I wonder about the "quality difference" between using an secondary side reference + optocoupler to provide voltage feedback in an isolated flyback design and using the third winding of the transformer.
As far es I understand things, "better" regulation is possible with first variant because the tolerances of voltage reference and optocoupler can be much tighter than the tolerance of the transformer winding ratio from secondary side to the third winding.
Now assume that i am happy with an output voltage regulation of +/- 10% , are there other benefits than better output voltage regulation when using the optocoupler variant? I heard that load regulation should be better but don't know why this should be the case.
I also saw that in the variant with third winding, the voltage is more or less (rectification) fed back to the controller FB pin whereas with optocoupler feedback you can directly "bypass the controller's error amplifier" because the optocoupler's feedback is a current signal that can be fed into the output of the controller's error amplifier(i.e. the compensation network). I don' t know if this is somehow a benefit.
NOTE: All the text abobe assumes an isolated flyback design with current mode regulation and a constant frequency controller. Also, I assume to only have one output, so please no explanations concerning cross regulation topics.