| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus and a method for correctly measuring an average current of currents running in windings of a motor when the motor is driven with PWM waveform signals. SOLUTION: An apparatus and method 10 for measuring an average motor current in a motor driven in a pulse width modulation mode is provided. A sensor 20 is coupled to the motor to measure a current of a winding of the motor. A first current normally proportional to the current of the motor winding is generated by a first current source 26. A second current almost proportional to a chopped output voltage is generated as well. The second current is subtracted from the first current. A circuit 28 is provided which detects a difference of the first and second currents and generates an output voltage representing the average motor current. The output voltage is chopped at a circuit 32, 34, whereby waveforms are generated with a duty cycle and a phase approximately the same as a pulse width modulation waveform driving the motor. |
