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DRV8711 drive the motor in high speed,the current is not sine wave,why?

user3641832
Prodigy 30 points
Other Parts Discussed in Thread: DRV8711

when I use drv8711 to drive the stepper motor, when in low speed, the current is sine wave, but in high speed ,the current  is not sine wave .I try to change the parameter, including the decay time ,the blank time and the mode,but it doesn't  work.

The internal indexer mode,128 step,TOFF  is 25us,TBLANK is 1us,the decay mode is" Slow decay for increasing current, mixed decay for
decreasing current (indexer mode only)", the mix decay time is 20us.when the step period is 140us,the wave is figue 1,but when in 9us,
the wave is figue 2.


  

figue 1

figue 2

  • 0
    TI__Guru** 114905 points
    Hi user3641832 ,

    The figures have not yet arrived.
    What is your system voltage? Is it possible you can increase the system voltage? If so you should see some improvement.

    We will look again later after the figures arrive.
  • 0 in reply to Rick Duncan
    Prodigy 30 points
    Thank you very much. I try to change the increase voltage from 24V to 36V ,not work ,also like the trianqle wave.Why the figures can not show,it has a delay,or I don't upload them sucess.
  • 0 in reply to user3641832
    TI__Guru** 114905 points
    Hi user3641832,

    Did you see any improvement at 36V vs 24V?

    This is not a problem with the DRV8711. As the motor speed increases, the BEMF reduces the rate of current change.

    To correct this, there are several options:
    1) Increase VM -- from the images above this may help but probably will not correct the sine wave
    2) Reduce the number of microsteps (try 1/32) -- this allows more time per step for the current to reach the specified value
    3) Reduce the speed of the step input
    4) Consider a lower inductance motor
  • 0 in reply to Rick Duncan
    Prodigy 30 points

    HI

    It has some improvement from 24V to 36V.I have two figures,the first one is 24V ,the second one is 36V :

    figure 1:24V

    figure 2:36V

    I have tried to reduce the number of  steps,1/4,not work ,also not the sine wave. I think I will consider a lower inductance motor.Thank you very much.