Review of Tuning Methods in Wireless Power Transfer Systems

Misalignment between the transmitter and receiver coils, manufacturing tolerance and temperature drift of the compensation capacitors in a wireless power transfer (WPT) system will inevitably affect its performances, such as efficiency, output power, zero voltage switching (ZVS) operation, and voltage and/or current stresses of the power semiconductor devices. The impedance detuning is the essence of the system performance deterioration. Therefore, it is mandatory to detect and regulate the resonant condition of the WPT system in real time. This manuscript provides a current state of art review of all available impedance tuning methods. The variable operation frequency control and resonant frequency regulation of the compensation topology are the two basic solutions. And their working principles and inherent characteristics are analyzed qualitatively and compared. Some topics worthy of research are also suggested to make contribution to the development and commercial applications of the wireless charging technique.