A high temperature ultrafast isolated converter to turn-off normally-on SiC JFETs

Silicon Carbide (SiC) components are accepted devices for high temperature and high efficiency applications. Normally-on SiC JFETs are now commercialized and will be used in future power converters. However, such devices are conducting when not driven with a sufficient negative voltage, which can lead to safety issues during start-up or abnormal operation of the gate driver. Therefore, it is needed to generate an auxiliary negative voltage to turn-off the JFET in order to protect the system. Moreover, insulation is necessary to cover all failure modes. Prior papers presented solution to protect such devices but no high temperature isolated solution were demonstrated. In this paper, a solution to protect JFETs used in a high temperature (200°C) voltage source inverter is proposed. The protection circuit, components selection and characterizations for high temperature application are detailed. Experimental results are provided and validate the design of the isolated normally-on protection circuit up to 200°C.