Sensing power MOSFET junction temperature using gate drive turn-on current transient properties

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 gatedrive 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.