Passive Resonant Level Shifter for Suppression of Crosstalk Effect and Reduction of Body Diode Loss of SiC MOSFETs in Bridge Legs

Abstract

Due to the presence of parasitic elements in switching devices and circuit realization, crosstalk phenomenon in bridge-leg configurations is unavoidable. A passive resonant level shifter that can suppress the effect of the crosstalk and deliver a low off-state gate-source voltage to reduce the forward voltage drop of the body diode of SiC mosfets is presented. The circuit is composed of two parts. The first one is a resistor-capacitor-diode (RCD) level shifter that delivers a static negative off-state gate-source voltage to the mosfets. The voltage level is designed to be close to zero, so that the forward voltage drop of the body diode is lowered. The second one is a series resonant tank circuit. It generates short voltage pulses to counteract the voltage pulses caused by the crosstalk. The gate-source voltage can then be maintained at a level below the threshold voltage of the mosfets. The proposed level shifter does not require any active devices or additional supply. It can be applied readily to commercially available gate drivers. A passive resonant level shifter module for four SiC mosfets in a 1-kW H-bridge inverter has been built and evaluated. Detailed performance comparison with the RCD level shifter will be given.