Buck/Boost,Cuk converter IC

Discussion in 'The Projects Forum' started by assuc, Aug 27, 2014.

  1. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    Greetings,
    I need to design buck/boost or CUK converter to charge a battery.
    Input= 16V 7Amp
    Output= 11~14V 5 Amp
    I need to know if their are any IC's AVAILABLE which can control the output via pwm from micro controller.
    I searched some of them but found it to be difficult
     
    Last edited: Aug 27, 2014
  2. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    What would you like to control?
    -------------------------------------------
    What is the battery chemistry?

    What is the charging algorithm?

    Battery terminal voltage?

    Charging current into the battery?
     
  3. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    Output voltage should be adjustable which will depend on varying duty cycle.
    Battery is lead-acid of 12V 45Ah, so i will be charging battery at 10% current that is 5Amps.
    The basic idea is to charge the battery at 14V if the input voltage varies between 10~16V, this will surely change the charging current but in most suitable case the converter should provide atleast 5amp max
     
  4. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    There are autonomous battery charge controller IC chips that do this without needing a microcontroller at all.

    Sounds like you would prefer doing the control of the charging protocol yourself using a microprocessor (use A/D to read battery voltage, PWM the gate of a FET used as part of a step-up switchmode supply)?
     
  5. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    yes, i want to control myself thru controller so i need a buck/boost ic so i dont need autonomous charging ic
     
  6. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Start by reading this app note.

    If you are going to use the u-controller to control the converter on a cycle by cycle basis, you don't need a chip, just the inductor, FETs, Schottky catch diodes, filter caps, etc. You will need to measure the input voltage to decide if the converter is running in boost or buck mode... You will need to measure the output voltage to control the PWM duty cycles...
     
  7. assuc

    Thread Starter Member

    Mar 23, 2012
    77
    1
    Actually i have made two of them 1 using buck/boost topology and other using cuk topology, both failed to work.
    both gave voltage output less than required with no current when applying load. so ,i thought why not try to use a ready made IC and control the it by implementing algorithms on controller.

    Okay ,so the app note u just posted is about calculating values of inductor and capacitor,and switchng current... not about the ic's so it left me no choice but to design again and make it work... but one thing i am confused should i use mosfet with gate drive or a power transistor without gate drive would work because it needs to be worked as a switch operating in saturation or cutoff mode??
     
    Last edited: Aug 28, 2014
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