| 摘要 |
PURPOSE:To maintain the linear rotating speed of a disc constant by varying the counted value of an up-down counter for controlling a motor, converting the digital value of the counter into an analog value and applying the converted output to the motor. CONSTITUTION:A demodulated clock signal is generated from a demodulation clock signal generator 6 on the basis of a data signal D0 detected from a disc 1, the demodulated clock signal and the reference frequency signal fr are compared in phase by a phase comparator 10, and a counter is switched in up mode or in down mode by the phase error signal. As a result, the counted value of an up- down counter 12 for controlling a motor 3 becomes variable, the digital value is converted by a digital-to-analog converter 16 to an analog value, which is further converted by a low pass filter 17 to a DC voltage, and the output is applied to the motor 3, thereby controlling the rotation of the motor. |
