TNY27x thermal shutdown issues

[pavithra_uk]

Few years ago I found a PSU (Delta, 500W) that works fine few minutes and then turn off itself. later I found that standby 5V (and ~12V to controller) ic TNY279 overheats and then shut down. replaced with new one and problem solved.


and I found few other PSUs with same problem. two mobile USB power packs too. all these had TNY278, 279



Anyone here had similar experience ?

How these chips fail such a way? looks like internal mosfet on resistance increase or current sense element failure..

[sam_sam_sam]

Re: TNY27x thermal shutdown issues

I have replaced a few of them myself I think they might just be over stressed and just fail

[limo]

Re: TNY27x thermal shutdown issues

While main competitors like ST or Fairchild or Linear have different package which require PCB thermal pads / vias on PCB to dissipate heat the top line TNY290PG claim 36W in SO-8 package (magic!). Conclusion is yours.

[PeteS in CA]

Re: TNY27x thermal shutdown issues

While main competitors like ST or Fairchild or Linear have different package which require PCB thermal pads / vias on PCB to dissipate heat the top line TNY290PG claim 36W in SO-8 package (magic!). Conclusion is yours.

Ummmmm ... is Power Integrations claiming their TNY290PG will dissipate 36 watts? Or are they claiming it can, with appropriate circuitry, produce 36 watts of output power? I think this is a, "To ask is to answer," situation.

Power Integrations has been around for at least 25 or 30 years. They aren't fly-by-night flakes.

[DriversScrew]

Re: TNY27x thermal shutdown issues

Found the TNY279PN faulty in a 580W bq atx power supply. Generating the 5VST. First checked all electrolytic caps and desoldered many other parts.
The power supply only works for about half a minute with all voltages ok. Then shutting down and after one more minute it is ready again.
Finally I had the chance to look at the ps with a thermal cam and could clearly see the TNY (half under heat sink) heating up until about 85°C. Then it shuts itself down and when cooled to around 50°C it comes back on...

I will look for a replacement part but it seems not the best solution in a ps like this to me.

[redwire]

Re: TNY27x thermal shutdown issues

+5VSB is running 24/7 constantly and every year is 8,760 hours. The Power Integrations TNY appear to age. The power mosfet inside seems to fade away and have high on-resistance and heat generation.

[CapLeaker]

Re: TNY27x thermal shutdown issues

All the TNY27x I come across had their lids blown off…

[DriversScrew]

Re: TNY27x thermal shutdown issues

Found the TNY279PN faulty in a 580W bq atx power supply. Generating the 5VST. First checked all electrolytic caps and desoldered many other parts.
The power supply only works for about half a minute with all voltages ok. Then shutting down and after one more minute it is ready again.

Short update:
After replacing the TNY, the psu is running fine.
The new TNY279PN isn't warming up at all.