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I am using the following motor driver to drive a motor via a pwm. enter image description here

I can successfully drive the motor, but I get small 'jumps' with current spikes when I change the duty cycle of the pwm. I am using a 20khz and 3.3V pwm.

What can you recommend to fix this problem?

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  • \$\begingroup\$ Can you describe these "'jumps' with current spikes"? \$\endgroup\$
    – user253751
    Aug 24, 2021 at 8:43
  • \$\begingroup\$ When I change the pwm duty I see the power supply go up to 0.40A and then back down to about 0.20A, and in the process I hear like little knocks coming from the motor. \$\endgroup\$
    – lasb3tas
    Aug 24, 2021 at 9:22
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    \$\begingroup\$ how quickly is the duty changing? Higher current is expected if the motor is accelerating, but little knocks aren't. \$\endgroup\$
    – user253751
    Aug 24, 2021 at 9:24
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    \$\begingroup\$ Can you show us the Oscilloscope waveform of the 'jumps' pictures? \$\endgroup\$ Aug 24, 2021 at 9:35
  • \$\begingroup\$ Christianidis Vasileios The jumps are more physical and auditory, the waveform on the oscilloscope is a simple square, completely normal. \$\endgroup\$
    – lasb3tas
    Aug 24, 2021 at 10:09

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Mechanical torque is a product of mass of inertia and angular acceleration \$T=J\alpha\$, meanwhile the electrical torque is proportional to the current \$T\propto I\$. When you increase the voltage the higer current accelerates the motor until the back EMF generated voltage from motor rises to approx. the applied voltage. So nothing unusual there.

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  • \$\begingroup\$ Thanks for the reply. is it feasible in your opinion to add a capacitor to alleviate these spikes? \$\endgroup\$
    – lasb3tas
    Aug 24, 2021 at 10:09
  • \$\begingroup\$ No, rather a ramp to increase/decrease PWM duty ratio. But you should do also a scope trace, there might be something else, for example a transition from discontinuous conduction mode to continuous. \$\endgroup\$ Aug 24, 2021 at 10:17

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