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Tang Umd 0117E 16477.Pdf (7.578Mb) ABSTRACT Title of Document: MINIATURIZED POWER ELECTRONIC INTERFACES FOR ULTRA-COMPACT ELECTROMECHANICAL SYSTEMS Yichao Tang, Doctor of Philosophy, 2015 Directed By: Professor Alireza Khaligh, Department of Electrical and Computer Engineering Advanced and ultra-compact electromechanical (EM) systems, such as kinetic energy harvesting and microrobotic systems are deemed as enabling solutions to provide efficient energy conversion. One of the most critical challenges in such systems is to develop tiny power electronic interfaces (PEIs) capable of addressing power conditioning between EM devices and energy storage units. This dissertation presents technologies and topological solutions toward fabricating miniaturized PEIs to efficiently regulate erratic power/voltage for kinetic energy harvesting and drive high-voltage actuators for microrobotic systems. High-frequency resonant-switching topologies are introduced as power stages of PEIs that allow small footprint of the circuit without suffering from switching losses. Two types of bridgeless resonant ac-dc converters are first introduced and developed to efficiently convert arbitrary input voltages into a regulated dc output voltage. The proposed topologies provide direct ac-dc power conversion with less number of components, in comparison to other resonant topologies. A 5-mm×6-mm, 100- mg, 2-MHz and 650-mW prototype is fabricated for validation of capability of converting very-low ac voltages into a relatively higher voltage. A resonant gate drive circuit is designed and utilized to further reduce gating losses under high-frequency switching and light-load condition. The closed-loop efficiency reaches higher than 70% across wide range of input voltages and output powers. In a multi-channel energy harvesting system, a multi-input bridgeless resonant ac-dc converter is developed to achieve ac-dc conversion, step up voltage and match optimal impedance. Alternating voltage of each energy harvesting channel is stepped up through the switching LC network and then rectified by a freewheeling diode. The optimal electrical impedance can be adjusted through resonance impedance matching and pulse-frequency-modulation (PFM) control. In addition, a six-input standalone prototype is fabricated to address power conditioning for a six-channel wind panel. Furthermore, the concepts of miniaturization are incorporated in the context of microrobots. In a mobile microrobotic system, conventional bulky power supplies and electronics used to drive electroactive polymer (EAP) actuators are not practical as on-board energy sources for microrobots. A bidirectional single-stage resonant dc-dc step-up converter is introduced and developed to efficiently drive high-voltage EAP actuators. The converter utilizes resonant capacitors and a coupled-inductor as a soft-switched LC network to step up low input voltages. The circuit is capable of generating explicit high-voltage actuation signals, with capability of recovering unused energy from EAP actuators. A 4-mm × 8-mm, 100-mg and 600-mW prototype has been designed and fabricated to drive an in-plane gap-closing electrostatic inchworm motor. Experimental validations have been carried out to verify the circuit’s ability to step up voltage from 2 V to 100 V and generate two 1-kHz, 100-V driving voltages at 2-nF capacitive loads. MINIATURIZED POWER ELECTRONIC INTERFACES FOR ULTRA-COMPACT ELECTROMECHANICAL SYSTEMS BY YICHAO TANG Dissertation submitted to the Faculty of the Graduate School of the University of Maryland, College Park, in partial fulfillment of the requirements for the degree of Doctor of Philosophy 2015 Advisory Committee: Professor Alireza Khaligh, Chair/Advisor Professor Robert W. Newcomb Professor Isaak D. Mayergoyz Professor Behtash Babadi Professor Sung W. Lee, Dean’s Representative © Copyright by Yichao Tang 2015 ACKNOWLEDGEMENT I would like to express my sincere gratitude to my advisor, Dr. Alireza Khaligh, for his guidance, supervision and encouragement throughout my thesis research and dissertation process. He not only offers me invaluable support including research topic guidance, constructive technical advices and dissertation writing instructions, but also serves on my committee to improve this work. I would like to thank my mother, Ms. Zhiqing Wu, and my father, Mr. Pengrong Tang, for their invaluable support and continuous encouragement throughout my entire education and research program. I am also grateful to the other faculty members, Dr. Robert W. Newcomb, Dr. Isaak D. Mayergoyz, Dr. Behtash Babadi, and Dr. Sung W. Lee, for their attendance of my proposal exam and dissertation defense. I would also like to thank the research group of Power Electronics, Energy Harvesting & Renewable Energies Laboratory