Leg Integrated Phase Shift Full Bridge Converter with Extended Zero Voltage Switching Range

Abstract

Paper proposes a leg-integrated method to extend ZVS(Zero Voltage Switching) range in a PSFB(Phase Shift Full Bridge) converter. The proposed PSFB converter shares all switch legs that implement 3 PSFB converters in 3 switch legs, and all switch legs are integrated legs. Therefore, all switch legs are treated as leading legs, so the leakage inductance less affects the ZVS. Hence, ZVS is possible even if the leakage inductance is significantly reduced in the light load condition. Therefore, duty cycle loss and the secondary voltage spike are reduced, so a voltage spike reduction circuit can be simply designed. In addition, the current cancellation effect occurs in integrated legs, reducing the RMS current, and the output current ripple can also be reduced because it automatically operates interleaved. Based on these characteristics, the proposed method can achieve improving its efficiency not only in light load but also in heavy load. A simulation is conducted to explain the proposed circuit’s effect.