Performance comparison of 3-phase DC/AC converters using SiC MOSFETs or SiC BJTs

Abstract

The superior electrical and thermal properties of silicon carbide (SiC), when compared to silicon (Si), has lead to it being used in power converter designs that require high efficiency and low volume. However while choosing the semi-conductor material for these high performance designs is relatively simple, the specific type of SiC device (e.g. JFET, MOSFET or BJT) is not so straight-forward. This paper compares the performance of 2-level, 3-phase DC/AC converters that were constructed with SiC MOSFETs and then SiC BJTs. From this comparison it was shown that the SiC BJT converter, using proportional regenerative gate drivers, produced results similar to the MOSFET converter whose gate drivers had an RG = 12.5Ω. The results also showed that the SiC MOSFETs could be successfully driven with zero gate resistance and the reverse recovery energy losses of the MOSFET's body diode were minimal indicating that there is no need for an additional external Schottky diode unlike the SiC BJT.