近年來，無線充電一直是眾人熱烈討論的新穎技術。過往有關電路部分的研究大多假設兩線圈完美地共振在操作頻率上，並著墨於如何解決線圈之間距離拉長而使接收端收到的能量降低，避免輸入端峰值電壓降低的情況下造成後端電路無法正常操作。然而，製造過程中所產生的非理想變異會使得線圈的共振頻率偏離操作頻率，並降低整體系統的表現與所得功率。本篇論文中，我們提出了一種新式接收端介面設計，利用時間點來控制接收端的運作與調整介面上的有效負載。此外，藉由控制介面電壓與迴路電流之間的相位差，我們成功地在迴路中做到共軛複數阻抗匹配，並達成最大功率傳輸。在接收端介面架構中，我們採用一改良後的直接交流-直流升壓轉換器，使用主動式二極體開關並減少傳輸路徑上所使用的開關數量，在10mW的輸入功率下達成70%的功率轉換效率。我們整體電路是採用台積電0.18μm CMOS製程進行設計。在6.78MHz的操作頻率下，模擬所得最大功率傳輸效率最大可至94%，交流-直流升壓轉換器最大的轉換效率為66%，而最終輸出端所得功率為6mW。

In recent years, wireless power transfer (WPT) has become a popular technology. Most prior work focuses on how to maintain the operation when the distance between coupling coils become larger by assuming that the coupling coils are perfectly resonating at operating frequency. However, frequency mismatch due to process variations decreases the system performance and the received power. In this work, we propose a new receiver interface that adjusts the effective loading at the power receiving interface with timing control of the receiver operation. Furthermore, by controlling the relative phase shift between the interface voltage and loop current, we achieve complex-conjugate impedance matching and therefore maximum power transfer. For the interface architecture, we adopt an improved direct AC-DC boost converter. The reduced number of switches in the power path along with the use of active diodes results in a power conversion efficiency of 70% at input power of 10mW. This interface circuit is designed in TSMC 0.18μm CMOS process. Operating at 6.78MHz, the simulated maximum power transfer efficiency and conversion efficiency are 94% and 66%, and the output power is 6mW.

1 Introduction.............................................1
2 WPT System Interface.....................................7
2.1 Tx/Rx Resonant Coils Design and Considerations.........8
2.1.1 Circuit Model Analysis...............................9
2.1.2 Design Considerations................................11
2.2 Impedance-Adjustable Receiver for Wireless Power Transfer System.....15
3 Circuit Design and Implementation........................26
3.1 Proposed Direct AC-DC Converter........................26
3.2 Control Circuit........................................31
3.3 Timing Controller......................................32
3.3.1 Controllable Delay...................................34
3.3.2 Differentiator.......................................35
3.4 Active Diode Controller................................36
4 Simulation Results.......................................38
4.1 Chip Layout............................................39
4.2 Pre and Post-Layout Simulation.........................40
4.3 Comparison.............................................44
5 Conclusion...............................................46
Bibliography...............................................47

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