Online Junction Temperature Monitoring Method for SiC MOSFETs Based on Turn-Off Miller Plateau Voltage

Online junction temperature monitoring of SiC
mosfet
based on turn-
off
Miller plateau voltage (
V
_MP,off
) has been explored in this article. As the junction temperature rises,
V
_MP,off
experiences a decline while extending its duration, thereby enhancing the precision of sampling
V
_MP,off
with a diminutive turn-
off
resistance (
R_g
,off
). A novel extraction approach for
V
_MP,off
is introduced, involving the continuous sampling of gate voltage via a network of resistances and an analog-to-digital converter (ADC).
V
_MP,off
is ascertained through the discrepancy between two consecutive output points of the ADC. Validation of this monitoring technique is conducted through double pulse tests and a buck converter under varying temperatures. Empirical findings demonstrate a commendable linear relationship between
V
_MP,off
and junction temperature. In the quest for a balance among thermal sensitivity accuracy, turn-
off
delay, and turn-
off
loss, a recommended value for
R_g
,off
of SCT3040KR stands at approximately 15 Ω. Employing a 15 Ω
R_g
,off
, the temperature sensitivity of V
_MP,off
for SCT3040KR and SCT3105KR hovers around −11.3 mV/°C and −9.1 mV/°C, respectively. With calibrations of aging and threshold voltages in advance, the proposed methodology exhibits promising potential in the realm of SiC
mosfet
junction temperature monitoring.