Thanks for the comments and inputs, really appreciate it.
Its been a while since I looked into this but there are a few things I recall. Most fets SOA are not tested they extrapolate. In reality the SOA graph isn't a straight line particularly when you get out at about 60% VDS it craps out. Some devices are more suitable to linear operation logic level fets aren't one.
So for your regulator if you are building a standard 0-30V one if you select a fet with a VDS in the 150-200V range it should be more reliable and less likely to self destruct.
AcHmed99, from your experience about on 60% VDS, so this should be the "true" SOA ?
Just for an example in this discussion, I randomly grabbed a mosfet in my components junk bin, its a cheap P-mos IRF9540 VDSS=-100V, -23 Amp (datasheet ->
www.irf.com/product-info/datasheets/data/irf9540n.pdf), attached two particular charts here :
Actually for constant working at linear zone, not pulsing, according to your experience on 60% mark, so these yellow regions are not even safe ? Mind explain and elaborate more on this, I'm really interested and eagerly to learn & hear from you.
I have used 500V T0-3P Fets in an electronic load blocking 200V 2 devices dissipating 80W each while blocking 200V for extended periods case temp never got much past 100C so the junction was maybe at 110C or so. These were bolted to a brick heatsink with an 80mm fan blowing right on the heatsink in free air. They are still being used periodically. I'm using it right now actually one did just fail quite spectacularly actually Drain to gate short put 200V on my control board vaporised pretty well everything including a 50V tant that did what they do best went up in flames.
I don't believe this was due to thermal failure a wire may have inadvertently touched were it shouldn't. They were only dissipating about thirty watts each I've had them at much higher.
Sorry to hear that incident toasted your control circuit, my stuff won't even near that working voltage and current level.
Damn, drain to gate short on failure, sounds really terrible and nasty.