Patent ID: 8174215

Claim:
A motor speed controller for controlling rotational speed of the motor on the basis of a pulse signal in which the pulse period varies in inverse proportion to the rotational speed, comprising: a count clock generator for generating a count clock with the clock frequency varying in accordance with a target rotational speed of the motor to keep a count value within the pulse period at the target rotational speed a constant target numerical value independent of the target rotational speed; and a feedback control section for bringing the rotational speed closer to the target rotational speed by feedback control, wherein the feedback control section comprises: a pulse period measurement section for counting the clock pulse in the pulse period at the current rotational speed and determining a measured count value; an error signal generator for generating an error signal that corresponds to the difference between the measured count value and the target count value; and a compensation instruction signal generator for generating a compensation instruction signal designed to adjust the rotational speed to the target rotational speed on the basis of the error signal, wherein the compensation instruction signal generator scales the compensation instruction signal at a scaling factor that is proportional to the target rotational speed.