Convert ATX PSU to run on 192V DC rail

[VWWall]

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.

This, obviously, should say: Your *192 V DC* is far too low. Put
another way, 192 V DC at the input to the switching circuits would
correspond to an input of 72/136 V AC, below the low limit design of
90/180 V AC. The PSU would not even attempt to start at this level.

Virg Wall

 

[kony]

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

IIRC, most if not all of the Active PFC units don't have a voltage
doubler, if we can take it for grated that having only one HV cap on the
HV side is evidence of a non-doubled design.

However, I"m not so sure of the viability of setting up this multi-dozen
system arcade as OP wants... It would require replacing all the power
supplies with, at a minimum, signficantly higher than average priced
units, then a customized power grid to deliver the 192V DC... it is not
going to meet code to use the existing AC wiring and outlets to deliver
192V DC, so less common, more expensive couplers will be needed at
multiple points.

Once one starts adding up the costs then the difference in energy
consumption, energy cost, may not be recouped within projected lifespan of
these gaming systems. If power generation is the issue then perhaps a
different UPS, modification to existing UPS, or alternate energy source
would be beneficial.

 

[VWWall]

This, of course should read: "Is it then applied to an invertor and..."
Typo: (240 x 1.414 = ~340 V DC)

*RECTIFY*???? a DC voltage??? NUTS! cannot be done!

Webster's Dictionary: rectify 1) To make or set right ;-)
4) To make an alternating current unidirectional.

Sorry, it was getting late! :-(

Virg Wall

 

[VWWall]

IIRC, most if not all of the Active PFC units don't have a voltage
doubler, if we can take it for grated that having only one HV cap on the
HV side is evidence of a non-doubled design.

I'm curious. I always thought they used something like "steering"
diodes to select the voltage range. I can't imagine a switching circuit
that would work over a range of 127-340 V DC (90-240 V AC input). That
would imply a current range of 2.67/1! What is the voltage at the HV
side? And how does it get there? Anybody know?

Schematics for any ATX supplies are scarce. Anybody have any sources?

Virg Wall, K6EVE

 

[kony]

I'm curious. I always thought they used something like "steering"
diodes to select the voltage range. I can't imagine a switching circuit
that would work over a range of 127-340 V DC (90-240 V AC input). That
would imply a current range of 2.67/1! What is the voltage at the HV
side? And how does it get there? Anybody know?

Schematics for any ATX supplies are scarce. Anybody have any sources?

Virg Wall, K6EVE

I have one, around here "somewhere", LOL...
Have been pretty busy these days but if I get a chance and can find it,
I'll take a look at it. Well, I can "look" at it now since I have a
picture handy but that's not quite enough.

http://69.36.189.159/usr_1034/liteon_side.jpg

 

[Ryan]

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?

What you want is a "full input range" ATX supply. Do not get an
"auto-switch" supply as these have voltage doublers that won't work
with DC.

I am willing to bet a full input range supply will work just fine on
DC without modification, and most spec 90-264 VAC which is 127-373
VDC; indeed within your 192 VDC rail.

Ryan

 

[N. Thornton]

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

You still dont seem to addressing the simple question of whether a PC
PSU is likely to work on 192dc. Thats the q here, marketing has
nothing to do with that. Design optimisation is not marketing.

Regards, NT

 

[Tam/WB2TT]

"Tam/WB2TT" <t-tammaru@c0mca$t.net> wrote in message


You still dont seem to addressing the simple question of whether a PC
PSU is likely to work on 192dc. Thats the q here, marketing has
nothing to do with that. Design optimisation is not marketing.

Regards, NT

Well, if you have a supply built for 95 -135 VAC operation that does not
use a voltage doubler it should work. 135 x SQRT(2) =190, close enough. Now
the question is does the supply need AC for other reasons. When the PC goes
into standby the fan stops; I don't know for a fact, but suspect the main
supply also might shut down. Where does the keep alive voltage come from?

Tam

 

[ric]

Well, if you have a supply built for 95 -135 VAC operation that does not
use a voltage doubler it should work. 135 x SQRT(2) =190, close enough. Now
the question is does the supply need AC for other reasons. When the PC goes
into standby the fan stops; I don't know for a fact, but suspect the main
supply also might shut down. Where does the keep alive voltage come from?

Depends on the supply design. Some use a small bias transformer off of
the AC input, and some use a switching design off of the 300v buss.
Whether his 192VDC would support the latter is a good question. If his
supply used the former, he'd be SOL.

I'd use an AT rather than a ATX supply, if possible.

 

[Robert Baer]

What you want is a "full input range" ATX supply. Do not get an
"auto-switch" supply as these have voltage doublers that won't work
with DC.

I am willing to bet a full input range supply will work just fine on
DC without modification, and most spec 90-264 VAC which is 127-373
VDC; indeed within your 192 VDC rail.

Ryan

Incorrect; any switcher will work from DC - by definition!
What do you think happens to the incoming AC?
It gets rectified, and due to a fairly large capacitor, gets turned
into.......
......
......
......
......
......DC!

