Constant Voltage Charging and Maximum Efficiency Tracking for WPT Systems Employing Dual-Side Control Scheme

The wireless power transfer (WPT) system has been gradually integrated into our daily applications due to its advantages of security, esthetics, and convenience. Generally, for a complete WPT system, two main goals need to be achieved: one is the constant voltage (CV) output and the other is the highest possible transfer efficiency. However, the highest possible transfer efficiency is difficult to achieve when the WPT system maintains the CV output against the time-varying load resistance and coupling coefficient. In this article, a new dual-side control scheme that employs transmitter-side high-frequency inverter (HFI) and receiver-side semi-active rectifier (SAR) is proposed to simultaneously achieve the CV output and maximum efficiency tracking (MET) control regardless of the variable load resistance and coupling coefficient. It is proved that the system can obtain the maximum transfer efficiency when the derivative of $\sin (\alpha /2)$ with $\sin (\beta /2)$ is a specific constant, which is determined by self-resistances of transceiver coils and system input and output dc voltage. In the above derivative, $\alpha $ and $\beta $ are phase shift angles of the HFI and SAR, respectively. The CV output is maintained by adjusting $\beta $ , while the MET control is performed by continuously adjusting $\alpha $ . A confirmatory experimental setup with the charging voltage of 72 V is built, and the experimental results fully prove the correctness and effectiveness of the proposed scheme.