More 11/750 PSU Qs - test-drb@ccmp.vtda.org

17 Apr 2002

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  From: ard(a)p850ug1.demon.co.uk (Tony Duell)
 Subject: Re: More 11/750 PSU Qs
 To: classiccmp(a)classiccmp.org
 Date: Tue, 16 Apr 2002 03:01:23 +0100 (BST)
 In-Reply-To: &lt;20020415200927.52402.qmail(a)web10301.mail.yahoo.com&gt; from "Ethan
Dicks" at Apr 15, 2 01:09:27 pm
 Sender: owner-classiccmp(a)classiccmp.org
 Reply-To: classiccmp(a)classiccmp.org

    > NO!. SMPSUs do not like being run in parallel
(unless designed to be
 > used like that). One PSU will end up attempting to supply all the
 > current and the other PSUs may not like having voltages applied to
 > their outputs. 

 And once the first one drops dead, the next
 most "powerful" one repeats the process.
 Proof by "induction" left as an exercise :-)

 *giggle* OK, ok, thought it was best to ask.... *laughs manically*  
 Presumably, if one could a) tolerate the voltage drops and b) find massive
 diodes (many amps for the intended application in an 11/750), it could be
 done safely.  Please feel free to correct me if I'm wrong. 
 Well, that would prevent one PSU from supplying a voltage to the outputs 
 of another (something that can really confuse the regulation circuitry!), 
 but it won't help with the current distribution problem. The PSU who's 
 output after the diode drop is the highest voltage will end up sourcing 
 all the current. Not what you really want. 
Aren't there some power supplies that can be run in constant-current
or "current-limited" mode?  I think I used to do that with a PDP8-E,
when the power drain of the add-in boards exceeded the original 1/2 Amp
per slot.  A booster supply to provide more current.

    carl
-- 
        carl lowenstein   marine physical lab   u.c. san diego
                                          clowenstein(a)ucsd.edu