Differential Mode Filter Design

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  • iamakda
    Member
    • Mar 2012
    • 46
    • Denmark
    #1

    Differential Mode Filter Design

    Dear All,

    I have a question regarding the selection of value of X-Capacitors that are used in Differential Mode Filters (EMI Filters).

    I have an Isolated Full Bridge DC DC Boost Converter of 3KW for which I have do design a input Differential Mode Filter. The inductor just after the dc source has a dc current of 100A over which a 40A (peak-to-peak) inductor ac current is superimposed which means that triangular current waveform of 40A (pk-to-pk). Vi=30 V.

    I have determined the corner frequency of LC Low pass filter as 90KHz.

    My first question is how can I calculate the Peak to Peak ripple voltage(out of the above defined current waveform of inductor) which a X-Capacitor must withstand?

    Second question is what value of X-capacitor shall I choose that can withstand the amount of ripple voltage that has been calculated in the first question I asked above?

    Your suggestions and help will be highly appreciated. I have also attached a picture for your convenience.

    Thanks.
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    • PeteS in CA
      Badcaps Legend
      • Aug 2005
      • 3578
      • USA, Unsure of Planet
      #2
      Re: Differential Mode Filter Design

      iamakda, your question is definitely well over my head. I'm thinking that the capacitor ripple current capability might be critical as well.
      PeteS in CA

      Power Supplies should be boring: No loud noises, no bright flashes, and no bad smells.
      ****************************
      To kill personal responsibility, initiative or success, punish it by taxing it. To encourage irresponsibility, improvidence, dependence and failure, reward it by subsidizing it.
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        Comment

        • iamakda
          Member
          • Mar 2012
          • 46
          • Denmark
          #3
          Re: Differential Mode Filter Design

          ok if we think in terms of capacitor's ripple current, then what would be the ripple current which will pass through this x-capacitor? how i can calculate this ripple current and then what value of x-capacitor should I use?
          Last edited by iamakda; 03-01-2012, 08:50 AM.

            Comment

            • iamakda
              Member
              • Mar 2012
              • 46
              • Denmark
              #4
              Re: Differential Mode Filter Design

              Originally posted by PeteS in CA
              iamakda, your question is definitely well over my head. I'm thinking that the capacitor ripple current capability might be critical as well.
              Dear PeteS,

              Please advice how can I calculate the value of X-Capacitor from scratch in order to design a Differential Mode Filter? Just to remind you I have found the cutoff freq. of filter is as 90KHz.

              Kindly help me out as I do not have any idea about it. Guide me please.

              I hope to hear from you.

              Thanks,
              Ishtiyaq

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