PLECS thermal model transient thermal impedance, is it correct?

Mikesim

Hi, I have a question regarding the thermal chain in the PLECS thermal description e.g.

CAB425M12XM3.xml

CAB425M12XM3_bodydiode.xml

It appears to me that the thermal chain has been added to the body diode as well as the FET. I don't think this is representative as in reality, the bodydiode is closely thermaly linked to the FET and share a common thermal chain. In most applications this will not matter much as the diode losses should be small. However, in pulse power applications or when modelling fault conditions the "paralleling" of the thermal chains will significantly underestimate the diode junction temperature. I can think of a workaround for this in PLECS but I'd have thought it would be better to use the FETD model so the losses ascoceated with both the FET and the body diode go through the same thermal chain.

I'd be interested to hear other opinions on this.

Cheers

Mike