Boost converter turn-off time

Discussion in 'General Electronics Chat' started by anhnha, Mar 18, 2016.

  1. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    For the boost converter below operating in DCM mode, the voltage conversion ratio is calculated as follows:

    M = V/Vg = 1 + D1/D2
    where
    V, Vg are output and input voltage respectively.
    From the formula, it is clear that the conversion ratio doesn't depend on D3. So, is there any requirement for D3 here?


    Boost converter - intuitive.PNG
     
  2. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,287
    1,252
    Just that the lower the voltage drop the more efficient the conversion.
    And of course the voltage and current ratings must be high enough.
     
  3. dl324

    Distinguished Member

    Mar 30, 2015
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    D3 is primarily determined by the load.
     
  4. anhnha

    Thread Starter Active Member

    Apr 19, 2012
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    47
    Thanks.
    How does it depend on load current?
     
  5. dl324

    Distinguished Member

    Mar 30, 2015
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    When the voltage at the cap drops below the target voltage, the switch needs to turn on. A higher load will discharge the cap faster, making it necessary for the switch duty cycle to be higher.
     
  6. anhnha

    Thread Starter Active Member

    Apr 19, 2012
    773
    47
    Can I reduce switching frequency instead of increase duty cycle? I think it is the same here.
     
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