Diggrr said:
*I like ProCooling's article that EgNatz linked to, it's actually a pretty tough little psu for for the job. I've built one myself, and it works fine, though I've not used it long-term, and would have my doubts.
*A 500+ watt computer power supply would probably run a pelt fine for a while, but remember what that psu is meant for. There's no computer (retail desktop) that draws this much power, therefor you can take for granted that a computer's psu is NOT made to deliver it's rated load full time...in the real world, it probably never would see full draw, ever. Don't kid yourself into thinking the maker of the psu don't know this and isn't willing to use less robust components.
I took a look at the ProCooling article and noticed a major problem is not addressed when the author discusses hooking PS's up in parallel. PC PSU's are not designed to be hooked up in parallel and load share.
Suppose you have two supplies of the same model, but one of them puts out 12.1V when loaded at it's max current and the other puts out 11.9V when loaded at it's max current. If you hook the two supplies in parallel and tie them to a load that draws 110% of the max current for a single supply, only one of the PS's is going to provide the vast majority of the current. The PS that sources 12.1V at max current may sag down to 12.0V at 110% load while the PS that sources 11.9V at max load sources no current at all, because it is detecting that its output voltage is at or above the voltage it is set to output.
What you have in this case is one supply running at 110% of it's maximum rated output and the other running in an unstable state due to a total lack of load current. This is just one of the nasty problems that can occur with supplies in parallel. There are much worse scenarios than this that are likely to occur if you load the parallel combination at more than 110% max rated current.
If you do want to hook up two supplies in parallel, first make sure that the 12V output is adjustable. (And, that you know how to adjust it.) Then with a load, equal to half the current output you are trying to achieve, adjust the power supply outputs to 12.00V as accurately as you can. This will help ensure that when the supplies are hooked in parallel to the full load they will each supply a substantial portion of the current. Because the values of electrical components drift over time, you should probably repeat this adjustment every 3 months to be on the safe side.
If you've done all this, you still haven't guaranteed safe and reliable operation of the paralleled supplies. You've only given them a fighting chance. If you don't understand all of this, don't try to hook supplies up in parallel. If you do understand this, and still want to hook supplies in parallel, and want to know how to do it in a way that truly is safe, let me know.
I agree with what Diggrr said about PC PSU's. They are designed with powering a normal PC in mind. The PSU manufacturers almost definitely cut corners where they can get away with it. (The profit margin on PSU's is razor thin.) Also, I looked up the spec's for the Antec 550W supply on the web. From an electrical engineer's standpoint, these spec's are seriously incomplete. There is no mention of temperature derating for example. They are not publishing the spec's an engineer would expect, when sourcing a general purpose supply for use in a new product. I personally consider a PC supply suitable for only one thing - powering a fairly normal PC.