Patent ID: 9048769
Filing Date: 2015-06-02
Classification: H02P

Abstract:
1. A motor driving circuit that controls driving of a motor with a PWM signal, comprising: a first converting circuit that outputs an analog voltage proportional to a rotational speed of the motor; a differential voltage calculating circuit that calculates a differential voltage between the analog voltage and a rotation instruction voltage that prescribes the rotational speed of the motor and outputs a differential voltage signal including information on the differential voltage; a duty controlling circuit that that outputs, based on the differential voltage signal, a duty controlling signal including information on a control duty that controls a duty of the PWM signal so as to bring the differential voltage between the rotation instruction voltage and the analog voltage close to zero; a motor driving waveform controlling circuit that generates the PWM signal in response to a signal based on the duty controlling signal and that outputs the PWM signal; a start duty calculating circuit that calculates a start duty of the PWM signal at a start of the motor and that outputs a start duty information signal including information on the calculated start duty; a switching circuit that is connected between an output of the differential voltage calculating circuit and an input of the duty controlling circuit and that one of permits and blocks a passage of the differential voltage signal from the differential voltage calculating circuit to the duty controlling circuit; and an adding circuit that adds the signal output from the duty controlling circuit and the signal output from the start duty calculating circuit and that outputs a resulting signal, wherein the motor driving waveform controlling circuit generates the PWM signal in response to the resulting signal output from the adding circuit and outputs the PWM signal.