On Tue, 17 Jan 2012 05:49:29 -0500, "Tom Del Rosso"
wrote:
Jim Thompson wrote:
Diode D7 prevents some really weird behavior from back conduction. If
there were a need to tighten up the efficiency, I'd replace it with
another P-channel, body in the opposite direction from MP1 (for lack
of finding a suitable transistor, modeled as a 0.3 Ohm device
extrapolated from my vast CMOS device library :-). Then I'd use a
comparator to make the drop like a near ideal diode as in...
http://analog-innovations.com/SED/Pe...rIsolation.pdf
Can a comparator really sense up to it's positive supply?
Remember the ripple detector post I made in response to _your_
question? That TLV3501 has a common mode range that extends about
0.3V beyond rails.
Surely not all of
them.
Plus all the ones I design to do that ;-) It's _really_ easy to do
with CMOS. That latest chip design of mine had two rail-to-rail (I/O)
OpAmps and 8 rail-to-rail (I/O) comparators.
And wouldn't it depend on which side of the 'diode' it is powered from?
Sure. But we know, in the hub dynamo case, which way we want current
to flow. From experience with those sims, I'd probably set it for +1V
of margin before I let the switcher go, with a resistive or diode
dropper,
...Jim Thompson
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