Switch-controlled capacitor (SCC) is a kind of variable capacitor with the merits of steplessly variable capacitance, soft-switching and small size. This paper applies SCC to both transmitter (TX) and authorized receivers (RXs) to implement a dual-side tuning encrypted wireless power transfer (WPT) system. Compared with the single-side tuning system where only authorized RXs are tuned, the proposed system is advanced in power transfer efficiency and output power because frequency matching of authorized power channels can be fully achieved. Moreover, A charge increment ratio (CIR) method is proposed to calculate the equivalent capacitance of SCC. Compared with the traditional fundamental wave approximation (FWA) method, the calculation result of proposed method is more accurate because of the absence of any approximation during derivation process, which leads to more precise tuning and higher efficiency. In addition, an explicit expression can be obtained by the CIR method which is much simpler than FWA method where numerical computation is needed. So CIR method is suitable for online real-time computing. The effectiveness of proposed method has been proved by theoretical analysis, simulations, and experiments.

dual-side tuning; encrypted WPT; equivalent capacitance calculation; steplessly variable capacitor.