High Efficiency Loosely Coupled Wireless Power Transfer


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HIGH EFFICIENCY LOOSELY COUPLED WIRELESS POWER TRANSFER SYSTEM VIA MAGNETIC INDUCTION
By ZHEN NING LOW
A DISSERTATION PRESENTED TO THE GRADUATE SCHOOL OF THE UNIVERSITY OF FLORIDA IN PARTIAL FULFILLMENT
OF THE REQUIREMENTS FOR THE DEGREE OF DOCTOR OF PHILOSOPHY UNIVERSITY OF FLORIDA 2009 1

© 2009 Zhen Ning Low 2

To my parents and wife 3

ACKNOWLEDGMENTS I would like to thank my advisor Dr. Jenshan Lin for this wonderful opportunity to work under his guidance and mentoring. I have truly enjoyed working for him over the years acquiring technical knowledge as well as other soft skills. I would also like to thank Dr. William Eisenstadt, Dr. David Arnold and Dr. Sumi Helal for their time and being on my committee. I would like to thank my project teammates, both past and present for which without them this work will not be possible. They are: Joaquin Casanova for electromagnetic analysis and coil design; Jason Taylor for PCB design and fabrication; Raul Chinga for all the late night prototyping work; and Ashley Trowell for ferrites and shielding work. I would like to thank WiPower and Florida High Tech Corridor for funding this project. I would like to thank Linear Technology and Terry Decker for their support and evaluation boards. I would also like to thank Shannon Chillingworth and all of the personnel in the EE office. Finally, I would like to thank my wife for her encouragement and unconditional support when things get rough. Without her, this would not be possible.
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TABLE OF CONTENTS
page
ACKNOWLEDGMENTS.................................................................................................................... 4
LIST OF TABLES................................................................................................................................ 8
LIST OF FIGURES .............................................................................................................................. 9
ABSTRACT........................................................................................................................................ 15
CHAPTER
1 INTRODUCTION....................................................................................................................... 16
1.1 History of Wireless Power Transmission ........................................................................ 18 1.2 Modern Wireless Power Transmission ............................................................................ 20 1.3 Background Information................................................................................................... 23
1.3.1 Fundamental Theory of Operation via Phase Response.....................................23 1.3.2 Class D Power Amplifier ..................................................................................... 26 1.3.3 Class E Power Amplifier...................................................................................... 30
2 WIRELESS POWER TRANSFER SYSTEM .......................................................................... 38
2.1 Single-channel Class E Power Amplifier ........................................................................ 39 2.2 Multi-channels/Stackable Class E Power Amplifier....................................................... 41 2.3 Inductive Coupling............................................................................................................ 42 2.4 Impedance Transformation Network ............................................................................... 44 2.5 Receiver ............................................................................................................................. 47
3 DESIGN OF IMPEDANCE TRANSFORMATION NETWORK.......................................... 50
3.1 Series-Parallel Impedance Transformation Network ...................................................... 50 3.1.1 Introduction ........................................................................................................... 50 3.1.2 Determination of Crx value................................................................................... 53 3.1.3 Determination of Cout value.................................................................................. 58 3.1.4 Determination of Cshunt value ............................................................................... 59
3.2 Parallel-Parallel Impedance Transformation Network ................................................... 60 3.2.1 Introduction ........................................................................................................... 60 3.2.2 Determination of Crx value................................................................................... 61 3.2.3 Determination of Ctx value ................................................................................... 63 3.2.4 Determination of Cshunt value ............................................................................... 67
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4 WIRELESS POWER TRANSFER SYSTEM SUPPORTING MULTIPLE RECEIVERS ............................................................................................................................... 69
4.1 Inductive Coupling............................................................................................................ 69 4.2 Switch Design.................................................................................................................... 72 4.3 Switch Simulation ............................................................................................................. 76 4.4 System Response with Receiver Switch .......................................................................... 79
5 EXPERIMENTAL VERIFICATION ........................................................................................ 83
5.1 High Power 300W Dual Channel System using Parallel-Parallel Impedance Transformation Network Topology ................................................................................ 83
5.2 Low Power Multiple Receivers System with decoupling Switch using SeriesParallel Impedance Transformation Network Topology ............................................... 95
6 INTEROPERABILITY BETWEEN DIFFERENT PLATFORMS (COIL SIZES) .............104
6.1 Test Bench Setup.............................................................................................................105 6.2 Experimental Verification ..............................................................................................107
7 LOAD/FAULT DETECTION AND POWER DELIVERY TRACKING ...........................111
7.1 Load/Fault Detection Scheme ........................................................................................ 112 7.1.1 Detection Circuit.................................................................................................112 7.1.2 Detection Flowchart/Logic.................................................................................115
7.2 Experimental Verification ..............................................................................................117 7.2.1 Test Bench and Circuit .......................................................................................117 7.2.2 Experimental Results..........................................................................................122
7.3 Extension of Load/Fault Detection Scheme ..................................................................130 7.3.1 M:N Coupling Structure.....................................................................................130 7.3.2 Removing Lout from Transmitter .......................................................................139
8 RECEIVER VOLTAGE CONTROL ......................................................................................146
8.1 Varying Supply Voltage to Achieve Receiver Voltage Control ..................................147 8.2 Varying Operating Frequency to Achieve Receiver Voltage Control .........................152 8.3 Varying Cout to Achieve Receiver Voltage Control ......................................................157 8.4 Conclusion ....................................................................................................................... 160
9 SUMMARY AND FUTURE WORK .....................................................................................162
9.1 Summary.......................................................................................................................... 162 9.2 Future Work..................................................................................................................... 164
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APPENDIX: FCC REGULATIONS............................................................................................166 LIST OF REFERENCES ................................................................................................................. 169 BIOGRAPHICAL SKETCH ...........................................................................................................172
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LIST OF TABLES

