LOW PASS FILTER (LC) resonanting.

Discussion in 'Misc Electronics' started by mikemillernow@gmail.com, Oct 28, 2013.

  1. Guest

    All,

    I am looking to design a low pass filter that has a cutoff frequency of 20 kHz. The filter needs to be able to handle about 20A of current so the direction I have taken is an LC filter. (Inductor with a high current rating).

    I simulated the low pass filter tonight (LTspice) using the values of 7.9 uH and 15 uF suggested from some of the online lowpass filter calculators.

    From the simulation I see 0 dB in most of the passband but then I see a huge resonance point of +32 dB at 14.49 kHz!


    Here is a link to the simulation result:

    http://i1001.photobucket.com/albums/af140/mikemillernow/LP_filter_79uH__15uF_zps5421958c.jpg


    1.) Is there a way to eliminate this resonance?

    2.) Is there a different filter that would have less peaking but still ableto handle the high current for this application (20A)?

    3.) There is an H-brige that will be modulated at 200 kHz (pwm) and this will going through the 20kHz lowpass filter to given a DC voltage without allthe pulses. If the resonance point is kept as it is what type of issues would this cause? Is this even a problem?

    4.) From the simulation I see a cutoff frequency of 22.7 kHz instead of 20 kHz. What is the best way to tune this? Maybe to keep the capacitor fixed (15 uF) and then sweep the inductance value in simulation?

    Thank you you so much for your thoughts.

    -Mike
     
    , Oct 28, 2013
    #1
    1. Advertisements

Want to reply to this thread or ask your own question?

It takes just 2 minutes to sign up (and it's free!). Just click the sign up button to choose a username and then you can ask your own questions on the forum.
Similar Threads
  1. Andrew Howard

    Low Pass Filter for subwoofer

    Andrew Howard, Mar 3, 2004, in forum: Electronic Basics
    Replies:
    4
    Views:
    1,729
    Andrew Howard
    Mar 6, 2004
  2. boki
    Replies:
    0
    Views:
    528
  3. Amanda Robin

    Square wave through low-pass filter

    Amanda Robin, Jun 17, 2004, in forum: Electronic Basics
    Replies:
    2
    Views:
    2,589
    Bob Masta
    Jun 18, 2004
  4. thomas

    RC Low pass filter Q

    thomas, Jul 2, 2004, in forum: Electronic Basics
    Replies:
    6
    Views:
    986
    Dbowey
    Jul 3, 2004
  5. Alan Adrian

    low pass filter questions...

    Alan Adrian, Jan 20, 2005, in forum: Electronic Basics
    Replies:
    4
    Views:
    469
    Alan Adrian
    Jan 21, 2005
  6. KeeperOfLogic

    Volume (decibel) Low-pass filter (NOT frequency filter)

    KeeperOfLogic, Oct 21, 2006, in forum: Electronic Basics
    Replies:
    9
    Views:
    1,718
    Bob Masta
    Oct 22, 2006
  7. john.agcos

    design very low active low pass filter

    john.agcos, Dec 12, 2013, in forum: Circuit Help
    Replies:
    6
    Views:
    798
    john.agcos
    Dec 16, 2013
  8. vasanth

    low pass or high pass filter

    vasanth, Apr 10, 2014, in forum: Electronics Homework Help
    Replies:
    2
    Views:
    481
Loading...