Two transistor forward converter simulation is noisy.

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T

treez

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Hello,
Our 160W two transistor forward converter simulaton (LTSpice) switches in a noisy and irregular manner when synchronous FETs are used with higher “Qg”.
(the ‘synchronous fets’ are the secondary side fets)

This seems to me that it may be a fault of the simulator(?), because changing the synchronous FETs to an almost similar FET, with a slightly lower Qg parameter, completely solves the problem, and it switchs smoothly. Is this a fault of the simulator?

Using IPB107N20N3 FETs causes noisy switching.
Using BSC900N20NS FETs switches smoothly and properly.


IPB107N20N3 FET datasheet:
https://www.infineon.com/dgdl/Infin...n.pdf?fileId=db3a3043243b5f170124968e7d1f18e7

BSC900N20NS FET datasheet:
https://www.infineon.com/dgdl/Infin...n.pdf?fileId=db3a30432ad629a6012b144f6b0619db

Please find attached the simulations (LTspice), with the non-noisy, and the noisy switching.

Do you believe this is a simulator fault?
 

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  • Two transistor forward_noisy.txt
    16.1 KB · Views: 70
  • Two transistor forward_not noisy.txt
    16.1 KB · Views: 63

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