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The use of lighting loads is one of the crucial matters which increases every year. The increasing use then leads to the development of brighter and longer-lasting sources. In addition, the conventional use of lighting loads today, which only emit light at its maximum intensity, does not allow the consumers to adjust the brightness level as needed. Consequently, this condition may cause energy wastage. The LED lighting system is gaining popularity as it is widely used in a wide range of applications. The advantages of LEDs, such as its compact size and varied lamp colors, replace conventional lighting sources. The linear setting of the driver topology using the flyback converter was aimed to control the LEDs with a constant current in order to adjust the variation of the LED light intensity. The closed-loop driver circuit with flyback converter topology was designed as an LED driver with a given load specification from the LED string. A dimmable feature was included for adjusting the intensity of the light produced by the LEDs. Eventually, the fuzzy logic controller (FLC) method was applied to the integrated change setting to obtain a dynamic response.

This paper presents a quantitative design analysis, performance prediction and practical testing of buck and half-bridge LLC resonant converters as a solution for a power control stage in the realization of a 180 W driver applied to LED street lighting lamp. As a starting point of the proposal, a product of the Zagonel Ltda Company was used. Regulatory requirements for LED street lights lamps brought by INMETRO Portaria No. 20 stipulate operating conditions for the device. These conditions are connected to power quality, electromagnetic compatibility and luminous efficacy, being the last one directly linked to system efficiency, allowing the discussion of alternative topologies for traditional solutions. The resonant LLC half-bridge converter has been widely studied as a potential LED drive circuit, with the premise of increasing the switching frequency and consequent reduction of filter elements, provided by its transition conditions of zero voltage switching in the inverter and zero current switching in rectifier. In addition, this converter topology brings insulation through a high frequency transformer. However, the implementation of converters with more active and passive elements has greater design complexity than basic circuits like buck topology. The design parameters and main efficiency conditions of buck and half-bridge LLC resonant converters are reviewed in this work. The Buck converter was evaluated under 33 kHz, 60 kHz and 100 kHz, and the LLC Resonant converter was evaluated under 100 kHz, 140 kHz, 180 kHz and 220 kHz. The tests shows that the total efficiency of the converters is very close under some design conditions, indicating that the study of losses for each component is necessary. As fundamental characteristics of project realization, the costs and volumes occupied by the through role components present in booth solutions are also analyzed, highlighting the price disadvantage for the implemented resonant circuit solution. Este trabalho apresenta uma análise quantitativa do projeto, previsão do desempenho e testes práticos dos conversores buck e meia ponte LLC ressonante, como solução para o estágio de controle de potência na realização de um driver de 180 W aplicado a iluminação pública com LEDs. Como ponto de partida da proposta foi utilizado um produto de mercado da empresa Zagonel Ltda. Requisitos normativos para luminárias públicas LED trazidos pela portaria nº 20 do INMETRO estipulam condições de operação para o dispositivo. Estas condições estão vinculadas à qualidade de energia, à compatibilidade eletromagnética e à eficácia luminosa, sendo esta última diretamente ligada à eficiência do sistema, propiciando a discussão de topologias alternativas para soluções mais tradicionais. O conversor meia ponte LLC ressonante vem sendo amplamente estudado como possibilidade para circuitos de acionamento LED, com a premissa de aumento da frequência de comutação e consequente redução dos elementos de filtro, proporcionados pela operação do mesmo em condições de transição com zero de tensão no inversor e zero de corrente no retificador. Além disso, esta topologia de conversor traz consigo isolação através de um transformador de alta frequência. Contudo, a implementação de conversores com mais elementos ativos e passivos possui uma maior complexidade de projeto perante a concepção de circuitos básicos como o conversor buck. A determinação dos parâmetros de projeto e das principais condições da eficiência dos conversores buck e meia ponte LLC ressonante são revisadas neste trabalho. Para a validação da análise, projetos do conversor buck com frequências de trabalho de 33 kHz, 60 kHz e 100 kHz, e projetos para o conversor LLC Ressonante com as frequências de 100kHz, 140kHz, 180kHz e 220kHz são avaliados. Os testes realizados demonstram que a eficiência total dos conversores são muito próximas em algumas condições de projeto, mostrando que o estudo das perdas para cada componente se faz necessária. Como características fundamentais de realização dos projetos, os custos e os volumes ocupados pelos componentes presentes nas soluções também são analisados, sendo notória a desvantagem em preço para a solução implementando o circuito ressonante.

This 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.; Cette thèse de doctorat porte sur les fluctuations temporelles du flux lumineux des lampes LED, ce phénomène portant le nom de papilottement (flicker). Le papillotement est habituellement considéré comme une perturbation en raison de son impact négatif sur la santé. Pour les systèmes d'éclairage à base de diodes électroluminescentes (LED), sa définition vient d'être formalisée dans la norme IEEE 1789:2015 et a été décrite pour les appareils alimentés en courant alternatif (CA). Ce papillotement alternatif résulte des interactions entre l'impédance du réseau, l'onde de tension, les courants harmoniques et le convertisseur de courant alternatif en courant continu (CA - CC). L'alimentation en courant continu est généralement obtenue via des convertisseurs à découpage. Par conséquent, les mêmes facteurs perturbateurs sont également présents sur les réseaux à courant continu. Cette thèse résume les diférences entre les propriétés caractéristiques du papillotement sous alimentation en CA et en CC. Il a été montré dans la littérature et aussi dans cette thèse qu'avec les LED, le facteur clé qui affecte le papillotement réside dans la conception du driver de LED - une partie indispensable des systèmes d'éclairage à LED. Cette thèse décrit une méthodologie d'évaluation de la sensibilité au papillotement des lampes LED sous alimentation en CC et analyse la façon dont cette sensibilité se modifie lorsque les drivers de LED sont simplifiés et adaptés à des alimentations CC. La thèse présente un ensemble d'expériences de mesure visant à déterminer la réaction typique du papillotement des lampes LED à la fois sous alimentation CA et CC. D'autres expériences ont été efectuées pour révéler l'impact de l'adaptation du driver à l'alimentation CC (en enlevant le pont redresseur à diodes). On constate que certaines lampes présentent une meilleure résistance au papillotement, tandis que d'autres lampes présentent une moindre résistance. Ces expériences sont accompagnées de simulations de drivers pour les lampes LED visant à reproduire et à expliquer les résultats des mesures. La thèse décrit en outre une expérience de mesure visant à montrer la sévérité typique de la variation de tension dans un réseau CC à basse tension couplé au CA domestique et son impact sur le papillotement. On conclut qu'un tel système est suisamment robuste pour filtrer les perturbations provenant du CA, mais une interaction indésirable entre la lampe et l'alimentation peut se produire.

