Accuracy of Three Interterminal Capacitance Models for SiC Power MOSFETs Under Fast Switching

This article presents a comprehensive analysis of nonlinear voltage-dependent capacitances of vertical silicon carbide power MOSFETs with lateral channel, focusing specifically on fast switching transients. The capacitance-voltage (C-V) device characteristics, (Cgs, Cgd, Cds), being dependent on both Vgsand Vds, are extracted by means of two-dimensional technology computer aided design simulations for a commercially available device in both off- and on-state modes. Different compact models for the power MOSFET are investigated, each employing a three interterminal capacitance model as typically used in power electronics. The performed analysis provides a detailed explanation for the importance of taking into account the dependence of Cgd, Cgs, and Cdson both of the voltages Vgsand Vds. This is especially important for fast switching transients (in the range of 10 ns) in order to accurately predict switching losses, driver losses, current, and voltage slopes, as well as current and voltage delays. As direct measurements for Cgd, Cgs, and Cdsin dependence of both Vgsand Vdsare highly demanding, the results presented in this article increase the understanding of both the underlying effects as well as of the tradeoffs between accuracy and computational complexity made by simplifying device models. In turn, this information is highly beneficial for enabling accurate and computationally efficient automated design procedures for power electronics.