Efficiency Impacts of 1.2kV Silicon Carbide MOSFETs for Isolated Two-stage AC-DC Power Conversion

Abstract

SiC power semiconductor devices is utilized in an isolated two-stage AC-DC converter in order to increase the power conversion efficiency. The two-stage high frequency isolated three-phase rectifier topology is adopted as a case study to compare the efficiency with silicon and SiC devices. Synchronous rectification of SiC MOSFET is used for the first Boost PFC stage to reduce conduction loss. For the second DC-DC stage, a phase-shift full bridge soft switching converter circuit is adopted. The 1200V SiC MOSFET based DC-DC converter efficiency compares with 600V Silicon super junction MOSFET performance in input-series-output-parallel combined converters. All SiC device-based circuit achieves 4% more efficiency at light load, 2% at heavy load compared with Si devices for the Boost rectifier stage due to low switching loss and reduced conduction loss from the synchronous rectification operation for 1.2kV SiC MOSFET. SiC MOSFET provides 2.5% efficiency benefit at light load and 1.2% benefit at heavy load conditions for DC-DC converter stage with low switching and conduction loss. The two-stage high frequency isolated three-phase PFC rectifier circuit prototype test results show that 1.2% power efficiency improvement with all SiC power semiconductor devices compared with all Si power semiconductor devices.