This 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.; Cette thèse de doctorat porte sur les fluctuations temporelles du flux lumineux des lampes LED, ce phénomène portant le nom de papilottement (flicker). Le papillotement est habituellement considéré comme une perturbation en raison de son impact négatif sur la santé. Pour les systèmes d'éclairage à base de diodes électroluminescentes (LED), sa définition vient d'être formalisée dans la norme IEEE 1789:2015 et a été décrite pour les appareils alimentés en courant alternatif (CA). Ce papillotement alternatif résulte des interactions entre l'impédance du réseau, l'onde de tension, les courants harmoniques et le convertisseur de courant alternatif en courant continu (CA - CC). L'alimentation en courant continu est généralement obtenue via des convertisseurs à découpage. Par conséquent, les mêmes facteurs perturbateurs sont également présents sur les réseaux à courant continu. Cette thèse résume les diférences entre les propriétés caractéristiques du papillotement sous alimentation en CA et en CC. Il a été montré dans la littérature et aussi dans cette thèse qu'avec les LED, le facteur clé qui affecte le papillotement réside dans la conception du driver de LED - une partie indispensable des systèmes d'éclairage à LED. Cette thèse décrit une méthodologie d'évaluation de la sensibilité au papillotement des lampes LED sous alimentation en CC et analyse la façon dont cette sensibilité se modifie lorsque les drivers de LED sont simplifiés et adaptés à des alimentations CC. La thèse présente un ensemble d'expériences de mesure visant à déterminer la réaction typique du papillotement des lampes LED à la fois sous alimentation CA et CC. D'autres expériences ont été efectuées pour révéler l'impact de l'adaptation du driver à l'alimentation CC (en enlevant le pont redresseur à diodes). On constate que certaines lampes présentent une meilleure résistance au papillotement, tandis que d'autres lampes présentent une moindre résistance. Ces expériences sont accompagnées de simulations de drivers pour les lampes LED visant à reproduire et à expliquer les résultats des mesures. La thèse décrit en outre une expérience de mesure visant à montrer la sévérité typique de la variation de tension dans un réseau CC à basse tension couplé au CA domestique et son impact sur le papillotement. On conclut qu'un tel système est suisamment robuste pour filtrer les perturbations provenant du CA, mais une interaction indésirable entre la lampe et l'alimentation peut se produire.

Mestrado em Engenharia Eletrónica e Telecomunicações A presente dissertação faz uma abordagem à eficiência energética em aplicações gerais de iluminação. Vem na sequência do projeto LITES, que teve como objetivo o estudo e demonstração da viabilidade económica de um sistema de iluminação inteligente. A Universidade de Aveiro participou neste projeto e a Ponte Pedonal do Crasto é um dos locais piloto, cuja iluminação existente foi totalmente substituída por um sistema de iluminação inteligente. A integração do LED em sistemas de iluminação é amplamente justificada pela eficiência energética que apresentam, conduzindo a uma muito significativa diminuição de custos. Inicialmente, será feita uma introdução à história da iluminação artificial, desde o seu aparecimento no período da pré-história, passando pela sua evolução, até à atualidade. A seguir será dado ênfase à iluminação LED, tal como, suas caraterísticas, regulamentações a que se encontram sujeitos os dispositivos referentes a este tipo de iluminação e principais aplicações. Nesta sequência, serão ainda caraterizados os drivers LED mais utilizados, módulos de comunicação sem os e alguns sensores de movimento/ presença, integrados em sistemas de iluminação inteligentes. Finalmente, ser a apresentado o projeto do circuito e respetiva implementação prática, análise de dados e resultados obtidos. This dissertation is an approach to energy e ciency in general lighting applications. Follows the project LITES, which aimed to study and demonstration of feasibility economic of an intelligent lighting system. The University of Aveiro participates in this project and the Footbridge of Crasto is one of the pilot sites, whose existing lighting was fully replaced by an intelligent lighting system. The integration of LED in lighting systems is widely justi ed by the energy e ciency they present, leading to very signi cant cost savings. Initially an introduction will be made to the history of arti cial lighting, since its appearance in the prehistoric period, through for its evolution to the present day. The following will enphasize the LED lighting, as well as its characteristics, regulations to which the devices related to this type of lighting and main applications are subject. In this sequence, the most commoly used drivers, wireless communication modules and some motion/presence sensores, integrated into intelligent lighting systems, will also be featured. Finally, the circuit design and its pratical implementation, data analysis and results will be presented.