Rectifiers

[pyrre]

moto can use DC-DC converters to make +5V


EDIT:
link

[pyrre]

After reading trough my electronics books.
It could be done fairly easy with a resistor and a zener diode of proper values....

[pyrre]

Wouldn't the output be too "dirty" for a computer?

I have no idea.
but

A Zener diode used in this way is known as a shunt voltage regulator (shunt, in this context, meaning connected in parallel, and voltage regulator being a class of circuit that produces a stable voltage across any load).
In a sense, a portion of the current through the resistor is shunted through the Zener diode, and the rest is through the load. Thus the voltage that the load sees is controlled by causing some fraction of the current from the power source to bypass it—hence the name, by analogy with locomotive switching points.

I cant see any reason why it would be...

[pyrre]

@ motorollin
Why not build a pico psu inside an a500 psu box...
pico psu wil provide 30, 60 or even 120W of power...
discrete packaging inside the a500 psu box as a bonus...

[pyrre]

here is a link to some psu's that might get you started.
I do not know if you have investigated upon the possibilities from mini-itx. But some of the psu's looks useful...
Some of them are made for var environments as well, and should provide sufficient fail safes for home use.

Good luck on your project.
Hope it helps.