At 11:58 AM 4/18/02 -0400, you wrote:
>I've been fascinated by Olin's charger design.
>
>I'm not really a hardware guy, but I wonder if somebody could comment on the
>variation of Olin's design shown in the attached schematic
>Did I analyze this right?
>Does it have a chance of working?
>
>Bob Ammerman

I quickly went over this as follows. Assume the top of D1 is at zero volts.
Assume the pwm voltage is one volt. Work it out, you get one volt across
the sense resistor.

Now assume the battery has charged up to where the top of D1 is at 3 volts.
Again, it works out.

I don't see yet where it will not work out. There is one small caveat
however. Since the pwm signal is around 10k impedance, there will be around
a 1% error due to the loading by the 1meg resistors.

If actually building this, I would check to make sure that it is stable,
frequency wise. Probably is, but worth a check.

Finally, this is extremely close to a Howland current pump configuration.
The exception is that your circuit appears (to me at least) to be easier to
analyze. I have been redrawing it to see if it looks more familiar; it
doesn't.  Very interesting.

Best regards
Tom M

ps If anyone sees an error here and can show that it doesn't really work,
by all means, please tell us.

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