Help to explain the waveform result

Discussion in 'General Electronics Chat' started by simpsonss, Jan 19, 2010.

  1. simpsonss

    Thread Starter Active Member

    Jul 8, 2008
    173
    0
    hi,
    ABCD0003.jpg
    ABCD0004.jpg
    ABCD0005.jpg

    ok.This waveform result is from the A point of the schematic i attached. After the switching happen in the primary side, is it the POINT A i labeled still an AC current?
    And is it because of the switching in primary side results to the waveform that i get from the POINT A?
    At point B i can get a 5vdc waveform. Since the 5vdc at point B looks constant then what is the use for the inductor after the point B?

    thank you.
     
  2. t_n_k

    AAC Fanatic!

    Mar 6, 2009
    5,448
    782
    Hi simpsonss,

    Your schematic makes no sense. The secondary windings are short circuited.

    Also what are the primary conditions - waveform type, voltage and frequency?
     
  3. simpsonss

    Thread Starter Active Member

    Jul 8, 2008
    173
    0
    Basically from what i can see on the SMPS that i bought, there is no model name on the transformer. so i just follow the pin out and draw out.How exactly is the windings inside i'm not sure. sorry for that drawing.

    For the primary conditions i didnt get any waveform because i tried once to measure from the DRAIN of the swtching IC then it strip happened. And after asking around i know that i had shorted the scope GND with the negative voltage of the primary side. So till this stage i couldn't manage to get any waveform from primary side yet.

    What i know from the switching IC's datasheet is its frequency is 65Khz.

    Any idea to help me on the waveform i get for POINT A?

    thank you.
     
  4. simpsonss

    Thread Starter Active Member

    Jul 8, 2008
    173
    0
    still waiting for help to solve this problem. The waveform at post#1 looks ripple, should it be in this way?
     
  5. simpsonss

    Thread Starter Active Member

    Jul 8, 2008
    173
    0
    hi,

    i just tried the add function on the scope and manage to measure the primary side of the SMPS. the switching part. From my scope, CH1 connect to the M02659R pin 1 and CH2 connect to pin 2 which is a GND pin. the waveform i get is exactly as below.

    22042010539.jpg

    22042010540.jpg

    22042010542.jpg

    After comparing the waveform between the waveform above and the waveform after the switching transformer(which i posted at post #1), i found that they have their similar part which looks like a switching waveform.

    The question is the waveform above is it the correct waveform which shows the switching of an SMPS.

    thanks.
     
  6. loosewire

    AAC Fanatic!

    Apr 25, 2008
    1,584
    435
    Look at your diagram,the lead from transfromer are touching together,
    that means they shorted ,where did you get diagram. Cut the wires
    and check the reading coming off the transformer with out anything
    being attached,you should get ringing picture.that looks like funnel.
     
    Last edited: Apr 22, 2010
  7. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    Looks to me like your input to the primary is going to resemble a square wave, and the oscillations you see on the secondary side ... hard to say, as one would normally be concerned about the waveform on the cap that is AFTER the diode.
     
  8. simpsonss

    Thread Starter Active Member

    Jul 8, 2008
    173
    0
    hi loosewire,
    for the transformer winding schematic i trace it myself from the SMPS circuit i bought.Below i attached a whole schematic diagram which i trace it out and draw it.

    For the transformer winding part, because i dont have the switching transformer part number so it's hard for me to draw. i draw it through this way. The transformer has 8 legs on itself.And i found out there are 2 pairs of leg shorting, so i treat it as it is at the same winding coil.

    Pin1 and 2 shorting, pin 3 and 4 shorting and pin 5 and 8 shorting.so i come out with the schematic below follow by the rest connection.

    23042010548.jpg
    ----------------------------------------------------------------------------------
    * to make it clearer and easy to refer i repost the post.

    I measure using CH1 to the GND pin of M02659R IC and CH2 to DRAIN pin of the IC. and i get this.
    1.jpg

    ---------------------------------------------------------------------------
    i measure on the cathode of SFR107, and i get this.
    23042010550.jpg

    It seems like, the waveform outputted from the DRAIN pin too much signal inside and i cant really see the switching waveform but the waveform after it pass though SFR107 diode, it has a clearer waveform looks like charging and discharging. Does this waveform prove the switching part?
    -------------------------------------------------------------------------
    i measure on leg 5 of the transformer and i get this
    2.jpg
     
    Last edited: Apr 23, 2010
  9. simpsonss

    Thread Starter Active Member

    Jul 8, 2008
    173
    0
    still waiting....
     
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