12v powersupplying notebooks and atx mainboards?

[okppko]

In eu an atx power supply is often 240v 500w.
A notebooks power supply's output can be about 18v 2a.

If power source is 12v are there options which goes from 12v to power supplying an atx main board or a notebook and not requiring the above mentioned power supplies?

 

[Eximo]

Not 100% sure what you are asking here.

A power supply that runs off the mains is converting AC into DC through rectification. What comes out is a very close approximation to a DC output.

If you have a DC source and attempted to power an ATX computer, you would need to convert whatever the DC input voltage is down to 12V, 5V, 3.3V and meet all the specifications. This can be accomplished with DC-DC converters.

Laptops are a little simpler, since they already run directly on a single DC input. Just has to be the right voltage and meet the power requirements. 18V 2A is a little light actually, average supply is 65W.

 

[okppko]

Thank you.

Not 100% sure what you are asking here.

If you have a 12v car battery you may convert 12v to 230v. Then use the power supply that came with the atx computer notebook. That must be not energy efficient. Can you go more straight from the 12v car battery to the computer?

 

[Eximo]

Running an AC inverter off of DC and then converting back to DC is quite inefficient. Using commercial grade products you are looking at roughly 20% losses each time. You pay for efficiency, so getting something 90% or more is going to be pricey, but they are out there. High end UPS are an option, and you can always increase the battery size with external batteries.

There are computers designed to run solely off of 12V. Industrial PCs, NUCs, and a few others, including some motherboards and older laptops also typically ran off 12V.

If you have a 12V source and standard computer that need to be run it depends on exactly what you are doing.

For your typical laptop at 18/19.5/20V that means a high efficiency boost converter that can handle the appropriate amount of current and maintain a constant voltage.

For an ATX system, that means DC - DC converters for the low voltages. Efficient ones are expensive, but they provide isolated power that is essentially ideal. Again you'll have to match the output requirements in terms of current. Many ATX supplies now provide 5V and 3.3 volt in this manner since it is more efficient than traditional voltage reduction, and/or cheaper then having a multi-tap transformer.

It may now be possible to bypass the entire rectification circuit in a late model supply and hook 12V directly to the 12V rail and still get out 5V and 3.3V. You would have to be sure the computer in question no longer needs the -12V and -5V that some older systems use, maybe. (I've not tried this)

If you have a high voltage DC source, think whole home battery backup, you can take an ATX supply, bypass the AC input and hook the high voltage directly across the main capacitors and it will operate as normal and produce low voltages. Though this is a dangerous configuration.