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Homework Help: Boost converter

  1. Sep 10, 2015 #1
    1. The problem statement, all variables and given/known data

    Does the voltage gain follows the a linear relationship when the switching frequency is 5 kHz? and does it still follow the linear relationship when it is 1k Hz?

    2. Relevant equations

    3. The attempt at a solution
    I am doing an experiment on this and I have found out that through simulation result using a software.
    When the Switching frequency is 5 kHz , it doesn't follows a linear relationship but it follow a linear relationship when it has been change to 1 kHz.

    On the actual experiment itself , for both cases (switching frequency is 5kHz or 1kHz) , it doesn't follow a linear relationship.

    so now I am confused. I have read on some website that for booster converter , voltage gain doesn't follow linear relationship.
  2. jcsd
  3. Sep 10, 2015 #2


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    Staff: Mentor

    Can you post your simulation results and you SPICE decks? :smile:
  4. Sep 11, 2015 #3
    In general . does switching frequency affect the linear relationship of voltage gain with respect to the duty cycle?
  5. Sep 11, 2015 #4

    I would like to ask one more question. Does this consider to be a linear relationship ? It doesn't look very linear to me?
  6. Sep 11, 2015 #5


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    Staff: Mentor

    Can you label the axes? Or say what they are?

    Does your simulation use real voltages for the diode and transistor switch? What about reverse recovery time of the diode, and the frequency characteristics of the transistor?
  7. Sep 11, 2015 #6

    rude man

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    Homework Helper
    Gold Member

    If you write the equation for the current thru the inductor at the end of the "ON" cycle, and the equation at the end of the "OFF" cycle, and realizing that the currenmt at the end of the "OFF" cycle must equal the current at the beginning of the "ON" cycle, then you can easily show that the relationship is not linear in the duty cycle δ defined as δ = "ON" time / ("ON" time + "OFF" time).

    This assumes that the output voltage is constant (large output capacitor, not too large a load). "ON" means the transistor is on. Also ideal transistor and diode characteristics.

    You can also show that for small δ the relationship between the duty cycle and the output voltage is approximately linear.
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