Patent ID: 9024568
Filing Date: 2015-05-05
Classification: H02P

Abstract:
1. A motor speed controller to control a motor speed, comprising: a reference clock generator to generate a reference clock based on a reference frequency signal; a phase reference pulse generator to divide frequency of the reference clock by a dividing ratio N for output as a phase-reference pulse; an encoder to output a frequency generator (FG) signal at a predetermined rotational angle of the motor; an edge detector to detect an edge of the FG signal for output as a FG pulse; an integer phase difference detector to detect a difference between the number of phase-reference pulses and the number of FG pulses for output as an integer phase difference; a decimal fraction phase difference detector to detect a time difference between an edge of the phase-reference pulse and the edge of the FG edge pulse in units of the reference clock for output as a decimal fraction phase difference; a mixer to add the integer phase difference to the decimal fraction phase difference at a predetermined ratio for output as a phase difference; and a controller to control driving of the motor based on the phase difference output from the mixer.