Impact of Diode Technology on the Switching Performance of 3.3 kV SiC MOSFETs

In this paper, the
$3^{\text{rd}}$
quadrant switching performance of 3.3 kV SiC MOSFETs with different diode configurations is compared. Switching energy measurements have been performed with a 2 kV DC link at different junction temperatures (from 25 to 150°C) and different switching rates up to 1.2 A/ns and 50 V/ns. The diode configurations include (i) body diode (BD), (ii) series connected 1.7 kV SiC Schottky Barrier Diode (SBD) with no BD conduction, (iii) series connected 1.7 kV SiC SBD in parallel with the body diode, (iv) 3.3 kV SiC SBD with no BD conduction, (v) 3.3 kV SiC SBD in parallel with the body diode, (vi) 3.3 kV SiC Merged PiN Schottky diodes (MPS) with no BD conduction, (vii) MPS diodes in parallel with the body diode and (viii) BD with synchronous rectification. The 3.3 kV SBD and 1.7 kV SBDs with no BD conduction demonstrate the best switching performance. The results also show that reverse recovery charge from the body diode contributes to additional losses when using two series 1.7 kV SBDs in parallel with the body diode due to high voltage drop across the SBDs. This paper also shows that using synchronous rectification significantly improves the switching performance of the BD when a dead-time of 240 ns is implemented between the high and low side transistors.