Problems with switching regulator TNY280 (Tiny-Switch)
Ladies and Gentlemen,
we have problems with your TNY280 switching regulator.
We develop and sell already very long power supplies with this switching regulator.
The shutdown of the switching regulator is done with an optocoupler on the "EN pin".
We use since optocouplers from Toshiba (TLP281). With these optocouplers we never had any problems and our power supplies worked very well.
Recently, we also want to use optocouplers from other manufacturers (COSMO, EVERLIGHT ...). Unfortunately then, problems occurred! The problem occurs when we turn our power supplies briefly of and on again. Then, the switching regulator (TNY280) does not oscillate. Our power supplies have no problems with Toshiba optocouplers. But we have Problems with other manufacturer.
All optocouplers have the same technical specifications.
Is this problem known?
Do you have a solution to this?
We could fix the problem with a 100pF capacitor between the pins EN and S of the TNY280. Unfortunately, we can not exactly explain why the capacitor has this effect. Do you have an explanation? There must also work without the 100pFcapacitor?!
Thank you for your help.
Comments
We never have this problem beofre, although TNY are used by a lot of custoemrs and applications. Could you PLS upload your schematic?
thanks
Hello,
thanks for your help.
This is our circuit with the TNY280.
Honestly I am not sure what is the root cause. Obviously the current through the opto makes some difference. At first I think it is caused by the leakage current, but then I realize leakge current can not be the root casue, since the cap has leakage current too.
You are right! The capacitor also has a leakage current.What other measurements can I do to narrow down the problem.
Nobody has an idea?
We never have this problem beofre, although TNY are used by a lot of custoemrs and applications. Could you PLS upload your schematic?
thanks