Sensing Power MOSFET Junction Temperature Using Gate Drive Turn-On Current Transient Properties

Abstract

Junction temperature sensing for high-bandwidth power MOSFET junction temperature protection is usually achieved on the power converter's high power side, by directly monitoring the power switches with additional temperature detectors. This requires special considerations for high voltage, high current, high temperature, and EMI protection. This paper presents a new method applied on the power converter's low power side (MOSFET gate drive) so that junction temperature sensing can be integrated into MOSFET gate drive. For the purpose of demonstrating MOSFET junction temperature sensing, a push-pull gate drive is applied to a switching current divider circuit. The gate drive turn-on current transient waveform is used for MOSFET junction temperature estimation. A “gate drive-MOSFET” switching dynamic model is implemented indicating the mechanisms of MOSFET gate drive output dynamics. Modeling includes gate-drive push-pull output, gate drive output parasitics, power MOSFET intrinsic parameters, PCB parasitics, and load parasitics. LTSpice simulation of this model is studied and compared with experimental results.