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This article puts forward a novel online method to measure the junction temperature ($T_{j}$) of silicon carbide (SiC) mosfets. In this method, the voltage spikes in the common source stray inductance are captured to obtain the turn-on and turn-off switching transients of SiC mosfets. The switching transients contain useful information pertaining to the temperature and are used to extract the junction temperature. By measuring both turn-on and turn-off switching transients, the technique effectively addresses the impact of aging on the online junction temperature measurement procedure. The proposed method enables the measurement of junction temperature without high-bandwidth current sensors. In order to improve precision, this approach converts the measured voltage spikes into digital signals with specific pulse width, which can be measured by high-resolution capture module in the microcontroller with an error of less than 1 $^{\circ }$C. Importantly, the proposed circuit has minimal impact on the normal operation of the converter and can be integrated into the gate driver integrated circuits (ICs). The effectiveness of this method is validated through experiments conducted on a double-pulse test setup and buck converter. The results confirm the practicality and viability of this approach.

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.

To achieve higher power density at a reduced cost, it is more advantageous to utilize the inherent body diode found in silicon carbide MOSFETs (SiC MOSFETs) rather than relying on an external Schottky barrier diode (SBD). Therefore, it is crucial to investigate the third quadrant operation of SiC MOSFETs and analyze the factors influencing the behavior and reliability of the body diode. By examining the intricate relationship among gate voltage bias, gate-oxide degradation, and third quadrant operation, this study contributes to a comprehensive understanding of the underlying mechanisms and provides insights into optimizing device performance and reliability. First, this article shows that the current flows through both the channel and the p-n junction during the third quadrant operation, which impacts the reverse recovery conduction and power losses. The characteristics of the body diode and technology-computer-aided design (T-CAD) results confirm that the distribution of current between the channel and the p-n junction can be controlled by adjusting the gate voltage bias. Consequently, the gate voltage can partially or fully obstruct the channel during reverse conduction, thereby enabling the regulation of the current flow. Second, the study demonstrates that the degradation of the gate oxide can impact the third quadrant operation and reduce the reverse recovery current. Finally, this article proposes a circuit that can monitor the gate-oxide degradation by monitoring the peak reverse recovery current (PRRC). The results are confirmed experimentally on a double pulse tester (DPT) setup.