TNY277 shut down issue

Posted by: cjf3 on 12/13/2011

We have a flyback design using the TNY277G that we have used on several different boards. We now have a new board for a new product that starts up OK but when we add a small additional load (turing on a small relay or removing the relay and jumpering the equiv ohms) it shuts down and won't restart without cycling the input power. The layout and circuitry is very simulair to a board that we have been building for several years and we have looked at all of the voltages and they look OK. What would cause it to shut down at may below current limit and to latch off?
Thanks

Comments

Hi,

As such from wht you are describing, it appears that the tinySwitch is latching off which can only happen if the over voltage fault is triggered.

Could you please provide me a schematic of your design? I would need this in order to investigate this problem.

Regards

PI-Sarek

Yes you are correcct. We finally found this cause. They winding which powered the BP/M pin was unloaded (due to easier to test before finish assembling) and when we added any load to the feedback winding, it went a little higher and caused an overvolt fault. Once we added the nominal load to that winding everything worked well.
Thanks

Thanks for confirming, good to known when issues are solved.

Cheers PI-Chekov