Noncontact SiC MOSFET Switching Time Monitoring in DC–DC Converter Using Switching Oscillation Amplitude Feature

The switching time of a silicon carbide metal–oxide–semiconductor field-effect transistor (SiC
mosfet
) is a crucial parameter that provides valuable insights into the device's operational performance and health status. However, direct measurement of switching time from the drain-source voltage or gate-source voltage may pose challenges in terms of safety and precision. To address these difficulties, this study proposes a noncontact method for monitoring the switching time of SiC
mosfet
using high-frequency switching oscillations in a dc–dc converter. We begin by analyzing the high-frequency switching oscillation current in a Buck converter, investigating its generation mechanism, including the excitation source, equivalent circuit, and analytical expression. Subsequently, the initial amplitude of the switching oscillation current (
I
_sw1
), which shows an explicit dependence on the switching time (
t
_sw
), is selected as the feature for monitoring the switching time. Then, a noncontact monitoring scheme for SiC
mosfet
switching time is devised, involving a high-frequency switching oscillation sensor and a calibration process to establish the
I
_sw1
-
t
_sw
characteristic. The effectiveness of the proposed method is confirmed experimentally, which exhibits outstanding electrical isolation safety and achieves ns-level accuracy under varying operating conditions.