Дисертації з теми "LED APPLICATIONS"
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Griffin, Chris. "Applications of micropixellated InGaN LED arrays." Thesis, University of Strathclyde, 2006. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.425904.
Повний текст джерелаLi, Fung Yuen Ken. "White LED for general illumination applications." Thesis, Massachusetts Institute of Technology, 2007. http://hdl.handle.net/1721.1/42151.
Повний текст джерелаIncludes bibliographical references.
In the 21st century, mankind faces problem of energy crisis through depletion of fossil fuels as well as global warning through the production of excessive greenhouse gases. Hence, there is an urgent need to look for new sources of renewable energy or ways to utilize energy more effectively. Solid state lighting (SSL) is a major area of research interest to use energy in a more efficient manner. Early light emitting devices (LEDs) were originally limited their use for low power indication lights. Later research produces high brightness LEDs (HB-LEDs) as well as blue color LEDs. This brings to reality of the entire visible light spectrum. White light is also made possible. As with other technologies, numerous obstacles will have to be surmounted in bringing LEDs from the laboratory to the marketplace. LEDs will also have to compete with established technologies such as incandescent and fluorescent lighting. This thesis will describe the current state of high powered LEDs, examine challenges faced by LEDs and look at future markets. Evaluation in the potential of LEDs for general illumination will be carried out through cost modeling and performance analysis.
by Ken, Li Fung Yuen.
M.Eng.
Yan, Xiao. "Phosphors for lighting applications." Thesis, Brunel University, 2012. http://bura.brunel.ac.uk/handle/2438/6954.
Повний текст джерелаSimmance, Timothy Graham. "New Carbazole-Based Materials for LED Applications." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.489740.
Повний текст джерелаBartos, Krzysztof Mirosław. "Efficient LED drivers for general illumination applications." Master's thesis, Universidade de Aveiro, 2014. http://hdl.handle.net/10773/14575.
Повний текст джерелаThe ever growing energy consumption trends and its impact on the environment has triggered worldwide attention. This has motivated several measures, such as the Kyoto protocol, or the 20 20 20 European strategy, aiming at the reduction of energy consumption. Globally, these measures defend a better and efficient usage of the available energy. This in turn is strongly linked to public awareness and the introduction of efficient electronic equipment. Public street lighting is a good example of these trends, where both aspects are of the utmost importance. The introduction of power LEDs as future lighting devices has motivated several advances coping with these strategies. On one side, LEDs are able to deliver higher efficiency when compared to conventional lighting devices. This has triggered the replacement of old style luminaires by LED based ones. However, their high cost has prevented full adoption and at the present stage, is acting as a slowing down force against this replacement trend. Better solutions are under research on the framework of several European projects. Power LEDs are solid-state devices able to support fast switching, a feature which was not fully supported by conventional lighting devices. Combining this feature with environmental sensing and intelligent control may lead to better power savings. A simple approach would be to consider the that the actual lighting demands depend on the street usage and surrounding lighting levels. For this purpose, the combination of twilight sensors, motion detectors and intelligent control schemes may provide a suitable approach. This way, the real lighting demands can be effectively taken into consideration, providing luminaires able to consume the least possible energy. For this to become a reality several challenges have to be addressed. One of the most important challenges is the LED driver design. Modern lighting systems based on LEDs, replace the traditional ballasts by LED drivers. When efficiency is a major concern, such as in public street lighting, these drivers have to be designed in order to be the most robust and efficient as possible. Recurring solutions resort to switched mode power supplies, able to support light dimming. One of the major problems with these drivers is the fact that their efficiency decreases for lower dimming levels. This is of the utmost importance for public street lighting, as most of the time during night, the luminaires are on a low lighting level (as changes to high lighting conditions depend on street usage). Thus, in order to promote better power savings, the efficiency of the driver should be high for both lighting conditions. Commercially available drivers, exhibit efficiencies on the 90% range for the high lighting conditions, with only 40% to 60% under the low lighting. On the framework of this master dissertation it was investigated the problem of LED driver design aiming at the highest possible uniformity of the efficiency curve, under different loading and dimming conditions. The selected approach was based on quasi-resonant flyback converter, backed up by an active power factor correcting block. The designed driver supports remote configuration and monitoring as well as sensor integration. The archived results show that this driver achieves a peak efficiency of 93% under maximum load and 100% duty-cycle. The efficiency for low dimming conditions (10% duty-cycle) achieves 75%.
As tendências de consumo de energia cada vez maior e seu impacto sobre o meio ambiente tem captado a atenção a nível mundial. Isso tem motivado várias medidas, tais como o Protocolo de Quioto, ou a estratégia Europeia 20 20 20, visando a redução do consumo de energia. Globalmente, estas medidas defendem um uso melhor e eficiente da energia disponível. Este, por sua vez, está fortemente ligado à consciência pública e à introdução de equipamento eletrónico eficiente. A iluminação pública é um bom exemplo dessas tendências, em que ambos os aspetos são de extrema importância. A introdução de LEDs como dispositivos de iluminação tem motivado vários avanços que lidam com essas estratégias. De um lado, os LEDs são capazes de oferecer uma maior eficiência quando comparados com dispositivos de iluminação convencionais. Isso provocou a substituição de luminárias convencionais por luminárias baseadas em LED. No entanto, o custo elevado destes dispositivos tem impedido a adoção plena e na fase atual, está mesmo a atuar como uma força negativa contra esta tendência de substituição. Melhores soluções estão sob investigação no âmbito de vários projetos europeus. Os LEDs são dispositivos de estado sólido, capazes de suportar a comutação rápida, uma característica que não é totalmente suportada por dispositivos de iluminação convencionais. Combinando esta característica com sensores ambientais e controlo inteligente pode-se ambicionar melhores poupanças energéticas. Uma abordagem simples seria a de considerar o que as exigências de iluminação reais dependem do uso das ruas e os níveis de iluminação circundantes. Para este efeito, a combinação de sensores de crepúsculo, detetores de movimento e regimes de controlo inteligentes podem propiciar uma abordagem adequada. Desta forma, os requisitos reais de iluminação podem ser efetivamente considerados, fornecendo luminárias capazes de consumir apenas a energia necessária. Para que isto se torne uma realidade vários desafios têm de ser vencidos. Um dos desafios mais importantes é o projeto LED driver. Nos sistemas de iluminação modernos baseados em LEDs, substitui-se os balastros convencionais por LED drivers. Quando a eficiência é importante, como no caso da iluminação pública, O LED driver têm de ser concebido de forma a ser o mais robusto e eficiente possível. Soluções recorrentes usam a fontes de alimentação comutadas, capazes de suportar o escurecimento adaptativo do fluxo luminoso. Um dos problemas principais no projeto destes drivers é o facto de a sua eficiência diminuir para níveis de regulação mais baixos. Isto é de extrema importância para a iluminação pública, pois na maioria dos casos durante a noite, as luminárias estão num nível de iluminação de baixo. Assim, com a finalidade de promover uma melhor economia de energia, a eficiência do driver deve ser elevada para ambas as condições de iluminação. Drivers comercialmente disponíveis, exibem eficácias na gama de 90% com elevado fluxo luminoso, e apenas 40% a 60% na condição de baixo fluxo luminoso. No âmbito desta dissertação de mestrado foi investigado o problema do projeto de driver LED visando a maior uniformidade possível da curva de eficiência, sob diferentes condições de carga e de fluxo luminoso. A abordagem escolhida foi baseada no conversor flyback quasi-ressonante, apoiado por um bloco de correção de fator de potência ativa. O driver projetado suporta configuração e monitorização remota, bem como de integração de sensores. Os resultados alcançados mostram que este driver atinge um pico de eficiência de 93% na condição de carga máxima e máximo fluxo luminoso. A eficiência em condições de baixo fluxo luminoso é superior a 75%.
