Motor driving apparatus and method for control of motor revolution

A method for control of motor revolution in an apparatus having:

• an output stage to a multiphase DC motor including a plurality of power elements to supply output voltages to a plurality of multiphase coils and a predriver to supply drive voltages to the power elements,
• a resistor for detecting a current flowing through the power elements, and
• a supply current detector which includes an ADC and a filter,
• the method comprising:
• detecting a voltage signal produced across the resistor as a supply current by using the ADC and the filter in the supply current detector;
• generating a PWM signal with a frequency lower than a sampling frequency of the ADC so that the detected supply current conforms to a current command for controlling the motor revolving speed;
• and
• transferring the PWM signal to the output stage for control of a motor revolving speed,
• wherein the filter has a transmission zero set at the frequency of the PWM signal.

A motor driving apparatus comprising:

• an output stage to a multiphase DC motor including a plurality of power elements to supply output voltages to a plurality of multiphase coils and a predriver to supply drive voltages to the power elements;
• a resistor for detecting a current flowing through said power elements;
• a supply current detector that detects a voltage signal produced across said resistor means as a supply current, using an analog to digital converter performing oversampling operation and a digital filter;
• and
• an output controller that generates a PWM signal with a frequency lower than the sampling frequency of the analog to digital converter so that the current detected by the supply current detector conforms to a current command for controlling the motor revolving speed, and transfers the PWM signal to the output stage,
• wherein the digital filter has a transmission zero set at the frequency of the PWM signal.