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Dear sir


I have made a 9 watt power supply with tny 280 switch.

i have used 0.1uF 50V BP/M capacitor.

in some power supplies i have noticed at the time of start-up the ic is fused(blows-up).

 after that the bypass and source pins are showing shorting. 

i haven't used under-voltage circuitry.


guide how to solve this problem




PS : blows-up or fused really doesn't mean that it burns out.

Please look for possible connection problem or improper component placement or underrated components. See if you can find any difference between a good board and the "bad" board.

Review your schematic to make sure the design is sound.