A New Secondary Clamp Diode for Phase-Shift Full-Bridge Converter

In this paper, a new clamp diode for a phase-shift full-bridge (PSFB) converter is proposed. The conventional clamp diode for the PSFB converter is actively used in industry since it can reduce the voltage oscillation of the rectifier diode while maintaining the same operation as the PSFB converter. However, the conventional clamp diode requires an external inductor, and the deterioration by the large freewheeling clamping current of the clamp diode may also occur. Meanwhile, the proposed secondary clamp diode can clamp the rectifier diodes without an external inductor, and there is also no freewheeling problem of the clamping current. In addition, the proposed clamp diode can achieve clamping of all rectifier diodes with only one low current diode. Consequently, the proposed clamp diode operates with better performance. The feasibility of the proposed secondary clamp diodes has been verified with an 800W prototype under 270-400 V input and 48V output conditions.