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Flyback Bias winding dropping out.

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eem2am

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Hello,

We all know that when an offline, isolated flyback goes "no-load" on its secondary, then it's bias winding drops out.

..and then the bias winding is not capable of supplying the PWM controller.

Is it true , that such "drop-out" of the bias rail, can be avoided by simply adding a large electrolytic capacitor to the bias rail.?
 

macubo

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not completely. It depends on many things: you may increase aux winding turns' number, reduce series resistance, use a schottky diode, reduce consumption of whatever is connected to it: resistive dividers, PWM IC and associated gate charge, etc.
Increasing the elcap is a viable approach, but not the best.
bye
 

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