Optimal DC-Link RC Snubber Design for SiC MOSFET Applications

This paper presents a design methodology for an optimal DC-link RC snubber that can effectively suppress the parasitic ringing in high-speed, hard-switched converters with modern SiC MOSFETs. Unlike the traditional RC snubber across the switch, a snubber across the DC-link dampens only the high-frequency ringing and doesn’t increase the switching loss. By analyzing a small-signal impedance network relating the time-domain ringing to the frequency-domain Bode plot, this work derives the R-C combination that achieves the best damping effect. Closed-form expressions are developed so that this method can be easily implemented in actual designs.