Physical analysis and modeling of the nonlinear miller capacitance for SiC MOSFET

Parasitic capacitances of silicon carbide (SiC) MOSFET exert an significant influence on the switching performance with direct determination of the switching speed, switching loss and EMI noises, among which the nonlinear gate drain capacitance (Miller capacitance) dominates due to the well-known Miller effect. A precise and comprehensive model of the miller capacitance is proposed according to the structure of SiC DMOSFET at a physical level. Comparing with the traditional “switch model” of SIEMENS, the proposed model is more compact with less parameters while keeps the merit of precision. The detailed parameter acquisition procedure is also given by nonlinear fitting. In addition, the principle of the widely used “switch model” of SIEMENS is explained clearly, which is absent in other literature. The proposed model is verified on a commercial SiC MOSFET and a perfect matching is obtained between the modeled and measured C-V curve.