Building a DC Power Supply for ATX system

So, where're you gonna get the DC input power?

The ubiquitous $50 PC AC-DC internal power supply is already a switching supply, and fairly efficient.

It's also DC-DC internally-- the internal DC bus is a bit over 300VDC with either a 120VAC or 240VAC source (using a voltage doubler arrangement in the former case).

Best regards, Spehro Pefhany

You want to replace the existing AC->DC supply (which is actually AC->DC->DCx3 with a AC->DC supply, a battery, and then another set of DC->DC supplies? That's going to cost a fortunte relative to the existing solution.

Firstly, where's the DC power going to come from? What you call "trickle charger" needs to put out several hundred watts at

We've done what you suggested, within some fairly tight constraints. Our Thin Client:

Has an auxilary board that, amongst other things takes 8-30 volts DC in and converts it to an output compatible with an ATX supply. Unfortunatly, it's not nearly as cheap to build as we had hoped, and it's output is sized for only a couple of mini-ITX motherboards.

Remember that you need to supply 2 or 3 sequenced voltages and a standby +5 volts, plus some reset logic. It's not an overly difficult design, but it's not trivial either. Especially if you want to do it for a reasonable price.

There's quite a bit of cleverness and cheap labor involved in producing a 400 watt, switched, multi- output power supply for for $50. But then what else is new. Can you build a VCR for $50?

yes it would work. how do you think laptops work? !!

but in a home PC the currents involved are quite high, as is the (summed) voltages.

pc's need +/- 12v (24v volt potential diff) & +/- 5v (10v potential diff)

if you did not use voltage doublers or inverters (DC-DC) the 24v system alone would need two (12v) batteries and the 5v perhaps one 6v but the current needed is very high.

thus a trickle charger would not be so, it would effectively be a PSU, where the battery only gave power when mains was dead...bingo a UPS as you stated.

as for you 1,2.3 bullet points, i can see none as being true.

mike

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Do not build it Buy it. There are several 12 volt ATX supplies on the market. Google for them. Apparently there is a market for Mobile PCs that are not laptops.

With switching Supplies If you have to ask if it can be done, you can.

well there are calls for this I work for a router maker and often only the teleco's want this "feature". Most companies see the 120 volt AC has just simple and easy.

The following links should help you understand the hardware I'm considering for the system I'm proposing.

~ 25AMP Switching Power Supply

~ 200 Watt DC-DC ATX Power Supply

~ The automotive battery and battery charger (with trickle feature) I'll leave to your imagination. :)

~ The next link was a cool hack I saw that got me thinking about using an ATX instead of an ITX motherboard.

If you can think of a better forum for this discussion, please let me know.

Trent

In comp.os.linux.embedded Computer Doctor wrote: : I don't know if the following has been done, but here goes:

: Would it be advisable to provide a DC-DC power supply (PS) to an ATX system : for the purpose of; : 1) Increased efficiency : 2) Decreased heat : 3) Decreased fan noise : If you used an automotive style sealed battery in the circuit and a trickle : charger, wouldn't you also provide a fairly substantial UPS system ? I've : seen DC-DC power modules that plug directly into the ATX power connecter : the size of a playing card. DC Regulated Switching Power Supplies are not : too expensive if you're trying to meet the above criteria.

: I believe that the computer industry has not utilized the DC-DC PS because : of the ubiquitous $50 PC AC-DC Internal PS. If I'm way off on my ideas, : please advise. If you can shoot holes in my ideas please do so.

Being done. There are several lower power MoBo's being powered by such a setup for automobile use etc. The ideas stands for any use. Several of the MiniITX and NanoITX mobo/equipment suppliers supply these DC/DC supplies.

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