Path: utzoo!utgpu!jarvis.csri.toronto.edu!rutgers!apple!ames!pasteur!ucbvax!agate!eos!jbm From: jbm@eos.UUCP (Jeffrey Mulligan) Newsgroups: sci.electronics Subject: Charging to 7 volts (was Re: HV Cap Fun!) Message-ID: <3854@eos.UUCP> Date: 2 Jun 89 21:30:26 GMT References: <5170036@hplsla.HP.COM> Organization: NASA Ames Research Center, California Lines: 41 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<