A novel self-excited ZVS half-bridge converter with energy stored transformer and capacitor

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.