An Approach for Online Estimation of On-State Resistance in SiC MOSFETs Without Current Measurement

While silicon carbide power mosfets have significantly superior figures-of-merit in comparison to conventional silicon devices, they have seen relatively limited adoption in high-power applications due to intrinsic reliability concerns. One of the most consistent precursors of early device failure is increased on-state resistance (R$_\mathrm{ds-\text{on}}$). This article presents the design of a nonintrusive health monitoring circuit (HMC) that can be embedded within the power converter to measure this resistance during operation. The HMC does not require load current information or any interaction with the gate driver. It is experimentally validated for a range of voltage and current levels including continuous operation in a buck converter and provides estimates of R$_\mathrm{ds-\text{on}}$ within $\pm$5% of the true value for all cases.