Isolated Gate Driver for Medium-Voltage SiC Power Devices Using High-Frequency Wireless Power Transfer for a Small Coupling Capacitance

A high-voltage operation and breakneck switching speed of medium-voltage (MV) silicon carbide (SiC) devices demand gate drivers (GDs) with high voltage withstanding capability, high common-mode (CM) transient immunity and a reliable short-circuit protection. An isolated GD to meet these challenging requirements is presented in this article. A novel isolated gate driver power supply using high-frequency wireless power transfer (WPT) with a nonoverlapped winding arrangement for a small coupling capacitance is proposed. Moreover, a grounded shield is added to further reduce the effective coupling capacitance and the CM current. The receiver (Rx) coil of the WPT system along with its power processing circuit have been epoxy encapsulated to achieve a very high breakdown voltage and an extremely small form factor without violating very demanding clearance and creepage distance requirements. The impact of epoxy, winding arrangement, Rx circuits, and the grounded shield on the coupling capacitance is analyzed in details. In addition, a sophisticated overcurrent protection (OCP) scheme with soft-turn-off capability for MV SiC devices is developed. The designed OCP scheme achieves fast protection and simultaneously avoids false tripping due to very high current overshoot associated with the MV SiC devices during turn-on transitions. An experimental prototype is developed and the performance of the proposed GD under various operating conditions is evaluated experimentally.