volume of air in the sealed chamber, the curvature and size of photoresist structure can be control. In the theoretical analysis, the ideal gas equation and shell theory can be deduced geometry of lens and relationship between process parameters and lens curvature, while imprinting the way through, producing the optical lens elements made by the polysiloxane resin material, and with a simple optical system which can measure the effect of both viewing angle and light uniformity.
40
Li, Jo-Ping, and 李若萍. "Multi-Greendicator: Optical Wireless Communication with Multi-LED Coding and Camera Decoding for Increased Bandwidth and Robustness." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/04023472259482569552.
Full textAbstract:
碩士國立清華大學
資訊工程學系
102
Use of blinking LED to convey useful status information to be decoded by smartphone cameras has been shown to be a useful feature for end users of devices in the Internet of Things (IoT). Previous techniques have been limited to decoding of a single LED, which is limited in bandwidth and response time. We propose to overcome these limitations by exploring the use of multiple LEDs in different ways: decoding multiple devices that output using their own single LED in parallel, and decoding a single device that raises bandwidth by using multiple LEDs to encode more information in a given time frame. Experimental results show the practical limits achieved by a modern smartphone-class device.
41
Chen, Yu-hsuan, and 陳毓璇. "Analysis of Light Pattern Uniformity and Reflector Design for Multi-chips LED." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/295p84.
Full textAbstract:
碩士逢甲大學
光電學系
103
The focus of this study is to discuss the effect of the uniformity of light pattern by change the space between each chip, the concentration of phosphor and the shape of reflector. And find the optimal threshold; define the various parameters to achieve the uniformity of conditions and thresholds. First, we use the ASAP to build the phosphor model and use this model for subsequent analysis. Second, we actually encapsulated the LED light source and fabrication the phosphor slices and reflector, complete the experimental architecture. Then define the calculation of uniformity and which point to take on the light pattern, to identify the most appropriate method of this study. Finally, analysis of light pattern uniformity by each variable result, find out the threshold successfully.
42
LIU, HSIEN-CHIH, and 劉咸志. "A Multi-Channel Highly Precise Current Matching LED Driver for Dimming Light." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/88263370381500766521.
Full textAbstract:
碩士國立臺灣科技大學
電子工程系
102
In this thesis, a LED driver with precise current matching is proposed. Through the help of highly matched layout scheme, the accurately matched LED currents for multi-channel are achieved with high tolerance to process, temperature and voltage (PVT) variations. The color shift problem of LED brightness can be avoided by using digital pulse width modulation (DPWM) control, and the DPWM technique has capability of linear dimming. Even with high voltage MOSFETs, the maximum current mismatch among LED channels is measured to be merely -0.385%~0.372% which is much better than those of the conventional ones. The temperature coefficient of this circuit is as low as 25ppm/℃ over -40℃ ~ 160℃ range for 20mA LED driving current. This circuit was fabricated in TSMC 0.25μm 60V high voltage 1P3M cmos process with a chip size of 1.15*1.9mm2.
43
Chen, Wen-Hou, and 陳文豪. "A Multi-level Genetic Allocation System for Reducing Incompleteness of LED Allocation." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/87945366606935292421.
Full textAbstract:
碩士國立高雄第一科技大學
系統資訊與控制研究所
101
A multi-level integer programming method based optimal LED allocation system (OLAS) was developed to allocate LED work orders according to combination of LED bin codes and light bars for reducing times and mistakes of manual allocation. After daily used in a company for years, this OLAS was detected an incomplete allocation problem due to bin-code dimensional limitation and unprivileged quantity allocation. The bin-code dimensional limitation occurs when an identical bin-code is requested by several work orders, consequently, the OLAS may appear shortage of available memory when currently allocating quantities of the work orders. Meanwhile, the unprivileged quantity allocation causes an individual work order failing in privileged allocated due to the goal of maximizing allocation amount so that none of the work orders can be fulfilled. This study proposes a genetic algorithm based LED allocation system (GA-LAS) to improve the incomplete allocation problem of OLAS. In structure, GA-LAS modifies the close matrix of bin-code to an open arrays to sequentially deriving results to release the bin-code dimensional limitation. In procedure, GA-LAS adopts the similar multi-level allocation procedure of OLAS including rare bin-code, single bin-code, and mixed bin-code allocation, and it also can allocate the individual work orders by priority while controlling the inventory bin codes. Finally, GA-LAS utilizes existing inventory information through genetic amount reduction and individual genetic increment methods so that the solving times are obviously reduced than that of using traditional genetic algorithms. The results show that, in bin-code dimensions, GA-LAS has released the limitation of OLAS and is free of out of memory problem during allocation. In privileged allocation, GA-LAS can allocate quantities of the specific work orders, such as early due date, while insufficient inventory. Additionally, GA-LAS can fulfill more than 45% of the work orders by OLAS within few minutes. Therefore, the proposed GA-LAS can provide users a practical and effective tool for LED quantity allocation.
