bittware
Full Member level 4
the initial current
I encountered a weird problem in permanent magnetic DC motor control application. I used L6204(from ST) as my H-bridge driver for a 11 watt DC motor. I set up the typical circuit named "Enable Chopping". Using DSP PWM output to drive the H-bridge enable input, I just implemented a simple position feedback and used position error to command a PID unit adjusting PWM duty cycle(0%~100%). The PWM modulation frequency was fixed on 20KHz. I used an oscilloscope to capture voltage across the sensing resistor. I had expected to watch a relative smooth waveform, but at the initial phase and end phase of the motor motion profile I found there existed significant period of zero current. I could not imagine why this did happen. So here ask for your help to explain such case.
Additionally, is this phenomenon normal? Does it have influence on motor running noise? If it is abnormal, what is the root cause and how to correct it?
Thanks in advance.
I encountered a weird problem in permanent magnetic DC motor control application. I used L6204(from ST) as my H-bridge driver for a 11 watt DC motor. I set up the typical circuit named "Enable Chopping". Using DSP PWM output to drive the H-bridge enable input, I just implemented a simple position feedback and used position error to command a PID unit adjusting PWM duty cycle(0%~100%). The PWM modulation frequency was fixed on 20KHz. I used an oscilloscope to capture voltage across the sensing resistor. I had expected to watch a relative smooth waveform, but at the initial phase and end phase of the motor motion profile I found there existed significant period of zero current. I could not imagine why this did happen. So here ask for your help to explain such case.
Additionally, is this phenomenon normal? Does it have influence on motor running noise? If it is abnormal, what is the root cause and how to correct it?
Thanks in advance.
