A Very Simple and Tiny PC Power Supply

william chan

It recently crossed my mind that some mini-itx motherboards (see www.mini-itx.com) with Compact Flash cards as hard disks
use so little currents compared to normal PCs that we might be able to get away with
a simple 12V Switching Adapter and a few linear regulators to convert to +5v, -5v, and -12v.

Any remarks or suggestions?

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Bruce Bates

William -

Let's put it this way - there is a good deal more to a PC power supply than just the voltage outputs you have listed. Take a look at a PC power supply motherboard connector to view the number of signals and voltages that must be present.

You do get credit for a rather interesting thought however!

Regards,

Bruce Bates

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"Genius is one percent inspiration and ninety-nine percent perspiration."

Thomas Alva Edison

RDL2004

A modern PC power supply connection looks complicated because it uses multiple circuits to deliver the large amount of power it needs. There is only +3.3, +5, +12, -12, -5 and ground. The -12 and -5 power requirements are small.

While you could possibly use linear regulators with some of the newer low power mini-itx boards I don't see what the advantage would be. I think that even with the low power needed you would need pretty hefty heat sinks and the power supply would be much larger than an equivalent switching supply. The picoPSU power supplies are not much bigger than the connector on a standard PC power supply. Granted they use an external 12 volt power brick, but you're going to need some kind of AC adapter even with a linear supply.

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- Rick

Franklin

www.mini-box.com/picoPSU-90?sc=8&category=13

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- Stephen

LoopyByteloose

I suspect that it is really difficult to get ahead of the industry's leading edge in power supply design. They really have wanted to reduce power consumption and supply size [noparse][[/noparse]including the batteres] because that is where most of the weight in laptops is. There was huge competition to get there first and with the best as millions of devices require low power.

Originally, we had big linear supplies with transformer and huge filter capacitors [noparse][[/noparse]the IMSI S100 bus computer]. Then we went to the bulky PC style switching supply that mostly drives the spin on the harddisk with it's 300 watts. Then came along a huge development in power supply related chips for laptops and cell phones. But we seem to have reached a point where nothing is going to get smaller unless both the consuming unit needs less power and the battery can provide more power per weight.
Little switching chips seem to be highly specialized for the target item and not available in single quatities.

So, any DIY solution seems to go backward in size [noparse][[/noparse]and maybe the quality of the output]. I suspect the board designers expect to profit equally from proving the small motherboard and it's mate, a small power supply that runs very cool and very quiet. The last part is a marketing gotcha.

For example, I haven't found a way to build a reliable litium battery charger for less than just charging the batteries in my old Nokia and using those cell phone batteries to power my projects. The ready made chargers cost as much or more than as a phone! The chips require specialize parts that I cannot get, like tuned coils.

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PLEASE CONSIDER the following:

Do you want a quickly operational black box solution or the knowledge included therein?······

···················· Tropically,····· G. Herzog [noparse][[/noparse]·黃鶴 ]·in Taiwan

sam_sam_sam

Kramer

For example, I haven't found a way to build a reliable litium battery charger for less than just charging the batteries in my old Nokia and using those cell phone batteries to power my projects. The ready made chargers cost as much or more than as a phone! The chips require specialize parts that I cannot get, like tuned coils.

This may what you are looking for

I have try this out and seem to work·just fine

I was and still looking a for a cheap two cell charger but have not

found one yet

I just built a set up where i use two Sony Lithium Ion Batteries 1600mah and two

LiPoly Charger - Single Cell and here is the link to that project

http://forums.parallax.com/showthread.php?p=709460





1··· 4 Sony Lithium Ion Batteries 1600mah CGR18650 18650

http://cgi.ebay.com/4-Sony-Lithium-Ion-Batteries-1600-mah-CGR18650-18650_W0QQitemZ310022728932QQihZ021QQcategoryZ34056QQssPageNameZWDVWQQrdZ1QQcmdZViewItem

#2 LiPoly Charger - Single Cell 3.7-7V Input .........You need two of them

http://www.sparkfun.com/commerce/product_info.php?products_id=726


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··Thanks for any··that you may have and all of your time finding them

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Sam

Post Edited (sam_sam_sam) : 2/21/2008 5:53:30 PM GMT