Scalability of Quasi-hysteretic FSM-based Digitally Controlled Single-inductor Dual-string Buck LED Driver To Multiple Strings

There has been growing interest in Single-Inductor Multiple-Output (SIMO) DC-DC converters due to its reduced cost and smaller form factor in comparison with using multiple single-output converters. An application for such a SIMO-based switching converter is to drive multiple LED strings in a multi-channel LED display. This paper proposes a quasi-hysteretic FSM-based digitally controlled Single-Inductor Dual-Output (SIDO) buck switching LED Driver operating in Discontinuous Conduction Mode (DCM) and extends it to drive multiple outputs. Based on the time-multiplexing control scheme in DCM, a theoretical upper limit of the total number of outputs in a SIMO buck switching LED driver for various backlight LED current values can be derived analytically. The advantages of the proposed SIMO LED driver include reducing the controller design complexity by eliminating loop compensation, driving more LED strings without limited by the maximum LED current rating, performing digital dimming with no additional switches required, and optimization of local bus voltage to compensate for variability of LED forward voltage (VF) in each individual LED string with smaller power loss. Loosely-binned LEDs with larger VF variation can therefore be used for reduced LED costs.postprin

An efficient self-configurable driver for color light emitting diode

To arrange an accurate load current for the different sets of color LEDs, an efficient LED driver must facilitate the current sharing among the LED strings using a constant current source. Effective utilization of power in an LED string is vital for display panels as it defines the magnitude of the undesirable phenomenon of flickering switching. An efficient and dimmable LED driver suitable for LED back-light drivers in the LED display panel is presented in this thesis. This thesis proposed a color LEDs driver with a self-configuration of the enhanced current mirror in multiple LED strings. In this proposed work, the load currents have been efficiently balanced among the identical and unequal loads of color LEDs. In a traditional current mirror, the buck converter is linked with a fixed current load. Nonetheless, in the proposed improved self-adjustable current mirror, the variation of LEDs load string could be addressed using a single buck converter. The improvement is based on the combinational circuits of transistor and op-amp with proper scheme biasing. The improved dimming circuit is then proposed for exploiting the range of dimming at the string and module level. Furthermore, the proposed current-balancing circuits excluded a separate power supply to control current in different load strings of LEDs (red/green/blue). Since the approach circuit is identical and modular, it could be scaled to any number of parallel current sources. The different bi-level pulsating driving have been performed to reduce the loss while running the LEDs at the high peak current. It is to create two driving parameters, which are the low/high current levels (pulse width modulation) and associated duty cycles, in having the capability to control luminosity effectively. It can be seen, the previous techniques had improved the luminous efficacy of LEDs by using n-level driving techniques but at the trade-off of losing efficiency with the introduction of resistors (variables in series) to create a bi-level phenomenon for the driver. Therefore, this thesis proposes to replace the resistors with the new approach dimming circuit to get a significant improvement in the overall system’s efficiency that can assist to dim an individual LEDs string based on designated color (red or green or blue) LEDs. Meanwhile, in improving illuminance through dimming, the hybridization of pulse width modulated (PWM) and amplitude modulated (AM) has been proposed. As a result, the proposed LEDs driver has shown effective current balancing through the color LEDs string with exploiting a large dimming range. The illumination analysis has also shown a significantly higher when compared with PWM (bi-level pulsating). The computation efficiency for red, green, and blue LEDs strings around range 92% to 99%

A Survey, Classification and Critical Review of Light-Emitting Diode Drivers

Based on a survey on over 1400 commercial LED drivers and a literature review, a range of LED driver topologies are classified according to their applications, power ratings, performance and their energy storage and regulatory requirements. Both passive and active LED drivers are included in the review and their advantages and disadvantages are discussed. This paper also presents an overall view on the technical and cost aspects of the LED technology, which is useful to both researchers and engineers in the lighting industry. Some general guidelines for selecting driver topologies are included to aid design engineers to make appropriate choices.published_or_final_versio

