online junction temperature measurement

bradp

Body diode voltage drop can be used at low current to estimate MOSFET junction temperature (e.g. the Simcenter T3STER claims +/- 0.01 deg accuracy). I'm looking for an online approach that is, say, +/-5 deg accurate. Do you have any relevant information?

TBhatia

Hello bradp,

Thank you for your message. Can you please elaborate further on what you mean by "online approach"?

There are multiple ways to estimate MOSFET junction temperature.

We have an online simulator called the SpeedFit 2.0 that can help you estimate the junction temperature for all our devices when you choose the topology and specifications according to your system with fairly accurate estimations. A full guide on how to use SpeedFit can be found in FAQs- https://forum.wolfspeed.com/categories/speedfit-design-simulator

Another way to estimate junction temperature is by measurement of the MOSFET case temperature which can be observed using a Thermal camera or by attaching a thermocouple on the MOSFET. The junction temperature Tj can then be calculated using the formula:

Where Tc is the measured case temperature, Ploss is the power loss of the device and Rth,jc is the thermal impedance from junction to case found in the datasheet. More details on thermal management and junction temperature estimation can be found in this Application Note Thermal Management of Bottom-Side Cooled Surface Mount Devices and Design Considerations

Hope this helps!

TBhatia

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