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MOSFET control using Digital Potentiometer

Discussion in 'General Electronics Discussion' started by stev067, Apr 25, 2011.

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  1. stev067

    stev067

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    Apr 25, 2011
    I would like to control the amplitude across a load (36V max). I would like to do this using a microcontroller and a digital potentiometer. I will try to explain the best I can without having a schematic, but I can draw one. It is a P-channel mosfet (9530). I was thinking of using the digital potentiometer in a voltage divider from VCC/source to ground with the gate in the middle so that when I vary the digital pot's resistance, the mosfet will be more/less on.

    Any suggestions and feedback will be greatly appreciated!
     
  2. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
    Your best bet, unless the current is very low is to design a variable voltage switchmode power supply. If the load is constant, you could simply use PWM in an open loop arrangement.

    You can't do it as simply as you suggest as the mosfet's response is not linear.

    You could use an op-amp to compare the voltage across your pot and your load and thus control the gate voltage to maintain them at the same value.
     
  3. stev067

    stev067

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    Apr 25, 2011
    Thanks for the reply, fellow Steve. Do you happen to know of a suitable part number or a link to a design?
     
  4. (*steve*)

    (*steve*) ¡sǝpodᴉʇuɐ ǝɥʇ ɹɐǝɥd Moderator

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    Jan 21, 2010
  5. stev067

    stev067

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    Apr 25, 2011
    Thank you again for your help. I think I've stumbled upon a proper design.

    I will use something like a LM2591HV "Simple Switcher" Buck Regulator IC whose load voltage can be controlled by varying Rf, which will be a digital potentiometer.
     
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