Kukacka, Leos. "Qualité de l'énergie dans les alimentations électriques : applications dans les réseaux d'éclairage." Thesis, Toulouse 3, 2018. http://www.theses.fr/2018TOU30011/document.
Повний текст джерелаThis dissertation thesis is concerned with temporal fluctuations of the luminous flux of LED lamps, a phenomenon referred to as flicker. Flicker is usually regarded as a disturbance due to its negative impact on human health. For lighting systems based on light emitting diodes (LED), its definition has recently been formalised in norm IEEE 1789-2015 and has been documented on devices supplied with AC voltage. AC flicker results from interactions between network impedance, voltage and current harmonics, and the AC to DC converter. DC supplies are generally obtained by switching converters. Consequently, the same perturbing factors are present on DC networks. The thesis summarises the differences between the characteristic properties of flicker under AC and DC supplies. It has been shown in the literature and also in this thesis that the key factor affecting flicker with LEDs is the design of the LED driver-a necessary part of the LED lighting systems. This thesis describes a methodology for the evaluation of the flicker sensitivity of DC supplied LED lamps and analyses how the sensitivity changes when the LED drivers are simplified and accustomed to DC supply. The thesis presents a set of measurement experiments aimed to determine the typical flicker response of LED lamps both under AC and DC supply. Further experiments were performed to reveal the impact of accustomising the driver to the DC supply (removing the diode rectifier). It was found that some lamps show better flicker immunity while other lamps show worse flicker immunity. These experiments are accompanied by LED driver simulations aiming to reproduce and explain the measurement results. The thesis further describes a measurement experiment aimed to show the typical severity of the voltage fluctuation in a low voltage DC network coupled to AC mains and its impact on the flicker. It is concluded that such a system is robust enough to filter out any perturbations coming from the AC supply, but an undesired interaction between the lamp and the supply may occur
Khon, Elena. "Synthesis and Applications of Heterostructured Semiconductor Nanocrystals." Bowling Green State University / OhioLINK, 2013. http://rave.ohiolink.edu/etdc/view?acc_num=bgsu1374512926.
Повний текст джерелаHarismah, Kun. "Development of New Carbazole Polymers for LED Applications." Thesis, University of Sheffield, 2008. http://ethos.bl.uk/OrderDetails.do?uin=uk.bl.ethos.500291.
Повний текст джерелаThomas, Jacob Matthew. "Photoacoustic CO2 Detection in Biomass Cookstove Applications." BYU ScholarsArchive, 2020. https://scholarsarchive.byu.edu/etd/8740.
Повний текст джерелаRanson, John (John David). "A merged two-stage converter for LED lighting applications." Thesis, Massachusetts Institute of Technology, 2012. http://hdl.handle.net/1721.1/85485.
Повний текст джерелаCataloged from PDF version of thesis.
Includes bibliographical references (pages 109-110).
Light Emitting Diodes (LEDs) are a very promising technology for developing more efficient lighting. For high-efficiency applications, a switching current regulator is necessary to control the power drawn by an LED string. This thesis investigates a merged two-stage LED driver for lighting applications, with a switched capacitor (SC) voltage preregulator and a HF resonant-transition inverted buck current regulator. The design, analysis and implementation of the HF stage are developed in detail, and a full merged two-stage system is implimented based on a SC stage pulled heavily from the work of Seungbum Lim.
by John Ranson.
M. Eng.
Tuzikas, Arūnas. "Niche applications of solid-state lighting with controllable colour-rendition, spatial, photochemical, and photobiological properties." Doctoral thesis, Lithuanian Academic Libraries Network (LABT), 2014. http://vddb.library.lt/obj/LT-eLABa-0001:E.02~2014~D_20141230_152911-81986.
Повний текст джерелаŠi disertacija yra skirta ištirti kietakūnio apšvietimo su valdomomis spalvų perteikimo, erdvinėmis, fotocheminėmis ir fotobiologinėmis savybėmis galimus nišinius taikymus. Kaip nišinių taikymų pavyzdžiai, kuriuose ryškiausiai atsiskleidžia valdomo apšvietimo privalumai, buvo pasirinkti dailės kūrinių apšvietimas ir gatvių apšvietimas. Šiame darbe pristatytas išmanusis spalvų perteikimo variklis (SPV), leidžiantis tolydžiai keisti metamerinius spektrinės galios skirstinius, pasižyminčius skirtingomis spalvų perteikimo savybėmis. Naudojant SPV validuotas statistinis apšvietimo spalvinės kokybės vertinimo metodas. Apžvelgti dailės kūrinių apšvietimo reikalavimai bei pristatomi SPV pritaikymo dailės kūrinių apšvietimui pagal du kriterijus tyrimai: a) įvertinant apšvietimo spalvinei kokybei teikiamos subjektyvios pirmenybės priklausomybę nuo dailės kūrinio turinio ir žiūrovų kultūrinės kilmės; b) parodant regimosios išraiškos pokytį, atsirandantį dėl apšvietos lygio kitimo, kuomet fiksuojama apšvietimo fotocheminė įtaka apšviečiantiems paviršiams, kintant kokybiniams apšvietimo parametrams. Pristatomi apšvietimo skirstinio pėsčiųjų zonai optimizavimo rezultatai, gauti įvertinus subjektyvius poreikius. Pasiūlytas žemo cirkadinio poveikio kietakūnis šviesos šaltinis, skirtas lauko apšvietimui. Įvertintos tokio šaltinio fotometrinės, kolorimetrinės, spalvų perteikimo, fotobiologinės ir šviesinės taršos savybės bei atlikti tyrimai, įvertinantys psichofizines savybes.
Zaidi, Tahir. "Ferromagnetic and multiferroic thin films aimed towards optoelectronic and spintronic applications." Diss., Georgia Institute of Technology, 2010. http://hdl.handle.net/1853/41110.
Повний текст джерелаKulakci, Mustafa. "Silicon Nanocrystals Embedded In Sio2 For Light Emitting Diode (led) Applications." Master's thesis, METU, 2005. http://etd.lib.metu.edu.tr/upload/3/12606557/index.pdf.
Повний текст джерелаMikula, Vladimír. "Aplikace LED pro signalizační a osvětlovací účely v dopravě." Master's thesis, Vysoké učení technické v Brně. Fakulta elektrotechniky a komunikačních technologií, 2009. http://www.nusl.cz/ntk/nusl-217884.
Повний текст джерелаHunt, Zachary. "Surface functionalized colloidal particles and polymer synthesis for LED based applications." Connect to this title online, 2008. http://etd.lib.clemson.edu/documents/1211389059/.
Повний текст джерелаLlenas, 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.
Повний текст джерелаLes 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
Kulakci, Mustafa. "Silicon Nanostructures For Electro-optical And Photovoltaic Applications." Phd thesis, METU, 2012. http://etd.lib.metu.edu.tr/upload/12614225/index.pdf.
Повний текст джерелаSereda, Alexandra. "Imagerie multi-spectrale par résonance des plasmons de surface : développement et applications." Thesis, Paris 11, 2014. http://www.theses.fr/2014PA112321/document.
Повний текст джерелаBiodetection 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
Zhu, Zhengbo, Donglin Ma, Qiaomu Hu, Yongqian Tang, and Rongguang Liang. "Catadioptric freeform optical system design for LED off-axis road illumination applications." OPTICAL SOC AMER, 2017. http://hdl.handle.net/10150/626573.
Повний текст джерелаSichirollo, Francesco. "Novel Offline Switched Mode Power Supplies for Solid State Lighting Applications." Doctoral thesis, Università degli studi di Padova, 2013. http://hdl.handle.net/11577/3426640.
