Tim said:
It pretty much has to work down to 0.9V or so if you're going to get
everything there is to get out of the battery -- a dry cell only puts out
1.5V when it is very lightly loaded for it's charge level.
With a 100% efficient converter, 2.5V at 500mA demands around 833mA out
of a 1.5V cell, and the current required goes up as the cell voltage goes
down.
Yes, very well understood..
Yes ago a made a concoction where I used a diode to isolate the Vcc of
a basic timer and had that drive a mosfet to buck switch a coil which
got its (+) before the diode. Then I back fed the final output of the
switch circuit which was 12 volts after regulation to the Vcc of the timer.
The source was a 6 volt arrogation battery system, a very large one
at that, however, there were some electronics that needed 12vs from that
and it needed to stay operating when the 6 volt battery drained down to
the point where it could no longer supply enough output in the buck
circuit to maintain 12 volts and back feed the timer. I had a comparator
switch in there to shut things down if the output reached 10 volts or less.
During the day solar panels were used to recharge this system if
possible and a emergency generator if needed. THe gen would start
if the buck circuit switched into shutdown.
The only problem with all of this of course, once the battery gets down
like that, you are not starting that circuit until it is up and happy
again
Oh the days of what I could do with timers, I also love the cmos
versions. I know there is more integrated IC's these days for that
and i've used a few, but those aren't as much fun!
Jamie