Design, performance evaluation, fabrication and testing of a SiC MOSFET gate driver

Silicon Carbide (SiC) is a compound semiconductor has ten times the dielectric breakdown field strength, three times the band-gap, and three times the thermal conductivity of silicon (Si). SiC MOSFETs can be operated at higher switching frequencies and higher ambient temperatures than Si MOSFETs. This paper deals with design, fabrication and testing of a gate driver circuit for driving SiC power MOSFETs at switching frequencies up to 1.0 MHz. SiC MOSFETs can be used in very high frequency (HF) and high voltage switched-mode power supplies (SMPS), uninterrupted power supplies (UPS), induction heating, welding power supplies etc. for better performance and efficiency than their silicon counterparts. In this paper, the selection of circuit components for gate drivers for SiC MOSFETs is discussed. A gate driver card is fabricated and is tested by switching a SiC MOSFET feeding a 50 W load at 1.0 MHz switching frequency. The waveforms at the different points of the gate driver circuit and the power circuit are presented. Short circuit protection is implemented through device voltage sensing. The effect of junction capacitance Cjd of the diode, which is used for sensing the device voltage, is studied. A procedure to overcome the drawbacks of the same is discussed and implemented successfully. Also a soft turn-off technique is implemented to turn off the device smoothly in the event of a fault, avoiding ringing and voltage overshoot.