Active zero voltage switching tracking controller design for class E inverter to counteract the resonant components shifting

On the basis of zero voltage switching (ZVS) operation, the class E resonant converter provides excellent conversion efficiency even though it works on high frequency. Unfortunately, the ZVS operation is sensitive to the circuit situations. While the circuit components are shifting, the ZVS working will drift around the dominant point and it may fail to work on ZVS. In this study, an active ZVS tracking control method is proposed to cope with the circuit components shifting. On the basis of an exact analysis of the ZVS operation conditions, first a searching procedure is proposed to decide the optimal switching frequency. Next, through the current phase feedback, the active ZVS tracking controller is built to retain the circuit works on optimum ZVS operation by adaptively tuning the switching frequency to counteract the components shifting. In addition to the theoretical analysis and computer simulation, the proposed tracking controller has been applied to implement a 1.3 MHz class E inverter with a field-programmable gate array (FPGA)-based controller.