This paper presents a novel ZVS bidirectional 1 kW class DC-DC converter used for a photovoltaic (PV) system. The proposed circuit is based on a boost&buckboost converter, which consists of a boost converter and a buckboost converter. Bidirectional soft switching is realized by using of coupled inductors and auxiliary switches in the circuit. From the analysis of the circuit operation, ZVS conditions of the switches are derived. In the experiment, the maximum efficiency of the proposed converter during forward power flow was 97.1% on output power of 320 W.

This paper presents a novel self-excited ZVS half-bridge converter. This converter including a self-oscillating control circuit is very simply constructed. The converter achieves excellent efficiency, low voltage stress across the switches and low EMI noise by using zero-voltage-switching technique. This converter stores not only magnetic energy in the primary winding of the transformer but also electrostatic energy on the resonant capacitor during the on-periods, so that the converter realizes the miniaturization of the transformer, the reduced conduction losses and the low current stress in the switch. This paper analyzes the behavior of static characteristics by using an extending state-space-averaging method and presents design equations. Based on the analysis, two prototype converters are designed for a 120 W output and a 350 W output. Experimental results are given for two converters and they confirm the validity of the theory. The proposed converters have displayed excellent performance.

This paper presents an analysis of the control characteristics of the series resonant converter with a parallel resonant circuit, especially under parallel resonant frequency. Operations of the circuit are classified into several modes. The control characteristics are calculated using the equations derived from equivalent circuits, and are verified by the experiments. From the analysis, the mechanism of a jumping phenomenon in the closed-loop control characteristics is clarified.