Sensing Power MOSFET Junction Temperature Using Circuit Output Current Ringing Decay

Junction temperature (T_j) sensing requirements for fast MOSFET junction temperature control and high-power fast switching power converter protection are not easily met with nonintrusive techniques. This paper presents a noninvasive circuit-model-based sensing method suitable for a high-bandwidth hard-switching converter power MOSFET junction temperature estimation without any additional temperature detector. For the purpose of demonstrating MOSFET junction temperature sensing, a chopper circuit is used. The ringing superimposed with a circuit load current is used for MOSFET junction temperature estimation. A “gate drive-R_DS-on-L-C” resonant model is implemented, indicating the mechanism of power MOSFET turn-on dynamics. Modeling includes the gate-drive output parasitics, power MOSFET intrinsic parameters, PCB parasitics, and load parasitics. To evaluate the methodology, LTspice simulation and experimental results are studied.