Design Method with High Precision CC and CV Charging for Wireless Power Transfer System

Existing constant current (CC) and constant voltage (CV) charging methods are prone to output fluctuations when the load resistance changes, which adversely affects the charging performance. This paper takes the parasitic resistance of the system into account and proposes a lightweight and high precision CC and CV control strategy suitable for wireless power transfer systems (WPT). The efficient transition between CC and CV modes can be achieved via frequency switching and the output fluctuation caused by load variations can be effectively suppressed via resonant inductance adjusting. Therefore, high system efficiency and high precision CC and CV output can be sustained. The reduced number of components and streamlined control strategies significantly enhance overall convenience. Finally, a 250W prototype with 5A CC charge current and 50V CV charge voltage is built. The experimental results demonstrate that the system achieves a peak efficiency of 92.5% and maintains an output precision less than 1% under various coupling conditions, thereby validating the effectiveness of the proposed design method.