Hello:
Recently, a 100W half-bridge power supply was made with reference to TI's LM5035 sample. The circuit schematics and manuals recommend the same circuit.
Produced 50 prototypes, a strange phenomenon appeared. There are 25 circuits that are normal, and 25 of them burn the MOS tube when they are powered on, and most of them burn the secondary rectification MOS tube, and also burn the primary MOS tube.
After replacing 25 burned MOS tubes with the prototype, the power supply is normal.
After the power supply is normal, I tested the drive waveform of the MOS tube and the voltage of the DS terminal when the prototype was started, which is normal.
Later, the product was subjected to high temperature experiments. During the experiment, 4 of the original 25 good MOS tubes were damaged, 2 was only damaged after one day of high temperature work, and 2 was just damaged by no-load power-on. The secondary rectification MOS tube has broken three, and the primary MOS has broken one.
I am very confused now. The tube is genuine, and the waveform is normal when the power supply is stable. After the MOS tube is broken, it will be replaced by a new one, but I can't find the reason. I don't know where it is. Now my heart is very low, maybe someday the prototype will fry the MOS tube.
Also ask the seniors to point out the maze, how can I find the reason? What other factors may cause this kind of good or bad?
