Velocity Reviews > Convert ATX PSU to run on 192V DC rail

# Convert ATX PSU to run on 192V DC rail

WiseIndian
Guest
Posts: n/a

 06-10-2004
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?

Ian Stirling
Guest
Posts: n/a

 06-10-2004
In sci.electronics.design WiseIndian <(E-Mail Removed)> 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?

Normal 200V AC input?
where are you?
Do you perhaps mean 220/240?

philo
Guest
Posts: n/a

 06-10-2004

"WiseIndian" <(E-Mail Removed)> wrote in message
news:(E-Mail Removed) om...
> 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?

yes, you are right

"switching" type power supplies first recity the A.C.
the D.C. is then inverted to high frequency A.C. where it is again
rectified... so in theory if your battery bank equaled the D.C. buss of
your supply, you could skip the first step...

however the power savings would probably be too small to bother with
unless you happen to be running a pretty niced sized "server farm"

VWWall
Guest
Posts: n/a

 06-10-2004
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?

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.)

ric
Guest
Posts: n/a

 06-10-2004
philo 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?

>
> yes, you are right
>
> "switching" type power supplies first recity the A.C.
> the D.C. is then inverted to high frequency A.C. where it is again
> rectified... so in theory if your battery bank equaled the D.C. buss of
> your supply, you could skip the first step...

Yes, but the OP's 192VDC is too low. A SMPS peak charges the input caps
to 1.414 times the input voltage. So, 200VAC would result in about 283VDC
on the caps. The OP's DC value of 192V corresponds to about the same as
134VAC. Much too low.

>
> however the power savings would probably be too small to bother with
> unless you happen to be running a pretty niced sized "server farm"

--
Better than hearing "Lady Day", or checking in at Monterey...

N. Thornton
Guest
Posts: n/a

 06-10-2004
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

Tam/WB2TT
Guest
Posts: n/a

 06-11-2004

"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

WiseIndian
Guest
Posts: n/a

 06-11-2004

>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 ?

>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?
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?

VWWall
Guest
Posts: n/a

 06-11-2004
N. Thornton wrote:

> 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.

Typo: This should be 240 x 1.414 = ~340 V 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.

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.

--
A foolish consistency is the
hobgoblin of little minds,........
Ralph Waldo Emerson
(Microsoft programmer's manual.)

VWWall
Guest
Posts: n/a

 06-11-2004
Tam/WB2TT wrote:

> "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.

I've never seen one without, have you? Actually the cost of switching
transistors is much more dependant on their current capacity than their
voltage ratings. Also, with a fixed "on" voltage drop, the heat will
increase with the current being passed, requiring larger heat sinks, and
resulting in lowered efficency.

For a 240 V DC input , there is no choice but to use the full peak
rectified DC! Check the price of filter caps. You'll find no where
near a double price! The output transformer primary turns are double,
at the higher voltage, but with half the wire size . The output
windings have fewer turns at the same wire size.

It may be serendipity, but the voltage doubling power supply represents
about the most economical design possible. When you consider that a
single SPST switch makes it a 115/130 V unit, you can see why the design
is so universal!

Virg Wall
--
A foolish consistency is the
hobgoblin of little minds,........
Ralph Waldo Emerson
(Microsoft programmer's manual.)