44
Tang, Cheng-Tsan, and 唐誠燦. "Development of LED Operating Lights for Surgical Treatment by Multi-Tune Reflection." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/28428291599309893534.
Full text
45
Cheng, Nai-Lun, and 鄭乃綸. "LED Induced Autofluorescence Imaging System for Oral Cancer Detection by Multi-Spectrum." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/80893374906288054853.
Full textAbstract:
碩士國立交通大學
生醫工程研究所
105
Oral cancer has been one of the main causes of death in both developing countries and developed countries over the past few decades. In addition to the economic burden of patients and their family, related medical care has been the main issue of national health. According to World Health Organization (WHO), more than 300000 new case of oral cancer has occur and caused 145000 death in 2012. Therefore, the detection of oral cancer has been the main topic of modern medical research. In this study, a hand-held imaging system with light-emitting diode (LED) excitation light and emission filter was used to screening oral mucosa tissues for oral cancer detection. The hand-held imaging system can be divided into two versions based on the number of the filter on the filter ring and the intensity of the light-emitting diode. The filter ring of version 1 and version2 imaging system contain four places and seven places for emission filter respectively.The difference between tumor tissue and normal tissue can be discriminate by the excitation light of LED with specific wavelength. Compare with the traditional method of naked-eye detection, the method of this study using multispectral fluorescent image provide a more objective detection method. Image will be excited by the light-emitting diode (LED) and pass through the selected spectral filter. Each grayscale intensity image of the fluorescent image’s RGB intensity is used for analysis. Both spatial and spectral methods are used in the analysis. Spatial analytical methods include entropy and fractal dimension, and spectral analytical methods include intensity and histogram. Data used in analysis will divide into two groups to implement the self-validation and cross-validation procedure. Finally, the average accuracy of self-validation and cross-validation is 83.48% using version 2 hand-held imaging system by 405nm excitation with Bi505 emission filter. In order to increase the efficiency of oral cancer detection, all kinds of excitation LED, emission filter and methods will be combined with the weight calculated by AUC. Finally, the sensitivity, specificity and accuracy of oral cancer detection are 94.44%, 85.18% and 89.81% respectively using version 1 imaging system. As for version2 imaging system, the sensitivity, specificity and accuracy of oral cancer detection are 88.35%, 88.35% and 88.35%. Finally, the specific emission filter will be picked up for oral cancer detection. Using version 1 imaging system with BP525 emission filter for oral cancer detection, the sensitivity, specificity and specificity are 90.74%, 68.52 and 79.63%.Compare with the full combination of methods, the oral cancer detection by BP525 emssion filter has much lower performance. Compare to version 1 imaging system, version 2 imaging system with BN470 and Bi505 emission filter have better performance. Version 1 imaging system with BN470 emission filter for oral cancer detection, the sensitivity, specificity and specificity are 89.32%, 86.41% and 87.86%, and the sensitivity, specificity and specificity can be better with Bi505 emission filter which are 89.32%, 89.32% and 89.32%.
46
Tsau, Fu-Shiung, and 曹富雄. "Study on Integrated Circuit Design for Multi-Color LED Pulse-Width Modulation." Thesis, 2011. http://ndltd.ncl.edu.tw/handle/54848658252273141285.
