Flyback Bias winding dropping out.

[eem2am]

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]

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