🚀 go-pugleaf

In article <92@decabo.enet.dec.com> (J. Brewer) writes:
>	I have a need to obtain 600VDC at about 150-200mA from an
>	800VDC supply. It need not be exceptionally well regulated
>	voltage-wise, but does anyone have a simple solution?
>	(not as simple as a resistive voltage divider however!)

Whew...that's a fairly high voltage. If the 800V is pretty stable, you
could use a voltage divider to give you a reference voltage of about 600V,
then feed that into a source follower (or emitter follower) if you can find
a transistor that'll handle the V & I you're wanting. You _might_ even dig up
an old triode (gasp!) that'll handle the current, and set it up in cathode
follower configuration...those three circuits are basically the same thing...
voltage followers. Very high input impedance, very low output impedance, with
the output voltage following (more or less) the input voltage. One base-emit-
ter drop wouldn't be worth worrying about at those potentials.

A switching regulator would be more efficient, but it may be more complex
than you want...it rapidly gets to the point where it's easier just to
build a 600VDC supply from scratch....

Another thought occurs to me, but I don't think it would handle the current:
You could stick several gas-discharge voltage-regulator tubes in series with
the supply to get the drop you want...IF you can still find those VR tubes
(type OA2, etc., if memory serves) and IF they'll handle the current.

A modern equivalent would be a 200V zener diode. I'm sure you could find
such a critter, but 200V * 0.2A is about 40 watts...and the diode has to
safely dissipate all that. If you can find such a diode, that's probably the
simplest method. Think "heat-sink".

Heh. You _could_ come up with a 200VDC supply, and put it in series with the
800V supply, polarity opposed. It would _work_...but it's kinda like swatting
a mosquito with an ax....

Lastly, perhaps a DC transformer...?   ;^)

						d



--
	"It's my _dessert_ that's gross! Look, a thermos full of phlegm!"
						-- Calvin
   Duke McMullan n5gax nss13429r phon505-255-4642 ee5391aa@hydra.unm.edu