High side Mosfet driver using n-channel

Discussion in 'The Projects Forum' started by jonfarrugia, Jan 5, 2014.

  1. jonfarrugia

    Thread Starter Member

    Feb 19, 2010
    20
    1
    I've been looking at different ways to control an N-channel mosfet as a high side switch for a 12VDC load.
    The signal to the circuit will be from an arduino it may or may not be a pwm output.
    I was considering using an LM2941CT set for 20vdc as the power for the MOSFET gate driver circuit.

    If I connect the arduino output to a transistor that controls either 20vdc or 0vdc to the high-side n-channel MOSFET gate, would this be ok? See attachment

    I was going to use this regulator because I want to use it's power to drive 20 MOSFET gates from 20 different Arduino Outputs.
     
  2. #12

    Expert

    Nov 30, 2010
    16,252
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    That looks right, give or take frequency related parts. Depends on how fast you want to run it.
     
  3. jonfarrugia

    Thread Starter Member

    Feb 19, 2010
    20
    1
    at most it would be about 1khz - 5khz
     
  4. THE_RB

    AAC Fanatic!

    Feb 11, 2008
    5,435
    1,305
    There are a heap of specialist small ICs called "high side FET drivers".

    Many of them even generate the higher voltage needed for the gate, so you don't need dual PSUs. :)
     
  5. #12

    Expert

    Nov 30, 2010
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    As the gate is passing 12 volts, going positive, there is 8 volts across the 10K resistor. That's .0008 amps. The gate is 190 pf. The gate voltage will be moving at 4.2 volts per microsecond if I did the math right. The half wave time of 5kHz is 100 usec. That says more than 2% of the 5Khz time will be spent in the last 8 volts.

    I think, speed it up a bit. 750 ohms for R1

    Still, RB has a better idea.
     
  6. jonfarrugia

    Thread Starter Member

    Feb 19, 2010
    20
    1
    Can u provide a link to a single ic driver that might work in this application?
     
  7. jonfarrugia

    Thread Starter Member

    Feb 19, 2010
    20
    1
    Thanks. I'll test this when the components come in.
     
  8. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Why not just use a PFet preceeded with an NPN? That also eliminates the need for a higher than 12V power supply or charge pump.
     
  9. jonfarrugia

    Thread Starter Member

    Feb 19, 2010
    20
    1
    Can u provide a circuit so I can understand what you mean?
     
  10. #12

    Expert

    Nov 30, 2010
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    Or move the N-fet to the other side of the load.

    There are 6 ways to do this. Why you choose the most difficult?
     
  11. jonfarrugia

    Thread Starter Member

    Feb 19, 2010
    20
    1
    I need high side switching for this application.

    I went with the above circuit cause I have the IRF510 MOSFET in stock.
     
  12. #12

    Expert

    Nov 30, 2010
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    Well, my answer (post #5) is in compliance with what you would probably have on hand.
     
  13. MikeML

    AAC Fanatic!

    Oct 2, 2009
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    Here it is without words. There are hundreds of PFets you could use for this application.
     
  14. #12

    Expert

    Nov 30, 2010
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    That pretty much confirms my math. The MikeML circuit has 3usec time one way and 8 usec time the other way. That demonstrates that a 10K drive resistor is going to be awful in this application.
     
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