Need +12V DC from +400V DC power supply

[Freddybaby]

Need +12VDC from +400VDC

Looking for a relatively simple solution to power some op-amp + sensors
from 400VDC supply. I can't seem to find an off the shelf DC-DC buck regulator
for this range.

Perhaps a high voltage mosfet series regulator ???

HELP!!!

 

[dick_freebird]

Need +12VDC from +400VDC

At that kind of load (maybe 1mA-10mA?) I'd think about
a series resistor and a shunt regulator. That will be pretty
tolerant of things like overvoltage (400V nominal, is
what, worst-case?). FET breakdown needs to accommodate
that and is more like a "cliff" while a resistor would just
get hotter by the incremental amount.

Some power MOSFETs don't especially like to be operated
linear (I've built some that work great switched and blow
right up when dissipating power).

 

[Freddybaby]

Need +12VDC from +400VDC

That is a good idea but I may need to operate a
small relay as well. Don't know the relay current yet.

I did find a DC-DC from Vicor (up to 525V in and 2-48V out) but they are expensive...