I would like to have your opinions about this short circuit protection. Here is the schematic associated given into the datasheet.
And you can find into the same datasheet how their short circuit protection works.
Here are my questions:
1 - " When the output of a flyback power supply is shorted, the primary VDD decreases due to the coupling polarity between the aux winding and the secondary winding of a transformer"
It means that the current flowing through the secondary windings which is high produces a flux (according to the Ampere's theorem) which can cross the inductance of the auxilliary winding and then have an influence on the auxilliary voltage? Theoritically, the mutual inductance between the secondary winding and the auxilliary inductance should be null? I.e. coupling factor = 0? So the datasheet assumes that the transformer is not well designed.
2:nd question: "However, it is possible that the VDD voltage remains higher than the UVLO level even if the output is shorted. This happens when the coupling between the aux and the primary winding is too good." Is it asking to reduce the mutual inductance between primary and auxilliary, ie to increase the leakage inductance on the primary side? What it really asking is to have a lower coupling between the primary and the aux and a better coupling between the output and the aux. Imagine I follow the instructions, as the current sink by the auxilliary winding is low, even if the coupling factor is poor, the flux which will not be tranfered to the auxilliary side and so will remain to the primary would not be able to produce a high leakage inductance? As Lleakage = remaining_flux/I_primary (I’m not sure of this last definition)