Junction temperature dynamics of power MOSFET and SiC diode

In this paper, junction temperature behavior of Si power MOSFET and SiC diodes when conducting significant current is investigated in detail by experiment and theoretical analysis. The dynamic variation and steady-state values of device junction temperatures when carrying different currents are studied. The results show that the device steady-state junction temperature versus current curve rises sharply after around 100°C and 150°C, for the Si power MOSFET and SiC diode, respectively. Maximum obtainable steady-state junction temperatures are found to be around 190°C for the MOSFET and 220°C for the SiC diode. The experimental results are well-matched by PSpice equivalent thermal circuit simulation and theoretical analytical calculation. While such limitation does not present as an issue for Si Power devices (as they are generally not expected to operate above 190°C), it could limit one's ability in exploring the intrinsic very high temperature capability of SiC power devices. System design approaches that can alleviate these limitations for the SiC power device are discussed and recommended.