DS Power MOSFET Switching Design for Moog PMSM - BLDC Motor Use-Case

This design is similar to the design "Ideal Switching Design for Moog PMSM - BLDC Motor Use-Case", but the ideal switches in the inverter are replaced with "Datasheet" Power MOSFET models. These models are calibrated to match the datasheet specified characteristics of an STW45NM50 device. This replacement required the conversion to the digital signals used to control the switch states, to actual gate voltages. So representative models of the necessary gate drivers were also added.

In addition, a "hot part monitor" model was added to one of the Power MOSFETs. This models the datasheet specified "Rthj_amb" (0.32 degrees C per Watt), in order to predict the internal junction temperature during different phases of inverter operation. A thermal time-constant of 1 ms was assumed, which may be quite unrealistic. It is possible to add much higher fidelity thermal network models of the heat transfer path if valid parameters are given.

Finally, one of the low-pass filters used in the current sense path was changed to reflect a possible circuit implementation using op-amps. This is to show the ability to move seamlessly between ideal signal-flow (or continuous transfer function block) modeling to circuit implementation modeling, anywhere in a system design.

You can also see a version of this design that uses the manufacturer provided SPICE model for the Power MOSFET: "STW45NM50 MOSFET Switching Design for Moog PMSM - BLDC Motor Use-Case"

Mike Donnelly's picture



Mike Donnelly

Joined November 8, 2013
Design added Saturday, April 13, 2019 | 8:43 am PDT