Analysis and design of dual-half bridge converter operating in discontinuous conduction mode

Dual-half bridge (DHB) converter is a novel family of phaseshifted full-bridge (PSFB) converter, and it can obtain a significant improvement in conversion efficiency compared to the traditional PSFB converter. However, the main drawback of DHB converter is that only the energy stored in leakage inductor can be used to discharge the junction capacitors of switches. All switches tend to lose zero-voltage switching (ZVS) under light load conditions, which will significantly degrade efficiency. This paper proposes a simple and effective method to extend the ZVS range of DHB converter. By making the DHB converter operating in discontinuous conduction mode (DCM) and widening the dead-time, the energy stored in the magnetizing inductors of transformers can be used to discharge the junction capacitors. Without additional auxiliary components, the ZVS operation under light load conditions can be obtained. Experimental results confirm the validity of proposed method. key words: full-bridge converter; dual-half bridge converter; zerovoltage switching; discontinuous current mode; light load conditions. Classification: Power devices and circuits