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FLyback Circuit Compensation design UC3845

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ku637

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Hello,

can someone help me how to design a compensation network for an optocoupler included flyback converter operating in DCM mode? say unniversal input to 12V /2A output.
Im using IC UC3845. Any step by step design procedure available?

Thanks
 

BradtheRad

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As a general concept, you want to configure the internal phototransistor to respond to the internal led, so that it delivers the correct volt level to the feedback pin.

You must create the proper amount of current going through the led. If output voltage changes, then it must cause led brightness to change.

In regard to the phototransistor, you install a resistance on its collector leg, which creates an output voltage that is usable by your control circuit. This must go up or down with led brightness.
 

treez

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Only Basso book tell you this. Christophe Basso. I only attach some, you need to buy this book
 

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