Повний текст джерелаNegli ultimi anni i dispositivi LED di potenza ad elevata luminosità (HBLED) hanno attirato in misura sempre crescente l'interesse della comunità scientifica, sia all'interno del mondo accademico che di quello industriale. Tra le varie caratteristiche, che rendono questo tipo di tecnologia interessante, le qualità più apprezzate sono certamente: la robustezza, l'elevata efficienza, le piccole dimensioni, la facilità di modulazione dell'intensità luminosa, il lungo tempo di vita, l'estrema rapidità di accensione e spegnimento e l'assenza di mercurio. Nonostante tutti questi aspetti sembrino dare alla tecnologia a stato solido un netto vantaggio rispetto alle tecnologie concorrenti, l'utilizzo dei LED di potenza nel campo dell'illuminazione rimane a tutt'oggi abbastanza limitato. La necessità di ulteriori progressi nella tecnologia dei dispositivi, da un lato, e dello sviluppo di soluzioni in grado di garantirne il corretto ed efficiente pilotaggio, dall'altro, ne hanno, infatti, fino ad ora frenato la diffusione rispetto alle attese. Quest'ultimo aspetto, in particolare, è al giorno d'oggi considerata il vero "collo di bottiglia" in vista dell'impiego su larga scala della tecnologia a stato solido, in sostituzione delle soluzioni, tutt'ora dominanti nel mercato dell'illuminazione, basate sull'utilizzo di lampade alogene e a fluorescenza. Se, da un lato, infatti, è vero che alcuni aspetti della tecnologia dei dispositivi (e.g. variabilità delle prestazioni con la temperatura, qualità della luce, calo dell'efficienza luminosa con l'aumentare della corrente, elevato costo per lumen, ecc...) necessitano di essere ulteriormente perfezionati, dall'altro è ormai universalmente riconosciuto che l'elemento chiave per l'ampia diffusione dell'illuminazione a stato solido è proprio l'ottimizzazione dello stadio di alimentazione. In particolare, le specifiche più importati che un ballast per lampade a LED è tenuto a soddisfare sono: elevata affidabilità ed efficienza, elevato fattore di potenza, capacità di regolazione della corrente di uscita e di modulazione del flusso luminoso, basso costo e minimo ingombro (soprattutto nell'illuminazione domestica). L'obiettivo principale è, quindi, riuscire ad ideare soluzioni basate sull'utilizzo di topologie semplici, caratterizzate da ridotto numero di componenti e limitati livelli di stress di corrente e tensione, che non prevedano l'impiego di componenti con breve tempo di vita come i condensatori elettrolitici. Inoltre, nelle applicazioni in cui la compattezza è considerata uno degli aspetti di maggior rilievo, anche la capacità di operare in soft-switching diviene una specifica indispensabile. Ciò è infatti necessario al fine di permettere la minimizzazione del volume delle componenti reattive, tramite l'aumento della frequenza di commutazione nel range delle centinaia di kHz, senza compromettere l'efficienza del convertitore. Per completezza, vale la pena di ricordare che, per ottimizzare il funzionamento dei LED ad elevata luminosità, andrebbero presi in considerazione anche altri aspetti, come ad esempio le problematiche legate alla gestione del calore dissipato dalla lampada, importanti al fine di limitare gli stress termici subiti dai dispositivi e, di conseguenza, migliorare la qualità della luce emessa e massimizzare il tempo di vita della lampada. Tuttavia, essendo il lavoro presentato in questa tesi centrato sulle questioni relative allo stadio di alimentazione, i suddetti problemi di gestione termica, come anche gli aspetti relativi allo sviluppo della tecnologia dei dispositivi non verranno esaminati. L'obiettivo principale del lavoro che verrà descritto nel corso dei prossimi capitoli, è, infatti, la ricerca di soluzioni innovative per il pilotaggio da rete elettrica di lampade basate su tecnologia a stato solido. Verranno pertanto approfonditamente trattate le tematiche relative ad analisi, ottimizzazione e sviluppo di topologie che siano in grado di soddisfare i requisiti precedentemente enunciati e di affrontare con successo le sfide proposte dalla continua evoluzione dello scenario del "general lighting". Per prima cosa, sarà fornita una visione di insieme riguardante lo stato dell'arte del mercato dell'illuminazione, le caratteristiche dei dispositivi di illuminazione a stato solido ed i principali aspetti relativi al loro pilotaggio. Dopo questa prima sezione introduttiva, la tematica relativa all'alimentazione da rete elettrica di tali dispositivi verrà approfonditamente discussa. Differenti modi di approcciare il problema, a seconda della specifica applicazione considerata, verranno discussi. Il primo tipo di approccio che verrà esaminato si basa sull'uso di una semplice struttura, formata da un singolo stadio di conversione di potenza. Essa è in grado di fornire al contempo il rispetto degli standard che limitano il contenuto armonico della corrente di ingresso, l'isolamento galvanico e la regolazione della corrente e dell'intensità luminosa in uscita. I vincoli, dettati dall'esigenza di garantire il rispetto della normativa EN 61000-3-2, in applicazioni di bassa potenza (<15W) prive di uno stadio dedicato alla correzione del fattore di potenza, verranno approfonditamente trattati. Saranno, poi, illustrati i risultati dello studio, sviluppo ed ottimizzazione di un convertitore a singolo stadio, operante ad elevata frequenza di commutazione, basato sulla topologia flyback a mezzo ponte asimmetrico. La semplicità, il ridotto numero di componenti ed il basso costo, che caratterizzano tale tipo di soluzione, la rendono adatta all'alimentazione di lampade per il settore residenziale, in cui la compattezza dello stadio di alimentazione è di fondamentale importanza al fine di consentirne l'alloggiamento nei classici socket E27. L'analisi effettuata, la procedura di progetto ed risultati ottenuti in simulazione ed a livello sperimentale durante lo studio di tale topologia verranno accuratamente descritti e discussi. Un altro interessante tipo di approccio che verrà considerato si basa sull'utilizzo di topologie integrate, nelle quali due diversi stadi di conversione vengono uniti tramite la condivisione dello stesso interruttore di potenza e della relativa circuiteria di comando. Nel convertitore che ne risulta, la correzione del fattore di potenza e la regolazione della corrente nei LED saranno dunque garantite dalla combinazione dei due semi-stadi, il cui interruttore comune dovrà essere in grado di gestire sia la potenza di ingresso che la corrente di uscita. Rispetto alla configurazione a due stadi convenzionale, la soluzione ottenuta tramite l'integrazione consente una minore complessità circuitale, un ridotto numero di componenti e, di conseguenza, una maggiore compattezza ed un minor costo. Tutto ciò viene guadagnato a scapito di un maggiore livello di stress nei componenti e della perdita di un grado di libertà nel progetto del convertitore. L'isolamento galvanico può essere garantito o meno a seconda del tipo di topologie che vengono selezionate per l'integrazione. Se la scelta ricade su topologie non isolate, la sicurezza dell'utente andrà comunque garantita isolando meccanicamente l'involucro della lampada. I problemi legati alla necessità di smorzare la componente alternata della potenza assorbita dalla rete, evitando al contempo l'utilizzo di componenti con basso tempo di vita, come i condensatori elettrolitici, verranno discussi. A tal proposito si studieranno le caratteristiche di un insieme di topologie integrate, al fine di fornirne un'analisi ed una procedura di design generalizzate. Se ne esaminerà, inoltre, la capacità di attenuare la componente ondulatoria della tensione di ingresso che viene trasferita al carico, dove si traduce in un'oscillazione della corrente di alimentazione fornita ai LED. Verrà proposta, poi, una soluzione basata su una topologia derivante dall'integrazione di due convertitori di tipo step-down (abbassatori di tensione), per applicazioni di "down-lighting", dimensionata per una potenza di circa 15W. Se ne discuteranno, in particolare, i dettagli di maggiore interesse relativi all'analisi effettuata, alla procedura di progetto ed ai risultati dei test effettuati in ambiente di simulazione. L'ultimo tipo di approccio considerato prevede, infine, l'utilizzo di una topologia multi-stadio, ritenuta una scelta appropriata soprattutto per applicazioni lighting di potenza elevata (>60W), come l'illuminazione stradale, in cui la compattezza dell'alimentatore non è ritenuta un aspetto di primaria importanza. Tramite questo tipo di soluzione è, infatti, possibile ottimizzare le prestazioni del convertitore sia dal lato della rete che dal lato del carico. Si riescono a garantire, in tal modo, un'efficace correzione del fattore di potenza, un adeguato controllo della corrente di uscita ed un'appropriata modulazione del flusso luminoso emesso dalla lampada. L'isolamento galvanico può essere fornito dallo stadio di ingresso o da quello di uscita o da un aggiuntivo stadio DC-DC intermedio, operante a catena aperta con rapporto di conversione di tensione costante. In quest'ultimo caso la struttura del convertitore, si trasforma, dalla classica configurazione a due stadi, in una topologia a triplo stadio. Il problema che nasce dalla necessità di assicurare un elevato livello di efficienza del sistema, nonostante l'interposizione di ripetuti stadi di conversione dell'energia tra la rete ed il carico a LED, può essere efficacemente risolto grazie alla flessibilità che caratterizza tale tipo di struttura. L'aumento del numero dei gradi di libertà in fase progettuale permette, infatti, di ottimizzare con semplicità ogni singolo stadio. Per comprovare limiti e potenzialità di tale tipo di approccio, si è deciso di studiare un ballast (dimensionato per una potenza nominale di 150W) basato sulla topologia a triplo stadio precedentemente menzionata, per applicazioni nell'ambito dell'illuminazione stradale. L'analisi condotta, la procedura di progetto ed i risultati delle simulazioni effettuate verranno discussi nel dettaglio, così come i risultati sperimentali dei test di laboratorio effettuati sul prototipo costruito.
