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Convert ATX PSU to run on 192V DC rail

 
 
VWWall
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Posts: n/a
 
      06-11-2004
WiseIndian wrote:

> thanks for your inputs guys.
>
>
>>Normal 200V AC input?
>>where are you?
>>Do you perhaps mean 220/240?

>
> yes i did mean 220/240V
>
>
>>however the power savings would probably be too small to bother with
>>unless you happen to be running a pretty niced sized "server farm"

>
> yes it is a 35 comp plus gaming center with the monitors on a seperate
> offline inverter line. the online UPS has a 16 battery bank and seems
> to
> working at 65-70% overall efficiancy, since we are running 24 hrs a
> day
> the saving potential is huge.
>
>
>>A SMPS peak charges the input caps to 1.414 times the input voltage.

>
> So, >200VAC would result in about 283VDC on the caps.
> true but considering that we run on clean battery power is it
> necessary to
> have them caps fully charged ?


The DC input to the switching circuitry has to be within design limits.
For 90-140 V this is 255-396 V DC. Your 292 V DC is far too low.
>
>
>>Where do you get the value for "the 192V DC rail"? 16 12V, (6 cell),
>>

>
> batteries in series will give this value. Is it then rectified and
>
>>converted to 120/240 V AC? This must be a very large UPS!

>
> it is a 6KVA UPS
>
>
>>The ATX PSU input is nominally 240V AC, which when rectified results

>
> in:
>
>>240 x 1.44 = ~345V DC. (For 120V AC input a doubler rectifier

>
> circuit
>
>>is used, resulting in about the same DC voltage.) This DC voltage is
>>supplied to the switching transistors, resulting in an output to the
>>final transformer at an equivalent of 40-60 K Hz. This high

>
> frequency
>
>>allows for the use of a much smaller transformer.
>>One could design a PSU to run from 192V DC with a somewhat lower
>>efficiency, but this would be a completely non-standard unit.

>
>
> actually i dont know too much about smps supplies, but since the smps
> is
> suppose to work in the range of 90-150V or 190-250V wouldnt that fall
> in the band on 192VDC?


You're forgetting the 1.414 factor between AC and peak rectified DC voltage.

> sometimes i wonder if the computer manufacturers have a deal with UPS
> manufactureres and power utlity companies in keeping us stuck with
> costly power guzzling online UPS's?


Switching all the ATX supplies and the UPS to 220V might gain a few
points in efficiency, but the re-wiring might not be worth it.

Virg Wall
--
A foolish consistency is the
hobgoblin of little minds,........
Ralph Waldo Emerson
(Microsoft programmer's manual.)
 
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Paul Hovnanian P.E.
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      06-11-2004
WiseIndian wrote:
>
> I am wondering if a normal 200V AC input ATX PSU can be converted to
> run on a 192V DC Rail, considering the enormous electricity my 16
> battery online UPS is using it must be more efficient running the
> computers directly an the 192V DC rail and running the monitors on a
> seperate offline inverter line . I am not very familiar with how the
> ATX PSU works , but it understand the first stage involves converting
> the 200V AC Input to 200V rectified DC. anyone guide me if it is
> possible?


Its possible but non-standard. Do you already have the 192 VDC rail
available or are you free to change the design?

There are ATX (and other) supplies already built to operate from 48 VDC
busses, this being a standard telecom system voltage derived from
batteries. Also available in 12 and 24 VDC I believe.

--
Paul Hovnanian mailto(E-Mail Removed)
note to spammers: a Washington State resident
------------------------------------------------------------------
Karate is a form of martial arts in which people who have had
years and years of training can, using only their hands and feet,
make some of the worst movies in the history of the world.
-- Dave Barry
 
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ric
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Posts: n/a
 
      06-11-2004
WiseIndian wrote:

> >A SMPS peak charges the input caps to 1.414 times the input voltage.

> So, >200VAC would result in about 283VDC on the caps.
> true but considering that we run on clean battery power is it
> necessary to
> have them caps fully charged ?


At a 230vac input rating, a SMPS will "breakout" at about 170vac, at
which time about 240vdc will be on the HV buss. This is at full load.
Whether or not it will go much lower depends on the load and on the
design of the PSU.

> actually i dont know too much about smps supplies, but since the smps
> is
> suppose to work in the range of 90-150V or 190-250V wouldnt that fall
> in the band on 192VDC?


