Please take a minute to review and accept our Terms of Use.
Welcome to the PLECS User Forum, where you can ask questions and receive answers from other members of the community.

Many technical questions regarding PLECS are answered on the Technical Solutions page of our website. Tutorial videos, specific application examples, and pre-recorded webinars are available on our YouTube page. Please follow us on LinkedIn for the latest Plexim news.

Interpretation of the thermal model - conduction loss graph

0 votes


After adding the manufacture thermal model in the MOSFET, I found the "Turn-on loss" and "Turn-off loss" tabs show graphs of E vs. V, I. While they make perfect sense, the "Conduction loss" tab shows the graph below which has NO "E" at all. So w/o. E values, how the conduction loss is calculated in the model??

(My understanding of the conduction loss is = Ion^2 * Ron where Ron = dVon/dIon. Is it correct??)

Thank you.

asked Mar 23, 2022 by (36 points)

1 Answer

+1 vote
Best answer
The conduction losses are P=v*i, or more clearly in this context P=v(i,T)*i where v(i,T) is from the look-up table posted with i as the current through the device and T is temperature.
answered Mar 25, 2022 by Bryan Lieblick (1,795 points)
selected Mar 28, 2022 by

Thank you for the answer Bryan.

May I ask in your eqn. "E=v*i" - Is "E" denoting the power (in W) or energy (in J)? Do you mean power P(in W)? If so, my another question is why the energy E (in J), in stead, is used in "Turn-on loss" and "Turn-off loss" (attached below)?

Thank you agian!


It would better to use "P" since v*i returns a power in watts.  I revised my response above.  Switching losses are joules since they are dirac-type impulses representing the total amount of energy emitted during the switching transient, which is instantaneous in PLECS.

So it means, in the graph, the given E(uJ) = P(uW) actually?

Assuming you are referring to the switching loss graph, the data entered in the table and Z axis in the graph is in energy (J, mJ, or uJ).  The voltages and currents in the graph are not multiplied since switching loss energy is a function of the voltage and current transients, as shown below. The Eon/Eoff values in the figure below would correspond to the entries in the table for a given voltage and current condition. The figure is from the thermal modeling section of the PLECS Manual.

It does make sense to me Bryan. I really appreciate your patience. So, actually E = integral of P(t) and the E in the graph the value for one switching cycle.