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AT Power Supply Minimum Loads

Discussion in 'Electronic Basics' started by Rob Paisley, Aug 2, 2004.

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  1. Rob Paisley

    Rob Paisley Guest

    I have been playing with an old AT computer power supply and found
    that for the PSU to stay ON, a minimum load of about 1 amp has to be
    maintained on the 5 Volt supply.

    No minimum load is required for the 12 Volt supply or the negative
    supplies.

    Is this typical for this type of supply or do some require a minimum
    12 Volt load as well?

    Thanks.

    Rob.

    Model Railroad & Misc. Electronics
    http://home.cogeco.ca/~rpaisley4/CircuitIndex.html
     
  2. Rich Grise

    Rich Grise Guest

    I've run one with just the +12 loaded. In the PSUs I've seen all
    the secondaries are on the same transformer, so I'd think that just
    pulling approx. 5 watts out of the thing should be enough to keep
    it on.

    Although, if you've tried this, and it didn't work, then I'm clearly
    wrong. ;-)

    Good Luck!
    Rich
     
  3. Ken

    Ken Guest

    My PSU need load only at the +12V
    http://w1.857.telia.com/~u85710476/docs/image/example/psu_antec550.png
     
  4. w_tom

    w_tom Guest

    Every power supply design is different. No one can answer
    your question without the manufacturer's specifications. Some
    switching power supplies require no load to start. Some can
    be intermittent when started with no load - works 99 times out
    of 1000. Some supplies definitely will not start without a
    load AND can be intermittent (99 out of 100 times OK) with a
    load too small. Some require loads on either or both 3.3 and
    5 volts.

    Did the supply provide manufacturer's specs? Do you have
    schematics? If not, then no one can answer your question for
    that power supply.
     
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