Novel Switching Control Method for Full-Bridge DC-DC Converters for Improving Light-Load Efficiency Using Reverse Recovery Current

The phase-shift full-bridge DC-DC converter has been widely used for electric vehicles. However, the conversion efficiency is degraded under light-load conditions due to switching losses of the semiconductor switches on the high-voltage side of the converter. In this paper, a novel switching control method for full-bridge converters is proposed for improving the light-load efficiency. To reduce switching losses with the method, lagging-leg switches stop switching in the off-state under light-load. The proposed converter exhibits zero voltage switching for all switches with the use of a reverse recovery current in the body diode of lagging-leg switches. The effectiveness of the method was experimentally verified by using a 2.8-kW prototype converter. Experimental results show that the proposed method increases light-load efficiency by 33% at a load ratio of 3% compared with the conventional phase-shift control.