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

Energy efficient control for power management circuits operating from nano-watts to watts

Thesis (Ph. D.)--Massachusetts Institute of Technology, Dept. of Electrical Engineering and Computer Science, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (p. 163-172).Energy efficiency and form factor are the key driving forces in today's power electronics. All power delivery circuits, irrespective of the magnitude of power, basically consists of power trains, gate drivers and control circuits. Although the control circuits are primarily required for regulation, these circuits can play a crucial role in achieving high efficiency and/or minimizing overall system form-factor. In this thesis, power converter circuits, spanning a wide operating range- from nano-watts to watts, are presented while highlighting techniques for using digital control circuits not just for regulation but also to achieve high system efficiency and smaller system form-factor. The first part of the thesis presents a power management unit of an autonomous wireless sensor that sustains itself by harvesting energy from the endo-cochlear potential (EP), the 70-100mV electrochemical potential inside the mammalian inner ear. Due to the anatomical constraints, the total extractable power from the EP is limited to 1.1-6.3nW. A low switching frequency boost converter is employed to increase the input voltage to a higher voltage usable by CMOS circuits in the sensor. Ultra-low power digital control circuits with timers help keep the quiescent power of the power management unit down to 544pW. Further, a charge-pump is used to implement leakage reduction techniques in the sensor. This work demonstrates how digital low power control circuit design can help improve converter efficiency and ensure system sustainability. All circuits have been implemented on a 0.18[mu]m CMOS process. The second part of the thesis discusses an energy harvesting architecture that combines energy from multiple energy harvesting sources- photovoltaic, thermoelectric and piezoelectric sources. Digital control circuits that configure the power trains to new efficient system architectures with maximum power point tracking are presented, while using a single inductor to combine energy from the aforementioned energy sources all at the same time. A dual-path architecture for energy harvesting systems is proposed. This provides a peak efficiency improvement of 11-13% over the traditional two stage approach. The system can handle input voltages from 20mV to 5V and is also capable of extracting maximum power from individual harvesters all at the same time utilizing a single inductor. A proposed completely digital timebased power monitor is used for achieving maximum power point tracking for the photovoltaic harvester. This has a peak tracking efficiency of 96%. The peak efficiencies achieved with inductor sharing are 83%, 58% and 79% for photovoltaic boost, thermoelectric boost and piezoelectric buck-boost converters respectively. The switch matrix and the control circuits are implemented on a 0.35pm CMOS process. This part of the thesis highlights how digital control circuits can help reconfigure power converter architectures for improving efficiency and reducing form-factors. The last part of the thesis deals with a power management system for an offline 22W LED driver. In order to reduce the system form factor, Gallium Nitride (GaN) transistors capable of high frequency switching have been utilized with a Quasi-Resonant Inverted Buck architecture. A burst mode digital controller has been used to perform dimming control and power factor correction (PFC) for the LED driver. The custom controller and driver IC was implemented in a 0.35[mu]m CMOS process. The LED driver achieves a peak efficiency of 90.6% and a 0.96 power factor. Due to the high power level of the driver, the digital controller is primarily used for regulation purposes in this system, although the digital nature of the controller helps remove the passives that would be normally present in analog controllers. In this thesis, apart from regulation, control circuit enabled techniques have been used to improve efficiency and reduce system form factor. Low power design and control for reconfigurable power train architectures help improve the overall power converter efficiency. Digital control circuits have been used to reduce the form factor by enabling inductor sharing in a system with multiple power converters or by removing the compensator passives.by Saurav Bandyopadhyay.Ph.D

Channel Estimation, Modulation Techniques and Decoding Algorithms for Hybrid WiFi-FSO (WiFO) WLAN of Femtocells

Due to the limitation of the radio frequency (RF) spectrum, it is increasingly more difficult to support billions of wireless devices in the age of Internet-of-Things. Consequently, many recent wireless indoor communication systems have been developed using free space optical (FSO) communication technologies that exploit the extremely large light spectrum to transmit data. This dissertation contributes three physical layer techniques to an FSO system called WiFO, which is integrated with the existing WiFi transmission. (1) We proposed a Pulse Amplitude Modulation (PAM) decoding scheme that estimates the channel parameters and determine the optimal decoding thresholds to minimize the average bit error rate (BER). The conditions on channel parameters for which signal recovery is impossible, are also determined. (2) A pre-shaping technique called Adaptive Sending Duration Algorithm (ASDA), that modifies the durations of input bits dynamically, is proposed to be used at an LED-transmitter. Simulation results show that ASDA working with equalization successfully improves the performance of BERs. (3) We propose a decoding scheme called Memory Decoding Algorithm (MDA) used at a receiver and show that it effectively reduces the bit error rates via maximum likelihood decoding principle

