相較於有線的充電方式，具有便利性和更安全的電感式無線電力傳輸系統已經被廣泛地使用在植入式的應用。在無線電力傳輸系統當中，有兩項設計指標尤為重要，分別為功率傳輸能力以及功率轉換效率。為了提升這兩項指標，過去的作法致力於提升傳送端或是接收端的效率。但是，無線電力傳輸系統的功率傳輸能力或是功率轉換效率會隨著耦合電路的參數誤差或是接收端的非線性操作，可能會有明顯的下降，而這將會造成充電時間過久以及過熱的問題。為了解決這些議題，本論文提出一具有可調整共振頻率之接收端電路設計。藉由在整流器之後置入一個開關，共振頻率可經由控制介面運作的逆電流量來調整。
設計並實作在0.18微米互補式金屬氧化物半導體製程，操作頻率在13.56百萬赫茲，量測結果顯示，相較於傳統被動式整流器架構的接收端設計，功率傳輸能力能提升至50%。當分別在傳送端和接收端的兩線圈耦合係數在0.04到0.11之間時，所提出的接收端電路可得到至少13.98毫瓦的功率輸出和26%的系統功率效率。在75歐姆的附載下，可達到31.33毫瓦的最大功率輸出和54.71%的最高系統功率效率。

Inductive-based wireless power transfer (WPT) system has been
widely used in implant applications with their convenience and
more safe operation compared to traditional charging method with
wire. Two design specifications are especially of great concern in
WPT system, which are power transfer capability (PTC) and power
conversion efficiency (PCE). In order to improve these two specifications, previous works have devoted to optimizing the efficiency of either the receiver or transmitter. However, the PTC or PCE of the WPT system may significantly degrade due to the variation of the coupling circuit parameters or nonlinear operation of the receiver, which resulting in long charging time and overheating problem. In order to solve these issues, a receiver design with adjustable resonant frequency is presented in this thesis. By inserting a switch after the rectifier, the resonant frequency can be tuned by controlling the amount of reverse current of the interface operation. Designed and fabricated in 0.18 mm CMOS process, with operating frequency of 13.56 MHz, measurement results show that the improvement of PTC can be up to 50 %, compared to conventional receiver design with passive rectifier structure. At least 13.98 mW of output power and 26 % of system power efficiency can be obtained with proposed receiver, when the coupling coefficient between two coils in transmitter and receiver is range from 0.04 to 0.11. The maximum output power of 31.33 mW and a peak system power efficiency of 54.71 % are achieved with 75 W loading.

Chapter 1 Introduction 1
Chapter 2 Inductive-Based Wireless Power Transfer System 5
Chapter 3 Receiver Design with Adjustable Input Impedance 39
Chapter 4 Measurement Results 72
Chapter 5 Conclusion 97

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