tny280 power on burn out

You need to check if drain voltage rings down to zero volts during brown out.If so then you may have transformer with excessive leakage inductance. Also check drain current for saturation of transformer core during start up and brown out.

Hi all, TNY276 is burnt out along with 10 ohm, 3W resistor (input of the circuit) which acts like a fuse. Both drain and source of TNY276 got shorted which creates high inrush current which leads to 10ohms resistor burnt. During analysis it was found that drain current reach a level of 720mA during start up. In steady state operation, drain current goes upto 380mA which is within the limits of TNY276.

Attached the schematic for your reference. Pls suggest the reason for the failure of TNY276 and input resistor 10 ohms.

Also suggest for any change need to be taken for RCD snubber circuit as well.

Hi,

Could you send us the drain voltage waveform and drain current waveform during startup. Could you also please send us the transformer construction document, your PIxls or PiExpert design file as well.

This post belongs to someone else. Could you also post your question as a new post.

Regards,

PI-NANO