Measures to prevent tube explosion of fast recovery diode

Measures to prevent diodee explosion of fast recovery diode.
After the breakdown of the fast recovery diode, it is equivalent to the output capacitance connected to the secondary of the transformer, which is essentially different from the output short circuit. After the rectifier diodee breakdown is equivalent to a short circuit on the secondary side of the transformer, the most intuitive thing is that the primary inductance is gone (except for a very small leakage inductance). At this time, the VCC of IC still exists.
Therefore, the original MOS will blow up in a cycle when the input voltage is relatively high, the higher the residual voltage of VCC, the longer the maintenance time of VCC, and the greater the short-circuit current when the secondary side is short-circuited, when the input voltage is lower, the VCC voltage is relatively lower, and the VCC falls more quickly below UVLO.
This is secondary, the most important is that the current flowing through the MOS is reduced at this time, so it may not blow up the machine, but when the output is short-circuited, the output capacitance is short-circuited, and the inductance on the primary side of the transformer still exists, and the IC will pull the duty to a larger position, causing the current on the primary side of the transformer to rise to trigger Isense protection in one to several cycles, so the machine will not be blown up if it is properly designed.