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

Автоматизированные системы освещения на основе светодиодных излучателей

В работе проведён литературный обзор современных систем управления освещением и применяемых в них источников света. В процессе исследования были выявлены преимущества и недостатки систем освещения и выбрано оптимальное решение для контроля осветителя на основе светодиодов. В работе была разработана интерфейсная схема управления светом на основе цифрового интерфейса DALI, и реализовано программное обеспечение на основе микропроцессорного модуля Raspberry Pi.A literary review of modern lighting control systems and the light sources used in them was carried out in the work. During the study, the advantages and disadvantages of lighting systems were identified and the optimal solution for controlling the illuminator based on LEDs was selected. In the work, a light control interface circuit based on the DALI digital interface was developed, and software based on the Raspberry Pi microprocessor module was implemented

Integrated Daylighting and Artificial Lighting Control based on High Dynamic Range Vision Sensors

One fifth of the electricity consumption of Swiss buildings is due to electric lighting. Integrated control of sun shading and artificial lighting can mitigate this demand while maintaining user comfort. However, the drawback of existing building control approaches is that they do not consider one of the main aspects of human-centric lighting: visual comfort. The goal of this doctoral thesis is to develop an integrated energy efficient sun shading and electric lighting control system that incorporates widely accepted visual comfort criteria and privileges daylighting over electric lighting. The first part is dedicated to High Dynamic Range (HDR) vision sensor calibration, programing, validation and preliminary testing. A sensor originally developed by the Centre Suisse dâElectronique et de Microtechnique (CSEM) was photometrically, spectrally and geometrically calibrated and validated with respect to reliable illuminance and multi-point luminance meters. This HDR vision sensor was then equipped with an embedded image processing routine in order to assess âon the flyâ discomfort glare indices. It has been demonstrated that the developed device, is able to serve as an enhanced visual comfort feedback sensor in building automation systems. On the other hand, it can be employed to characterize highly glazed facades and workspaces regarding visual comfort and glare risks, as demonstrated in a project in Singapore. Two monitoring campaigns are reported in the second part of this thesis. Firstly, 30 human subjects occupied two identical office rooms of the LESO solar experimental building for 15 afternoons to compare the performance of a fuzzy logic control system incorporating two HDR vision sensors with respect to a âbest-practiceâ controller. Subjective self-reported visual comfort surveys, paper- and computer-based visual tests and monitoring of the electric lighting consumption were carried out simultaneously in both offices. It was shown that the electricity demand of the office with the advanced controller is 32% lower than that of the reference room, while the subjectsâ visual performance remained comparable. Secondly, an eight-month data monitoring campaign was carried out in the same building in order to study the ability of a novel control approach to maintain optimal visual and thermal comfort conditions while reducing the energy performance gap of a room as well as its electric lighting demand. The experimental results showed that the advanced controller mitigated the performance gap during the heating season by 72% with regard to standard occupant behavior and by 19% with respect to a best-practice automated system. This system reduced backup heating demand leading to lower CO2 gas emissions. At the same time, visual comfort constraints regarding Daylight Glare Probability (DGP) and workplane horizontal illuminance were respected during work hours. Finally, a self-commissioning integrated controller for Venetian blinds enhanced with a learning module was developed and validated for 22 days in a daylighting testbed at the Fraunhofer Institute for Solar Energy (ISE) in Freiburg, Germany. It has been shown that the visual comfort constraints are respected for 96% of the work hours and that the controller can successfully limit the number of shading movements. The market potential for HDR vision sensors and integrated control platforms has been studied and possible commercialization tracks have been identified

Advanced Trends in Wireless Communications

Physical limitations on wireless communication channels impose huge challenges to reliable communication. Bandwidth limitations, propagation loss, noise and interference make the wireless channel a narrow pipe that does not readily accommodate rapid flow of data. Thus, researches aim to design systems that are suitable to operate in such channels, in order to have high performance quality of service. Also, the mobility of the communication systems requires further investigations to reduce the complexity and the power consumption of the receiver. This book aims to provide highlights of the current research in the field of wireless communications. The subjects discussed are very valuable to communication researchers rather than researchers in the wireless related areas. The book chapters cover a wide range of wireless communication topics

Energy Efficiency

This book is one of the most comprehensive and up-to-date books written on Energy Efficiency. The readers will learn about different technologies for energy efficiency policies and programs to reduce the amount of energy. The book provides some studies and specific sets of policies and programs that are implemented in order to maximize the potential for energy efficiency improvement. It contains unique insights from scientists with academic and industrial expertise in the field of energy efficiency collected in this multi-disciplinary forum