A Novel Boost Converter Based LED Driver Chip Targeting Mobile Applications

abstract: A novel integrated constant current LED driver design on a single chip is developed in this dissertation. The entire design consists of two sections. The first section is a DC-DC switching regulator (boost regulator) as the frontend power supply; the second section is the constant current LED driver system. In the first section, a pulse width modulated (PWM) peak current mode boost regulator is utilized. The overall boost regulator system and its related sub-cells are explained. Among them, an original error amplifier design, a current sensing circuit and slope compensation circuit are presented. In the second section – the focus of this dissertation – a highly accurate constant current LED driver system design is unveiled. The detailed description of this highly accurate LED driver system and its related sub-cells are presented. A hybrid PWM and linear current modulation scheme to adjust the LED driver output currents is explained. The novel design ideas to improve the LED current accuracy and channel-to-channel output current mismatch are also explained in detail. These ideas include a novel LED driver system architecture utilizing 1) a dynamic current mirror structure and 2) a closed loop structure to keep the feedback loop of the LED driver active all the time during both PWM on-duty and PWM off-duty periods. Inside the LED driver structure, the driving amplifier with a novel slew rate enhancement circuit to dramatically accelerate its response time is also presented.Dissertation/ThesisDoctoral Dissertation Electrical Engineering 201

Design and Control of Power Converters 2019

In this book, 20 papers focused on different fields of power electronics are gathered. Approximately half of the papers are focused on different control issues and techniques, ranging from the computer-aided design of digital compensators to more specific approaches such as fuzzy or sliding control techniques. The rest of the papers are focused on the design of novel topologies. The fields in which these controls and topologies are applied are varied: MMCs, photovoltaic systems, supercapacitors and traction systems, LEDs, wireless power transfer, etc

