A Gate-Oscillation-Based Miller Platform Voltage Online Monitoring Circuit for SiC-Mosfets

With the rapid advancement of semiconductor manufacturing technologies and the growing demand for high-frequency and compact power converters, SiC MOSFETs are expected to replace IGBTs as the dominant power devices in the market. This trend makes online health condition monitoring and assessment of SiC MOSFETs increasingly important. As a temperature-sensitive electrical parameter (TSEP), the Miller plateau voltage exhibits a highly linear relationship with the chip junction temperature and can therefore be used to map the junction temperature and device health condition. This paper proposes a novel online monitoring circuit for the Miller plateau voltage, which offers several advantages: it does not require additional high-voltage and high-power components, thereby reducing cost; it can be implemented in parallel without altering the operation of the original circuit; it avoids the use of analog components such as operational amplifiers and comparators, as well as RC charging–discharging networks, and does not rely on MCU I/O ports to directly drive the separation between Miller platform voltage and the gate–source voltage, which reduces design complexity and maximizes the response speed of the trigger signal; furthermore, the operating principle of the proposed circuit does not rely on the presence of a Kelvin source, allowing it to be applicable to both three-terminal and four-terminal SiC MOSFETs. Finally, functional validation is carried out on a built double-pulse test platform. The proposed online monitoring circuit can effectively extract the Miller plateau voltage and exhibits a clear linear response to temperature variations.