# Issues driving a simple motor driver

I am using the following motor driver to drive a motor via a pwm.

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?

• Can you describe these "'jumps' with current spikes"? Aug 24, 2021 at 8:43
• 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. Aug 24, 2021 at 9:22
• how quickly is the duty changing? Higher current is expected if the motor is accelerating, but little knocks aren't. Aug 24, 2021 at 9:24
• Can you show us the Oscilloscope waveform of the 'jumps' pictures? Aug 24, 2021 at 9:35
• Christianidis Vasileios The jumps are more physical and auditory, the waveform on the oscilloscope is a simple square, completely normal. Aug 24, 2021 at 10:09

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.