Design Techniques of Highly Integrated Hybrid-Switched-Capacitor-Resonant Power Converters for LED Lighting Applications

The Light-emitting diodes (LEDs) are rapidly emerging as the dominant light source given their high luminous efficacy, long lift span, and thanks to the newly enacted efficiency standards in favor of the more environmentally-friendly LED technology. The LED lighting market is expected to reach USD 105.66 billion by 2025. As such, the lighting industry requires LED drivers, which essentially are power converters, with high efficiency, wide input/output range, low cost, small form factor, and great performance in power factor, and luminance flicker. These requirements raise new challenges beyond the traditional power converter topologies. On the other hand, the development and improvement of new device technologies such as printed thin-film capacitors and integrated high voltage/power devices opens up many new opportunities for mitigating such challenges using innovative circuit design techniques and solutions. Almost all electric products needs certain power delivery, regulation or conversion circuits to meet the optimized operation conditions. Designing a high performance power converter is a real challenge given the market’s increasing requirements on energy efficiency, size, cost, form factor, EMI performance, human health impact, and so on. The design of a LED driver system covers from high voltage AC/DC and DC/DC power converters, to high frequency low voltage digital controllers, to power factor correction (PFC) and EMI filtering techniques, and to safety solutions such as galvanic isolation. In this thesis, we study design challenges and present corresponding solutions to realize highly integrated and high performance LED drivers combining switched-capacitor and resonant converters, applying re-configurable multi-level circuit topology, utilizing sigma delta modulation, and exploring capacitive galvanic isolation. A hybrid switched-capacitor-resonant (HSCR) LED driver based on a stackable switched-capacitor (SC) converter IC rated for 15 to 20 W applications. Bulky transformers have been replaced with a SC ladder to perform high-efficiency voltage step-down conversion; an L-C resonant output network provides almost lossless current regulation and demonstrates the potential of capacitive galvanic isolation. The integrated SC modules can be stacked in the voltage domain to handle a large range of input voltage ranges that largely exceed the voltage limitation of the medium-voltage-rated 120 V silicon technology. The LED driver demonstrates > 91% efficiency over a rectified input DC voltage range from 160 VDC to 180 VDC with two stacked ICs; using a stack of four ICs > 89.6% efficiency is demonstrated over an input range from 320 VDC to 360 VDC . The LED driver can dim its output power to around 10% of the rated power while maintaining >70% efficiency with a PWM controlled clock gating circuit. Next, the design of AC main rectifier and inverter front end with sigma delta modulation is described. The proposed circuits features a pair of sigma delta controlled multilevel converters. The first is a multilevel rectifier responsible for PFC and dimming. The second is a bidirectional multilevel inverter used to cancel AC power ripple from the DC bus. The system also contains an output stage that powers the LEDs with DC and provides for galvanic isolation. Its functional performance indicates that integrated multilevel converters are a viable topology for lighting and other similar applications

Controladores LED eficientes para aplicações de iluminação geral

Mestrado em Engenharia Eletrónica e TelecomunicaçõesThe 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%

Beyond Power over Ethernet : the development of Digital Energy Networks for buildings

Alternating current power distribution using analogue control and safety devices has been the dominant process of power distribution within our buildings since the electricity industry began in the late 19th century. However, with advances in digital technology, the seeds of change have been growing over the last decade. Now, with the simultaneous dramatic fall in power requirements of digital devices and corresponding rise in capability of Power over Ethernet, an entire desktop environment can be powered by a single direct current (dc) Ethernet cable. Going beyond this, it will soon be possible to power entire office buildings using dc networks. This means the logic of “one-size fits all” from the existing ac system is no longer relevant and instead there is an opportunity to redesign the power topology to be appropriate for different applications, devices and end-users throughout the building. This paper proposes a 3-tier classification system for the topology of direct current microgrids in commercial buildings – called a Digital Energy Network or DEN. The first tier is power distribution at a full building level (otherwise known as the microgrid); the second tier is power distribution at a room level (the nanogrid); and the third tier is power distribution at a desktop or appliance level (the picogrid). An important aspect of this classification system is how the design focus changes for each grid. For example; a key driver of the picogrid is the usability of the network – high data rates, and low power requirements; however, in the microgrid, the main driver is high power and efficiency at low cost

Revision of the EU Green Public Procurement Criteria for Street Lighting and Traffic Signals - Preliminary Report

Lighting is used on more than 1.6 million km of roads in EU28 countries, accounting for some 35 TWh of electricity consumption (1.3% of total electricity consumption) and costing public authorities almost €4000 million each year. A broad review of relevant technical, policy, academic and legislative literature has been conducted. This report examines the current market situation and the potential for reducing environmental impacts and electricity costs by assessing the recent developments in road lighting technology, particularly LEDs. Particularly important areas identified relate to energy efficiency, light pollution, product durability and, specifically for longer lasting and rapidly evolving new LED technologies, reparability and upgradeability. The information in this report shall serve as a basis for discussion with stakeholders about the further development and revision of EU GPP criteria for street lighting and traffic signals.JRC.B.5-Circular Economy and Industrial Leadershi

