A Study on SiC Devices in Synchronous Rectification of DC-DC Converter

This paper shows the feasibility of synchronous rectification for SiC MOSFET in dc-dc converter applications. The SiC MOSFET is compared with the conventional Si MOSFET in dc characteristics to the gate voltage for forward and backward direction, at first. Then, their turn-on and turn-off switching characteristics are evaluated in single device operation. Finally, their operations in a practical circuit of dc-dc buck converter are experimented, and the feasibility of their operation in synchronous rectification are discussed. The body diode in SiC MOSFET shows less reverse recovery than the body diode in Si MOSFET. Then, SiC MOSFET gives superior performance in the synchronous rectification of high voltage dc-dc converter with fast switching. This paper also studies the effect of externally connected free-wheel SiC SBD in anti-parallel to MOSFET. The body diode of SiC MOSFET is comparable to the SiC SBD in the reverse recovery characteristics. The conduction loss in free-wheeling period can be reduced by the application of SiC SBD. They are confirmed in the dc characteristics and in the dc-dc buck converter operation.