Variable input voltage charge pump

Discussion in 'General Electronics Chat' started by iulian28ti, Jan 3, 2010.

  1. iulian28ti

    Thread Starter Member

    Dec 4, 2009
    I wish to design a charge pump whose input is variable.
    input 0-8v, output 3v, and has 2 capacitors for each of the two phases.
    when one phase charges, the other discharges

    the regulation will be controlled through feedback, meaning that each phase will be charged to a specific voltage (high limit), then discharged to another specific voltage (low limit). high ripple is inevitable, but that's not a problem.

    consider that maximum input power is never drawn because of decaying current through a capacitor (Pw(in)<Pw(max)), and that V(in) variates. Is it safe to assume (by using the conservation of energy theory) that when Pw(in)=Pw(out), it will take same time to charge a phase as discharge the other ?

    remember that RC time constant is quite irrelevant here because V(in) and also R(s) varies. The only thing that interests me is the relation between power and duration of charge/discharge.

    Tough one, huh ? :D
  2. Duane P Wetick

    AAC Fanatic!

    Apr 23, 2009
    Consider using a couple of Tri-state Analog switches, which are run by a 555 Astable Multivibrator. The first switch allows a small capacitor to charge, then it shuts off (tri-state) and a second switch dumps the charged capacitor into your bank. When the second switch shuts off (tri-state), the first switch then allows your small capacitor to charge up again...and the cycle repeats. Like a little bucket brigade.

    Cheers, DPW [ Everyone's knowledge is in-complete...Albert Einstein]