Improved Proportional Base Driver for SiC BJTs

The benefits of high-power silicon carbide (SiC) bipolar junction transistors (BJTs) in terms of low conduction and switching losses, high-temperature capability, and increased reliability associated with the lack of gate oxide have been partially shadowed by the high-power consumption of its driver. This paper focuses on the optimization of SiC BJT base drivers and presents an innovative design of a proportional base current driver. The driver is a stand-alone system achieving instantaneous tracking of the collector current without the need for a current sensor and can also account for variations of the BJT's dc current gain with the temperature. Implementation of these two features is realized by sensing the collector-emitter voltage, which is conditioned to be used as a reference voltage for a switching regulator featuring a megahertz synchronous buck converter. This leads to a variable base current that is proportional to the instantaneous collector current for the SiC BJT. The concept is validated using a 1.5-kW boost converter, which shows a significant reduction in power consumed by the driver.