AT Power Supply Minimum Loads

[Rob Paisley]

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

 

[Rich Grise]

Rob Paisley wrote:

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?

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

 

[Ken]

On 1 Aug 2004 21:00:35 -0700, rpaisley4@cogeco.ca (Rob Paisley) wrote:

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?

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

 

[w_tom]

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.

Rob Paisley wrote:

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