Motor control apparatus using speed and phase control in a first loop

Abstract

In a motor control system, a first servo loop for a phase system and a second servo loop for a speed system are provided the pull-in operation of the motor during the transition time period is made stable, and also the operation efficiency of the low-speed CPU is not deteriorated. In the motor control system, the first servo loop is arranged by a speed detector for outputting a voltage corresponding to a frequency of a first reference signal used to set a rotational speed of the motor, a phase comparator for comparing a phase of the first reference signal with a phase of a control signal; and an adder for adding an output of the speed detector to an output of the phase comparator. The second servo block is arranged by a voltage-to-frequency converter for producing a second reference signal having a higher frequency than the frequency of the first reference signal, corresponding to a voltage signal outputted from the adder, and a phase servo block for comparing the second reference signal outputted from the voltage-to-frequency converter with a rotational speed signal of the motor, and for controlling the rotational speed of the motor based on the comparison result. Under such a circumstance, the output from the phase comparator is not applied to the adder until the motor starts its rotation and then the rotational speed thereof reaches a predetermined rotational speed.