Looking for any information on how to possibly convert a standard ATX psu to run off of DC input (say 12-30v). I know there are commercially available DC-DC psu's, I'd just like to make use of one or more of the old psu's I have lying around.
Not without a lot of work. The ATX supplies, in general want something over 300VDC into the primary of their transformer (some 115V supplies only want about 150v, but most use a switchable input topology, with a voltage doubler connected when
115v is selected), so conversion, would require complete redesign of the main transformer. Not a small task. If you are not worried about efficiency, then you could make a DC to AC inverter, and leave the ATX supply as it is. There are plenty of circuits for these on the web, but be prepared for how large the transformer will need to be for a unit able to run a ATX supply. Given that you should not need the isolation offered by the ATX supply, a DC-DC buck inverter, would be simpler and cheaper to make, and could feed the main PC rails. There are off the shelf IC's, which control an external FET to give this sort of supply, which in combination with a suitable inductor, and a couple of discretes, would give one of the rails, for only a very few dollars. Some rails you can probably ignore (The -5v rail has been dropped from the latest ATX specs, and many boards do not require -12v, except for serial ports). Unless you have a very big DC source, you might be much better off, assuming this is to run a PC, looking at a board and processor specifically designed for this sort of operation. A typical modern PC, will draw about 10A at 12v, continuously, and may peak at over 30A. Conversely, a proper 'low power' system, based on something like the Mini-itx board, with 2.5" disk drives, and basic video card, will have only perhaps 1/4 the performance, but typically draw less than a couple of amps...Best Wishes
I was planning on using it to power an mini-itx board, used only as a router (mainboard, fc-pga celeron, compact flash). The idea was to drop the primary side of the psu, and just use the secondary side. I'm not sure what the output voltages are from the secondary side of the transformer(s) are though. I'd imagine one would have to change/remove some of the components on the secondary side in order to get it to work.
This quite an involved task. Many parts would have to be replaced. I'd forget it.
Graham
It doesn't work like that. All the voltage regulation is done one the primary side.
If the load is quite small you could easily build your own psu using switching ( or even linear ) regulators.
Why do you want 12-30 V DC input nayway ?
Graham
snip
Case size constraints, as well as lowering heat inside the case. There isn't enough room for either an micro atx or flex atx psu, though the commercially made dc-dc atx psu's would fit fine (at a costly $50-100).
If you really want to do this, my suggestion would be to build an inverter from 12VDC to 170VDC, and connect that to the input of the ATX supply. I would try to use the transformer from a second PC power supply along with a couple of power MOSFETs and a switched-mode power supply controller IC. This would be quite challenging but probably educational. Provided you construct everything within well earthed metal enclosures, make sure all capacitors are discharged before opening the enclosures, and provided you test it with a dummy load rather than your new mobo, I think it could be a good project for someone with plenty of time.
Chris
There are plenty of 12V dc (car battery) to 120V ac converters out there, the technology is not real hard. Build or buy?
-- JosephKK Gegen dummheit kampfen die Gotter Selbst, vergebens. --Schiller
I would certainly buy an off-the-shelf inverter and plug the ATX power supply into it.
The ATX power supply probably starts by rectifying the incoming AC and then chops it. So, without major redesign, the only thing you can do is add a stage ahead of it to step up the DC voltage (and convert it to AC). That's exactly what the inverter does.
Now there may be somebody who has designed a 12-volt DC-input ATX power supply -- which would be a quite different beast from an ordinary ATX power supply.
This should have been posted to news:alt.binaries.schematics.electronic instead of text newsgroups that may or may not propogate your images.
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