Exactly analysis of ZVS behavior for class E inverter with resonant components varying

Abstract

Class E resonant power amplifier (or inverter) is often applied to design a high frequency switching power converter. The zero voltage switching (ZVS) or zero current switching (ZCS) operation leads the converter to high converting efficiency even the converter works at high frequency. Theoretically, with a high speed power transistor, the class E amplifier can work from several megahertzes to dozen of megahertzes. While the resonant components of class E inverter are varying, the ZVS operation will be shifting around the dominant operating point. In this paper, an exact circuit model is proposed to analyze the circuit behavior for the class E inverter. Unnecessarily mathematical assumption and complicated numerical iteration, the proposed model is easy to analyze the class E circuits in frequency domain. Through this model, a close form formula is proposed to solve the load current and drain-source end voltage of MOSFET at switching instants for steady state without a complicated numerical iterating. By this formula, the optimal and suboptimal conditions for the ZVS operation are expressed in terms of the shifting angle of load current with respect to drain-source voltage. Also, some practical design examples are given to demonstrate the formula calculating results that are good agreement with the numerical iterating results.