Might be a dumb question, but the expensive part of a UPS is converting the
AC to DC for storage, then back to AC for use.
Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
12v and 3.3v... and the -5v, etc if necessary. It could possibly even mount
into a 5.25" drive bay.
On Fri, 07 Sep 2007 09:04:51 GMT, "Noozer"
<dont.spam@me.here> wrote:
>Might be a dumb question, but the expensive part of a UPS is converting the
>AC to DC for storage, then back to AC for use.
>
>Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
>12v and 3.3v... and the -5v, etc if necessary. It could possibly even mount
>into a 5.25" drive bay.
>
>Sounds simple, doesn't it?
>
You write about putting it in a 5.25" bay which would
require very small batteries, meaning it couldn't have much
runtime. If long runtime for a system (only, including no
monitor or other peripherals if not powered by the system)
is not required, then we avoid the expensive larger,
traditional UPS, and can instead use one of the basic
commodity $40 types.
Building something that will sell only in low volume and
that requires more technical skill to implement by the
system integrator or end user will end up costing more.
A (computer, switching) PSU has feedback, such that it not
only regulates but in regulating, allows for the voltage to
remain reasonably constant (within ATX specs, hopefully)
regardless of the load on it. With a battery array set to
n.nV, the voltage will drop significantly as the load
increases. You would need this UPS-after-PSU to regulate
the output, and in doing so you have created a second power
supply in addition to the first one, making it all that much
harder to cram it into a small space or keep cost low.
It could be implemented a different way, if the mainboard
only needed 12V input (regulating that down to lesser
voltages on the mainboard subcircuits) or the main system
PSU was one like those used in Epia car-PCs that takes the ~
+12V input and regulates to all the needed rail voltages,
then the primary AC-DC PSU for the system could be a 12V
output (only) type that is then charging only a 12V battery
which is then directly powering the car-PC PSU in event of
power outtage.
This will also cost more since it's a niche product, and is
stil not likely to fit within a 5.25" drive bay unless only
a very short runtime is needed and the system doesn't use
much current. Although avoiding the DC-AC conversion would
make it smaller than a traditional UPS and could be more
efficient, it wouldn't be THAT much more efficient so the
battery size wouldn't decrease very much. Just buying a
proprietary sized battery in itself instead of a common type
used in an UPS would probably cost as much as the entire $40
UPS I'd mentioned above.
"kony" <spam@spam.com> wrote in message
news:2dd2e39g86vtkcf8lmmt655ieccvi6tu5f@4ax.com...
> On Fri, 07 Sep 2007 09:04:51 GMT, "Noozer"
> <dont.spam@me.here> wrote:
>
>>Might be a dumb question, but the expensive part of a UPS is converting
>>the
>>AC to DC for storage, then back to AC for use.
>>
>>Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
>>12v and 3.3v... and the -5v, etc if necessary. It could possibly even
>>mount
>>into a 5.25" drive bay.
>>
>>Sounds simple, doesn't it?
>>
>
>
> You write about putting it in a 5.25" bay which would
> require very small batteries, meaning it couldn't have much
> runtime. If long runtime for a system (only, including no
> monitor or other peripherals if not powered by the system)
> is not required, then we avoid the expensive larger,
> traditional UPS, and can instead use one of the basic
> commodity $40 types.
True, but I'm thinking of something that would let the PC run for a 10
second interruption, then signal the PC to hibernate. Probably looking at
about 2 minutes of run time. No extra loads like monitors or printers to
worry about either.
Considering how much people rely on PC's I'm surprised that there isn't a
better power solution than the 120v AC UPS's.
....not to mention that most consumer UPSs put out really crappy power and
don't do ANYTHING to protect against power surges/etc.
Noozer wrote:
> Might be a dumb question, but the expensive part of a UPS is converting the
> AC to DC for storage, then back to AC for use.
>
> Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
> 12v and 3.3v... and the -5v, etc if necessary. It could possibly even mount
> into a 5.25" drive bay.
>
> Sounds simple, doesn't it?
