supressing harmonics in transformer

Discussion in 'General Electronics Chat' started by lokeycmos, Feb 22, 2013.

  1. lokeycmos

    Thread Starter Active Member

    Apr 3, 2009
    432
    7
    i built this circuit just for fun:

    http://electroschematics.com/220/12v-dc-220v-ac-converter/

    It is a square wave oscillator. i subtituted high power mosfets for the darlingtons. the circuit works great, but there is a lot of harmonic buzzing comming from the transformer. it draws 2 amps at idle. my question is, is there a way to suppress of get rid of the unwanted buzzing harmonics? mabey a capacitor somewhere? the transformer does not buzz when fed properly with mains. i am reading 60hz on the output.
     
  2. crutschow

    Expert

    Mar 14, 2008
    13,023
    3,236
    You are feeding the transformer a square-wave which has a lot of harmonics. The only way to get rid of that is to drive it with a sine-wave which requires a more complex circuit.
     
  3. ScottWang

    Moderator

    Aug 23, 2012
    4,855
    767
    If you want to try, then you can try this:
    You may using two stages of RC Integral circuit, and one stage of transistor to Amplify the signal.

    You can try one stage of RC Integral circuit first:
    CD4047 Square wave → one stage RC Integral circuit → Transistor Amp circuit → MOSFET → Transformer.

    Two stages of RC Integral circuit:
    CD4047 Square wave → Two stages of RC Integral circuit → Transistor Amp circuit → MOSFET → Transformer.

    Two stages of RC Integral circuit can make the Square wave change to kind of sinewave, but it will reduce the voltage amplitude, so you need to Amplify the signal.

    Here has a problem to be concerned, that is the phase will be moving backwards, I'm not sure will it has any affect when two sides of RC is not matched.
     
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