We have a power supply to fail to pass the thermal test. This power supply is based on the PMP4450 (UCC28703) reference design from TI (it is built with exactly components with PMP4450). During the test, when the environment temperature reaches to 85℃ with 250mA load, the 5VDC output will drop to around 0.8VDC. (we have checked operating temperature of components on the board and all range are rated between -20 to 125 °C
Below are the test condition:
Input power: 230VAC / 60Hz
Environment temperature 85℃
DC output: 5VDC / 250 mA
Would please let me know if you have a solution for the issue.