Design and Verification of Gate Driver for 6.5 kV SiC MOSFET Module

Abstract

Gate driver for 6.5kV /25A Silicon Carbide (SiC) MOSFET module, which features low coupling capacitance, is proposed in this paper. In contrast to 6.5 kV Silicon (Si) IGBT module, 6.5 kV SiC MOSFET module captures the ability to switch at a much higher frequency, improving the power density greatly. However, the common mode current, which flows through the coupling capacitance between primary and secondary sides of the isolation transformer of gate driver produced by high dv/dt during quick switching, may produce annoying electromagnetic interference (EMI). Firstly, the coupling capacitance of single ring transformer and double ring transformer is simulated based on electrostatic Finite Element Method (FEM). Then, these two schemes are adapted to make isolation transformer of the gate driver for 6.5kV SiC MOSFET module. In the end, double pulse test circuit is built, and thus, double pulse test is carried out so as to assess the designed gate driver. Experimental results show that, compared with single ring transformer, common mode current, which flows by the coupling capacitance between primary and secondary sides of the double ring isolation transformer, has been reduced by 13.10/0. In addition, the 6.5kV SiC MOSFET module is switched on and switched off by the designed gate driver at 4500V supply voltage and 15A current with low oscillation at gate-source voltage. To be specific, voltage overshoot during turn off is no more than 200V, about 4.5% of the bus voltage, and, the amplitude of reverse recovery current is about 3A during turn on process, all of which verify the gate driver's effectiveness.