Full textAbstract:
碩士國立暨南國際大學
電機工程學系
99
Light-Emitting Diodes are widely used. However, light in a variety of colors would make a person have a different sensibility. This paper takes advantage of digital dimming auto-control pulse width drive Light-Emitting Diodes to let the light in terms of brightness fade to gray by degrees and have the effect of mixture of colors. Also, Light-Emitting Diodes in such three primary colors as red, green, and blue mix with one another to yield various colors. Therefore, better stability, simpler structure and better effect of dimming. Besides, it can coordinate with a Digital Pulse Width Modulation circuit to control the respective output of pulse width of the red, green, and blue Light-Emitting Diodes. Moreover, it succeeds in utilizing red, green, and blue Light-Emitting diodes at room temperature to change Color Rendering Index of the cool white Light-Emitting Diodes. The design of the circuit makes use of the manufacturing technique of Very Large Scale Integration to make the completion of Integrated Circuit.
47
Chen, Peng-rung, and 陳芃榕. "Flickering Phenomenon Study of AC LED Based on Multi-phase Power Supplies." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/20285056155444963042.
Full textAbstract:
碩士國立臺灣科技大學
電機工程系
100
The purpose of this dissertation is to explore light emitting and flickering characteristics of current LED and AC LED and conducted flicker measurement and evaluation based on the theory and method of measurement and evaluation of light flicker. After actual measurement of the waveform of light output conversion voltage and output power waveform, we found that the variation of light output waveform is proportional to the output power. Thus we proposed the definition of relative flickering rate represented by output power of light source, which means the ratio of the variation of light output power to the average output power has been used to represent the degree of flickering. In light of the high flickering phenomenon of AC LED, in this dissertation we propose to improve the flickering of single AC LED with “Multi-phase AC LED module driven by multi-phase power supply”. The positive correlation between output power of light source and relative flickering rate was used to induce the impact of power supply phase difference on relative flickering rate among modules of all phases; we found that when there are symmetric phase differences among modules of all phases, which means the phase difference equals to “180o divided by total number of phases”, the variation of total output power is zero, leading to the minimum overall relative flickering rate of AC LED module. Then we used circuit simulation software SIMPLIS 6.1 to simulate the relative flickering rate with respect to ideal and non-ideal characteristics of AC LED. In addition to verifying the result of the theoretical derivation, it also explores the impact of various phase differences on relative flickering rate so as to prove that the relative flickering rate of AC LED has the same variation trend as the phase differences among all power supplies. Therefore we suggest that this can be regarded as the ideal characteristic during future trend analysis with respect to the variation of relative flickering rate of LED or AC LED in order to facilitate easy and speedy evaluation. In the end, in this dissertation the capacitive starting circuit architecture of single-phase induction motor was used as the blueprint for actual fabrications of a series of dual-phase AC LED light emitting modules with various phase differences in order to evaluate the actual variation of overall relative flickering rate of AC LED with respect to multi-phase power supplies with various phase differences. With the measurements based on the theory and method of flickering measurement evaluation under identical measurement conditions, in addition to obtaining the same variation trend as the simulation result, we also found the rather obvious decline of relative flickering rate of dual-phase module by 20% to 50% when the phase differences among power supplier of all phases is greater than 45°.
48
Lee, Yun-Lin, and 李昀霖. "A Low Loss Passive Current Balancing Method for Multi-Channel LED Driver." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/60707961566442513305.