Fault Tolerant DC–DC Converters at Homes and Offices

The emergence of direct current (DC) microgrids within the context of residential buildings and offices brings in a whole new paradigm in energy distribution. As a result, a set of technical challenges arise, concerning the adoption of efficient, cost-effective, and reliable DC-compatible power conditioning solutions, suitable to interface DC microgrids and energy consuming elements. This thesis encompasses the development of DC–DC power conversion solutions, featuring improved availability and efficiency, suitable to meet the requirements of a comprehensive set of end-uses commonly found in homes and offices. Based on the energy consumption profiles and requirements of the typical elements found at homes and offices, three distinctive groups are established: light-emitting diode (LED) lighting, electric vehicle (EV) charging, and general appliances. For each group, a careful evaluation of the criteria to fulfil is performed, based on which at least one DC–DC power converter is selected and investigated. Totally, a set of five DC–DC converter topologies are addressed in this work, being specific aspects related to fault diagnosis and/or fault tolerance analysed with particular detail in two of them. Firstly, mathematical models are described for LED devices and EV batteries, for the development of a theoretical analysis of the systems’ operation through computational simulations. Based on a compilation of requirements to account for in each end-use (LED lighting, EV charging, and general appliances), brief design considerations are drawn for each converter topology, regarding their architecture and control strategy. Aiming a detailed understanding of the two DC–DC power conversion systems subjected to thorough evaluation in this work – interleaved boost converter and fault-tolerant single-inductor multiple-output (SIMO) converter – under both normal and abnormal conditions, the operation of the systems is evaluated in the presence of open-circuit (OC) faults. Parameters of interest are monitored and evaluated to understand how the failures impact the operation of the entire system. At this stage, valuable information is obtained for the development of fault diagnosis strategies. Taking profit of the data collected in the analysis, a novel fault diagnostic strategy is presented, targeting interleaved DC–DC boost converters for general appliances. Ease of implementation, fast diagnostic and robustness against false alarms distinguish the proposed approach over the state-of-the-art. Its effectiveness is confirmed through a set of operation scenarios, implemented in both simulation environment and experimental context. Finally, an extensive set of reconfiguration strategies is presented and evaluated, aiming to grant fault tolerance capability to the multiple DC–DC converter topologies under analysis. A hybrid reconfiguration approach is developed for the interleaved boost converter. It is demonstrated that the combination of reconfiguration strategies promotes remarkable improvements on the post-fault operation of the converter. In addition, an alternative SIMO converter architecture, featuring inherent tolerance against OC faults, is presented and described. To exploit the OC fault tolerance capability of the fault-tolerant SIMO converter, a converter topology targeted at residential LED lighting systems, two alternative reconfiguration strategies are presented and evaluated in detail. Results obtained from computational simulations and experimental tests confirm the effectiveness of the approaches. To further improve the fault-tolerant SIMO converter with regards to its robustness against sensor faults, while simplifying its hardware architecture, a sensorless current control strategy is presented. The proposed control strategy is evaluated resorting to computational simulations.O surgimento de micro-redes em corrente contínua (CC) em edifícios residenciais e de escritórios estabelece um novo paradigma no domínio da distribuição de energia. Como consequência disso, surge uma panóplia de desafios técnicos ligados à adopção de soluções de conversão de energia, compatíveis com CC, que demonstrem ser eficientes, rentáveis e fiáveis, capazes de estabelecer a interface entre micro-redes em CC e as cargas alimentadas por esse sistema de energia. Até aos dias de hoje, os conversores CC–CC têm vindo a ser maioritariamente utilizados em aplicações de nicho, que geralmente envolvem níveis de potência reduzidos. Porém, as perspectivas futuras apontam para a adopção, em larga escala, destas tecnologias de conversão de energia, também em equipamentos eléctricos residenciais e de escritórios. Tal como qualquer outra tecnologia de conversão electrónica de potência, os conversores CC–CC podem ver o seu funcionamento afectado por falhas que degradam o seu bom funcionamento, sendo que essas falhas acabam por afectar não apenas os conversores em si, mas também as cargas que alimentam, limitando assim o tempo de vida útil do conjunto conversor + carga. Desta forma, é fulcral localizar a origem da falha, para que possam ser adoptadas acções correctivas, capazes de limitar as consequências nefastas associadas à falha. Para responder a este desafio, esta tese contempla o desenvolvimento de soluções de conversão de energia CC–CC altamente eficientes e fiáveis, capazes de responder a requisitos impostos por um conjunto alargado de equipamentos frequentemente encontrados em habitações e