Noise from H-Bridge using IR21844

Discussion in 'The Projects Forum' started by bytraper, May 8, 2012.

  1. bytraper

    Thread Starter Active Member

    Sep 28, 2010
    126
    4
    Hi Guys,

    I am having a problem with this circuit. I can't find the source of the fault.
    It throws a crapload of noise throughout the circuit as soon as I install the mosfets, even without any loads.

    If i leave the mosfets out, the circuit is fine, theres no noise and the drivers seem to perform normally. But as soon as I put the mosfets in, the whole circuit goes unstable!

    Any ideas? or can anyone see any faults or things I may have missed?
     
    Last edited: May 1, 2014
  2. shortbus

    AAC Fanatic!

    Sep 30, 2009
    4,000
    1,512
    How far are the mosfet gate connections from the driver connections? They should be as close as possible, under one inch.

    The 220 ohm resistors on the gates is kind of high, should be <~50 ohm. Mosfet gates have a tendency to "ring" when switching off, the gate resistor is just to stop the ringing and not for part of the "timing" of them.
     
  3. bytraper

    Thread Starter Active Member

    Sep 28, 2010
    126
    4
    Gate lengths are all identical at 24.4mm. Gate resistors are 22 Ohm (just looks like 220)
     
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