# Can V\*I be used to calculate switching losses of a Limited di/dt MOSFET?

**URL:** <https://forum.plexim.com/t/can-v-i-be-used-to-calculate-switching-losses-of-a-limited-di-dt-mosfet/688>\
**Category:** PLECS\
**Tags:** di, dt, mosfet, limited\
**Created:** [August 22, 2019, 9:12am UTC](https://forum.plexim.com/t/can-v-i-be-used-to-calculate-switching-losses-of-a-limited-di-dt-mosfet/688 "2019-08-22T09:12:46Z")\
**Posts on this page:** 2\
**Page:** 1

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**Author:** ![purp](https://avatars.discourse-cdn.com/v4/letter/p/f07891/32.png) [@purp](https://forum.plexim.com/u/purp)\
**Post date:** [August 22, 2019, 9:12am UTC](https://forum.plexim.com/t/can-v-i-be-used-to-calculate-switching-losses-of-a-limited-di-dt-mosfet/688/1 "2019-08-22T09:12:46Z")

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Hi There,

I am modelling a circuit using the limited di/dt MOSFET, which does not support thermal models.

Can I use V\*I to calculate the switching and conduction losses of the MOSFET, as the PLECs user manual states

“Since the voltage and current transient waveforms are simplified, the model is not suited for the simulation of switching losses.”

Does this imply that the current and voltage waveform during the state changes are not accurate values?

Thanks,

B

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**Author:** ![Kris\_Eberle](https://dub1.discourse-cdn.com/flex006/user_avatar/forum.plexim.com/kris_eberle/32/6_2.png) [@Kris\_Eberle](https://forum.plexim.com/u/Kris_Eberle)\
**Post date:** [August 23, 2019, 2:28pm UTC](https://forum.plexim.com/t/can-v-i-be-used-to-calculate-switching-losses-of-a-limited-di-dt-mosfet/688/2 "2019-08-23T14:28:38Z")

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Hello,

Correct, we do not recommend that you use the voltage and current waveforms of the two switch components with limited turn-on and turn-off for loss calculation. The peak magnitudes of overvoltage and overcurrent waveforms are accurately calculated, but the higher order growth and decay curves in the real device’s behavior are highly dependent on the external circuitry so we don’t want you to assume your model corresponds to a hardware implementation. The standard MOSFET should be used for loss calculation with a thermal description and cooling circuit.

Regards,

Kris