Lots of suggestions for turning an ATX power supply into 12V, but what about the other way around?

long story short: I have an ATX board I want to use for an RV project, and would like to be able to run it off of 12V “house” power. there are lots of guides and converters for taking an ATX AC power supply and letting it run 12V stuff, but not the other way around. does anyone have any suggestions for how to do this?

There isn’t a good way to mod one, the whole supply is designed around 120VAC-240VAC. Best I can see, you have 4 options-

  1. use a 12V power inverter to feed the ATX supply. This is simplest, but has significant efficiency losses, particularly when the inverter is left on with no load it’s 0% efficiency and could have quite a bit of idle current draw. That idle draw tends to scale with inverter size. Most people say to use a pure sine inverter on these, although I’m confused as to why an ATX supply would care. Sine inverters are typically more expensive and higher idle current.

  2. Get a DC-input ATX supply. They’re rare, and I am only familiar with 48VDC ones. This would require a DC-DC converter to turn 12V into 48V, which is still better efficiency than a 12V-to-120VAC power inverter
    SDX-6200-G48 SUNPOWER ATX 1U 48V 200W POWER SUPPLY | eBay

  3. Find a solution that doesn’t need an ATX supply. Laptop.

  4. OK this probably won’t work, and would require strange hardware. The ATX supply rectifies 120VAC to make an HVDC rail and then the switching transformer converts and isolates. That should have caps after the rectified charge to 170VDC. It MIGHT function with a ~170DC input. But I don’t know that this will work, it depends on supply implementation. And you’d need a DC-DC converter that can do hundreds of watts into 170VDC. The only benefit here is improved efficiency over a power inverter.

Back when car PCs were more of a thing, 12-input ATX power supplies suitable for mini-ITX systems were pretty common. how much power do you need? Do you care about ATX mechanical form factor, or just the electrical characteristics?

A quick Google turns up a bunch of boards like this one: https://www.amazon.com/Output-Computer-Connect-Suitable-Mini-ITX/dp/B07TY121LT

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holy shit. I think this is exactly what I need! how did you find this?! don’t care about mechanical form-factor at all, it just needs to have the right connector and right voltages on the right rails. it’s going to go into a Turing Pi 2, if you’re familiar with those. https://turingpi.com/

incidentally I ended up getting this one. Amazon.com none of them seem to have a lot of reviews, but this one at least didn’t have any complaints.

so this one actually looks even better – way better ability to adjust to variable input voltage: DC-DC ATX PSUs