SMPS design problems

[mtwieg]

Hi.
I think using optocoupler feedback in half - bridge converters without additional subterfuges possible only for chips with pulse-by-pulse shutdown feature, like UC3825 or SG3525.
However this scheme must be runnable -

There's nothing wrong with using optocoupler feedback in a voltage mode half bridge supply. In fact, current mode control in half bridge supplies is more difficult to get working because you need to take additional measures to enforce charge balancing on the series capacitor(s).

Anyways, Hz2020 I see your new compensation circuit, how did you go about calculating the component values? I think the problem may lie there.

Can you verify that this circuit works as a simple proportional controller? Strip C1, C2, and R5 out, and see if it is actually able to control duty cycle all the way from 0 to 50% when changing Vout. This can be done without actually closing the loop.

 

[Hz2020]

Thanks mtwieg
i really made that design which was in example in my book (POWER SUPPLY COOKBOOK Marty Brown)

this design is a pole zero compensation
this is the details as i read from that example

thanks in advance

 

[Hz2020]

please i need a help. i need to finish that project