Experimental Evaluation of SiC MOSFETs in Comparison to Si IGBTs in a Soft-switching Converter

SiC MOSFETs have shown superior characteristics to Si IGBTs, bringing in significant performance improvement such as enabling more compact, higher efficiency converters that are not feasible with conventional Si IGBTs. Currently, there is a lack of systematic and conclusive investigation into soft-switching inverters using SiC MOSFETs in comparison to Si IGBTs. This paper, therefore, presents a comparative evaluation of a soft-switching inverter, i.e. the auxiliary resonant commutated pole inverter (ARCPI) using SiC MOSFETs or Si IGBTs. The switching transition, switching device current stress, neutral point ripple current, electromagnetic interference (EMI), efficiency and cost are compared on identical ARCPI setups, i.e. with the same PCB and under identical driving conditions (gate drivers). Experimental results show that the ARCPI using SiC MOSFETs has better performance than that using Si IGBTs due to its faster switching speed. Firstly, the ARCPI using SiC MOSFETs performs full zero-voltage switching and the switching transition behaviour is more predictable. Unlike Si IGBTs, SiC MOSFETs have no turn-off tail current and forward voltage drop during switching transitions. Secondly, the ARCPI using SiC MOSFETs endures less current stress and smaller ripple current in dc-link capacitors. Thirdly, the ARCPI using SiC MOSFETs exhibits better EMI performance and higher efficiency. Specifically, a maximum 20 dBμV harmonic reduction can be achieved around 800 kHz and a 3.1% improvement in efficiency can be achieved at 6 kW. However, the cost analysis shows the cost of the ARCPI using SiC MOSFETs is about 80% higher than that of using Si IGBTs.