Table

page

5-1 Component Values for High power 300W Dual Channel System using ParallelParallel Impedance Transformation Network Topology ..................................................... 84

5-2 Component Values for Low Power Multiple Receivers System with decoupling Switch using Series-Parallel Impedance Transformation Network Topology ...................96

6-1 Specification of the three different platforms.....................................................................105

6-2 Coupling parameters of nine possible combinations with first three as intended pairs...106

7-1 Component Values for Load/Fault Detection Test Bench.................................................118

A-1 FCC Part 18.307 conduction test limits ..............................................................................166

A-2 FCC Part 15.109 emission limits at 3 m range...................................................................167

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LIST OF FIGURES

Figure

page

1-1 Block diagram of the multiple receivers wireless power transfer system using inductive coupling. ................................................................................................................. 17

1-2 Complex plane of inductive and capacitive load. ................................................................ 24

1-3 Phasor diagram. ...................................................................................................................... 25

1-4 Class D power amplifier. ....................................................................................................... 26

1-5 Class E power amplifier......................................................................................................... 31

2-1 Wireless power transfer system diagram. ............................................................................. 38

2-2 Schematic of the dual-channel Class E power amplifier. .................................................... 41

2-3 Topologies for a single-element impedance transformation network.................................45

2-4 Input voltage of a half wave rectifier and a full wave rectifier. .......................................... 48

3-1 Windings of a 20cm x 20cm transmitting coil used for experimental verification............51

3-2 Normalized power deliver with respect to location of transmitting coil in Figure 3-1 using a receiving coil of 9 cm x 6 cm. .................................................................................. 52

3-3 Simplified schematic of wireless power transfer system using series-parallel impedance transformation network and Class E transmitter. Ztx – Impedance looking into the transmitter load network. Ztxcoil – Impedance looking into the transmitting coil. Zrx – Impedance looking into receiver network. RLoad is the equivalent resistance looking into the rectifier. ....................................................................................................... 53

3-4 Resistance and reactance of Zrx versus load resistance at different with different Crx. (50 nF, 100 nF and 150 nF) ................................................................................................... 54

3-5 Peak resistance response looking into the transmitting coil with respect to Crx. ...............56 3-6 Resistance and reactance looking into the transmitting coil. .............................................. 56

3-7 Coupling efficiency with respect to load resistance............................................................. 57

3-8 Ztx phase response with respect to load resistance for various Cout capacitance values. ...58 3-9 Transistor drain voltage waveform for different load resistance. (Cshunt = 10 nF).............59

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3-10 Simplified schematic of wireless power transfer system using parallel-parallel transformation network and Class E transmitter. Ztx – Impedance looking into the transmitter load network. Ztxcoil – Impedance looking into the transmitting coil. Zrx – Impedance looking into receiver network. RLoad is the equivalent resistance looking into the rectifier. ..................................................................................................................... 61
3-11 Optimum receiver capacitor value versus load resistance................................................... 61 3-12 Coupling efficiency and transformed impedance looking into the transmitting coil.........63 3-13 Reactance of Ztxcoil versus load resistance with different Ctx. ............................................. 65 3-14 Amplitude and phase of impedance of unloaded Ztx versus Ctx.......................................... 66 3-15 Rtx and Xtx versus load resistance. (Ctx: 105 nF).................................................................. 66 3-16 Phase of Ztx versus load resistance. (Ctx: 105 nF) ................................................................ 67 3-17 Transistor drain voltage waveform for different load resistance. (Cshunt = 19 nF).............67 4-1 Power delivery to loads for a single receiver setup and a dual receivers setup with
one of the load fixed at 1000Ω. ............................................................................................ 71 4-2 Block diagram of the proposed switch.................................................................................. 72 4-3 Schematic of the proposed switch circuit. ............................................................................ 74 4-4 Schematic of the improved proposed switch circuit. ........................................................... 75 4-5 Schematic of the switch in Advanced System Design with a resistive as load..................76 4-6 Switch control waveform (0 V for off and 3 V for on). A minimum of 1 V is required
to turn on the transistor. ......................................................................................................... 77 4-7 Generated switch control waveforms.................................................................................... 78 4-8 Output waveform of the switch before the rectifier. ............................................................ 79 4-9 Proposed half-wave rectifier receiver architecture. ............................................................. 79 4-10 ADS schematic of test bench for receiver architecture in Figure 5-10...............................81 4-11 Simulation results of test bench (Figure 4-10). Red: Low voltage control
signal.Black: Receiver rectified voltage. .............................................................................. 82 5-1 Photograph of the dual-channel Class E power amplifier. .................................................. 85 5-2 Photograph of the transmitting coil – 10 turns (embedded into the table top) and
receiving coil – 5 turns (placed on top). ............................................................................... 85
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High Efficiency Loosely Coupled Wireless Power Transfer