Hello TI team,
I have building a fly back regulator with the UCC28700 few months ago. With our first samples I had no problems. Now we have produced 60 items and now we have startup problems (starting again and again) with about 10 % of all. A small cap (10pF) at the VS pin solved this problem. My question is now: can I get any trouble with this small cab in the feature in relation to the control behavior of the fly back?
The VS input resistor divider is 82.4k / 27k. I used the schematic of design example “PMP10344 - 85VAC-480VAC Input, 12V/25W Flyback”.