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    control design for pwm converter

    Hi Guys,

    I am a starter here.
    here attached is my design and the problems i have.

    please can someone be of help?

    Best regards
    Hubert

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  2. #2
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    Re: control design for pwm converter

    Both the inputs to your error amplifier are actually the outputs of your system.
    VLED and the Current.

    If VLED is 0V, then the Current and hence the INA210 output is also 0V.
    Therefore, both the inputs of the error amplifier are 0V, hence its output is 0V.
    This would mean that the PWM would never generate and the MOSFET would never turn ON which will in turn keep your VLED always at 0V.


    Your system can be reduced to

    VLED = [VLED - {VLED-(I×R35)}×GainINA210] × System Transfer Function

    The problem here is that your system could have many solutions and the above 0V solution is also one of them.

    This is because, like i mentioned in the beginning, you have used the outputs of your systems as the input of your error amplifier. There is no actual reference for the system to compare against which was there in your original design.

    This is just a top level understanding, I have not gone through your circuit or transfer function in detail.
    -- Bilgotidia Fertiganed



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  3. #3
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    Re: control design for pwm converter

    Hi,

    thanks for response, but i still don't get it how I can merge the INA210 in my new system. In place of VLED in the error amp, i have placed the output of the INA210 with the reference voltage maintain still nothing happens.
    Please for helps



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    Re: control design for pwm converter

    The control topology makes no sense. You can either operate the system with current or voltage controlled feedback. But what's the purpose of substracting voltage and a current proportional value?


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  5. #5
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    Re: control design for pwm converter

    @ Fvd,
    Thanks for your response, you are correct, a system can be operated either by current or voltage controlled feedback.
    In my first circuit, i operated my system with a voltage controlled feedback, it was perfect.
    In the second circuit, i am trying to operate the system with a current controlled feedback by using the INA210. meanwhile looking for means to eliminate Vref.



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