Novel Switching Control Method for Synchronous Rectifier of Phase-Shifted Full-Bridge Converter in Light-Load Conditions

This paper proposes the new switching control method for the synchronous rectifier (SR) of phase-shifted full-bridge (PSFB) converter in light-load conditions, where it usually operates in discontinuous conduction mode (DCM) to reduce the effective duty ratio and core loss caused by reverse current. However, it has the problem that the current flows through the body diode instead of the channel of SR. This causes undesirable conduction loss. The proposed switching control method of SR reduces the conduction loss by optimizing its turn-on time to minimize the conduction ranges of body diode without an auxiliary circuit. In particular, its boundary condition and loss calculation is mathematically analyzed. Then, its practical effectiveness is verified by experimental tests based on hardware implementation for the PSFB converter of 400 W.