mini itx laptop

muchalucha · Post by **muchalucha** » Sun May 11, 2008 8:21 pm

For a while I have been building a mini itx laptop, but i have run into a problem which i hope you guys can help me on. I have aquired a 16V 5 amp switch mode power supply, I want to use this to power the laptop but the teeny tiny 55W ATX power supply takes 12V and anymore would kill it.

Basiclly i need a 5A 12V regulator circuit, i have looked on the internet but all of the ones on the internet are too sophsticated for my needs (variable ones) and im stumped for a diagram.

Simon Windisch · Post by **Simon Windisch** » Sun May 11, 2008 9:16 pm

Try this regulator and this circuit.

Of course, it might blow up your device, so beware.

Simon

Post by **BeligerAnt** » Mon May 12, 2008 6:39 pm

Whilst that regulator may do the job, dropping 16V down to 12V at 5A means the regulator is dissipating 20W. It will need a VERY BIG heatsink. Not very laptop-ish!

You need a switched-mode regulator. Whilst there are plenty around, they are not easy to design with, and it's very easy to get it wrong and then very difficult to put it right. Especially if it has blown up your expensive piece of kit in the process

If you can find any data on the 16V PSU, the best solution would be to modify it to produce 12V, assuming you can get inside it.

muchalucha · Post by **muchalucha** » Mon May 12, 2008 8:31 pm

its a very old 16V 4.36A IBM think pad power supply, its sealed but i could get inside it, if i did how would i mod it for 12V?

Post by **BeligerAnt** » Wed May 14, 2008 7:45 pm

Forget it, you'll never find the detailed information you need, and you really shouldn't go digging around in a PSU like that unless you REALLY know what you're doing.

Since you need to ask, you don't know what you're doing...

Your best bet would be to ditch the 16V PSU and look for a 12V one. Probably cheaper and quicker in the long run.

The linear regulator solution will not work, since 55W @ 12V = 4.6A and your PSU will only supply 4.3A. A switched-mode regulator is the only solution, but I wouldn't recommend you try it.

This may be an off-the shelf solution to running your ITX board from your 16V PSU:
http://linitx.com/viewproduct.php?prodid=11142

muchalucha · Post by **muchalucha** » Wed May 14, 2008 8:58 pm

I now realize that that just wouldent work, so im going to have a dig around and try and find a 12V power supply.

I dont know if anyone here is good with linux, but i have been using knoppix and pen drive linux on the laptop, knoppix boots fine repatedly until i plug it into my computer, at which point it needs a re isntall, and pen drive linux just keeps on giving me linux kernel I/O port errors ( which is strange as the pc has no keyboard, no mouse, no screen, no hard drive, no cd drive, basicly a power supply usb hub and usb bits and bobs like the 4gb memory stick)

I gave up with the original plan for ubuntu on a memory stick.[/quote]

muchalucha · Post by **muchalucha** » Wed May 21, 2008 7:28 pm

I have found a 1.5A 12v power supply and after a while of trying to cut every last piece unnecesery power consumption out ( even the 2 case LED's!!!) it works, its not overloaded but it does run fairly hot (the power supply) and for a brief moment on startup it shoots up to 1.8 amps, but it works .... safely.

that sort of makes this obselete, thanks for the help.