Model Based Junction Temperature Profile Control of SiC MOSFETs in DC Power Cycling for Accurate Reliability Assessments

Accurate control of junction temperature swing is crucial in DC power cycling tests for reliability assessments. In this work, a model based aging independent closed-loop junction temperature profile control method is proposed. Specifically, the temperature ramp rate and dwell time at the maximum junction temperature are controlled. The device's on-state resistance measurements are used to accurately estimate its junction temperature. A code and memory efficient technique is presented for mapping measured resistance to junction temperature. The proposed technique also considers the variation in aging related on-state resistance change. Specifically, SiC MOSFET's body-diode forward voltage drop (
$V_{f}$
) at negative gate voltage and small current is used as an aging independent temperature sensitive electrical parameter (TSEP) to adjust the temperature reference to compensate for aging related shifts. The detailed algorithm, filter and controller design methods are presented in detail. The proposed algorithm is validated on a custom DC power cycling test bench.