Buffolo, Matteo. "Reliability of III-V laser diodes and LEDs for lighting and telecommunication applications." Doctoral thesis, Università degli studi di Padova, 2018. http://hdl.handle.net/11577/3421834.
Повний текст джерелаL'ultimo decennio di ricerca nell'ambito dei dispositivi optoelettronici ha contribuito allo sviluppo e alla successiva introduzione sul mercato di rivoluzionarie tecnologie, sia in ambito illuminotecnico, grazie agli innovativi sistemi di illuminazione basati su LED e laser in Nitruro di Gallio, che in ambito telecomunicazioni, dove la Silicon photonics promette di stravolgere l'odierno approccio alla trasmissione a larga banda. Innumerevoli laboratori di ricerca universitari e privati concorrono nell'incrementare le performance e l'affidabilità dei dispositivi. Tale obbiettivo, tuttavia, è ostacolato dalla complessa natura dei dispositivi optoelettronici e, ancor più, dei sistemi su di essi basati. Una conoscenza approfondita dei materiali, delle proprietà dei dispositivi e dell'ottimizzazione a livello di sistema risultano essere indispensabili per l'identificazione dei meccanismi fisici che limitano il tempo di vita utile dei dispositivi, e per lo sviluppo di possibili soluzioni. Scopo di questa tesi è descrive i risultati di un'estesa analisi finalizzata ad identificare i processi fisici che limitano l'affidabilità e le prestazioni degli innovativi sistemi optoelettronici basati su semiconduttori III-V. Per tale scopo sono stati realizzati specifici esperimenti di degrado accelerato e stress a breve termine su dispositivi allo stato dell'arte, che hanno permesso di individuare i processi fisici responsabili del degrado, graduale o catastrofico, cui possono essere soggetti i moderni dispositivi optoelettronici durante la propria vita operativa. Nello specifico, le analisi condotte su LED ad emissione nel visibile basati su Nitruro di Gallio (GaN) hanno innanzitutto rivelato che la prolungata polarizzazione del dispositivo con tensioni inverse vicine al valore critico di breakdown è accompagnata dall'instaurarsi di un processo di degrado tempo-dipendente che induce l'aumento della corrente di leakage del LED, portandolo eventualmente alla failure catastrofica. La peculiare distribuzione statistica del tempo di failure, unita all'andamento temporale di corrente e segnale di elettro-luminescenza durante lo stress in inversa, sono stati interpretati supponendo che il Nitruro di Gallio, portato in svuotamento spinto dalle elevate tensioni inverse, possa comportarsi come un dielettrico con perdite che degrada nel tempo a causa della percolazione di difetti, con un processo del tutto simile al breakdown tempo-dipendente del dielettrico presente nei MOS in Silicio. Lo studio sugli effetti a breve termine di elevate correnti di polarizzazione su LED in GaN ad alta potenza ha invece evidenziato una localizzazione della failure dei dispositivi in prossimità dei principali punti di iniezione di corrente, specificatamente associabili alla particolare struttura del dispositivo in analisi. Tale tipologia di stress si è inoltre rivelata altamente dannosa anche per la struttura epitassiale del dispositivo, che, a causa delle elevate temperature e densità di corrente in gioco, ha mostrato incrementi di resistività localizzati. Una più marcata dipendenza delle modalità e delle condizioni di failure dalla struttura e dal layout superficiale è emersa dall'analisi degli effetti di eventi di overstress di breve durata su LED bianchi ad alta potenza. I risultati sperimentali hanno portato all'identificazione della tipologia di LED più adeguata da adottare in ambienti soggetti a disturbi elettrici, mostrando inoltre come le problematiche relative ad eventi di overstress elettrico siano determinate più dalle debolezze di elementi estrinseci del LED che dal chip di semiconduttore. L'attività di ricerca ha poi evidenziato come per LED bianchi a media potenza in condizioni operative limite i processi di degrado graduale delle caratteristiche ottiche ed elettriche del dispositivo, ed in particolar modo relativi al package plastico, possano risultare deleteri per l'affidabilità a lungo termine della sorgente allo stato solido. L'analisi affidabilistica su tale tipologia di LED è stata poi estesa a livello di sistema, andando ad investigare i meccanismi di degrado che interessano le comuni lampadine a bulbo basate per l'appunto su LED bianchi a media potenza. La maggiore complessità del sistema illuminante sotto stress ha impattato negativamente sulle performance a lungo termine del bulbo, la cui affidabilità è risultata essere per lo più limitata da elementi estrinseci al LED, quali la cupola diffusiva oppure il driver di corrente. Nella seconda parte di questa tesi sono state analizzate le proprietà affidabilistiche di uno di questi elementi estrinseci: i fosfori. In collaborazione con l'organizzazione per lo sviluppo delle nuove energie e delle tecnologie industriali del Giappone (NEDO), è stata condotta un'estesa ricerca sull'affidabilità di fosfori ad emissione nel blu per eccitazione nel vicino UV tramite sorgenti a stato solido, in particolare laser. Attraverso una serie di stress termici e/o sotto fascio ottico ad elevate intensità, è stato possibile identificare il principale meccanismo fisico responsabile del degrado delle performance di fotoluminescenza del materiale fosforescente in esame. Nello specifico, correlando quest'ultimo fenomeno con le variazioni delle proprietà chimico-fisiche del materiale, è stato possibile identificare nell'autoionizzazione otticamente e/o termicamente indotta dei centri otticamente attivi di Eu2+ la principale causa di degrado del fosforo. La stress ottico a breve termine su pigmento luminescente di seconda generazione ha poi permesso di identificare un valore limite di intensità per il pompaggio ottico continuo. Oltre tale soglia, le performance del materiale luminescente calano per effetto congiunto della perdita di efficienza dovuta alle alte temperature di esercizio e al degrado non reversibile del materiale stesso. Nella terza parte di questa tesi vengono analizzati i meccanismi di degrado di diodi laser IR ibridi basati su semiconduttori III-V e Silicio progettati per sistemi di telecomunicazione e di interconnessione integrati. Esperimenti di degrado accelerato condotti a corrente costante hanno permesso l'identificazione di diversi processi di degrado graduale, tra i quali: (i) l'aumento della corrente di soglia, (ii) la decrescita della tensione di turn-on del diodo (iii) e l'incremento della concentrazione di carica apparente in prossimità della regione attiva. Sulla base della correlazione tra tali processi, è stata formulata l'ipotesi secondo la quale l'origine del degrado ottico del dispositivo risieda nell'aumento del rate di ricombinazione non radiativa, possibilmente dovuto alla diffusione di difetti verso la regione attiva. Al fine di investigare l'origine della specie diffondente sono state impiegate tecniche di analisi spettroscopica che hanno permesso l'identificazione di diversi livelli trappola all'interno del dispositivo, il principale dei quali, localizzato 0.43 eV al di sopra della banda di valenza, è risultato essere compatibile con un difetto d'interfaccia caratteristico del materiale semiconduttore utilizzato per la crescita della regione attiva dei dispositivi in esame.
