ripple current

Discussion in 'General Electronics Chat' started by ariemeir, Mar 24, 2013.

  1. ariemeir

    Thread Starter Member

    Jun 24, 2011
    Hi all ,

    I would like to ask about ripple current in capacitors.

    I am designing a high pulse generator:
    basically i have a high voltage (~200v), low current (~30ma) power supply which charges a large capacitor (~5000uf), which i discharge once in a while (typical rate: 4 hz with
    100us of discharge pulse at a time).

    when i need to specify my capacitors, i care about the ESR (since my load can be as heavy as several ohms so that can be comparable to the ESR).
    Since the currents during the discharge can be high (~20A), i am wondering
    if i should worry about the ripple current specification.

    I'm not sure i understand this parameter completely - if my capacitor is charged through dc, and discharged through a resistive load - how should
    i take the ripple current into consideration ?
    If there is something else i might be overlooking, I would appreciate some advice.

    Kind regards,
  2. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    The ripple current causes heating in the cap, due to the ESR of the cap and the current (I squared R) heating.

    If you know the ESR of the cap and the currents involved (sounds like you do) then you can calculate the heating produced in the cap and keep that below the safe limit considering your cap size and ambient temperature.
  3. ariemeir

    Thread Starter Member

    Jun 24, 2011
    the_rb, thank you very much for the answer.
    it makes sense.