Impact of Diode Characteristics on 1.2 kV SiC MOSFET and Cascode JFET Efficiency: Body Diodes Vs SiC Schottky Barrier Diodes

Abstract

In this paper, the performance of 1.2kV SiC planar MOSFETs, Trench MOSFETs and 1.2 kV SiC Cascode JFETs is compared under 3 conditions. Firstly, the devices are switched with SiC Schottky Barrier Diodes (SBDs) with no contribution from the body diode (BD). Secondly, without SiC SBDs thus relying on the BD. And thirdly, with both SiC SBDs and BD in parallel (SBD+BD). Under the first condition, an auxiliary diode is required in series with the transistor to prevent BD operation in the 3rd quadrant. This contributes to additional conduction losses and has an impact on switching losses which are different between the different technologies. Simulations of a hard-switched converter have been used to compare the losses of these diode configurations with synchronous rectification (SR). The results show that the auxiliary diode is justified only for SiC Cascode JFET at high switching frequencies and the switching losses of the Trench MOSFET are unaffected by the diode configurations. For the Planar MOSFET, while using an SBD gives the best performance, there is no justification for the auxiliary diode. When the SBD is not used, SR is beneficial for all technologies except the Cascode JFET.