Yalavarthi, Krishna Kumari. "Interplay of Electrical, Mechanical and Thermal Fields in III-N Nanostructures for LED Applications." OpenSIUC, 2013. https://opensiuc.lib.siu.edu/dissertations/708.
Повний текст джерелаChapel, Anthony. "Etude du comportement photochimique de revêtements composites polymère/particules luminescentes pour applications à l'éclairage éco-énergétique à base de LEDS. Impact du vieillissement sur les performances optiques." Thesis, Clermont-Ferrand 2, 2016. http://www.theses.fr/2016CLF22672/document.
Повний текст джерелаPhosphor-converted LEDs are emerging as an eco-friendly solution for the next generation lighting. Despite lifetimes claimed over 50 000h, a loss of the optical properties was noticed. This work focuses on the influence of photodegradation of the materials on the optical properties of the polymer/phosphor composite that is used to encapsulate the semiconductor chip. Luminescent composites were made from a polymer matrix (EVA or PMMA) and an inorganic phosphor: Y3BO6 :15% Eu3+. The evolution of physical, chemical and optical properties of these composites was investigated under irradiation in accelerated conditions (λ>300 nm) and in the use conditions of UV LED (λ=365 nm). The phosphor showed no pro-degrading effect on the photooxidation of the polymer. A loss of the optical properties of the composite was observed and ascribed to the photodegradation of the polymer in the case of the EVA matrix. The evolution of photometric parameters of the emitted light by the luminescent composite during photoaging can be attributed to the accumulation of photoproducts in films. However, for PMMA/phosphor composites, the chemical structure and optical properties of such composites are kept for accelerated photoaging time up to 4000h
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.
Повний текст джерелаWith 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
Ogudo, Kingsley. "Development of edge-emitting Si/SiGe based optical sources operating in the visible and near visible range wavelength for sensing and communication applications." Thesis, Paris Est, 2018. http://www.theses.fr/2018PESC1060/document.
Повний текст джерелаWe propose a low cost full-silicon optical links utilizing 650 – 850 nm propagation wavelengths. The creation of large-scale opto-electronic integrated circuits and optical data “highways” inCMOS integrated circuitry, utilizing Si CMOS compounds, have been envisioned and hold much promise [1] - [3] The latest attempts for realizing optoelectronic systems in CMOS technology have until now mainly been focused on utilizing wavelengths at 1550 nm [4] - [6], mainly because of the ease of design and fabrication of waveguides in this wavelength regime. However, no effective high-speed optical sources and Si detectors are available at this 1550nmwavelength. Today solutions to overcome the problem are mostly focused on the integration of group III-V elements based optical sources on Silicon through molecular bonding [7a] – [7b]. If optical sources, detectors, waveguides, and sensors could be realized on the same Si CMOS chip at, say, 750 nm wavelength, various low power consuming, light and miniature on-chip-based micro-photonic systems can be designed and realized. While Silicon optical sources may not yet be at the required performance level for very-high speed communications, the low cost “all silicon”opto-electronic systems still remain a great grail. These sources could lead as well to new field that could be appropriately named “Si photonic microsystems” opening the route to new sensing applications and products especially for the medical, biomedical optics, optical interconnect and bio-photonics field. These systems also do not require ultrahigh frequency bandwidths to transmit, and the emission powers of our avalanche Si light-emitting diodes(LEDs) may be sufficient to sustain the operation of such systems. This PhD thus deals with low cost SiGe/Si optical links using Microwave-Photonics devices such as, Bipolar integrated SiAvLED, Silicon Nitride and Silicon Oxide optical waveguides, SiGeHPTs, Si and SiGe/Si LEDs. It focuses on the combined integration of micron-scale optical sources, optical waveguides and detectors on the same chip to form a complete communication link for various applications involving short wavelength links (750nm to 950nm). The progress provided by this PhD to previous works could be synthesized as below:• Optical source, waveguide and the detector were all integrated and aligned on the same chip, in an industrial based technology, to form complete on-chip micro-optical links at750nm wavelength, with a SiGe radio frequency (RF) 0.35µm bipolar process.• A series of second generation of on-chip optical communication links of 50µm length, utilizing 650 – 850 nm propagation wavelengths, have been designed and realized inSiGe. Micron dimensioned optical sources, waveguides and detectors were all integrated ion the same chip to form a complete communication on-chip micro-optical links. Avalanche based Si LEDs (Si Av LEDs), Schottky contacting, TEOS densification strategies, Silicon-Nitride based waveguides, and state of the art SiGe bipolar detector technologies were used as key design strategies.• R-soft simulation software (Beam Prop) was used as a mathematical capable simulation tool to model various Silicon-Nitride optical waveguide structures, before the designing, the fabrication, characterization and testing of the device. Various device structures were modeled, simulation iterations were performed on several optical waveguide designed structures before the device design, and the devices were tested experimentally.• Best performances of the designed on-chip optical links show a conversion loss as low as30dB from source to detector with up to 500MHz in cut off frequency. The good alignment and the good efficiency of each device are then clearly achieved. Higher frequency performances are also envisaged from preliminary measurements
Diac, Andreea Petronela. "Design, synthesis and supramolecular architectures of new heterocyclic compounds with potential applications in material chemistry and photovoltaic conversion." Thesis, Angers, 2015. http://www.theses.fr/2015ANGE0019/document.
Повний текст джерелаThe thesis entitled “Design, Synthesis and SupramolecularArchitectures of New Heterocyclic Compounds with PotentialApplications in Material Chemistry and Photovoltaic Conversion” isstructured into five chapters concerning new: a) heterocycliccyclopenta[c]pyrans; b) indenopyrone derivatives with fluorescentproperties; c) potential devices of molecular electronics; d)donors for organic photovoltaics and e) electroluminescent carbon‘quantum’ dots.The first chapter presents a study of pseudoazulenederivatives having a cyclopenta[c]pyran unit. The survey comprises thesynthesis, structural analysis and reactivity towards electrophilicsubstitution in order to obtain fluorescent compounds.The second chapter deals with the separation odiastereoisomers and the study of fluorescent propertiesindenopyrone derivatives.The third chapter describes the synthesis of newarchitectures based on cyclopenta[c]pyran unit that can be structurallymodified by the influence of a chemical or electrochemical stimulus inorder to work as potential devices in molecular electronics.In the fourth chapter, the synthesis andelectronic properties of new molecular donors for organic solar cellswas described.The fifth and last chapter outlines the passivation of surfacedefects on carbon nanoparticles using small organic molecules orpolymers in order to obtain photoluminescent carbon nanoparticlesdubbed as carbon‘quantum’dots
Happel, Kathrin [Verfasser], Edgar [Akademischer Betreuer] Dörsam, and Tran Quoc [Akademischer Betreuer] Khanh. "LED-Based Light Scattering Measurements of Papers for Printing Applications / Kathrin Happel. Betreuer: Edgar Dörsam ; Tran Quoc Khanh." Darmstadt : Universitäts- und Landesbibliothek Darmstadt, 2011. http://d-nb.info/1106113454/34.
