A new proportional base driver technique for SiC bipolar juction transistor

Abstract

As one of the most attractive post-silicon power semiconductor devices, SiC bipolar junction transistor (BJT) has been studied intensively and commercialized in the past few years. However, SiC BJT has not been widely accepted in the market because of high driver loss in the on-state, which is induced by a relatively large constant base current in order to ensure its fully turning on. In this paper, a new proportional base driver for the SiC BJT is proposed in order to reduce its driver loss. It utilizes a silicon MOSFET as a variable resistor between the base driver and the base of the SiC BJT. The gate voltage of the silicon MOSFET decreases with the collector current of the SiC BJT via a Hall device, thus the on-state resistance of the MOSFET increases and the actual base driver current of the SiC BJT decreases. Comparing to the conventional SiC BJT driver, the proposed new proportional base driver can achieve the decrease of the base current with the decreasing of the collector current of SiC BJTs and has simple circuitry, resulting in the reduction of base driver loss. The simulation and experiment have verified that the proportional base driver of SiC BJT can reduce the driver loss by approximately 70% under the light load condition.