LC Filter Design

Discussion in 'The Projects Forum' started by lijoostenk, Jan 26, 2013.

  1. lijoostenk

    Thread Starter New Member

    Jan 25, 2013
    12
    0
    I need to design a simple LC filter for eliminating the ac ripples at the output of a rectifier. My circuit involves series connected high power LED's which receives its input from the filter.
    So I need a filter which can tolerate such high currents (>2A). Can anyone help me out in designing this filter?
     
  2. antonv

    Member

    Nov 27, 2012
    149
    27
    A simple LC filter (series inductor followed by a parallel capacitor) may work fine. Important things to pay attention to are that the inductor has a saturation current of maybe twice the 2A and also low dc resistance, and that the capacitor can handle high ripple currents. How much depends on what your are driving and probably the frequency you are using.
    How much inductance the inductor needs will also depend on your frequency. How well the whole circuit works will also depend a lot on how you wire it. Long wires in the wrong places can wreck the filter's performance.
     
  3. thatoneguy

    AAC Fanatic!

    Feb 19, 2009
    6,357
    718
    For an RC filter, C is roughly:

    C=\frac{8.6}{f \cdot R \cdot Ripple%}

    C is in Farads, f is rectified frequency (100 or 120 Hz for 50 or 60Hz), %ripple is deviation from average voltage, R is load defined by: \frac{Vout}{Iout}.
     
  4. #12

    Expert

    Nov 30, 2010
    16,261
    6,768
    Inductors were used a lot, 50 years ago. They have been replaced by excellent, inexpensive capacitors. I would recommend you do not use any inductor at all unless this is a homework assignment.

    In addition, LEDs are not very picky about the cleanliness of the DC power. A whole volt of ripple would not be a problem in this case.
     
  5. crutschow

    Expert

    Mar 14, 2008
    12,995
    3,229
    The OP wants an LC filter. ;)

    Here's a reference that may help.
     
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