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need help for flyback converter

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pmt107

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can some1 help me to calculate Rf and R1.Iam just an amater but have to make the flyback converter in lab tommorrow. I searched a formula to calculate them but T.T .Thanks a lot in advance
Uin= 30-63V Uout=10v=const,f=100khz
Screen Shot 2012-05-01 at 22.02.21.png Screen Shot 2012-05-01 at 22.02.58.png Screen Shot 2012-05-01 at 22.03.10.png
 
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Dear pmt107
Hi
It is simple !
Just it is enough to know that vout=2.5*(1+R1/R2) and for Rs = 1/Iprimary
Best Wishes
Goldsmith
 
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    pmt107

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thank you for your fast response
but i mean Rf . i read a bachelor thesis : output frequency of uc3845 = 1/2 switched frequency= 50khz. and output frequency = 1.72/Rf*cf.
i dont know where the value 1.72 come from.
 

The formula for switching frequency is expected to be arbitrary. It depends on the reference voltage and the amplitude of the oscillator ramp. The derivation of the formula isn't really important.
 

Yes , i'm agree with mtwieg . it isn't really important .
Best Luck
Goldsmith
 

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