Powering a computer without inverting.

[Nigel Goodwin]

This is very interesting Glyph, I will have to look into it!

By the way, thanks everyone.
I have considered almost every reply.

Have you considered google?, in-car MP3 players based on computers were really common a few years ago, here's one, complete with homemade direct from 12V PSU.
**broken link removed**

 

[mneary]

Originally Posted by Glyph
PC power supplies can actually run off DC if the voltage is equal to the peak voltage of the AC they are supposed to run on.

Every PC SMPS that I have disassembled used a small transformer from the 60 Hz AC line to provide the startup bias voltages. This will burn with a DC input.

 

[Nigel Goodwin]

Every PC SMPS that I have disassembled used a small transformer from the 60 Hz AC line to provide the startup bias voltages. This will burn with a DC input.

Must admit I don't recall EVER seeing a conventional mains transformer in a PC power supply?. The startup is usually done by a high value resistor, which commonly goes O/C, I've replaced quite a few over the years.

 

[Hero999]

I think I have seen one PC power supply with a small low frequency transformer but it was very old. I don't think any modern PC power supplies use this kind of transformer anymore.

 

[blueroomelectronics]

Just a thought, is -5V (RAM & very old PROMs) and -12V (RS232) even used on modern motherboards anymore?
PS most standard ATX motherboards might be pretty unreliable in a mobile (bumpy) environment, PCI cards will probably come loose.
Mini ITX car enclosures are available
**broken link removed**

 

[Gordz]

A lot of early PC power supplies had a small mains transformer to power the start-up circuitry, used to be a problem to get replacements.