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Feeding a square pulsed DC into a transformer's primary winding.

Discussion in 'General Electronics Discussion' started by BlackMelon, Apr 18, 2016.

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  1. BlackMelon

    BlackMelon

    188
    5
    Aug 7, 2012
    Hi there!

    The attached photo is a circuit with an input waveform. Do I get it correctly? I'm so worried about the increasing current very much. (As you know, the inductor current is an integration of its voltage. Because the voltage is always greater or equal to zero, this current will keep going up)

    Background story:
    I'm trying to control a forward converter in this link: http://www.onsemi.com/pub_link/Collateral/TND378-D.PDF
    The circuit is on page 47and48. Unfortunately, the PWM controller is not with a high-side MOSFET driver, so the author did it in page 48. When Q301 is on and the other is off, the voltage across the primary winding is Vcc. Subsequently, Q302 operation gives 0V to the winding. This will be a square pulsed DC like in the attached photo.

    PS. Sometimes it's funny that the high side driver like HIP4082 does not come with a feedback pin and a pin for a setpoint resistor. while the ONSEMI has a feedback and a setpoint resistor, but no high side driver.

    Thank you
    BlackMelon
     

    Attached Files:

  2. Alec_t

    Alec_t

    2,890
    775
    Jul 7, 2015
    No. DC doesn't get through the transformer. The secondary winding current will settle down, after an initial displacement from zero, to a square-wave oscillation symmetrical about zero. Like this:-
    TransformerCurrent.PNG
     
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