Agreed and besides, even if this diode could handle the 2 Amp from the EPS when the FET is turned off, it is in the wrong direction to protect the FET from the back EMF.
Agreed and besides, even if this diode could handle the 2 Amp from the EPS when the FET is turned off, it is in the wrong direction to protect the FET from the back EMF.
Depending on the switching frequency and rise and fall times it's not uncommon to rely on the MOSFETs internal body diode. Depends on the actual peak voltage created by the coil, and the MOSFET's specs.
I can't calculate the decay time since I don't know the inductance of the MPS.
If it was say 1 Henry and, given it draws 2A at 12 Volt, it must have a resistance of 6 Ohm, therefore the time constant would be 1/6 second so the 1N4148 would curl up and die.
I suggest you look at the data sheet of the 1N4004.
The resistance of the coil is about 5Ohm, so your estimations are about correct. I'm in Czech Republic at the moment so I'll have a look when I get back to the UK on Monday.