Повний текст джерелаGough, Kathryn M. "Designing community-driven, social benefit applications using locative, mobile and social web technologies." Thesis, Queensland University of Technology, 2016. https://eprints.qut.edu.au/97742/1/Kathryn_Gough_Thesis.pdf.
Повний текст джерелаRoome, John William. "Creative applications of basic computer software: a practice-led exploration of visual art and design thinking drawing and animation." Thesis, Cape Peninsula University of Technology, 2013. http://hdl.handle.net/20.500.11838/1336.
Повний текст джерелаDigital drawing and animation, using basic computer software, opens up new possibilities in creative practice-‐led research. The digital medium, with its relative ease of reproduction and storage of images, facilitates a reflective method of thinking-‐while-‐ drawing, thereby stimulating the creative process and providing a unique means of reflection-‐in-‐action. The computer’s ability to record images allows for temporal disruption, providing possibilities for exploring alternative creative solutions as well as retrospective, reflection-‐on-‐action. This thesis presents an interrogation of the researcher’s creative practice, as well as the findings and creative artefacts of other relevant practitioners in the field of digital drawing, animation, and related creative activities. A reflexive methodology was used to investigate the relationship between making, doing, and knowing in creative practice. The findings are supported by creative outputs (making), reflection on the creative process in relation to supporting literature (doing), and knowledge resulting from this reflection together with related theoretical research (knowing). The research revealed that digital drawing and animation supports new modes of making resulting in the production of original creative artefacts. It was further revealed that in relation to “doing”, the digital medium supports reflective practice by enabling the creative practitioner to document and reflect on these outputs both during and after making. The resulting reflexive actions combined with theoretical research lead to revelations concerning the relationship between thinking and drawing when using digital media as well as in a broader sense. The study thus contributes insights concerning art and design thinking, and makes a contribution to new developments in visual arts and design research. Practice-‐led research introduces a theoretical paradigm that has methodological implications particularly in the context of the current re-‐structuring and transformation of art and design education at South African Universities of Technology. The findings indicate that digital drawing and animation can encourage a critical and reflective approach not only in the work of creative practitioners by supporting new modes of making, but that it also has positive implications for visual arts research and teaching. In this regard the research highlights the need for promoting the integration of theory and practice in visual arts and design education curricula.
Ronchi, Emanuele. "Neural Networks Applications and Electronics Development for Nuclear Fusion Neutron Diagnostics." Doctoral thesis, Uppsala universitet, Institutionen för fysik och astronomi, 2009. http://urn.kb.se/resolve?urn=urn:nbn:se:uu:diva-108583.
Повний текст джерелаLu, Yan-Ting, and 盧彥廷. "Applications of LED Technology." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/52614450093781101616.
Повний текст джерела吳鳳科技大學
光機電暨材料研究所
102
The main purpose of this study is to develop an LED fixture which collaborates with creative and innovative ideas and design, serves as a replacement of the traditional lighting appliances, and most of all is environment friendly. The two of advantages of LED lighting over conventional lighting are the better energy efficiency and the longer expected lifetime, which significantly lead to the phase out of the traditional ones as the LED technology advances. This thesis explores the performances in power consumption and brightness for various types of LED lamp driver circuits. In determining the availability of the designed LED lamp on multiple appliances, the author carried out a variety of tests and found out that the experimental results meet the general requirements for regular users.
"A Novel Boost Converter Based LED Driver Chip Targeting Mobile Applications." Doctoral diss., 2016. http://hdl.handle.net/2286/R.I.38525.
Повний текст джерелаDissertation/Thesis
Doctoral Dissertation Electrical Engineering 2016
Chen, Chun-Yu, and 陳俊宇. "LED Lighting, Detection and Its Extended Applications." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/21458365513502456982.
Повний текст джерела崑山科技大學
電子工程研究所
100
LED (Light Emitting Diode) is the lighting market of mainstream.The paper will LED application of detection and its Extended. In the control side,this thesis is a system of FPGA Based digital control platform to order to achieve design of the three control systems: Both color temperature and illumination of the LED detection system. Illumination detection system to implement chip And Luminaries with lighting and communication functions LED.The three control systems are all of the independent individual.
LEE, CHIN-PING, and 李金屏. "Single-Stage Converter Power LED Lighting Applications." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/vbee54.
Повний текст джерела臺北城市科技大學
資訊應用產業碩士專班
106
ABSTRACT In recent years, LED lighting has gradually been widely used in lighting products, while the traditional incandescent and fluorescent lamps are slowly being replaced by the trend. We uses a single-stage power converter in LED lighting, with small size, high power factor, economical, energy-saving carbon reduction and other advantages. The single-stage converter power supply provides high-precision constant-current mode that reliably stabilizes the current on the LED and allows for uniform LED brightness for improved light quality.
Lai, Li-Wen, and 賴俐文. "Applications for Waste Heat Recovery of LED Lighting." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/56927224451610201190.
Повний текст джерела大葉大學
電機工程學系
103
With the increasing depletion in global energy and greenhouse-effect issues, green energy has attracted the worldwide attention. The research of renewable energy is focused on solar, biomass ethanol, wind power and geothermal. On the other hand, waste heat recovery is the other method for improving energy efficiency. This thesis proposes waste heat recovery of light emitting diode (LED) that utilizes a thermoelectric generator (TEG) to withdraw the waste heat of LED module with a temperature gap between LED module and ambient air and produce DC electricity. The recovered energy can be used to provide a DC fan with heat sink for the active cooling of LED devices. The simulation model is built using MATLAB/Simulink and compared with the measurement results by utilizing LabVIEW-based measurement system. The temperature of LED module can be controlled under . The autonomous and self-sufficient characteristics are demonstrated.
Liu, Ding-Feng Peng, and 彭劉鼎烽. "Study on the LED applications for plant factory." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/01623625211421462339.
Повний текст джерела清雲科技大學
電子工程所
101
In recent years, the rise of the plant factory has promoted the agricultural development in Taiwan. Besides, the illuminant light source of the plant has been gradually replaced by an artificial light source. Because LED is with the advantages such as a small size and low power consumption over the traditional light source, it has been widely used as the artificial light source of the plant factory in the United State of American, Japan, Taiwan, and other countries. In fact, it has been successfully demonstrated that LED provides the necessary light of the growth of the plants, e.g., butterfly orchids, oriental lilies, lettuces, cabbages, strawberries, etc. In the past few decades, there has been attracted much attention on the light source of the plant factory. Among the articles, the researchers almost focused on the effect of light source on the plant growth in wavelength and light intensity. In the thesis, a new method based on optical design is used to improve the lighting way of the plant factory by way of the software named as Advanced System Analysis Program (ASAP). In this research, the parallel light is used as the light source by combining the mining color light, which is formed by using white, red, and blue LEDs, and Fresnel Lens. However, the improved light source is with the merits of power saving compared to the traditional light source. In addition, the light intensity and uniformity can be analyzed by ASAP. Of course, the optimization of the optical model can be also obtained by the improved method. And its feasibility is demonstrated.
Lin, Wei-Shiang, and 林煒翔. "Flyback Converter for Low Power LED Lighting Applications." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/68674151606894577308.
