Invalid conduction loss for mosfet

PLECS
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1

Hi,

There is one mosfet with large current in the topology. It is used for synchronous rectification. If the output voltage is 400v, the thermal simulation is ok. But when it is 500v( the max current of this mosfet is -70A, befor the circuit is stable, the current is even much higher), there is a invalid conduction loss error before the circuit is stable. I don’t know what to do. Thank you very much for your time and help.

Best regards,

Emma

2

Hi Emma,

Unfortunately, your question is not entirely clear. If you could provide a PLECS model that demonstrates the issue, along with the associated thermal description, it would help us better understand the situation and get on the same page.

3

Hi Munadir，

Thank you for your reply.I used the mosfet datasheet(model: Infineon IMW120R030M1H) to complete the thermal modal manually.Could you tell me how to find the thermal simulation file of this model for direct import? I couldn’t find it on Infineon’s official website. Thank you very much for your help.

4

Hi Emma, If you could share your PLECS model along with the thermal model you created, that would be helpful.

If a prebuilt model isn’t available on Infineon’s website, you would need to reach out to the Infineon team directly. They generate and maintain these thermal models and can provide the appropriate file for direct import.

5

Hi Munadir,

I’m sorry i can’t upload the model because it is applying for a patent. Thank you very much for your help.

6

Ok that makes sense. If you could share the thermal description that you are using that would also provide some insight. Also, if there is a error message could you post that as well?

Could you clarify that you mean:

  • the max current rating of this mosfet is -70A
  • during transient condition your model is experiencing currents that are beyond the max rating - is that correct?
7

Hi Munadir,

微信图片_20260311191531_1193_97
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During the transient condition,the current of the mosfet can be several thousand amperes.Should I give some initial values to all the inductors and capacitances? I tried a method today. I changed the value of Rm( the parallel resistance of the transformer) from 1e8 to 1e2 so that the model can run through starting time period. And I saved the state when the circuit is stable and changed the value back, then I can see the loss calculation when the circuit is stable.I am not sure if I should still try to give intial values and let it run correctly even in transient condition.

8

Hi Emma, from your description it would appear that you are experiencing an issue similar to Error Messages — PLECS 5.0 Documentation . If your FET is rated for 70A but you are seeing several thousand amps during startup and that appears to be the root cause I would recommend to update your control strategy to include a soft-start scheme or precondition your circuit simulation to avoid these large stress to your device. This would prevent the large inrush of current through your device at startup and potentially alleviate the simulation error you are experiencing.

Unfortunately, without a model it is a bit difficult to provide targeted guidance. If you are unable to share your model in a public setting but able to share it with Plexim, please email your model to support@plexim.com with a brief description of the issue and a link to this forum post.

Hope this helps!

9

Hi Munadir,

OK, I will try giving some initial values. Thank you very much your time and help!