Sensing Power MOSFET Junction Temperature Using Circuit Output Current Ringing Decay

Junction temperature sensing requirements for fast MOSFET junction temperature control and high power fast switching power converter protection are not easily met with non-intrusive techniques. This paper presents a non-invasive 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-RDS-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.