Improved 6.5kV FREEMD-Pair based on SiC JFET and Si IGBT

Abstract

The newly proposed FREEDM-Pair is an ideal and economical solution to address high cost issue in high power SiC power devices. The FREEDM-Pair, in which a Si IGBT and a SiC JFET are connected in parallel, combines the advantages of SiC JFET's low switching losses and Si IGBT's superior forward conduction characteristics. One issue of the JFET based FREEDM-Pair is the incompatible gate drive voltage for the SiC JFET and Si IGBT which complicates the gate driver design and increases the total cost. Also, the high voltage SiC JBS reverse diode in FREEDM-Pair is indispensable for the reverse current conduction, leading to higher cost and larger package size. To address these issues, an improved FREEDM-Pair is proposed in this paper, in which the SiC JBS diode is eliminated and the normally-off SiC JFET is operated in cascode configuration to unify the gate driver voltage level and speed up the switching of the JFET. The design and operation of improved FREEDM-Pair is elaborated and experimental results verified its advantages. Also, the affordable cost demonstrates that this promising concept is an ideal step to introduce high voltage SiC power devices.