Compound Voltage Clamped Class-E Converter With ZVS and Flexible Power Transfer for WPT System

The class-E converter with soft-switching has been widely used in high-frequency wireless power transfer (WPT) system. However, the high voltage stress on the switch limits its application. In this article, a compound voltage-clamped class-E converter, consisting of an auxiliary clamped circuit and class-E converter, is proposed in the WPT system to solve the issue. Through impedance analysis, SP (series-parallel) resonance network is employed for the proposed converter to reach high transfer efficiency. Meanwhile, based on the analysis of voltage stress on the switches and the boundary condition for zero-voltage-switch (ZVS) operation, the optimal operation region could be obtained, leading to a reduced voltage stress and switching loss together. Moreover, as the conduction duty-cycle becomes a controllable freedom in the proposed converter, the relationship between conduction duty cycle and output power is given out, which makes power transfer more flexible while maintaining ZVS operation synchronously. Finally, a prototype was built to verify the performance of the proposed topology, and the experiments agreed well with the calculation.