Attempting Ultralow Turn-off Loss of SiC MOSFET with Active Gate Charge Control Technique

This paper analyzes the turn-off process of SiC MOSFETs, and derives the Miller effect gain coefficient of turn-off transient based on output characteristic in saturation region. Furthermore, the drain-source voltage slew rate that can be generated by the ideal MOSFET model ignoring junction capacitance is derived, the relationship between channel current, drain current, and junction capacitance is analyzed. Therefore, the maximum drain-source voltage slew rate of actual MOSFET is obtained. Hence, the conditions for achieving quasi zero current turn-off are obtained, and is satisfied by controlling gate charge to provide sufficient turn-off current. Double-pulse tests are conducted under an DC voltage of 600 V. At a load current of 300 A, compared with conventional gate drive, proposed active gate driver can reduce turn-off thermal loss by 80%, with no significant change in voltage and current oscillations.