Drive several NMOS as switches

Discussion in 'The Projects Forum' started by dkester13, Feb 17, 2016.

  1. dkester13

    Thread Starter New Member

    Aug 14, 2013
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    Hi,

    This is my first post!

    I am working on a project where a need to use MOSFET's as switches.
    Driving a sigle MOSFET on should not be a really big problem. The problem arrises when a want to connect several MOSFET's in series like in the picture.
    I want to use the MOSFET as switches. But the current that goes through the "switch" should by isolated from the ground of the control signals from the switch.

    I know one has to take special care with the Vds and Vgs. But without a good reference, I dont know how to begin.

    Could someone explain to the things I should take into account? This schematic is just to test the concept, at the end, I need to have around 100 MOSFET's connected as in the diagram!

    PS. I know this diagram has no meaning, as the there should be always a short circuit. But I made this to make sure I know when the MOSFET is on.

    Thanks for you help in advance!
     
  2. Dodgydave

    Distinguished Member

    Jun 22, 2012
    4,969
    744
    If the two grounds are connected together, then U1, U4 are connected back to back.
     
  3. AnalogKid

    Distinguished Member

    Aug 1, 2013
    4,516
    1,246
    100 shorting switches in series ... electric vehicle battery stack?
     
  4. crutschow

    Expert

    Mar 14, 2008
    12,990
    3,226
    How rapidly do you need to switch them on and off?
     
  5. dkester13

    Thread Starter New Member

    Aug 14, 2013
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    You are close, I think. I would like to design a balancing circuit. Maybe the attached picture gives you a better idea.
     
  6. dkester13

    Thread Starter New Member

    Aug 14, 2013
    7
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    up to 400kHz maybe. After I fully understand the circuit, I will find an optimal switching frequency. I hope it will be around 100kHz
     
  7. dkester13

    Thread Starter New Member

    Aug 14, 2013
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    UPDATE: in the picture, i forgot the diodes. The group should not be the reference for the current source. I hope I made this clear. if not, let me know!
     
  8. ronv

    AAC Fanatic!

    Nov 12, 2008
    3,282
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    Switched capacitor or inductor balancer?
     
  9. dkester13

    Thread Starter New Member

    Aug 14, 2013
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    It is based on the switched capacitor. Do you have any ideas how I could solve my problem?
     
  10. ronv

    AAC Fanatic!

    Nov 12, 2008
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    1,233
    Take a look at this one. It is for 12 volt batteries. I have a clock circuit for it somewhere.
     
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