臺灣博碩士論文加值系統

無線電力傳輸系統的技術在近年來逐漸提升，眾多的商用電子設備對於功率上有著更大的要求，因此，高功率且高效率便成了一個重要的課題。在無線電力傳輸系統中包含了發射端及接收端，傳輸的過程中，負載及相對距離的改變皆會影響傳輸的功率及效率，最常見的解決方法為變頻，然而此方式將會牴觸A4WP對於頻率的規範(fSW=6.78MHz±15KHz)，而另一種直覺的做法為利用數個補償電容以數位方式去諧調傳輸線圈以達到匹配的要求，不幸地，為了在高功率的要求下抵抗寬的負載變動，此種調變方法必須搭配多組高壓開關及補償電容，將會占據較大的PCB面積並降低控制效率。本文提出了採用切換式E類功率放大器配合氮化鎵功率電晶體作為發射端的主架構，輔以控制電路使得氮化鎵功率電晶體達成零電壓切換及零電壓導數切換，使得電力傳輸能夠同時達到高功率及高效率的要求，此外，相較於前述兩種方法，本文所採用之壓控補償電容為類比式的諧調方法，控制上較為簡易且節省大量面積。

Wireless power transfer system (WPT) technology in recent years gradually improves. A large number of commercial electronic equipment have great demands for high power. Thus, high power and high efficiency become an important issue. WPT system includes transmitter (TX) and receiver (RX). During the transmission, the changes of load and the relative distance affect transmission power and efficiency. Generally speaking, the most common solution is the frequency modulation technique but it contradicts the switching frequency requirement in the A4WP specifications. That is, the modulated frequency is far from the desired switching frequency which is defined as 6.78MHz ± 15kHz. Another intuitive practice is to use a number of compensation capacitors to digitally modulate and achieve the matching requirements corresponding to the variations of WPT system. Unfortunately, in order to resist wide load variation in high power demands, this modulation method must be combined with multiple high voltage switches and compensation capacitors, thereby occupying a larger footprint area and reducing control efficiency. In this thesis, a main structure with a Class-E power amplifier and a Gallium Nitride (GaN) power transistor used at the TX terminal are proposed. The control circuit causes the GaN power transistor to reach zero voltage (ZVS) switching and zero voltage derivative (ZVDS) switching. The power transmission achieves high power and high efficiency simultaneously. Moreover, compared with the state-of-the-arts, due to the voltage controlled compensation capacitor in the analogy modulation method, the control is relatively simple and area efficient.

摘 要 i
ABSTRACT ii
誌 謝 iii
Contents iv
Figure Captions vi
Table Captions viii
Chapter 1 Introduction 1
1.1 Background of Wireless Power Transfer (WPT) system 1
1.1.1 Benefits of Wirelss 2
1.2 Category of Wireless Power Transfer (WPT) system 3
1.2.1 Toghtly coupled magnetic induction power transfer 3
1.2.2 Loosely coupled magnetic resonance power transfer 4
1.2.3 Microwave/RF wave power transfer 5
1.2.4 Comparison 5
1.3 Motivation 6
1.4 Thesis Organization 6
Chapter 2 Prior Arts and Design Goals 7
2.1 Efficiency degradation in WPT system 7
2.2 Structure of Power Amplifier used in WPT system 9
2.2.1 Class-D PA 9
2.2.1 Class-E PA 11
2.3 Tuning adjustments 12
2.3.1 Frequceny modulation 12
2.3.2 Capacitor modulation 13
2.3.3 Duty control modulation 14
2.4 Design Goals for the proposed 6.78MHz resonant WPT system 15
2.4.1 Choosing of PA 15
2.4.2 Choosing of power switch 16
Chapter 3 Circuit implementation of the proposed WPT system 17
3.1 Architecture of the proposed WPT system 17
3.2 Optimum operation of class-E PA 18
3.3 Efficiency failure in class-E PA 21
3.4 Impedance matching network (IMN) 22
3.5 Voltage Controlled Capacitor (VCC) 25
3.6 Closed-loop controller 26
3.6.1 AMPS control loop 26
3.6.2 Variable slope voltage biasing (VSVB) circuit 28
3.6.3 ALCC control loop 31
3.7 Ringing voltage suppression (RVS) technique 36
Chapter 4 Experimental Results 36
4.1 Chip micrograph 36
4.2 Measured RVS technique 37
4.3 Measured AMPS and ALCC control loops 38
4.4 Comparisions of other WPT system methodologies 42
Chapter 5 Conclusion and Future Work 44
5.1 Conclusion 43
5.2 Future work 43
Reference 44

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