Electromagnetic Interference in Silicon Carbide DC-DC Converters

Abstract

A comparison of radiated noise for Silicon and Silicon Carbide converters is presented. SiC JBS diodes were used in this evaluation to enable fast switching times, whilst minimizing the transistor junction temperature. Radiated electromagnetic-interference measurements showed the highest noise signature for the SiC JFET and lowest for the SiC MOSFET. The negative gate voltage requirement of the SiC MOSFET introduces up to 6 dBµV increase in radiated noise, due to the induced current in the high frequency resonant stray loop in the negative power plane of the gate drive. The SiC JFET and MOSFET have shown overall converter efficiencies of 96% and 95.5% respectively. This efficiency shows only a weak frequency dependence, in contrast to the CoolMOS/SiC JBS diode combination which demonstrated an efficiency drop from 95% to 92.5% when increasing the frequency from 100kHz to 250kHz.