A 15 kV SiC MOSFET gate drive with power over fiber based isolated power supply and comprehensive protection functions

This paper presents a 15 kV SiC MOSFET gate drive circuit, which features high common-mode (CM) noise immunity, small size, light weight, and robust yet flexible protection functions. To enhance the gate-drive power reliability, a power over fiber (PoF) based isolated power supply is designed to replace the traditional design based on isolation transformer. It delivers the gate-drive power by laser light via optical fiber over a long distance (>1 m), so a high isolation voltage (>20 kV) is achieved, and the circuit size and weight are reduced. More importantly, it eliminates the parasitic CM capacitance coupling the power stage and control stage, and thus eradicates the control signal distortion caused by high dv/dt in switching transients of the high-voltage SiC devices. In addition, the gate drive circuit design integrates comprehensive protection functions, including the over-current protection, under/over-voltage lockout, gate-clamping, soft turn-off, and fault report. The over-current protection responds within 400 ns. Experimental results from a 15 kV double pulse tester are presented to validate the design.