Buck Converter Closed Loop

Discussion in 'General Electronics Chat' started by onceinalifetim, Dec 7, 2014.

  1. onceinalifetim

    Thread Starter New Member

    Feb 9, 2014
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    Hello

    I really need help in this. i know how open loop buck converter works,
    but i don't know how does closed loop buck converter works.. pls help
     
  2. MrAl

    Well-Known Member

    Jun 17, 2014
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    Hello,

    What do you need to know about this? There are various aspects of the circuit.
    Also, do you already know how a linear (non switching) regulator works?
     
  3. ian field

    Distinguished Member

    Oct 27, 2012
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    Maybe the first thing you need to decide - is PWM or burst mode.
     
  4. Papabravo

    Expert

    Feb 24, 2006
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    Well in a closed loop system the output voltage is monitored and some aspect of the control is altered to raise or lower the output voltage ass appropriate.
     
  5. onceinalifetim

    Thread Starter New Member

    Feb 9, 2014
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  6. ian field

    Distinguished Member

    Oct 27, 2012
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    One of the simplest PWM buck designs is the hysteretic.

    There are some reference designs incorporating linear type regulators as voltage sensing devices incorporated within a hysteretic design.

    IIRC; the TL431 application notes include such a circuit example - most of the main manufacturers include pretty much the same examples in their appnotes, but the hysteretic design isn't in every manufacturers offering.
     
  7. crutschow

    Expert

    Mar 14, 2008
    12,995
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    In general a closed-loop buck converter feeds back voltage from the output, compares it to a desired reference voltage, and adjusts the PWM duty-cycle to keep the output voltage at the reference voltage (negative feedback).
    If you use linear feedback, the loop will generally require some frequency compensation circuits to stabilize the loop and prevent it from oscillating.
    If it's a hysteretic (bang-bang) converter than you don't need compensation.
     
  8. onceinalifetim

    Thread Starter New Member

    Feb 9, 2014
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    @crutschow thanks the tips. i roughly know what is going..
    do you have any website link regard of get the transfer function of buck converter???
     
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