for their help and suggestions on my technical review and preliminary research. In addition, I would like to appreciate the kindness of Dr. Sarah Bergbreiter and her research group of Micro Robotics Laboratory for accessing their research facility. This work is sponsored partly by the Maryland Industrial Partnerships (MIPS) Grant and the Minta Martin Aeronautical Research Program, which are gratefully acknowledged. ii TABLE OF CONTENTS Page ACKNOWLEDGEMENT ....................................................................................... ii TABLE OF CONTENTS ......................................................................................... iii LIST OF TABLES ................................................................................................... v LIST OF FIGURES ................................................................................................. vi CHAPTER 1. INTRODUCTION ............................................................................................. 1 1.1. Description of Tiny Electromechanical Systems ........................................... 2 1.1.1. Kinetic Energy Harvesting .................................................................... 3 1.1.2. Autonomous Mobile Microrobots ........................................................ 8 1.2. Challenges of PEI Design and Miniaturization ............................................. 9 1.3. State of the Art of PEI Topologies for Energy Harvesting Generators ......... 10 1.3.1. Voltage Rectifiers of Dual-stage AC-DC Converters ........................... 10 1.3.2. Single-stage AC-DC Switching Converters ......................................... 13 1.3.3. PZ-specified Converters ....................................................................... 17 1.3.4. ES-specified Converters ....................................................................... 20 1.3.5. Soft-switching Converters .................................................................... 23 1.4. State of the Art of PEI Topologies for Driving High-voltage Actuators ....... 25 1.4.1. Single-stage Drive Converter ................................................................ 25 1.4.2. Dual-stage Drive Converter .................................................................. 27 1.4.3. Resonant Drive Converter .................................................................... 28 1.5. Fabrication Techniques toward PEI Miniaturization ..................................... 29 1.5.1. CMOS Technology ............................................................................... 29 1.5.2. Bare Die and Chip-scale Package ......................................................... 33 1.5.3. Micro-coil and Micro-core .................................................................... 37 1.6. Thesis Objective and Contribution ................................................................ 40 1.7. Dissertation Overview ................................................................................... 44 1.8. Summary .................................................................................................. 46 2. MINIATURIZATION OF POWER ELECTRONIC INTERFACES FOR TINY ELECTROMECHANICAL SYSTEMS ................................................. 47 2.1. Design of Bridgeless Resonant AC-DC Converters ...................................... 47 2.1.1. Circuit Description ................................................................................ 47 2.1.2. Principle of Switching Operation ......................................................... 50 2.2. Circuit Analyses of Resonant AC-DC Converters ........................................ 58 2.2.1. Steady-state Operating Characteristics ................................................. 58 2.2.2. Electrical Stresses ................................................................................. 64 iii 2.3. Gate Drive and Controller .............................................................................. 66 2.3.1. Resonant Gate Drive ............................................................................. 66 2.3.2. Module On/Off Control Strategy .......................................................... 69 2.4. Testing and Discussion .................................................................................. 73 2.4.1. Prototypes and Experimental Results ................................................... 73 2.4.2. Efficiency Analyses .............................................................................. 80 2.5. Summary ................................................................................................... 82 3. MINIATURIZED PEI DESIGN FOR MULTI-CHANNEL KINETIC ENERGY HARVESTING SYSTEMS ................................................................ 85 3.1. Electrical Model
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