[time-nuts] Low Drop Out Voltage Regulator

Robert Atkinson robert.atkinson at genetix.com
Fri Mar 9 03:29:37 EST 2007


Hi Brian,
One fairly elegant solution is to use a DC-DC converter module. The 50
watts you need is a bit high but possible. The Vicor VI-200 (100W) and
VI-J00 (50W) < http://www.vicorpower.com/products/dc-dc/converters/
>would suit. They are expensive but do turn up on eBay. Typical input
range is 18-36V for a nominal 24V unit. This will get the most out of
your battery pack. Some will take 9-36V! You don't have to use a 24V in
24V out unit, +_ 12V out units are more common and as the output is
generally isolated you can ground the -12V and ignore the 0V tap.
A 12V input unit would allow for fewer (higher capacity) cells and
"incar" charging, while a "telco" 48V input one would allow for smaller
cells but more of them.
One downside is that they can be noisy; a good LC filter on the output
and possibly Wenzel's "finesse" shunt regulator all in a metal box will
help.
One other thing is that I've noticed the cost of in-car laptop power
adaptors has dropped recently. Many of these will provide 24V out and
can be used to support small 24V unit wile on the move. I'm not sure I'd
trust a cheap one as a long term system component though.
I'm currently building a portable OCXO based on a FTS (Datron)1000B
using a 20W DC-DC converter as the regulator.

On the original question, I'd use an LM150 (TO3) or LM350 (TO220)
regulator. These are the 3A version of the LM317 adjustable. They
typically work at 1.5V differential and drop out gracefully.

Robert. 

-----Original Message-----
From: time-nuts-bounces at febo.com [mailto:time-nuts-bounces at febo.com] On
Behalf Of Brian Kirby
Sent: 09 March 2007 04:23
To: Time Nuts
Subject: [time-nuts] Low Drop Out Voltage Regulator

Can anybody recommend a low drop out voltage regulator that will work
with a 2 volt input differential, and a output of 22 volts at 2 amps ?

What I have in mind is a 28 volt DC power supply, and 24 volt batteries,
and a rubidium oscillator that will run at 22 volts.

Brian N4FMN


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