paralleling computer power supply outputs: can they be connected in parallel...

[jarthel]

to get more current?

I've done it before in linear supplies but I'm not so sure with smps (I assume computer supplies uses smps).

Is it as simple as connecting "red wire" from 1st supply to the "red wire" of the 2nd supply?

thank you

[unclejed613]

the SMPS supplies sometimes have feedback connections to the outputs (as do most linear supplies). it's best to use small value high wattage resistors to balance the load between supplies. you might want to fuse the outputs as well, to protect the other supplies in case you have a rectifier diode or cap short on one of them. now that i think of it, the resistance of the wires (usually #18 or #20) will probably suffice for balancing the loads. fuse the supplies for about 90% of their rated current or less. although SMPS's have overcurrent shutdown, two or more supplies operating in pulsed shutdown might react unpredictably in event of a short.

[Scott Novak]

The biggest problem you will have trying to parallel switching power supplies is getting the load to balance between the 2 power supplies. This is pain in the butt even when you are designing the system yourself. Using series resistors between each power supply and the load may help to some degree, but then you will be affecting the power supply regulation.

I wouldn't recommend trying to parallel switching power supplies unless the power supplies were designed to be operated in parallel.

Scott Novak

[unclejed613]

another way to parallel SMPS's is to parallel through high current schottky diodes to isolate the supplies from each other. using schottky diodes gives only a 300mV forward drop across the diodes. if you want a "no-drop" diode, this is done with MOSFETs. there's a few ways of doing this. look up "lossless diode MOSFET" or "ideal diode MOSFET" in a search engine. if you can diode isolate the supplies, you will avoid some of the squirrely things that can happen with the interaction between two or more SMPSs.

one of the tricks that worked with linear open frame supplies, but is more difficult with SMPSs unless you know where the feedback is tapped off, is to run the sense line to the other side of the isolation diode, so that the supply will compensate automatically for the diode drop.

[coloradosound]

There are dual redundant computer power supplies on the
market. Have you checked into those. I picked up some
off the bay of E place. They share a common chassis and
have the load balncing resistors and the schottky diodes
(or MOSFET equiv.) which blocks the supplies as unclejed613
mentions and be cause of that they are hot swappable!
(If one supply goes down, you can usually flip some type
of locking lever and pull out the bad unit while powered up
and plug in replacement later, again while powered up!)