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F28335 control card+docking system getting disconnected from ccs3.3

Sachin Devassy
Intellectual 435 points


Hi

I am generating PWM using F28335 , for single phase inverter. However when the dc link voltage of the inverter exceeds say about 50 V, the 28335 gets disconnected from ccs 3.3 even though the pwm output is still there.The pwm is given through an optoisolator (6n1370 ) to mosfet drivers. I have attached the screen shot at the time of error.What could be the cause of this problem.Thanking you.

  • 0
    Genius 5885 points

    Hi Sachin,

    You seem to have problems with EMI. Most of the time you can get away by making a few turns on ferrite core with USB cable as USB is usually the weakest link of the PC-MCU connection.

    But in the big picture, your power stage generates too much EMI. Even if you can continue to work with mentioned solution, you'll probably have to deal with it sooner or later. I'd recommend you to deal with it sooner as if it affects USB link, it might also affect your analog section, thus interfering with control loop, etc.

    Usual culprits are: weak snubber design, to high di/dt or du/dt, ground loops, ...

    Regards, Mitja

  • 0 in reply to Mitja Nemec
    Intellectual 435 points

    Hi Mitja

    I put the the pc-control usb through a  torroidal ferrite core with about 10 turns.But still the problem shows up when the inveretr dc link voltage is increased say beyond 50v. Did i understand u correctly when u mentioned " by making a few turns on ferrite core with USB cable ".

    Thanks