🚀 go-pugleaf

From article <5170036@hplsla.HP.COM>, by tomb@hplsla.HP.COM (Tom Bruhns):
 
> Interesting question:  Can you design a simple circuit to connect the
> two caps and end up with 7.07 volts on each? (no other energy source)
> (I'll take a ckt that even manages to get 7 volts :-)

Obviously this can't be done if charge is conserved, but if we can use
a little energy to get some charge from somewhere...

How about this:

               switch S1         big inductor

	  |------/ .--------|----OOOOOOOOOOO--------|
	  |                 |                       |
         ---                -                      ---
 cap C1  ---                ^  diode D1            ---  cap C2
	  |                 |                       |
	  |                 |                       |
	  |-----------------|-----------------------|

Initially, C1 is charged to 10 volts, switch is open, no charge on
C2, no current flowing.  Switch is closed.  Current flows through the
inductor onto C2.  When the voltage on C1 drops to 7.07 volts,
the switch is opened.  Current "inertia" through the inductor causes
current to be pulled through the diode.  If we ignore resistive losses,
diode drop, etc., charge on C2 should be 7.07 by conservation of energy.


I have used a similar circuit for voltage doubling:  replace S1 by another
diode (pointing to the right), C1 is a power supply, C2 is an electronic
flash discharge cap (C2<<C1).  C2 is momentarily shorted by the flashtube,
The inductor prevents the tube from shorting out the power supply,
and subsequently charges C2 to twice the voltage on C1.


-- 

	Jeff Mulligan (jbm@aurora.arc.nasa.gov)
	NASA/Ames Research Ctr., Mail Stop 239-3, Moffet Field CA, 94035
	(415) 694-6290