[time-nuts] Parallel voltage regulators

Magnus Danielson magnus at rubidium.dyndns.org
Thu Oct 25 18:43:57 EDT 2007

From: Bruce Griffiths <bruce.griffiths at xtra.co.nz>
Subject: Re: [time-nuts] Parallel voltage regulators
Date: Thu, 25 Oct 2007 13:51:47 +1300
Message-ID: <471FE8A3.1060304 at xtra.co.nz>

> ); SAEximRunCond expanded to false
> Errors-To: time-nuts-bounces+magnus=rubidium.dyndns.org at febo.com RETRY
> Magnus Danielson wrote:
> > It is not that hard to acheive 2 A at 24 V after all. The old uA723 and
> > variants would probably do the trick good enought for you with external
> > transitor(s).
> >
> > I recommend to at least include fold-back for over-current protection, but
> > adding an over-voltage in form of a crow-bar setup isn't too hard either.
> > The point of the crow-bar is to cause fold-back and if that fails, blow the
> > fuse, so include a fuse on the unregulated supply side.
> >
> > Cheers,
> > Magnus
> >   
> Hej Magnus
> Using a 723 correctly configured with a low pass filter on the reference
> is a very low noise regulator solution with its output noise at least
> 20dB lower than that produced by a typical 3 terminal regulator.
> Most of the OEM open frame linear supplies use 723 regulators with
> external (to the 723) series pass transistors.
> These regulators have varying degrees of sophistication, some even use a
> zener plus emitter follower preregulator for the LM723.
> Some foolishly omit bleeder resistors across the reservoir capacitors
> which can lead to damage when making connections after powering the
> supply on and then off as the residual energy stored in the reservoir
> capacitors is more than sufficient to destroy the 723 should the output
> terminals be shorted.

While the 723 isn't the highest degree of sofistication these days, it does
alow for building more or less complete linear regulators. In another hobby of
mine they are in plentiful use and provide stable enought regulation.


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