Russell McMahon wrote:
>
> Challenge:
>
>     Convert low voltage DC such as battery or 3v or 5v rail
>     to "somewhat higher" dc voltage at modest power levels
>     for e.g. processor operation, FET gate drive, LED drive,
>     Op-Amp supply, Programmer Vpp supply, and more.

> Target efficiency is "as high as possible and as low as appropriate". e.g. a
> design that rings an inductor and uses a clamp zener to dissipate any
> surplus energy would have poor efficiency at less than full power output but
> such an approach may well be acceptable in many applications.

> Lowest possible starting and operating voltage
> A "run the 1.5v cell utterly dry" design  will
> ideally run on under 0.9v and will hopefully also start on less than a volt.


Hi Russell, when I was fiddling with the 2-tran
SMPS circuits I tried a 2-tran boost circuit to
run from a single 1.5v cell.

I got it starting (and running) reliably from around
0.8v up to 1.6v, giving (about) 5v out. I say "about"
5v as Vout:Vin and Vout:Iout regulation were not
great. Efficiency was about 55% to 60% with 1v input.

But it did run a 5v PIC from a cell, and was mega
cheap with 2 cheap transistors and one simple inductor
and 1N4148 boost diode.

At the time I was not really impressed with the
efficiency or regulation, and didn't bother writing
it up properly. Lately I bought one of the Dick Smith
1.5 -> 9v converter kits, and was disappointed to find
that even with specialist chip it only run down to
about 1.2v input, efficiency only 60% and regulation
was quite poor also!

I still have the circuit and some tested figures
if you think it qualifies for your requirements.
-Roman

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