A New Proportional Base Drive Technique for SiC Bipolar Junction Transistor

As one of the most attractive postsilicon power semiconductor devices, SiC bipolar junction transistor (BJT) has been studied extensively and commercialized in the past few years. However, SiC BJT has not been widely accepted in the market partially because of high driver consumption in the on-state, which is induced by a relatively large constant base current in order to ensure it is fully turned on. In this paper, a new proportional base driver with a simple circuitry is proposed in order to reduce the steady-state base driver consumption of SiC BJT. It utilizes a silicon small-signal mosfet as a variable resistor placed between the driver and the base of the SiC BJT. The collector current of the SiC BJT is measured via a Hall current sensor whose output is connected to the gate of the mosfet. When the collector current decreases, the gate voltage of the mosfet decreases and its on-state resistance increases, resulting in the decrease of the actual base driver current of the SiC BJT. The operation principle of the proposed proportional base drive technique has been verified by theoretical analysis and experimental demonstration of a 1200 V 10 A-SiC BJT-based dc-dc boost converter. Theoretical calculation, PSpice simulation, and experimental results have shown that the steady-state power consumption of the SiC BJT's proportional base driver is reduced by approximately 70% under the light load condition compared to conventional base driver with a constant base current.