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  1. #41
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    Re: uc3842/3843 Vcc problem in smps.

    it will cause a lot of extra primary current - a bad thing ... when the main mosfet has to turn off



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  2. #42
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    Re: uc3842/3843 Vcc problem in smps.

    how to decrease large primary current if an smps transformer have large core gape, what to do with primary

    winding to decrease the primary current so that power mosfet my not cutout, i have a core from a tv circuit having gape of

    of about 1.2mm
    it is not cracked, i wind it myself but every time i use it in my flyback smps circuit it silently cutout the power mosfet.

    i also have the problem as mention in above post#41.



  3. #43
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    Re: uc3842/3843 Vcc problem in smps.

    the problem solved through interleaved centered winding of a tv smps xformer.
    Click image for larger version. 

Name:	interleaved..JPG 
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ID:	158311



  4. #44
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    Re: uc3842/3843 Vcc problem in smps.

    Edaboard users might be interested to know which tool is used to design/sketch the transformer.



  5. #45
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    Re: uc3842/3843 Vcc problem in smps.

    according to my experience of winding smps transformer whether it is flyback, forward or half Bridge

    powerEsim is the best tool that tells us about the "core Area, air gape, numbers of turns of primary,

    feedback & secondary winding, inductance & switching frequency of the power FET
    ". but a little trial & error may be required to correctly match the frequency

    of the oscillator with the designed transformer because of the sometimes the unavailability of the mentioned core within the tool.

    link to the tool -----> https://poweresim.com/
    Last edited by codemaster11; 21st March 2020 at 12:14.


    1 members found this post helpful.

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