Hello team
The 150W SMPS was designed using UCC29950.
It works without any problem under normal conditions
However, FAIL occurs due to RESET of UCC29950 during SURGE test.
Test conditions are L-N 1KV / L (N) -F.G 2KV.
It is judged that the result of various tests is not influence between EMI filter composition and pattern.
It seems that the reset is caused by the influence of AC1, AC2, SUFG and SUFS of UCC29950.
When AC line surge occurs, it is doubtful whether RESET occurs due to influence of Depletion mode FET (BSS126).
Send the circuit configuration together.
Let me know if there's anything I should be careful about.
Please help ...