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UCD3138FW-HSFB: Full-bridge hard-switching power supply, the input voltage rises, and when it is no-load, it will blow up the machine. How to check?

Part Number: UCD3138FW-HSFB
Other Parts Discussed in Thread: UCD3138

According to the UCD3138 full-bridge hard-switch development board, four full-bridge hard-switching power supply prototypes were made.

The input Vin: 20V~50V, no-load test.

When the input voltage is gradually increased from 20V, when the Vin reaches 40V-48V, 4 prototypes have 3 primary MOS tubes blown up.

2 fried ones were on the upper tube and one only fried one bridge arm.

It looks like a fried MOS tube caused by straight-through, because it is empty, the tube is 80V withstand voltage.

However, I observed the primary 4-way drive waveform and found no abnormalities.

Now I don't know how to start troubleshooting. When the voltage rises, I feel worried.
I hope that the expert guidance will find out why.