Gate driver based soft switching for SiC BJT inverter

This paper presented a new soft switching building block (SSBB) concept based on the development of a SiC BJT inverter. The primarily goal of proposing the SSBB based inverter is to find a simple but effective way to achieve soft transition. In particular, a gate driver based zero voltage switching SiC BJT inverter scheme is proposed. The base driver consists of one IGBT and one MOSFET to help turn-on and turn-off of the SiC BJT transistor in a Darlington like configuration. The proposed base drive method can proportionally drive SiC BJT at near-saturate condition. In addition, the zero voltage turn-on for BJT can be adaptively achieved at all load current range with a single gate signal. The proposed soft switched schemes can significantly simplify the BJT base driver design. Unlike other soft switching inverters in the literature, the control of a soft-switching inverter based on SSBB structure is very simple since only six standard hard switching PWM signals are needed to drive the soft-switching inverter. No phase current sensing and complicated timing control are needed to achieve optimal soft switching operation. Although the research is carried out with the need of SiC BJT inverter the basic concept can be applied to Si device as well. A demonstration of all SiC BJT inverter capable of operating at elevated temperature had been built to drive a 7.5 HP induction motor. Experimental results verified the feasibility of the driver based soft switching scheme.