>
>
Some years back a friend and I started working on an uber-UPS which
would solve the runtime problem quite effectively by floating a
diode-isolated bank of series-connected 12V batteries across the
rectified primary DC of a computer's PS. We ran into concerns, not the
least of which was potential safety problems, and never got much past
the measuring and dreaming stage.
Given the weight and volume of even the small 6AH alarm gel batteries we
were intending to use it would not have been a lightweight solution (10
or 11 batteries) and the volume would have necessitated an external
battery enclosure in all except the most humongous AT tower cases of the
time but it would probably yield outstanding runtime. In modern
universal supplies the primary voltage is twice what we were assuming so
the number of batteries would have to be correspondingly doubled also.
On Fri, 07 Sep 2007 14:37:58 GMT Noozer <dont.spam@me.here> wrote:
|
| "kony" <spam@spam.com> wrote in message
| news:2dd2e39g86vtkcf8lmmt655ieccvi6tu5f@4ax.com...
|> On Fri, 07 Sep 2007 09:04:51 GMT, "Noozer"
|> <dont.spam@me.here> wrote:
|>
|>>Might be a dumb question, but the expensive part of a UPS is converting
|>>the
|>>AC to DC for storage, then back to AC for use.
|>>
|>>Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
|>>12v and 3.3v... and the -5v, etc if necessary. It could possibly even
|>>mount
|>>into a 5.25" drive bay.
|>>
|>>Sounds simple, doesn't it?
|>>
|>
|>
|> You write about putting it in a 5.25" bay which would
|> require very small batteries, meaning it couldn't have much
|> runtime. If long runtime for a system (only, including no
|> monitor or other peripherals if not powered by the system)
|> is not required, then we avoid the expensive larger,
|> traditional UPS, and can instead use one of the basic
|> commodity $40 types.
|
| True, but I'm thinking of something that would let the PC run for a 10
| second interruption, then signal the PC to hibernate. Probably looking at
| about 2 minutes of run time. No extra loads like monitors or printers to
| worry about either.
|
| Considering how much people rely on PC's I'm surprised that there isn't a
| better power solution than the 120v AC UPS's.
|
| ...not to mention that most consumer UPSs put out really crappy power and
| don't do ANYTHING to protect against power surges/etc.
That's becaus emost consumers don't want to pay all the extra cost of a
better power supply. They want the lowest prices. Manufacturers want to
keep getting a profit. The end result is you get what you pay for.
Some better power supplies _will_ ride through very short (less than one
second) power blinks just from the capacitors inside. If you overrate
the power supply (for example use an 800 watt one when 250 would have
been enough) you'll get bigger capacitors and maybe even 2 or 3 seconds
ride time. That's only good if the power comes back on real fast, not
enough for a clean hibernate.
There are power supply units that use DC input, like 12 volts or 48 volts.
Other voltages used in other markets might also be available (28, 36, and
72 volts). Some of them can take a wide voltage swing as well, giving you
plenty of range by using batteries aimed at the top voltage.
Note that these voltages are not the choice for most power efficiency.
Designing a data center for the most efficient use of power would likely
involve a 360 volt DC bus feeding each machine. The lower current would
mean less loss on the bus. Because power supplies actually convert the
voltage UP to around this level first, before converting back down to the
voltages the mainboard and devices use, a smaller more efficient power
supply could be used in each machine when the source voltage is in this
range. But such a setup would be far too hazardous for typical home use
(that is, not something sold commercially for a consumer market, even
though an engineer hobbyist might have no problem with it).
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-09-29-0832@ipal.net |
|------------------------------------/-------------------------------------|
On Fri, 07 Sep 2007 17:22:57 -0400 John McGaw <nobody@nowh.ere> wrote:
| Noozer wrote:
|> Might be a dumb question, but the expensive part of a UPS is converting the
|> AC to DC for storage, then back to AC for use.
|>
|> Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
|> 12v and 3.3v... and the -5v, etc if necessary. It could possibly even mount
|> into a 5.25" drive bay.
|>
|> Sounds simple, doesn't it?
|>
|>
|
| Some years back a friend and I started working on an uber-UPS which
| would solve the runtime problem quite effectively by floating a
| diode-isolated bank of series-connected 12V batteries across the
| rectified primary DC of a computer's PS. We ran into concerns, not the
| least of which was potential safety problems, and never got much past
| the measuring and dreaming stage.