Повний текст джерела國立雲林科技大學
電機工程系碩士班
101
ABSTRACT This thesis presents a Flyback converter for lighting emitter diode (LED) applications. Instead of traditional light up circuit and Cold Cathode Fluorescent Lamp (CCFL), the LED is popular in lighting industry applications. Flyback converter with the low cost and simple structure is adopted to drive the LED lamp. The LED constant voltage and constant current loop are used to prevent the LED damage clue to the voltage and current variation. Finally, according to the analysis and design consideration in this paper, a convertor with P_o=12W, v_ac=85~265V, v_o=31V was implemented to verify the performance of the proposed converter. Keywords:Flyback converter, Constant voltage control, Constant current control.
Li, Tung-Yen, and 李東諺. "Development of LED Module and Optical Interference Technology for TFT-LCD Applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06840965574085265079.
Повний текст джерела國立中央大學
電機工程學系
101
Recently, TFT-LCD is the most popular display application in the flat panel display application. The main parts in the TFT-LCD system includes: LCD panel module, backlight module and electronic driver module. This paper provides the novel design of direct-in backlight module of the TFT-LCD system and the inspection method for the gap mura defect of the LCD panel. We applied the LED light source, secondary light-guide component and micro reflector structure to design the novel backlight module. Compared with West’s work in 2003, the uniformity ratio for our new design shows an increase of 24%, from 60% to 84%, and the luminance a 23.29% improvement, from 10 000 nits to 12 329 nits. On the other hand, we combine the optical interference method and neural network classification to detect the gap mura defect of the LCD panel. Three kinds of mura defects including non-uniformity sealant panel; panel with foreign material and fiber-cluster panel are tested. After learning process of Neural Network Classification method, the Mean Squared Error could decrease less than 0.01. By this method, we could sort out the bad panel and increase the yield rate of the production line.
Hsu-Kuan, Lin. "ZnO based TCL contact for GaN based LED applications." 2006. http://www.cetd.com.tw/ec/thesisdetail.aspx?etdun=U0016-0109200613412366.
Повний текст джерелаChiu, Yu-min, and 邱育民. "Applications of Recycled Nanosize Copper in CPU/LED/Biomedicine." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/52986506280493549940.
Повний текст джерела國立成功大學
環境工程學系碩博士班
97
Copper (CuO (52%) and Cu2+ (48%)) in chemical mechanical polishing (CMP) wastewater can be effectively enriched with saccharides. In addition to recycling of copper from the CMP wastewater, the core-shell nanoparticles (Cu@C) can be synthesized by carbonization of copper-saccharides complexes. The Cu@C core-shell nanoparticles have been studied to explore potential applications in thermal interface materials (TIMs) and thermal dissipation of CPU and LED as well as photothermal cancer therapy. A simple and inexpensive method for synthesis of M@C (M: Cu, Ni, Ag, bimetallic or alloy metals) with saccharides as the carbon source has been developed. By adjusting C/M ratios, nanosize-controllable metal (Cu) encapsulated in the carbon shells (thickness = 3-5 nm) can be synthesized by carbonization of the metal-starch complexes at 673-773 K. The carbon shells can prevent the nanosize core metal from oxidation and aggregation. Expetimentally, dispersion of a small amount (5%) of the Cu@C nanoparticles (Cu size = 14 nm) in a commercial thermal grease (Y-500), its thermal conductivity can be increased by at least 60%. The smaller (7 nm) or larger (80 nm) Cu in the Cu@C nanoparticles cause an increase of the thermal conductivity by 10-30%. In addition, for the long-time heat-dissipation applications, the shell carbon may consume the residual oxygen (C+O2�彪O2) in the grease and expose the core copper for a better thermal conductivity (391 W/m-K). Kinetic parameters of shrinking of carbon on Cu@C by steam refoming have been obtained. The Arrhenius activation energy (Ea) for shrinking of the carbon on Cu@C with Cu sizes of 7 nm is 165.5 kJ mol-1, which are much less than that (Ea = 240.5 kJ mol-1) of the hollow carbon sphere (H@C) with cage size of 7 nm at 573-973 K. Thermal dissipation of heat pipes can be enhanced with coating of Cu by shrinking of the carbon from Cu@C on the internal surfaces of heat pipes. The photothermal behaviors of metals and alloys encapsulated in carbon shells has been investigated with the NIR laser. The temperature raise of the Cu@C with Cu size of 14 nm under the exposure of an 809 nm Ti sapphire femtosecond laser with the power of 51 W/cm2 is 30 K. The core-shell nanoparticles with an excellent photothermal characteristic have immense potential for photothermal therapy of eradicated malignant tumors.
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.
Повний текст джерела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.
Lin, Hsu-Kuan, and 林旭冠. "ZnO based TCL contact for GaN based LED applications." Thesis, 2006. http://ndltd.ncl.edu.tw/handle/85723326999689826626.
Повний текст джерела國立清華大學
電子工程研究所
94
This thesis work demonstrated the high performance of a light emitting diode (LED) which is able to illuminate visible light at very high lumen (eg. 254 mcd); the LED is formed by five InGaN/GaN quantum wells and a high voltage enduring contacting structure which is composed of Nickel (Ni)/Aluminum doped Zinc Oxide (AZO). In order to enhance the high voltage enduring capability of the LED, one of the contacting structures is formed as a p-i-n structure. By depositing a thick layer of ZnO (i.e. 440 nm) as the i layer of this p-i-n structure, a large portion of voltage is sustained by this i layer, which makes the LED able to increase its voltage tolerance to as high as 65 VDC. Also attributed to the transparent property of the contacting structure, the light emitting capability of this LED demonstrated an unabated one due to the non-transparent electrode; this trait further assures such device as a viable technology solution for tomorrow’s household illuminating devices. With further development on this LED and its processing technology, this LED bears the potential to be directly connected to the household power source -- 110 VAC.
Tu, Jen-Hung, and &;#20931;任鴻. "Defect Characterization of GaN Epilayer Template for LED Applications." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/84358428630812387930.
Повний текст джерела國立中興大學
材料科學與工程學系所
98
In this thesis, we report an approach for efficiently improving the threading dislocation (TD) density and internal quantum efficiency of InGaN-based near-ultraviolet (~400 nm) light-emitting diodes (LEDs). A combination of selective etching of GaN defects and patterned sapphire substrate (PSS) techniques forms a growth mask of TDs in GaN epitaxial layers. This selective etched-GaN/PSS structure can efficiently achieve defect centralization and the defect density can be reduced to 105 cm-2. The structural properties of the regrown GaN epilayers were investigated in details using double-crystal X-ray diffraction, cathodeluminescence, and secondary ion mass spectroscopy. Under a 350-mA injection current, the output power of the SiO2-block/PSS LED is enhanced by 46% compared with that of the conventional GaN/sapphire one. The improvement of the output power is not only due to the decrease in dislocation density, but also to the enhancement of extraction efficiency using PSS. In addition, we investigate the characteristics of near-ultraviolet (~400 nm) InGaN multiple-quantum well based LED using a SiLENS simulation program. Simulations of light-output power versus current are performed for GaInN/GaN light-emitting diodes grown on GaN-on-sapphire templates with different threading dislocation densities. The energy band diagrams, carrier concentrations, radiative recombination efficiency, light-current curves, and external quantum efficiency are taken into account in detail. Low-defect-density devices exhibit a efficiency peak followed by droop as current increases. However, the high-defect-density devices show low peak efficiencies and little droop. The simulation results suggest that improvement of internal quantum efficiency is mainly due to the increase of radiative recombination at high current injection.
YANG, ZHENG-HAO, and 楊証皓. "Design of Imaging Lens for LED Light Pipe Applications." Thesis, 2016. http://ndltd.ncl.edu.tw/handle/95437623242682875775.