escritórios. Com base nos perfis de consumo de energia eléctrica e nos requisitos impostos pelas cargas tipicamente utilizadas em habitações e escritórios, são estabelecidos três grupos distintos: iluminação através de díodos emissores de luz, carregamento de veículo eléctrico (VE) e aparelhos eléctricos em geral. Para cada grupo, é efectuada uma avaliação cuidadosa dos critérios a respeitar, sendo com base nesses critérios que será escolhida e investigada pelo menos uma topologia de conversor CC–CC. No total, são abordadas cinco topologias de conversores CC–CC distintas, sendo que os aspectos ligados ao diagnóstico de avarias e/ou tolerância a falhas são analisados com particular detalhe em duas dessas topologias. Inicialmente, são estabelecidos modelos matemáticos descritivos do comportamento das principais cargas consideradas no estudo – díodos emissores de luz e baterias de VEs – visando a análise teórica do funcionamento dos sistemas em estudo, suportada por simulações computacionais. Com base numa compilação de requisitos a ter em conta em cada aplicação – iluminação através de díodos emissores de luz, carregamento de veículo eléctrico (VE) e aparelhos eléctricos em geral – são estabelecidas considerações ligadas à escolha de cada topologia de conversor não isolado, no que respeita à sua arquitectura e estratégia de controlo. Visando o conhecimento aprofundado das duas topologias de conversor CC–CC alvo de particular enfoque neste trabalho – conversor entrelaçado elevador e conversor de entrada única e múltiplas saídas, tolerante a falhas – quer em funcionamento normal, quer em funcionamento em modo de falha, é avaliado o funcionamento de ambas as topologias na presença de falhas de circuito aberto nos semicondutores activos. Para o efeito, são monitorizados e analisados parâmetros úteis à percepção da forma como os modos de falha avaliados neste trabalho impactam o funcionamento de todo o sistema. Nesta fase, é obtida informação fundamental ao desenvolvimento de estratégias de diagnóstico de avarias, particularmente indicadas para avarias de circuito aberto nos semicondutores activos dos conversores em estudo. Com base na informação recolhida anteriormente, é apresentada uma nova estratégia de diagnóstico de avarias direccionada a conversores CC–CC elevadores entrelaçados utilizados em aparelhos eléctricos, em geral. Facilidade de implementação, rapidez e robustez contra falsos positivos são algumas das características que distinguem a estratégia proposta em relação ao estado da arte. A sua efectividade é confirmada com recurso a uma multiplicidade de cenários de funcionamento, implementados quer em ambiente de simulação, quer em contexto experimental. Por fim, é apresentada e avaliada uma gama alargada de estratégias de reconfiguração, que visam assegurar a tolerância a falhas das diversas topologias de conversores CC–CC em estudo. É desenvolvida uma estratégia de reconfiguração híbrida, direccionada ao conversor entrelaçado elevador, que combina múltiplas medidas de reconfiguração mais simples num único procedimento. Demonstra-se que a combinação de múltiplas estratégias de reconfiguração introduz melhorias substanciais no funcionamento do conversor ao longo do período pós-falha, ao mesmo tempo que assegura a manutenção da qualidade da energia à entrada e saída do conversor reconfigurado. Noutra frente, é apresentada e descrita uma arquitectura alternativa do conversor de entrada única e múltiplas saídas, com tolerância a falhas de circuito aberto. Através da configuração proposta, é possível manter o fornecimento de energia eléctrica a todas as saídas do conversor. Para tirar máximo proveito da tolerância a falhas do conversor de entrada única e múltiplas saídas, uma topologia de conversor indicada para sistemas residenciais de iluminação baseados em díodos emissores de luz, são apresentadas e avaliadas duas estratégias de reconfiguração do conversor, exclusivamente baseadas na adaptação do controlo aplicado ao conversor. Os resultados de simulação computacional e os resultados experimentais obtidos confirmam a efectividade das abordagens adoptadas, através da melhoria da qualidade da energia eléctrica fornecida às diversas saídas do conversor. São assim asseguradas condições essenciais ao funcionamento ininterrupto e estável dos sistemas de iluminação, já que a qualidade da energia eléctrica fornecida aos sistemas de iluminação tem impacto directo na qualidade da luz produzida. Por fim, e para aprimorar o conversor de entrada única e múltiplas saídas tolerante a falhas, no que respeita à sua robustez contra falhas em sensores, é apresentada uma estratégia de controlo de corrente que evita o recurso excessivo a sensores e, ao mesmo tempo, simplifica a estrutura de controlo do conversor. A estratégia apresentada é avaliada através de simulações computacionais. A abordagem apresentada assume vantagens em múltiplos domínios, sendo de destacar vantagens como a melhoria da fiabilidade de todo o sistema de iluminação (conversor + carga), os ganhos atingidos ao nível do rendimento, a redução do custo de implementação da solução, ou a simplificação da estrutura de controlo.This work was supported by the Portuguese Foundation for Science and Technology (FCT) under grant number SFRH/BD/131002/2017, co-funded by the Ministry of Science, Technology and Higher Education (MCTES), by the European Social Fund (FSE) through the ‘Programa Operacional Regional Centro’ (POR-Centro), and by the Human Capital Operational Programme (POCH)

