Voltage-Dependent Capacitance Extraction of SiC Power MOSFETs Using Inductively Coupled In-Circuit Impedance Measurement Technique

The voltage-dependent capacitances of silicon carbide power metal-oxide-semiconductor field-effect transistors (MOSFETS) affect the switching characteristics and have a direct impact on the electromagnetic compatibility (EMC) performance of the power conversion circuit. To predict and mitigate the potential impact on EMC in the early design phase, the capacitances have to be obtained accurately. In this paper, a novel method is proposed based on an inductively coupled in-circuit impedance measurement technique. The proposed method extracts the voltage-dependent capacitances of a MOSFET under its actual biased voltage without making any direct electrical contact, and hence eliminates potential safety hazards. Once the inductive probes are characterized, there is no need to re-calibrate the setup prior to each measurement, and therefore, it simplifies the whole measurement process. The accuracy of the extracted voltage-dependent capacitances for the SiC power MOSFET has been validated experimentally.