Normally-off SiC-JFET inverter with low-voltage control and a high-speed drive circuit

A highly efficient inverter was achieved by using normally-off SiC-JFETs (silicon carbide junction FETs) as switching devices. A precise control system for the gate voltage and the high-speed driver circuit are quite important issues in the realization of an inverter system for operating JFETs with threshold voltage lower than 2V and for the reduction of switching loss. A two step push-pull circuit for precise control of the gate voltage and a speed-up capacitor circuit for high-speed operation are developed and high-speed switching of 600 V/2A SiC-JFET modules is demonstrated. The 50 W fan motor for an exterior unit of an air conditioner has been successfully operated by these SiC modules and developed driver circuits, and the the inverter efficiency was improved by about 6%, compared with conventional IGBT inverters.