Re: Converting a ATX PS to 13.8v
- From: Franc Zabkar <fzabkar@xxxxxxxxxxxxxxxxx>
- Date: Wed, 05 Aug 2009 13:38:41 +1000
On Tue, 04 Aug 2009 13:46:35 +0100, "Dave Plowman (News)"
<dave@xxxxxxxxxxxxxxx> put finger to keyboard and composed:
In article <7dqhp6F2cmvdtU1@xxxxxxxxxxxxxxxxxx>,
Adrian C <email@xxxxxxxxxxxx> wrote:
Arfa Daily wrote:
Jacking these PSUs up a couple of volts is not usually that hard.
There's often an 'adjustable zener' IC on the primary side, which is
fed from the secondary side via an opto coupler. This zener serves as
the reference to set the PWM for the desired output voltage. Altering
that voltage is just a case of changing one resistor to alter the
reference voltage.
Another resource.
http://www.pavouk.org/hw/en_atxps.html
The above schematic could be frigged about with by selecting a new value
for R25.
Typical 13.8v project.
http://www.webx.dk/oz2cpu/radios/psu-pc1.htm
The one I have to hand is a bit more modern and uses an all in one SG6105
supervisor IC.
Datasheet for SG6105:
http://www.datasheetarchive.com/pdf-datasheets/Datasheets-6/DSA-104265.pdf
There is an application circuit on page 8.
It seems to me that your +13.8V modification would be very easy.
Just remove the 5V sense resistor from the SG6105's IN pin. Then
reprogram the 12V and SS resistors so that the voltage at the IN pin
is equal to +2.5V when the 12V rail is at +13.8V.
Gnd o-- 2K5 --o-- 11K3 --o +13.8V
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IN
Remove the connections to the V33, V5, and V12 over/undervoltage sense
pins and then construct a potential divider (see below) with the
+13.8V output rail at the top end, and taps at +12V, +5V, and +3.3V
connected to each of the sense pins. In this way you would be
monitoring only the +13.8V rail and faking the others.
Gnd o-- 3K3 --o-- 1K7 --o-- 7K --o-- 1K8 --o +13.8V
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V33 V5 V12
- Franc Zabkar
--
Please remove one 'i' from my address when replying by email.
.
- References:
- Converting a ATX PS to 13.8v
- From: Dave Plowman (News)
- Re: Converting a ATX PS to 13.8v
- From: Arfa Daily
- Re: Converting a ATX PS to 13.8v
- From: Adrian C
- Re: Converting a ATX PS to 13.8v
- From: Dave Plowman (News)
- Converting a ATX PS to 13.8v
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