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.

--
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| 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 |
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