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.