Повний текст джерела明道大學
材料與能源工程學系碩士班
104
This research is the imaging lens design combined with LED light pipe, The use of three types of available lens group reached a minimum correction of all aberrations film features combine to make the light guide tube, image is clear and bright as the goal neached, The Lens deaign of three designs can be used for image capture, image capture even further extension of medical uses, such as endoscopy, etc. Simulation to achieve the desired results through Zemax software.Which is the MTF value has reached 0.45@ 40c⁄mm for all fields. Keyword:LED. Lightpipe. Three lens groups. Video shooting. Image Capture
Hung, Chien-Chung, and 洪健忠. "High Power RGB-LED Model and its Circuit Applications." Thesis, 2008. http://ndltd.ncl.edu.tw/handle/12189294601121264832.
Повний текст джерела和春技術學院
電機工程研究所
96
The purpose of this thesis is to investigate the optical and electrical characteristics of high power LEDs under different current and ambient temperature. At the same time, Is Spice software is used to build its model and modulize it. In this thesis, integrating sphere system is used to measure the variation of characteristics of 1W RGB-LED, such as luminous flux, dominant wavelength and equivalent resistance, etc., at the driving current from 100mA to 350mA and ambient temperature controlled at 10oC to 70oC. Based on experimental data, a model is built for further verification by practical circuit application after the establishment of such module. The performance of this modulized model is found more accurate through comparison between simulation result and experimental data using a lighting circuit design composed of 5 pieces of 1 W-LED. This finding could provide a reference for future design aiming at high power LED driving circuit to reduce development and design cost.
Lee, Cheng-Huan, and 李政翰. "An Evaluation of Novel Packaging Material on LED Applications." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/xvk8wj.
Повний текст джерела國立虎尾科技大學
光電與材料科技研究所
101
In present, the thermoplastic polymer has been commonly utilized as one of LED packaging materials, in which thermoplastic-based PPA(Polyphthalamide) and PCT(Poly1,4-cyclohexylene dimethylene terephthalate)-based material are abundantly used. The PPA and PCT are mainly used for low- and medium-power applications, and both are the most commercial available materials in the LED packaging market. However, with reducing cost and increasing input power in LED solid-state lighting applications, the new packaging materials with better resistance to impact, humidity, heat, and encapsulant yellowing, have been developing for passing different environmental loads. Hence, there are some thermosetting polymer-based materials developed to meet the requirement, such as EMC (Epoxy Molding Compound) and SMC (Silicone Molding Compound), etc. The study is mainly focused on the applications of EMC package (with thermosetting polymer-based material) in high-power LED products, which is driven by greater than input power of 2W. First, it is to make a detailed analysis on each LED packaging process, such as sandblasting and punching, etc, and to further measure the initial light intensity of the package, relating to EMC''s reflectivity after packaged. Next, the material heat resistance and optical characterization for the package were examined before and after the long-term high-temperature aging and several reflow cycling tests. Finally, the adhesive bond at an interface between EMC material and silver leadframe was observed with a red ink experiments. In the mean time, the light decay and lifetime for the package were also determined by experimentally recording the LED light intensity when continually operated at a certain driven I=400mA under different ambient temperature conditions of 25 oC, 60 oC, 80 oC for a long time. Keywords: LED, Package, EMC thermosetting-based packaging material, PPA thermoplastic-based packaging material
ANKITA and VIDHI. "SPECTROSCOPIC CHARACTERIZATION OF DY3++IONS DOPED PHOSPHATE GLASSES FOR EPOXY-FREE WHITE LED APPLICATIONS." Thesis, 2022. http://dspace.dtu.ac.in:8080/jspui/handle/repository/19556.
Повний текст джерелаTsai, Tsung-Yen, and 蔡宗晏. "Epitaxial Growth of GaN Templates by MOCVD for LED Applications." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/06016724983150070441.
Повний текст джерела國立中興大學
材料科學與工程學系所
100
Gallium nitride (GaN) is a binary III/V direct bandgap semiconductor that has been widely used in light-emitting diodes (LEDs) since the 1990s. The compound is a hard material with a Wurtzite crystal structure. The wide band gap of 3.4 eV provides the material with special properties that facilitate its application in high-power and high-frequency devices. In this dissertation, GaN was grown on three different templates by metal organic chemical vapor deposition. The first two templates were selectively-etched GaN (SE-GaN, type I) and strip-patterned sapphire (SPS, type II) template, created with the aim of effectively reducing threading dislocation (TD) densities and increasing the internal quantum efficiency. The final template was a Ga2O3 template (type III), which could separate the sapphire substrate via a chemical etching process. We aim to enhance the effectiveness of this process as an alternative to laser lift-off technology, and to reduce the epitaxial cost. The type I SE-GaN templates were created using selective etching of GaN defects and the patterned sapphire substrate (PSS) technique. These templates acted as a TD growth mask in the GaN epitaxial layers, and achieved defect centralization. The etching pit density (EPD) of GaN grown on the SE-GaN template can reduce to 1.6 × 105 cm-2, and the output power of the SE-GaN LED sample under a 350 mA injection current can be enhanced by 46% as compared with that of the conventional GaN/sapphire LED one. The type II SPS templates were fabricated using photolithographic and wet-etching processes. The etching maximized the sapphire substrate area and graphics, which increased the light extraction efficiency and reduced TDs. The EPD of GaN grown on SPS templates can reduce to 5.3 × 106 cm-2. The output power of the SPS LED sample under a 350 mA injection current was enhanced by 40% as compared with that of the conventional GaN/sapphire LED one. The type III Ga2O3 templates, deposited using pulsed laser deposition on sapphire substrates, were used for the epitaxial growth of crystalline GaN on the Ga2O3 templates. An N2 ambient atmosphere was adopted because a severe degradation of the oxide material occurred under a H2 ambient atmosphere at high temperatures. Finally, the GaN LED structures were successfully grown on the.Ga2O3 template. A thin film LED was demonstrated, where the sacrificial Ga2O3 was easily achieved using a HF etchant; and the GaN and sapphire substrate can be successfully separated.
Tu, Pei-Yu, and 杜佩鈺. "Design and Applications of Energy Saving andComfortable LED Pendant Lighting." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/864hr8.
Повний текст джерела國立臺北科技大學
建築與都市設計研究所
102
Due to the limited angle of LED light-emission, light scattering from the LED light source and lamp combination can be poor, resulting in dark spots on the lamp shade. The objective of this study is to use lamp design and LED arrangement to achieve comprehensive light scattering. After review of the literature and case analysis, the author carried out the design based on IDEO design thinking. The focus of the design is on the LED light source characteristics and the degree of innovation of the lamps. Optical simulation software was applied for ray tracking, and one project was selected to be made into a physical model. Afterward, the investigator interviewed experts for suggestions on the light source and the style and appearance of the lamp. Suggestions from the experts were analyzed, integrated and adapted to correct shortcomings. Results from interviewing experts are summarized below. First, the lamp can create a comprehensive scattering effect that is similar to the light scattering of regular lamps. Secondly, with two light sources, top and bottom, and a dimmer controller, the lamp can be used to create spatial atmosphere, and the user can select iii the most comfortable light source. Third, color temperature change can be integrated into the light sources to create various types of atmosphere and styles. Fourth, according to consumer need, the lamp as designed has an adjustable pole that can accommodate rooms and space of different height. Lastly, there was a lack of experiments and tests during the design process. The investigator should also try to apply various types of light and materials because combining them can create many possibilities and opportunities.
Happel, Kathrin. "LED-Based Light Scattering Measurements of Papers for Printing Applications." Phd thesis, 2011. https://tuprints.ulb.tu-darmstadt.de/2850/1/Dis_Happel_20111206_online.pdf.
Повний текст джерела