Question about charge pumps capacitors

Discussion in 'General Electronics Chat' started by yuvi1, Feb 12, 2014.

  1. yuvi1

    Thread Starter Member

    Feb 1, 2013
    hi all,

    I know that charge pump is a DC to DC converter that uses capacitors for creating an output voltage that is either higher or lower than the input voltage .

    how does it creates at the output a higher voltage than the input ?
    is it lowers the current at the output in the same ratio ?

    thanks !
    Last edited: Feb 12, 2014
  2. Potato Pudding

    Well-Known Member

    Jun 11, 2010
    A charge pump restacks voltages.

    For a voltage increase-
    You charge a capacitor and then raise the negative node to a positive value, then take current off of the positive node.

    With a 5 Volt supply you would likely charge the capacitor to 5 Volts then change the connections so that the capacitors negative node is raised to 5 Volts which would make the positive node 5 Volts, + 5 Volts. Diode drops will reduce that to less than 9 Volts actual output. Repeat continuously and very fast to get a reasonably steady output.

    The load current must be very small or else you will end up with much less than 9 Volts out in this example.
  3. yuvi1

    Thread Starter Member

    Feb 1, 2013
    first of all , thanks for your answer

    and regard to your answer:
    how do we change the connections ? with some king of switching ?
    voltage increase (dc to dc) must have some king of switching in order to work ?
  4. crutschow


    Mar 14, 2008
    Yes, you need switches. Typically MOSFETs are used for that purpose.