Comparison between ig integration and vgs derivation methods dedicated to fast short-circuit 2D diagnosis for wide bandgap power transistors

This study presents and compares two original high-speed protection circuit methods, namely, ig integration and vgs derivation, against short-circuit types, referred to as, the hard switch fault and fault under load. Since the gate–drain capacitor Cgd of a power device depends on the drain to source voltage vds, it can become an original native sensor to monitor the switching operation and so detect the unwanted vds transition or the absence of the vds transition by monitoring only vgs. The use of only low-voltage monitoring, such as vgs, is an essential step to integrate fast and embedded new detection methods into a low-voltage application-specific integrated circuit gate driver, in particular for wide bandgap power transistors. The Cgd capacitor plays a major part in the two detection methods. The first method is based on dedicated two-dimensional monitoring of the gate charge transferred in a time interval combined with gate voltage monitoring. The second method consists of the reconstruction of the dvgs/dt by means of a capacitive current sensing to provide the vgs derivation combined with the vgs monitoring. Comparison and simulation of the methods based on a C2M0025120D SiC MOSFET device under LTspice™ are made to verify the validity of the methods. In terms of detection speed of the short circuit, a detection time of 200 ns is obtained for both methods. Experimental waveforms based on C3M0120090J SiC MOSFET device were included into LTspiceTM to push furthermore the methods to their limits and validate the approaches. Both methods are easy to design and to integrate. However, the robustness and the speed of detection trade-off of all these methods should be analysed and compared relative to the critical functionalities.