# Convert ATX PSU to run on 192V DC rail

Discussion in 'Computer Information' started by WiseIndian, Jun 10, 2004.

1. ### VWWallGuest

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

VWWall, Jun 11, 2004

2. ### konyGuest

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.

kony, Jun 11, 2004

3. ### VWWallGuest

This, of course should read: "Is it then applied to an invertor and..."
Typo: (240 x 1.414 = ~340 V DC)
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, Jun 11, 2004
4. ### VWWallGuest

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

VWWall, Jun 11, 2004
5. ### konyGuest

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

kony, Jun 11, 2004
6. ### RyanGuest

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

Ryan, Jun 11, 2004
7. ### N. ThorntonGuest

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

N. Thornton, Jun 11, 2004
8. ### Tam/WB2TTGuest

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

Tam/WB2TT, Jun 12, 2004
9. ### ricGuest

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.

ric, Jun 12, 2004
10. ### Robert BaerGuest

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!

Robert Baer, Jun 12, 2004
11. ### Tam/WB2TTGuest

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

Tam/WB2TT, Jun 12, 2004
12. ### Ian StirlingGuest

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

Ian Stirling, Jun 12, 2004
13. ### Nico CoeselGuest

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.

Nico Coesel, Jun 12, 2004
14. ### WiseIndianGuest

saving potential is huge.
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.

actually i am more intrested in the loss at the online UPS end, from
what I measured the UPS Input= [email protected] and output = [email protected]
thats a loss of 25% our 6KVA ups is drawing like 80KWh daily.

WiseIndian, Jun 13, 2004
15. ### DevilsPGDGuest

In message <>
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.

DevilsPGD, Jun 13, 2004
16. ### Rich GriseGuest

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, Jun 15, 2004
17. ### Rich GriseGuest

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

Rich Grise, Jun 15, 2004
18. ### CBFalconerGuest

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.

CBFalconer, Jun 15, 2004
19. ### Paul Hovnanian P.E.Guest

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.

Paul Hovnanian P.E., Jun 16, 2004
20. ### Ken TaylorGuest

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

Ken Taylor, Jun 16, 2004

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