Actually, it is 90-132 vac. 132vac would result in about 370VDC on
the buss (due to doubling), and 180vac would result in about 254VDC.

You would have to modify the supply to stop the doubling, and use
the 90-132 setting (and pray.)
 
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N. Thornton
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      06-11-2004
"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message news:<(E-Mail Removed)>...
> "N. Thornton" <(E-Mail Removed)> wrote in message
> news:(E-Mail Removed) om...
> > VWWall <(E-Mail Removed)> wrote in message

> news:<JT1yc.9134$(E-Mail Removed) nk.net>...
> > > WiseIndian wrote:
> > >
> > > > I am wondering if a normal 200V AC input ATX PSU can be converted to
> > > > run on a 192V DC Rail, considering the enormous electricity my 16
> > > > battery online UPS is using it must be more efficient running the
> > > > computers directly an the 192V DC rail and running the monitors on a
> > > > seperate offline inverter line . I am not very familiar with how the
> > > > ATX PSU works , but it understand the first stage involves converting
> > > > the 200V AC Input to 200V rectified DC. anyone guide me if it is
> > > > possible?
> > >
> > > Where do you get the value for "the 192V DC rail"? 16 12V, (6 cell),
> > > batteries in series will give this value. Is it then rectified and
> > > converted to 120/240 V AC? This must be a very large UPS!
> > >
> > > The ATX PSU input is nominally 240V AC, which when rectified results in:
> > > 240 x 1.44 = ~345V DC. (For 120V AC input a doubler rectifier circuit
> > > is used, resulting in about the same DC voltage.) This DC voltage is
> > > supplied to the switching transistors, resulting in an output to the
> > > final transformer at an equivalent of 40-60 K Hz. This high frequency
> > > allows for the use of a much smaller transformer.
> > >
> > > One could design a PSU to run from 192V DC with a somewhat lower
> > > efficiency, but this would be a completely non-standard unit.
> > >
> > > Virg Wall

> >
> > There are supplies that will run happily on anything from 110 ac to
> > 240 ac. Not the ones with voltage switches, but ones that will cover
> > the whole range. One of those should do 192dc ok, though really it
> > depends on the rectifier/reservoir arrangement. I couldnt guarantee
> > all will work.
> >
> > Regards, NT

>
> There is no guarantee that a 120VAC supply will have a voltage doubler. For
> the same power (~300W), I suspect a 170V input supply is cheaper to build
> than a 350 V supply. For the voltage doubler, you about doubled the price of
> the filter caps, used more expensive transistors, and transformers with more
> turns. If you make a million power supplies, and save a dollar on each one,
> you start approaching serious money.
>
> Tam


so youre saying more or less all universal supplies should work on 192 IIUC.

Regards, NT
 
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Ian Stirling
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Posts: n/a
 
      06-11-2004
In sci.electronics.design WiseIndian <(E-Mail Removed)> wrote:
> thanks for your inputs guys.
>
>>Normal 200V AC input?
>>where are you?
>>Do you perhaps mean 220/240?

> yes i did mean 220/240V
>
>>however the power savings would probably be too small to bother with
>>unless you happen to be running a pretty niced sized "server farm"

> yes it is a 35 comp plus gaming center with the monitors on a seperate
> offline inverter line. the online UPS has a 16 battery bank and seems
> to
> working at 65-70% overall efficiancy, since we are running 24 hrs a
> day
> the saving potential is huge.


Why not simply stick in a offline UPS?
 
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glen herrmannsfeldt
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Posts: n/a
 
      06-11-2004
VWWall wrote:

(snip regarding ATX power supplies run on 192VDC)

> You are forgetting the 1.41 factor in converting RMS AC to peak DC.


> At nominal 115/230 V AC input the switching circuits run at ~325 V.
> The ATX PSU is specified to run at 90V AC. This results in 254 V DC at
> the output of the doubler. 192V DC is far too little for the switching
> circuit to provide the correct DC outputs, without changing the turns
> ratio in the output transformer. Even then, the switching transistors
> would be running at about 35% higher current for the same output current.


> Even if a current design ATX PSU would work at this voltage, one would
> have to provide a non standard input for the 192V DC to the "front end"
> DC circuitry in the ATX supply.


