[SOLVED] 1000w smps feedback loop help

[Salvu]

I have built a 1000w smps which I decided to add feedback to it.
The smps reached a peak of 1200watts and the output voltage dropped to 125v un-regulated.

I made a feedback loop with an opto coupler and another reference with a TL431.

My Problem is that if I have an amp load on the output and add another 400w all works well but when I am at minimum load say 80 watts and then add another 400w load to it the smps trips on over current protection. The protection is set to 11 amps at 120v on the output.

Can someone help me arrange the feedback loop to work better or perhaps tell me what can I do to correct this problem?

Regards, Salvu

 

[schmitt trigger]

Your overcurrent protection is prone to noise, as the very first comparator does not have hysteresis.

I would fix that for starters.

 

[Salvu]

Thanks a lot Shmitt trigger. I have been playing a bit with the smps today and when I added some decoupling to the input of the TL431 the problem was solved. Yet I still have some problems with center tap wonder as if I load only at the ends without using the center tap the voltage will shift (4-5v). However when I loaded with a couple of 100w bulbs between the positive and ground and negative and ground the voltage centered well within around 0.5v difference. I guess I have to use a larger output inductor (25-30uH)and this will cure but again more resistance is involved and it will not sustain the regulated voltage at 1000 watts.
If there is another way that I can balance the voltage please let me know.

Regards, Salvu