Operation analysis of a phase‐shifted full‐bridge converter during the dead‐time interval

Abstract

During the dead-time interval for a phase-shifted full-bridge (PSFB) converter, switches can achieve zero-voltage switching (ZVS) operation by using the energy stored in the transformer leakage inductance to discharge or charge the output capacitance of the switches. The value of dead-time has a great effect on ZVS range so it is a key parameter that needs to be optimised during designing the converter. This study develops theoretical analysis to estimate the dead-time as a function of load current for PSFB converter. The equivalent circuits of PSFB converter during the dead-time interval with considering magnetising inductance are mainly analysed in this study. Compared with previous analyses, the influences of dead-time on ZVS range and efficiency are discussed in detail. The analysis results show that the magnetising inductance of transformer can ensure ZVS over a wide range of load conditions, especially under discontinued current mode operation, without a penalty on the heavy-load efficiency. By adjusting the dead-time dynamically, both conduction and switching losses can be reduced. A 1 kW prototype is implemented and experimental results are consistent with the theoretical analysis.