 

[Tam/WB2TT]

from?

Depends on the supply design. Some use a small bias transformer off of
the AC input, and some use a switching design off of the 300v buss.
Whether his 192VDC would support the latter is a good question. If his
supply used the former, he'd be SOL.

I'd use an AT rather than a ATX supply, if possible.

Thanks, that's what I was guessing. More things to consider are the fact
that the 192V would actually be about 225 the instant the charger stops, and
around 170 when the battery is about to poop out. Also, there are two basic
kinds of UPS. The full time runs the output off the inverter all the time,
on the other kind the load is run off the AC line, and then switches to the
inverter when the AC goes bad. In the second, the inverter efficiency is
irrelevant except when running off the battery. In an elaborate system like
this, though, it may be full time.

There are people who run hundreds of servers in one location. It would be
interesting to find out what they do. Surely they must have backup power.
Common backup voltages in other applications are 48, 135, and 270V. Not sure
they make an AT supply with the right output voltages.

Tam

 

[Ian Stirling]

Incorrect; any switcher will work from DC - by definition!
What do you think happens to the incoming AC?
It gets rectified, and due to a fairly large capacitor, gets turned
into.......

I've seen some (few) that require AC to startup.

 

[Nico Coesel]

thanks for your inputs guys.

yes i did mean 220/240V

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 dump the on-line UPS and buy an offline UPS? Problem solved.
An on-line UPS is more prone to problems anyway because its inverter
is always on.

 

[WiseIndian]

saving potential is huge.

Why not dump the on-line UPS and buy an offline UPS? Problem solved.
An on-line UPS is more prone to problems anyway because its inverter
is always on.

The maximum offline UPS capacity I can lay hands on is 3KVA and can
support maximum of 6 Machines and since we use 17" CRT( LCD cannot
refresh fast enough for gaming) the unit's we tested worked @ just 50%
reliability during outages.

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

actually i am more intrested in the loss at the online UPS end, from
what I measured the UPS Input= 24Amps@210V and output = 17Amps@220V
thats a loss of 25% our 6KVA ups is drawing like 80KWh daily.

 

[DevilsPGD]

In message <[email protected]>

The maximum offline UPS capacity I can lay hands on is 3KVA and can
support maximum of 6 Machines and since we use 17" CRT( LCD cannot
refresh fast enough for gaming) the unit's we tested worked @ just 50%
reliability during outages.

Do you need 6 machines on one UPS? In general, individual UPSes will be
more economical until you're looking at a minimum of 20 PCs or so, only
then is it worth investing in a commercial unit to run an entire office.

Ballpark pricing was done about two years ago, but I doubt much has
changed other then everything has dropped somewhat.

 

[Rich Grise]

thanks for your inputs guys.

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?

Your safest bet is to take one of the existing power supplies, open
it up, and measure the raw DC. If it's like half, or 2X, try the
comp. PS on a different line voltage.

It might have enough input compliance to manage 192V, but if you
get something wacky like 250 VDC, I'd be a little iffy about connecting
it directly. (i.e., if they somehow get 250VDC for the rectified line,
I wouldn't put 192V into it.)

And if it is in an iffy range, go ahead and get a proper fuse, and
hook one up and see if it smokes!

Have Fun!
Rich

 

[Rich Grise]

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.

If the 192 supply is a stack of ordinary lead-acid batteries, there
must be 48V taps. And depending how many you need, 192V input might
not be that much more money.

Good Luck!
Rich

 

[CBFalconer]

.... snip ...

If the 192 supply is a stack of ordinary lead-acid batteries,
there must be 48V taps. And depending how many you need, 192V
input might not be that much more money.

If it is lead-acid cells, a normal cell voltage is 2.2, which
means that the 192 V nominal will probably be 211 V. I would not
be surprised to see 224. All assuming 96 cells.

 

[Paul Hovnanian P.E.]

If the 192 supply is a stack of ordinary lead-acid batteries, there
must be 48V taps. And depending how many you need, 192V input might
not be that much more money.

The question is whether the OP already has a 192V DC rail that he has to
put to use, or if its early enough in the design stage to change the
spec to an industry standard. Telecom gear uses 48V extensively, so
chargers, supplies and other goodies are readily available.

 

[Ken Taylor]

The question is whether the OP already has a 192V DC rail that he has to
put to use, or if its early enough in the design stage to change the
spec to an industry standard. Telecom gear uses 48V extensively, so
chargers, supplies and other goodies are readily available.

92VDC UPS rails are indeed a standard value. There are companies which do DC
input PC power supplies (two at hand are VOXTechnologies and BPS), they may
be able to help with a 192VDC in supply. Alternatively, a 192V to 48V
converter plus one of the 48VDC in supplies. best advice would be to ask the
UPS manufacturer which of these they could provide or recommend.

I don't want to be a PITA, but I assume that is a *big* 3-phase UPS - you DO
realise it can kill you??

Ken