High Temperature Unclamped Inductive Switching Mode Evaluation of SiC JFET

Silicon carbide (SiC) unipolar transistors are an efficient choice in the design of high temperature 1200 V switching power supplies and dc-dc converters. To reduce the form factor and increase the power density of the circuit, the switching frequency must be high. This intensifies the negative impact of parasitic inductance and results in high voltage spikes that can drive a switching device into breakdown, followed by rapid destruction. To study the device performance under unclamped inductive switching (UIS) conditions, a normally-ON 1200 V/13-A SiC junction field-effect transistor (JFET) is driven into punch through breakdown using a single pulse. The testing is performed using an UIS setup, in which energy initially stored in an inductor is discharged through the JFET. The testing comprises of 90 single pulses each at 25 degrees C and 100 degrees C case temperatures for different gate voltages and drain current values. The peak energy and power dissipated in the JFET are 621 mJ and 16 kW, respectively, at the rated 1200 V blocking voltage and 13-A drain current. The JFET triode breakdown characteristics are unchanged after 180 single-pulse switching events indicating the robust nature of the device under extreme breakdown conditions. In addition, the 621 mJ peak UIS energy and its corresponding 8871 mJ/cm(2) density dissipated in the JFET are the highest reported for any SiC power device.