Estudio del estado del arte de las lámparas de iluminación LED y su comportamiento armónico

Este trabajo de final de master ha estudiado el estado del arte de los sistemas de iluminación LED así como las diferentes topologías de los circuitos electrónicos que alimentan la cadena de LEDs de las lámparas con el objeto de conocer las corrientes consumidas por dichas lámparas, poder determinar su emisión de armónicos y analizar posteriormente su impacto en la red eléctrica

Estudio del estado del arte de las lámparas de iluminación LED y su comportamiento armónico

Este trabajo de final de master ha estudiado el estado del arte de los sistemas de iluminación LED así como las diferentes topologías de los circuitos electrónicos que alimentan la cadena de LEDs de las lámparas con el objeto de conocer las corrientes consumidas por dichas lámparas, poder determinar su emisión de armónicos y analizar posteriormente su impacto en la red eléctrica

조명 장치에서 플리커를 낮은 위험 수준으로 줄이기 위해 두 개의 평행한 플로팅 벅 구조를 사용한 교류-직류 엘이디 구동 회로

학위논문 (박사)-- 서울대학교 대학원 : 전기·컴퓨터공학부, 2016. 8. 정덕균.This dissertation presents an ac-dc LED driver that consists of two parallel floating buck converters. To buffer the twice-line-frequency energy, one floating buck converter conveys energy to a storage capacitor, simultaneously performing the power factor correction (PFC). The other floating buck converter regulates the LED current to maintain a constant brightness in the LEDs for reducing the light flicker to low-risk levels. The proposed architecture reduces the voltage stress and the size of the storage capacitor, enabling the use of a film capacitor instead of an electrolytic capacitor. Considering the power factor and the flicker standards, a de-sign procedure to achieve a high power factor, while minimizing the storage capac-itance and the LED current ripple, is presented. A prototype of the proposed LED driver has been implemented with an on-chip controller IC fabricated in a 0.35 μm CMOS process and its functionality and performance have been verified experi-mentally. It demonstrates a power factor of 0.94 and a peak power efficiency of 85.4% with an LED current ripple of 6.5%, while delivering 15 W to the LEDs.CHAPTER 1 INTRODUCTION 1 1.1 MOTIVATIONS 1 1.2 FLICKER METRICS AND STANDARDS 5 1.3 PRIOR WORKS 9 1.4 THESIS OBJECTIVES AND ORGANIZATION 15 CHAPTER 2 BACKGROUND ON LED DRIVER 17 2.1 POWER CONVERTER TOPOLOGIES 17 2.1.1 LINEAR REGULATOR 17 2.1.2 SWITCHED-CAPACITOR CONVERTER 18 2.1.3 INDUCTOR-BASED CONVERTERS 19 2.2 BASICS FOR LED DRIVERS 31 2.2.1 LED CONFIGURATIONS 31 2.2.2 CURRENT SENSING TECHNIQUES IN LED DRIVERS 32 2.3 PFC TECHNIQUES IN LED DRIVERS 35 2.3.1 POWER FACTOR 35 2.3.2 PASSIVE PFC CIRCUIT 35 2.3.3 ACTIVE PFC CIRCUIT 36 2.4 DIMMING TECHNIQUES 38 CHAPTER 3 DESIGN OF AN AC-DC LED DRIVER WITH A TWO PARALLEL FLOATING BUCK TOPOLOGY 40 3.1 PROPOSED SYSTEM ARCHITECTURE AND OPERATION PRINCIPLE 40 3.1.1 OVERALL ARCHITECTURE 40 3.1.2 OPERATION PRINCIPLE 42 3.1.3 DISCUSSION ON DIMMING 50 3.2 DESIGN OF THE PROPOSED TOPOLOGY 52 3.2.1 RELATIONSHIP BETWEEN THE INPUT CURRENT WAVEFORM AND THE POWER FACTOR 52 3.2.2 DESIGN CONSIDERATIONS FOR DECIDING THE STORAGE CAPACITOR VOLTAGE 54 3.2.3 ANALYSIS OF THE PROPOSED LED DRIVER WITH LINE VOLTAGE VARIATIONS 57 3.2.4 DESIGN OF THE FLOATING BUCK CONVERTER FOR PFC AND ENERGY BUFFERING 59 3.2.5 DESIGN OF THE FLOATING BUCK CONVERTER FOR LED CURRENT REGULATION 63 3.3 CIRCUIT IMPLEMENTATION 67 3.3.1 CONTROLLER CIRCUIT ARCHITECTURE 67 3.3.2 LED CURRENT REGULATION LOOP DESIGN 68 3.3.3 BUILDING BLOCKS 70 CHAPTER 4 EXPERIMENTAL RESULTS 79 4.1 EXPERIMENTAL SETUP 79 4.2 MEASUREMENT RESULTS 84 CHAPTER 5 CONCLUSION 93 BIBLIOGRAPHY 94 초록 101Docto