Hi All,
We have built a small form factor, UCC28880 based 85-265 VAC /50Hz to 5 VDC (30mA) supply which in turns feeds into an LDO to provide 3V @ 30 mA
We have tested it rigorously, but out of every 500 or so, the UCC will blow up without notice.
We are unable to understand the exact cause, I am detailing the circuit and conditions below, community support would be much appreciated.
BOM:
U1 -> UCC28880
L1 -> 1mH, 100mA
L2 -> 1.2mH, 100mA
D1, D2, D3 -> IN4007
Conditions of Use:
The circuit is connected in parallel to large load (2 KW power tools (inductive loads)), usually when the 220 VAC is being generated by a generator supply. We have tested the circuit extensively under all possible stress conditions of load, short, surge. But mysteriously every now and then 1 blows up, without much explanation. The UCC usually either blows up when it is powered on for the 1st time or even it works perfectly for the first time and blows upon powering it up again.
We are absolutely clueless about the solution and where to look.
Doubts:
Could there be a design flaw on our part or some measure we forgot to incorporate? Or maybe an issue with the inductor(s) [L1 and/ or L2] which causes it to stay charged and burst current through the UCC28880D?
What could be the possible diagnosis of this issue?
Much appreciate the support in advance!
Thanks,
Rohit