Zero voltage switching performance of 1200V SiC MOSFET, 1200V silicon IGBT and 900V CoolMOS MOSFET

This paper evaluates zero voltage switching (ZVS) performance of 1200 V SiC MOSFET with respect to 1200 V silicon IGBTs (PT and FST) and 900 V CoolMOS MOSFET. The converter topology chosen for the study is a dual active bridge (DAB) dc-dc converter. Typically, in a high power DAB converter, ZVS is achieved through LC resonance of leakage inductance of the high frequency transformer and external capacitance across the drain and source (or collector and emitter for IGBTs) terminals. However, the SiC MOSFET offers a completely new set of parameters for ZVS when compared to its Silicon counterparts. In this paper, it is shown that a high power converter is possible with ZVS turn-on as well as low-loss turn-off using SiC MOSFETs, with out adding any external capacitance. The unique features of the SiC MOSFET that helps in achieving this are its CDS value, the variation of CDS with drain voltage, and low current turn-off time. The corresponding parameters of the silicon IGBTs and CoolMOS devices are presented to show the uniqueness of the SiC MOSFET. Simulation results corresponding to a 6 kW, 100 kHz DAB converter are presented with the SiC MOSFET as well as the silicon IGBTs and CoolMOS to provide a comparative ZVS performance.