Design and Testing of Electronic Devices for Harsh Environments

In this thesis an overview of the research activity focused on development, design and testing of electronic devices and systems for harsh environments has been reported. The scope of the work has been the design and validation flow of Integrated Circuits operating in two harsh applications: Automotive and High Energy Physics experiments. In order to fulfill the severe operating electrical and environmental conditions of automotive applications, a systematic methodology has been followed in the design of an innovative Intelligent Power Switch: several design solutions have been developed at architectural and circuital level, integrating on-chip selfdiagnostic capabilities and full protection against high voltage and reverse polarity, effects of wiring parasitics, over-current and over-temperature phenomena. Moreover current slope and soft start integrated techniques has ensured low EMI, making the Intelligent Power Switch also configurable to drive different interchangeable loads efficiently. The innovative device proposed has been implemented in a 0.35 μm HV-CMOS technology and embedded in mechatronic 3rd generation brush-holder regulator System-on-Chip for an automotive alternator. Electrical simulations and experimental characterization and testing at componentlevel and on-board system-level has proven that the proposed design allows for a compact and smart power switch realization, facing the harshest automotive conditions. The smart driver has been able to supply up to 1.5 A to various types of loads (e.g.: incadescent lamp bulbs, LED), in operating temperatures in the wide range -40 °C to 150 °C, with robustness against high voltage up to 55 V and reverse polarity up to -15 V. The second branch of research activity has been framed within the High Energy Physics area, leading to the development of a general purpose and flexible protocol for the data acquisition and the distribution of Timing, Trigger and Control signals and its implementation in radiation tolerant interfaces in CMOS 130 nm technology. The several features integrated in the protocol has made it suitable for different High Energy Physics experiments: flexibility w.r.t. bandwidth and latency requirements, robustness of critical information against radiation-induced errors, compatibility with different data types, flexibility w.r.t the architecture of the control and readout systems, are the key features of this novel protocol. Innovative radiation hardening techniques have been studied and implemented in the test-chip to ensure the proper functioning in operating environments with a high level of radiation, such as the Large Hadron Collider at CERN in Geneva. An FPGA-based emulator has been developed and, in a first phase, employed for functional validation of the protocol. In a second step, the emulator has been modified as test-bed to assess the Transmitter and Receiver interfaces embedded on the test-chip. An extensive phase of tests has proven the functioning of the interfaces at the three speed options, 4xF, 8xF and 16xF (F = reference clock frequency) in different configurations. Finally, irradiation tests has been performed at CERN X-rays irradiation facility, bearing out the proper behaviour of the interfaces up to 40 Mrad(SiO2)

The Effects of Spread-Spectrum Techniques in Mitigating Conducted EMI to LED Luminance

Rapid voltage and current changes in recently ubiquitous LED driver have a potency to interfere other devices. Solutions with special converter design, component design, EMI filter, and spread-spectrum techniques have been proposed. Due to cost-size-weight constraints, spread-spectrum technique seems a potential candidate in alleviating EMI problem in LED application. In this paper, the effectiveness of conducted EMI suppression performance of the spread-spectrum technique is evaluated. Spread-spectrum techniques applied by giving disturbance to the system LED driver with 3 profile signals, filtered square, triangular, and sine disturbance signal to the switching pattern of a buck LED driver. From the test results, 472.5 kHz triangular and 525 kHz sine signal can reduce EMI about 42 dBuV whilethe filtered square signal can reduce EMI 40.70 dBuV compare with fundamental constantfrequency reference 669 kHz. The average reduction in the power level of the third signal inthe frequency range of 199 kHz to 925 kHz for 5.154281 dBuV and the filtered square signal can reduce the average power level better than other signal disturbance of 5.852618 dBuV.LED luminance decrease when the spread-spectrum technique is applied to the system about 2814 lux

An Experimental Study of Conducted EMI Mitigation on the LED Driver using Spread Spectrum Technique

LED driver has the potential to interfere the system of electronic devices if the voltage and current change rapidly.  Several previous studies presented various solutions to overcome this problem such as particular converter design, component design, electromagnetic interference (EMI) filters, and spread-spectrum techniques. Compared to other solutions, the spread-spectrum technique is the most potential way to reduce the EMI in LED applications due to its limited cost-size-weight. In this paper, the effectiveness of conducted EMI suppression performance and the evaluation of its effect on LED luminance using spread-spectrum techniques are investigated. Spread-spectrum is applied to the system by modifying the switching frequency by providing disturbances at pin IADJ. The disorder is given in the form of four signals, namely square, filtered-square, triangular, and sine disturbance signals. The highest level of the EMI suppression of about 31.89% is achieved when the LED driver is given 800 mVpp filtered-square waveform. The highest reduction power level occurs at fundamental frequency reference, when it is given 700 mVpp square disruption signal, is about 81.77% reduction. The LED luminance level will reduce by 85.2% when it is given the four waveforms disruption signals.  These reductions occur as the switching frequency of the LED driver does not work on a fixed frequency, but it varies in certain bands. LED brightness level has a tendency to generate a constant value of 235 lux when it is given the disruption signals. This disturbance signal causes the dimming function on the system that does not work properly