The design I thinking of a while back involved gating (using gate-turn-off
thyristors) each battery into a large capacitor, timing it so only one was
ever on at any one time, and wiring the capacitors themselves in series.
The thyristors would have to see the sum voltage, but the batteries would
not.
| Given the weight and volume of even the small 6AH alarm gel batteries we
| were intending to use it would not have been a lightweight solution (10
| or 11 batteries) and the volume would have necessitated an external
| battery enclosure in all except the most humongous AT tower cases of the
| time but it would probably yield outstanding runtime. In modern
| universal supplies the primary voltage is twice what we were assuming so
| the number of batteries would have to be correspondingly doubled also.
Legacy inverter design requires that. By developing your output voltage
across N capacitors in series, you can pump each capacitor one at a time
(at a high frequency) from a lower voltage.
--
|---------------------------------------/----------------------------------|
| Phil Howard KA9WGN (ka9wgn.ham.org) / Do not send to the address below |
| first name lower case at ipal.net / spamtrap-2007-09-29-0847@ipal.net |
|------------------------------------/-------------------------------------|
>Because power supplies actually convert the
>voltage UP to around this level first, before converting back down to the
>voltages the mainboard and devices use, a smaller more efficient power
>supply could be used in each machine when the source voltage is in this
>range.
The difference would be negligible, when a PSU uses a
roughly 360VDC input to the chopper transistors it is merely
a bridge rectifier followed by capacitors. Active PFC units
have to maintain a level above the peak rectified DC so 360V
wouldn't be enough margin. The PSU will still need
capacitor(s) for this 360V so the only thing removed would
be the bridge rectifier, roughly 1% efficiency difference
and practically no difference in PSU size.
Further, commodity grade electrical supply line wire is not
very expensive relative to most other components, the loss
on the (existing AC, or per your idea going to DC) supply
wiring is also negligible.
>But such a setup would be far too hazardous for typical home use
>(that is, not something sold commercially for a consumer market, even
>though an engineer hobbyist might have no problem with it).
It would be impractical and expensive, but the hazard not
significantly different than present 110/220V AC delivery
systems. All that to save a trivial amount of power.
> Might be a dumb question, but the expensive part of a UPS is converting the
> AC to DC for storage, then back to AC for use.
>
> Why not put the UPS *after* the PSU... three (?) mini UPS's actually - 5v,
> 12v and 3.3v... and the -5v, etc if necessary. It could possibly even mount
> into a 5.25" drive bay.
>
> Sounds simple, doesn't it?
If you could charge a 12v battery from 12v it would be extremely
simple. You cant though, so the ups would have to charge itself
with a convertor.
But given the tiny capacity and low charge speed, such a unit
would be quite doable. The miniature battery bank would need to
use something with fast discharge, maybe NiFe cells, maybe NiCds.
The one downer is that the user would need to open the pc up to fit
it, and thus it would never see the sales volume of plug-in units,
and the resultant low prices. This is a rather big downer! That could
maybe be solved by creating a British Standard for a connector
position in a 5.x" bay, so that such units could just slot in, no
case
opening required.
PS for 10 seconds of use one could possibly go with no
output regulation and stay in spec.
12v is 10x nicds, (and is non critical anyway.)
5v is 4x nicds = 4.8v
3.3v is 3x nicds = 3.6v - a schottky diode.
It would only need to stay in spec for enough seconds to hibernate.
To minimise costs one could charge the 5v pack from 12v line and
the 3.3v pack from the 5v line, so only the 12v pack would need a
small upconvertor.
That just leaves the q of controlling the UPS's output.
>PS for 10 seconds of use one could possibly go with no
>output regulation and stay in spec.
>12v is 10x nicds, (and is non critical anyway.)
It's not so easy to assume a cell is 1.2V. They range from
1.45 or so (float, typical might be closer to 1.35V with a
load) down to 0.8 per cell depending on remaining capacity
and cell impedance vs discharge rate. This could easily put
the pack outside of a stable (ATX spec) voltage range.
DC-DC UPS? 
Linear Mode
