H bridge driver with floating ground help

Discussion in 'General Electronics Chat' started by santini, Mar 3, 2009.

  1. santini

    Thread Starter New Member

    Nov 14, 2008
    4
    0
    Hi all,

    I'm trying to use a IRS21094 to drive a H bridge with a PWM input as show in anex below.

    I'm using two differents sources. One is +12V between Vcc and Vss and another is +90V between drain of top MOSFET and COM.

    If I connect COM and Vss, the circuit works without error, but to avoid spikes and noise from motors, I want to disconnect the two grounds. When I disconnect COM and Vss, the circuit stops to work.

    I think that when I disconnect the grounds, the circuit stops because of the absolute maximum ratings says that Vcc must to be between -0.3V and 25V of COM and this isn't true in my circuit.

    Any help?

    Thanks
     
  2. SgtWookie

    Expert

    Jul 17, 2007
    22,182
    1,728
    You have to have a common ground.
     
  3. thingmaker3

    Retired Moderator

    May 16, 2005
    5,072
    6
    Have you considered using bypass caps instead?
     
  4. santini

    Thread Starter New Member

    Nov 14, 2008
    4
    0
    Hi thingmaker3,

    I'm using a electrolytic 1uF, and a ceramic 100nF for any IC. They are really close of ICs irs21094. This don't solve my noise problems.

    Thanks
     
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