臺灣博碩士論文加值系統

無線電力傳輸系統在近幾年逐漸成為了趨勢，同時擁有高功率又有高效率成為了最重要的課題。WPT系統中包括了發射端(TX)和接收端(RX)，其中TX端會因為負載變化以及傳輸距離長短所造成的反射阻抗變化而造成影響，進而使共振頻率點偏移，此對效率和功率有著相當嚴重的影響。基於上述，最直觀亦是最常見的方法就是變頻，但因為A4WP規範其頻率必須處在6.78百萬赫茲正負15千赫茲，除此之外，會將此問題轉移至RX端，導致接收端也要變換頻帶至發射端一致的頻率。接著另一個方法就是藉由電容陣列去補償反射阻抗所偏移的量，但隨著功率上升，和電容串聯的開關就必須是可以承受高壓的元件，以及此電容陣列佔據了相當大地印刷版電路的面積。
由於當功率開關上的電壓是硬切換或逆向導通時，效率會大幅下降，因此零電壓及零電壓斜率轉換是非常重要的。本文採用了一個由E類差動無線功率發射器做為TX端的主體架構，並使用了一個總是關閉的電晶體作為壓控電容對其作類比式的補償，除了可以解決上述開關上高壓的問題外，亦可以達到高效率以及高功率的實現。

Wireless power transmission systems have gradually become a trend in recent years, having high power and high efficiency has become an important issue. The WPT system includes a transmitting side (TX) and a receiving side (RX). When the TX end is affected by the change of the reflected impedance due to the load change and the length of the transmission distance, it will let the resonance frequency point shift and impacts the efficiency and power. Based on the above, the most intuitive and most common method is frequency tuning, but the frequency must be at 6.78 MHz ± 15 kHz by the A4WP specification. Besides, the RX side needs to tune the frequency to the corresponding band. Then another method is to compensate the reflected impedance by the capacitor array, but as the power rises, the switch in series with the capacitor must be a component that can withstand high voltage, and the capacitor array occupies a relatively large PCB area.
Since the switching state on the power switch is hard-switched or reverse-conducted, the efficiency is low, so zero-voltage-switching (ZVS) and zero-voltage derivate switching (ZVDS) is important. This paper uses a class-E differential wireless power transmitter as the main structure of the TX side, and use an always-off transistor as a voltage-controlled capacitor in the analogy compensation. It not only solves the above-mentioned high voltage on the switch but achieves high efficiency and high power.

摘 要 i
ABSTRACT ii
誌 謝 iii
Contents iv
Figure Captions vi
Table Captions vii
Chapter 1 Introduction 1
1.1 Background of Wireless Power Transfer system 1
1.1.1 Benefits of Wireless 2
1.2 Category of WPT system 3
1.2.1 Magnetic induction power transfer 3
1.2.2 Magnetic resonance power transfer 5
1.2.3 Microwave/RF wave power transfer 6
1.2.4 Comparison 7
1.3 Motivation 8
1.4 Thesis Organization 8
Chapter 2 Prior Arts and Design Goals 9
2.1 Efficiency degradation in WPT system 9
2.2 Structure of Power Amplifier used in WPT system 11
2.2.1 Class-D PA 12
2.2.2 Class-E PA 13
2.3 Tuning adjustments 14
2.3.1 Frequency modulation 14
2.3.2 Capacitor modulation 15
2.3.3 Duty control modulation 16
2.3.4 Fractional capacitance tuning modulation 17
2.4 Design Goals for the proposed 6.78MHz resonant WPT system 18
2.4.1 Choosing of PA 19
2.4.2 Choosing of power switch 19
Chapter 3 Circuit implementation of the propesed WPT system 22
3.1 Architecture of the proposed WPT system 22
3.2 Optimum operation of Class-E PA 23
3.3 Wrong conduction state in Class-E PA 25
3.4 Impedance matching network (IMN) 27
3.5 Voltage Controlled Capacitor (VCC) 31
3.6 Differential Class-E power amplifier 33
3.7 Differential dead-time control 34
3.8 Discrete components design 35
3.9 Closed-loop controller 36
3.9.1 Time-Based Matching point Searching (TBMS) 36
3.9.2 Charge Area Matching Point Searching (CAMS) circuit 38
3.9.3 Matching Bias Generator (MBG) circuit 40
Chapter 4 Experimental Results 42
4.1 Chip Micrograph 42
4.2 Measured TBMS technique 42
4.3 Measured CAMS technique 44
4.4 Comparisons of other WPT system methodologies 46
Chapter 5 Conclusion and Future Work 48
5.1 Conclusion 48
5.2 Future Work 48
Reference 49

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