Common mode noise for SMPS

Discussion in 'General Electronics Chat' started by karas, Oct 30, 2016.

  1. karas

    Thread Starter Active Member

    Sep 8, 2011
    205
    0
    I have flyback power supply has noise in its output and this noise is common mode noise ,I did try different common mode filter but still noisey, is any suggestion for how to get ride of the common mode noise.
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,659
    2,817
    Do you mean the output is noisy? Isn't the output just a voltage and ground?
     
    karas likes this.
  3. karas

    Thread Starter Active Member

    Sep 8, 2011
    205
    0
    The output is noisy and this 15 vdc and current 4A and 15vdc and its return is noisy , the Specification is the return of 15vdc to the chassis of the unit to be very low noisy ,less than 20Uvdb
     
  4. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,659
    2,817
    Is the return grounded to the chassis?
    How about a schematic and a picture of the noise.
    The more information you can give us the better.
     
  5. crutschow

    Expert

    Mar 14, 2008
    20,262
    5,737
    What is the common-mode inductance of the filter you are using?
    Try one with a higher common-mode inductance.
     
    karas likes this.
  6. karas

    Thread Starter Active Member

    Sep 8, 2011
    205
    0
    the return is not connected to ground and for schematic I do not have it right now
     
  7. karas

    Thread Starter Active Member

    Sep 8, 2011
    205
    0
    Thanks so much, I will try this tomorrow when I get to work
     
  8. crutschow

    Expert

    Mar 14, 2008
    20,262
    5,737
    Another question:
    Is there a switching transistor attached to a grounded heatsink?
    That can put noise into the ground.
     
  9. karas

    Thread Starter Active Member

    Sep 8, 2011
    205
    0
    No ,i did try the common mode filter, it fix the range from 1mhz and above ,but i still have noise in the range lower than 1Mhz.
     
Loading...