Bidirectional Bootstrapped Gate Driver for High-Density SiC-Based Automotive DC/DC Converters

Abstract

Bootstrap-based gate drivers are one of the simplest and cheapest solutions for driving the high-side devices in half-bridge-based power converters. Unfortunately, bootstrapped gate drivers are unable, on their own, to supply the negative gate–source voltage needed for safe turn off of SiC MOSFETs. This article proposes a novel and simple level shifter, applied to bootstrap-based gate drivers, able to supply a negative gate voltage to isolated-gate power devices during turn off. A fully analytical model of the proposed circuit is given, targeting both steady-state and transient performance. Modeling of the power loss connected to the driver is included as well. Performance of the gate driver with a level shifter is assessed experimentally, and the circuit layout for the power stage of a dual active bridge automotive dc/dc converter, set on an insulated metal substrate, is presented, comprising the power devices together with the proposed gate drivers and ancillary circuits.