Full textAbstract:
碩士中原大學
電機工程研究所
100
This thesis proposed a low loss current balancing method to drive multi-channel LEDs. With a strategy that power source uses LLC resonant converter to supply the AC voltage. It takes the advantages such as improving the power loss, simplifying balancing apparatus and reducing the cost. For this study, the proposal is directed to a passive current balance driving method and which circuit topology is only utilize some passive elements-capacitance components and capable of driving a multi-channel LEDs simultaneously. The load characteristic of each of the LED strings is designed to identical during the continuous periodical variation of the positive and negative waveform of the AC power source through the passive current balance driving apparatus. Accordingly, the current flowing through each of the LED strings is basically or substantially to identical and thus can be well balanced. Furthermore, the LLC resonant converter has been used to supply the AC voltage source due to it is favorable advantages such as high efficiency. To confirm the validity of the proposed driver, its operation and performance are verified on a prototype for a 37” LCD TV. The features of this thesis include as: 1. Lower power loss: Due to the loss occur on current regulation chip or current sink transistor, the efficiency of active component is lower than capacitance components. Moreover, the soft-switching mode of the LLC resonant has using to supply the AC voltage source. Therefore, those strategies can achieve high efficiency requirement. 2. Improved reliability: Through the removal of the active device, the capacitance components have better reliability. 3. Reduced product cost: This proposed passive balancing method can arbitrarily choose the number of regulation driving channels. That is better than the ready-made and generally fixed current regulation chip. Therefore, there would not be unnecessary costs.
49
Hung-WeiChen and 陳宏尉. "Developing an Optimal LED Allocation System based on Multi-level Integer Programming." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/90012315066608210027.
Full textAbstract:
碩士國立成功大學
製造資訊與系統研究所碩博士班
100
When adopting LED as lighting source of light-bar for panel display, due to LED characteristics being normal distributed in chromaticity, illumination and voltage, a LED is characterized by BIN codes. In light-bar combination, a light-bar can be combined from one of several LED items; a LED item can be consisted from various BIN codes; the same LED item can use different BIN codes. Hence, high exchangeable BINs are easily used than low exchangeable BIN codes, a.k.a. side-BIN codes, such that a challenge is how to optimize cross-site inventory of side-BINs under fast inventory falling price loss. This work based on multi-level integer programming method proposes an optimal LED allocation system (OLAS) to allocate LED quantities by work-order, while reaching the objectives of maximizing order fulfillment and minimizing side BINs. In computing efficiency, this work based available stock proposes a simplified bin Control Matrix method to significantly reduce required computation time for allocation optimization. In controlling inventory, according to low exchangeability first policy, the allocating policy by levels of OLAS are as follows: level zero is to use the side BIN codes; level one is to interlace two BIN codes for allocation; level two can allocate single or two interlaced BIN codes to order; and level three reserves extra quantities to prevent production loss. Additionally, this system can satisfy pallet constraints to meet requirements of symmetric BIN codes usages. After applying OLAS to a panel display company for one month, the result shows that the required data can be reduced more than 71% than the original data amount by using the simplified Control Matrix method; the mean solving time is less than two minutes by utilizing ILOG engine; finally, first allocated the low exchangeable BIN code’s inventory after adopting the four-level integer programming model.
50
Hsieh, Kun-Yu, and 謝坤佑. "Current-balancing driver for multi-channel LED light bar implemented by microchip controller." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/7j9c7b.
Full textAbstract:
碩士國立臺北科技大學
電能轉換與控制產業碩士專班
101
In the lighting application of backlight modules, multiple parallel-connected LED light bars, which consist of multiple serial-connected LEDs, must be driven simultaneously. When we use single power source to drive this multi-channel LED circuit, the inconsistent internal Vf of every LED often results in different currents flowing through LED. Thus, the LED life will be reduced, the luminance will not be uniform, and related issues of unstable system will arise. Due to the booming development of mobile devices, this thesis proposes an integrated software/hardware system feasible for the application on LED light bars. The hardware emphasizes the digital power electronics technique by using Arduino micro-controller unit as the control core. Besides all available functions and efficiency that typical analog techniques can achieve, the proposed system can monitor the current status and have the capacity of fine-tuning the parameters online and real-time through the mobile devices. The hardware of this system uses Arduino micro-controller unit to control the boost converter and the current-balancing multi-channel LED circuit. The software involves the development of App programs through App Inventor provided by Google. Then, the compiled App installed in mobile devices can monitor the status and parameters stored in the Arduino micro-controller unit, which receives the commands and activates the hardware circuit. As shown in the experiment results, the mobile devices can monitor and control the hardware circuit smoothly. The output current of each LED light bar can be balanced and maintain within ±0.2% of an ideal value whereas the current balancing tolerance is smaller than 0.25%. The output current of each LED light bar can be balanced under any dimming mode.