Building a DC Power Supply for ATX system

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I don't know if the following has been done, but here goes:

Would it be advisable to provide a DC-DC power supply (PS) to an ATX system
for the purpose of;
1) Increased efficiency
2) Decreased heat
3) Decreased fan noise
If you used an automotive style sealed battery in the circuit and a trickle
charger, wouldn't you also provide a fairly substantial UPS system ? I've
seen DC-DC power modules that plug directly into the ATX power connecter
the size of a playing card.  DC Regulated Switching Power Supplies are not
too expensive if you're trying to meet the above criteria.  

I believe that the computer industry has not utilized the DC-DC PS because
of the ubiquitous $50 PC AC-DC Internal PS.  If I'm way off on my ideas,
please advise.  If you can shoot holes in my ideas please do so.

TIA,
Trent M. Gunnarson

Re: Building a DC Power Supply for ATX system

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So, where're you gonna get the DC input power?

The ubiquitous $50 PC AC-DC internal power supply is already a switching
supply, and fairly efficient.

--

Tim Wescott
Wescott Design Services
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Re: Building a DC Power Supply for ATX system
On Fri, 14 Jan 2005 07:56:43 -0800, the renowned Tim Wescott

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It's also DC-DC internally-- the internal DC bus is a bit over 300VDC
with either a 120VAC or 240VAC source (using a voltage doubler
arrangement in the former case).


Best regards,
Spehro Pefhany
--
"it's the network..."                          "The Journey is the reward"
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Re: Building a DC Power Supply for ATX system

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You want to replace the existing AC->DC supply (which is
actually AC->DC->DCx3 with a AC->DC supply, a battery, and then
another set of DC->DC supplies? That's going to cost a fortunte
relative to the existing solution.

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Firstly, where's the DC power going to come from? What you call
"trickle charger" needs to put out several hundred watts at
14V.  That's hardly a "trickle". Then you're going to run a set
of DC->DC converters to regulate 14V that down to 12,5 and 3.
Except for the battery, how's that any different than the
supplies that are used now?

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Grant Edwards                   grante             Yow!  Yow! STYROFOAM...
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Re: Building a DC Power Supply for ATX system
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We've done what you suggested, within some fairly
tight constraints.  Our Thin Client:

http://www.jkmicro.com/products/thinclient.html

Has an auxilary board that, amongst other things
takes 8-30 volts DC in and converts it to an output
compatible with an ATX supply.  Unfortunatly, it's
not nearly as cheap to build as we had hoped, and
it's output is sized for only a couple of mini-ITX
motherboards.

Remember that you need to supply 2 or 3 sequenced
voltages and a standby +5 volts, plus some reset
logic.  It's not an overly difficult design, but
it's not trivial either.  Especially if you want
to do it for a reasonable price.

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There's quite a bit of cleverness and cheap labor
involved in producing a 400 watt, switched, multi-
output power supply for for $50. But then what else
is new.  Can you build a VCR for $50?


Re: Building a DC Power Supply for ATX system
yes it would work.
how do you think laptops work?  !!

but in a home PC
the currents involved are quite high, as is the (summed) voltages.

pc's need +/- 12v (24v volt potential diff) & +/- 5v (10v potential diff)

if you did not use voltage doublers or inverters (DC-DC)
the 24v system alone would need two (12v) batteries
and the 5v perhaps one 6v but the current needed is very high.

thus a trickle charger would not be so, it would effectively be a PSU, where
the battery only gave power when mains was dead...bingo a UPS as you stated.

as for you 1,2.3 bullet points, i can see none as being true.

mike

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system
trickle



Re: Building a DC Power Supply for ATX system



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Do not build it Buy it.  There are several 12 volt ATX supplies on the market.
Google for them.
Apparently there is a market for Mobile PCs that are not laptops.

With switching Supplies If you have to ask if it can be done, you can.



Re: Building a DC Power Supply for ATX system
well there are calls for this I work for a router maker and often only the
teleco's want this "feature".  Most companies see the 120 volt AC has just
simple and easy.


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Re: Building a DC Power Supply for ATX system
The following links should help you understand the hardware I'm considering
for the system I'm proposing.

~ 25AMP Switching Power Supply
http://www.circuitspecialists.com/prod.itml/icOid/1064

~ 200 Watt DC-DC ATX Power Supply
http://www.mini-box.com/s.nl/sc.8/category.13/it.A/id.300/.f

~ The automotive battery and battery charger (with trickle feature) I'll
leave to your imagination. :)

~ The next link was a cool hack I saw that got me thinking about using an
ATX instead of an ITX motherboard.
http://www.mini-itx.com/projects/cluster /

If you can think of a better forum for this discussion, please let me know.

Trent

Re: Building a DC Power Supply for ATX system
: I don't know if the following has been done, but here goes:

: Would it be advisable to provide a DC-DC power supply (PS) to an ATX system
: for the purpose of;
: 1) Increased efficiency
: 2) Decreased heat
: 3) Decreased fan noise
: If you used an automotive style sealed battery in the circuit and a trickle
: charger, wouldn't you also provide a fairly substantial UPS system ? I've
: seen DC-DC power modules that plug directly into the ATX power connecter
: the size of a playing card.  DC Regulated Switching Power Supplies are not
: too expensive if you're trying to meet the above criteria.  

: I believe that the computer industry has not utilized the DC-DC PS because
: of the ubiquitous $50 PC AC-DC Internal PS.  If I'm way off on my ideas,
: please advise.  If you can shoot holes in my ideas please do so.

Being done. There are several lower power MoBo's being powered by such  a
setup for automobile use etc. The ideas stands for any use.
Several of the MiniITX and NanoITX mobo/equipment suppliers supply these
DC/DC supplies.



Re: Building a DC Power Supply for ATX system

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