A fast short-circuit protection method using gate charge characteristics of SiC MOSFETs

This paper describes a fast protection circuit for silicon carbide metal-oxide semiconductor field-effect transistors (SiC MOSFETs) subjected to hard-switching faults (HSFs). In terms of reliability of power converters, the protection of power semiconductors against short-circuit failures is of great concern. The reverse transfer capacitance increases with decreasing drain-source voltage during normal turn-on transient. Under HSF conditions, on the other hand, it hardly changes because the drain-source voltage remains high. As a consequence, quite a significant difference appears in gate charge characteristics between under HSF conditions and normal turn-on operation. Hence, an HSF can be detected by monitoring both the gate- source voltage and the amount of gate charge. The proposed protection circuit has high noise tolerance because it monitors not only the gate-source voltage but also the amount of gate charge. The validity of the protection circuit is verified by experiment. The proposed protection circuit can detect the HSF within only one microsecond.