Boost converter with tl494

Discussion in 'General Electronics Chat' started by mohammadhossein ajorloo, Aug 27, 2016.

  1. mohammadhossein ajorloo

    Thread Starter New Member

    Aug 27, 2016
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    Hi every body
    I want to make 12 to 36 volt boost converter with tl494, but i can not run ic. I know that pin 12 is vcc, pin7 gnd, pin 6 and 7 for frequncy set, but I can not work with pin 1,2,15,16,4 and actually pin3 that is for feedback.
     
  2. Dodgydave

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    Jun 22, 2012
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  3. mohammadhossein ajorloo

    Thread Starter New Member

    Aug 27, 2016
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  4. Dodgydave

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    Jun 22, 2012
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    R6,R7 form a voltage divider across the 5v reference supply, this is set at 0.5v here for the deadband dropout, R5, Rref are for the gain setting for the op amp.
     
  5. mohammadhossein ajorloo

    Thread Starter New Member

    Aug 27, 2016
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    Hi
    Finally I can run ic. But I have a problem, I have 36v in none load mode and when I put 60ohm resistor in out put my out put voltage drop about 3 volt.
     
  6. mohammadhossein ajorloo

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    Aug 27, 2016
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    The mine boost 12v-36v circuit.
     
  7. Dodgydave

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    Sounds like your circuit isn't working correctly, did you use the circuit from the datasheet..
     
  8. mohammadhossein ajorloo

    Thread Starter New Member

    Aug 27, 2016
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    I saw it. It just have a buck converter and I need a boost converter.
     
  9. Alec_t

    AAC Fanatic!

    Sep 17, 2013
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    I think the feedback resistors are giving the wrong feedback voltage. If R1=R2 then the voltage at pin 1 is 2.5V; so the feedback loop will try to adjust the voltage at pin 2 to 2.5V. That means your voltage divider from Vout needs to provide 2.5V. A 47k resistor and 1k pot (if I've read the values correctly) can't do that if you want a 36V output.
    With R3=1k and R4=15k (?) the error amplifier gain is only about unity. Try swapping them over. Why didn't you use values similar to those in the datasheet?
     
  10. Dodgydave

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    Jun 22, 2012
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    looking at your circuit pins 1,2 need reversing, you need to remove R3/4 and connect pin 1 to the output resistor divider preset , pin 2 should be used as the reference source pin.

    Like this circuit example....http://i.imgur.com/8ndwf.png


    Note if the reference voltage on pin 2 is set to 2.5v, then your output voltage will be at 2.5v on pin 1 at shutdown, so use a 1k preset and 4.7k resistor.
     
    Last edited: Aug 30, 2016
  11. mohammadhossein ajorloo

    Thread Starter New Member

    Aug 27, 2016
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    hi
    i can finally solve my broblem with yours help. the problem was about my diod, it just can cross 2 amper bout i need 5A. and my feed back had a little broblem. i should thanks Dodgydave and Alec_t that help me a lot
     
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