looking for electronics wizard

[wedge]

I'm trying to install a PC into my car. I'm running into power issues. I don't want to use an inverter because it's inefficient/wasteful to convert 12v to 120v and then back to 12v again. So I plan to run the computer directly off the car battery. The problem is that PC's also require a 5v source.
So, does anyone know how to create a low-cost DC to DC converter, with 12v input, 5v output, with a minimum 20W of power?
I'm usually good at that stuff, but I don't feel like doing my own thinking right now.

[Luc]

You can look into those LDO or switching regulators from Linear Technology or Maxim IC. For a 20-W 5V output, you'll need something that can output 4-A. Typically, if you follow the guidelines for using the appropriate capacitor and inductor parts, you'll get a steady output. For a 4-A output, those passive parts will be pretty big, typically, you want to allow some headroom. You can find something that has a dual output with a single input. For a switching regulator, do pay attention to the switching frequency because that may cause the output to fluctuate, thus, those passives must be used properly. FYI, a PC will need a 3.3V and -5V output as well for the ATX specification. So it isn't easy (or cheap) as it may seem.

[wedge]

Thanks dude,
I'm just going to be running either a 486 or maybe a P1. Either of which run off a PS2 power supply. So there is no 3.3v output, and it will work fine without the -5v.

[alex]

i'm lazy and would just use an inverter......who cares if its inefficent.......i'm american, thats what i'm good at

[Luc]

Thanks for you input. If you have something else better to suggest, please do.

[ZXLNT]

Also the inverters are not only inefficent the 110V they provide isn't the most clean. You dont want a lot of noise powering your computer..