Integrated circuits for efficient power delivery using pulse-width-modulation

Circuits and architectures for efficient power delivery have become crucial in emerging smart systems. Switching power amplifiers (PA) are very attractive for such applications, because they exhibit better efficiency compared to linear PA designs, due to saturated operation. Switching PAs also allow for utilization of deep submicron CMOS technologies, due to which these designs can be easily integrated with digital circuits, and can benefit from process scaling, in performance as well as in area. Pulse-width-modulation (PWM) is commonly used with switching PAs. A PWM signal typically employs a high-frequency switching pulse waveform as a carrier signal, wherein the pulse-width or duty-cycle of each pulse is modulated by a given low-frequency input signal. The carrier frequency can vary from several kHz to GHz, and is typically determined by the target application. In this thesis, efficient power-delivery circuits that use PWM with switching class-D stages are presented. Advanced circuit techniques, as well as architectures for PWM are proposed to enhance efficiency and circumvent the limitations of conventional architectures. A digitally-intensive transmitter using RF-PWM with a class-D PA is described in the first part of the thesis. The use of carrier switching for alleviating the dynamic range limitation that can be observed in classical RF-PWM implementations is introduced. The approach employs the full carrier frequency for half of the amplitude range, and the second harmonic of half of the carrier frequency, for the remainder of the amplitude range. This concept not only allows the transmitter to drive modulated signals with large peak-to-average power ratio (PAPR), but also improves the back-off efficiency due to reduced switching losses in the half carrier-frequency mode. A glitch-free phase selector is proposed that removes the deleterious glitches that can occur at the input data transitions. The phase-selector also prevents D flip-flop setup-and-hold time violations. The transmitter has been implemented in a 130-nm CMOS process. The measured peak output power and power-added-efficiency (PAE) are 25.6 dBm and 34%, respectively. While driving 802.11g 20-MHz 64-QAM OFDM signals, the average measured output power is 18.3 dBm and the PAE is 16%, with an EVM of -25.5 dB. The second part of the thesis describes a high-speed driver that provides a PWM output using a class-D PA. A PLL-based architecture is employed which eliminates the requirement for a precise ramp or triangular signal generator, and a high-speed comparator, which are typically used for PWM generation. Multi-level signaling is proposed to enhance back-off as well as peak efficiency, which is critical for signals with high PAPR. A differential, folded PWM scheme is introduced to achieve highly linear operation. 3-level operation is achieved without the requirement for additional supply source or sink paths, while 5-level operation is achieved with additional supply source and sink paths, compared to 2-level operation. The PWM driver has been implemented in a 130-nm CMOS process and can operate with a switching frequency of 40-to-170 MHz. For 2/3/5-level PA operation, with a 500 kHz sinusoidal input and 60 MHz switching frequency, the measured THD is -61/-62/-53 dB and corresponding efficiency is 71/83/86% with 175/200/220 mW output power level, respectively. Performance has also been verified for 2/3-level PA operation with a high PAPR signal with 500 kHz bandwidth. While intended as a general purpose amplifier, the approach is well-suited for applications such as power-line communications (PLC). The final part of the thesis introduces an efficient buck/buck-boost reconfigurable LED driver that supports PWM and PFM operation. The driver is based on peak current control. Rectified sin as well as sin² functions are employed in the reference signal to improve the power factor (PF) and total harmonic distortion (THD) of the buck and buck-boost converters. The design ensures that the peak of the inductor current maintains a constant level that is invariant for different AC line voltages. The operating mode of the design can be changed between PWM and PFM. The LED driver has been implemented in a 130-nm CMOS process. PF and THD are improved when the proposed reference is employed, and peak PF and lowest THD are 0.995/0.983/0.996 and 7.8/6.2/3.5% for the buck (PWM), buck (PFM), buck-boost (PFM) cases, respectively. The corresponding peak efficiency for the three cases is 88/92/91%, respectively.Electrical and Computer Engineerin

Challenges and New Trends in Power Electronic Devices Reliability

The rapid increase in new power electronic devices and converters for electric transportation and smart grid technologies requires a deepanalysis of their component performances, considering all of the different environmental scenarios, overload conditions, and high stressoperations. Therefore, evaluation of the reliability and availability of these devices becomes fundamental both from technical and economicalpoints of view. The rapid evolution of technologies and the high reliability level offered by these components have shown that estimating reliability through the traditional approaches is difficult, as historical failure data and/or past observed scenarios demonstrate. With the aim topropose new approaches for the evaluation of reliability, in this book, eleven innovative contributions are collected, all focusedon the reliability assessment of power electronic devices and related components