In 230V mode it is a bridge rectifier into the filter capacitors.
In that case 300VDC should pass through just fine. I have
never had a 300VDC power source to test it on, but have believe
that it would work, at least for AT power supplies.

ATX power supplies have the stand by power to supply the
turn on circuits. I don't know how that one works,
but it may have a transformer.

It is convenient that a SPST switch can convert a bridge and
two capacitors into a voltage doubler.

-- glen

 
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Robert Baer
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Posts: n/a
 
      06-11-2004
WiseIndian wrote:
>
> I am wondering if a normal 200V AC input ATX PSU can be converted to
> run on a 192V DC Rail, considering the enormous electricity my 16
> battery online UPS is using it must be more efficient running the
> computers directly an the 192V DC rail and running the monitors on a
> seperate offline inverter line . I am not very familiar with how the
> ATX PSU works , but it understand the first stage involves converting
> the 200V AC Input to 200V rectified DC. anyone guide me if it is
> possible?


The ATX supply is a switcher and if the switch in the back is in the
240V position (not the 129V position), i believe it would not care DC or
AC (25Hz, 50Hz, or 400Hz).
All of these designs rectify the input voltage first, producing a DC
voltage for the switcher.
The "trick" of allowing 120VAC or 240VAC, i think, is switching in a
voltage doubler for the 120V capability.
I would have to dig into one to see exactly what is done.
In any event the efficency is almost exactly the same if run from a DC
source or an AC source, so there will not be any observable gain or
merit.
Also, the efficency will not observably change between a 120VAC source
and a 240V source.
Now, if that inverter is running from 192V DC, thenone would bypass
the conversion loss of the inverter, if the ATX PSUs were connected
directly; make damn sure the switch (for each one) is in the 240V
position!
I think it would be safe, but since i have not investigated these
supplies, i cannot bs absolutely certain.
 
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Robert Baer
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Posts: n/a
 
      06-11-2004
VWWall wrote:
>
> WiseIndian wrote:
>
> > I am wondering if a normal 200V AC input ATX PSU can be converted to
> > run on a 192V DC Rail, considering the enormous electricity my 16
> > battery online UPS is using it must be more efficient running the
> > computers directly an the 192V DC rail and running the monitors on a
> > seperate offline inverter line . I am not very familiar with how the
> > ATX PSU works , but it understand the first stage involves converting
> > the 200V AC Input to 200V rectified DC. anyone guide me if it is
> > possible?

>
> Where do you get the value for "the 192V DC rail"? 16 12V, (6 cell),
> batteries in series will give this value. Is it then rectified and
> converted to 120/240 V AC? This must be a very large UPS!
>
> The ATX PSU input is nominally 240V AC, which when rectified results in:
> 240 x 1.44 = ~345V DC. (For 120V AC input a doubler rectifier circuit
> is used, resulting in about the same DC voltage.) This DC voltage is
> supplied to the switching transistors, resulting in an output to the
> final transformer at an equivalent of 40-60 K Hz. This high frequency
> allows for the use of a much smaller transformer.
>
> One could design a PSU to run from 192V DC with a somewhat lower
> efficiency, but this would be a completely non-standard unit.
>
> Virg Wall
> --
> A foolish consistency is the
> hobgoblin of little minds,........
> Ralph Waldo Emerson
> (Microsoft programmer's manual.)


*RECTIFY*???? a DC voltage??? NUTS! cannot be done!
 
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Keith Wootten
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Posts: n/a
 
      06-11-2004
In message <(E-Mail Removed) >, WiseIndian
<(E-Mail Removed)> writes

<snipped>

>actually i dont know too much about smps supplies, but since the smps
>is
>suppose to work in the range of 90-150V or 190-250V wouldnt that fall
>in the band on 192VDC?


Just in case it's not clear to the OP, a 'voltage doubler' as used on
the 90-150V can only work with an AC input.

Cheers
--
Keith Wootten

 
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Tam/WB2TT
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      06-11-2004

"N. Thornton" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
>
> so youre saying more or less all universal supplies should work on 192

IIUC.
>
> Regards, NT


I am saying this is a marketing issue, not an engineering issue. Also, for
multi voltage use, having to change a strap from bridge rectifier to voltage
doubler is not the preferred way. Preferred by whom? depends on your
management and marketing types.

Tam


 
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