
The picture shows a power supply I am building, using DC-DC Converters as I need isolated input and output grounds.
When not specified, the electrolytic caps values are 220uF.
The converters are the Mornsun B1212S (in 12V and out 12V, 83mA max) and the B1209S (in 12V, and out 9V, 111mA max).
The problem I am having is that the Q2 Mosfet sometimes blow up. The reverse protection Mosfet also blows up sometimes.
These Mosfets have a max Vgs of + - 20V and a current of about 4A max.
I expect a max current drain of about 700mA.
The circuit is supplied with 12V, I have the over voltage protection because the DC-DC converters max voltage is 13.2V
Resistors R10 and R11 help bringing the trigger voltage close to 13.2V. I used a trimmer to find the correct values.
the protection works good. But if I turn the power ON and OFF a few times one or other mosfet will blow up and become a low resistance between all its pins. Even if i remove the protection circuit, leaving only the reverse Polarity Mosfet (Q1) in the circuit, and connect the 12V to the converters by touching the power Bus using a little wire, I can see some spark when connection is made, and after a few times, the Mosfet blows up

So, I guess I might be seeing some High (inrush?) current when closing the circuit.
my question is, what can I do to deal with this?
Higher current Mosfets? Slow down the Mosfet turn ON time? How?
I think hese Mosfets should be able to handle 700mA, as their max is around 4A, right?
But of course if the initial current is much higher, then I understand that they could blow up

In case you are wondering why i want to build this, it is to power my self made guitar pedalboard. this will allow me to power all effect pedals with isolated grounds and avoid ground loops. The ground between pedals will be shared only by the signal jack connector..
Thanks in advance for your help..
João
EDIT: Before I decided to use the over voltage protection circuit, I had a 12V regulator(7812) with heatsink. If I fed it with 15V it felt quite hot to touch. perhaps it shouldn't?? If powered by 12V only, it didn't become so hot, but obviously the output voltage was lower than 12V. Still ok for the converters because they need a minimum of about 10.5V to work. But the BS1209S were outputting about 8V only, instead of 9V..
The thing is, with the 12V regulator, I naver had Q1 blowing up.. So, why that? the regulator starts slower?