UPS MOSFET burns on switching

[Manoj Sharma]

My ups is not switching from battery to main supply.
when there is main supply it works fine.
but then it doesn't switches from mains to battery in case if main supply fails.
If i switch off the mains and power it on it works fine on battery.
but when the main supply is turned on while the ups is running on battery the mosfet(p80nf55-08) burns out quickly.
the ups is driven by pic 16f72 that drives 4 relays(each 250v 5A) by uln2003apg. also there is one lm380n opamp.
i think any one relay is dead. but i'm not sure.
please help!

 

[goldsmith]

My ups is not switching from battery to main supply.
when there is main supply it works fine.
but then it doesn't switches from mains to battery in case if main supply fails.
If i switch off the mains and power it on it works fine on battery.
but when the main supply is turned on while the ups is running on battery the mosfet(p80nf55-08) burns out quickly.
the ups is driven by pic 16f72 that drives 4 relays(each 250v 5A) by uln2003apg. also there is one lm380n opamp.
i think any one relay is dead. but i'm not sure.
please help!

Hi Manoj Sharma
I think first of all you must tell did you design it or you just built it or perhaps bought it ?
2nds step : deliver the schematic !
Because we are not ray charles ! you just say it drove with ... ok but how ?!
Best Luck
Goldsmith

 

[schmitt trigger]

"We are not Ray Charles"....thank you Goldsmith, your comment made me smile.

Also, to the original poster: the LM380 IS NOT an op amp, is an audio amplifier.

 

[Electro nS]

remove the relay , desolder if required , and check then by multimeter "beep" tester

 

[goldsmith]

"We are not Ray Charles"....thank you Goldsmith, your comment made me smile.

Hi schmitt trigger

Your Welcome ! ;-)

Also, to the original poster: the LM380 IS NOT an op amp, is an audio amplifier.

Hit to the point !