Analysis and Suppression of 6.5kV SiC MOSFET Turn-on Current Overshoot

Abstract

SiC MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor) combines the advantages of high withstand voltage and high switching speed, and has obvious advantages in high-voltage and high-power applications. In the actual application process, the SiC SBD (Schottky Barrier Diode) is usually connected in anti-parallel at both ends of the SiC MOSFET for freewheeling to avoid the bipolar degradation of the body diode during long term operation. This paper analyzes the mechanism of the device turn-on current overshoot when SiC MOSFET and SiC SBD are used in parallel in bridge circuit topology. Based on the research group's self-developed 6.5kV SiC device, the switching characteristics of 6.5kV SiC MOSFET and SiC SBD in parallel are evaluated. The test results show that the 6.5kV SiC device has a large turn-on current overshoot due to the combined action of the body diode and SBD, and causes current distortion. By applying a negative gate bias to the freewheeling device, the turn-on current overshoot is suppressed to a certain extent. Finally, this article discusses and gives suggestions for suppressing the overshoot of the turn-on current of high voltage SiC MOSFET devices.