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Why Buck converter no RHP zero??

Leo Chen
Prodigy 50 points

I'm curious about why Buck converter no RHP zero??
Other topologies such as Boost and flyback all have RHP zero stability issues.

Could you give me an intuitive idea about why buck has no RHP zero, but boost have?

  • +1
    TI__Mastermind 23845 points

    Hi, 

    The generic answer is because in buck converter deliver the energy during the on time of the High Side FET switch (D time) whereas the other topology delivers the energy during the off time of the switch (1-D time). Therefore there is an inherited "delay" in the buck or buck boost or Flyback topology and that is represented by RHP zero. 

    Thanks

    -Arief

  • 0 in reply to Arief Hernadi
    Prodigy 50 points

    Hi Arief,

    Thank you for your intutive and clear explanation.

    For futher question about RHP zero,

    Why DCM RHP zero is much far away than CCM ??

    Could you still give me some intuitive idea about this phenomenon?

    Thanks

  • 0 in reply to Leo Chen
    TI__Mastermind 23845 points

    Hi Leo,

    I think it is related to the equation of RHP zero location. For example in a Boost, the location of RHP zero is indicated by this equation

    Therefore in DCM, Rout is quite large and hence the wr (2*pi*Frhpz) value above is also large. Hence the location of RHP zero also increases

    Thanks

    -Arief