| 摘要 |
PURPOSE:To obtain a playback image in a short time when a disk is loaded by switching response characteristics of a motor servo loop on the basis of the detection output of a disk size detecting device. CONSTITUTION:Rotation detection pulses obtained by a motor 6 are passed through a waveform shaping circuit 1 and phase-compared by a phase comparator 2 with a reference frequency signal from a reference oscillator 3. The difference signal is inputted to a motor driving circuit 5 through an active filter 4 to control the motor 6 to a constant rotating speed. Time constants of a filter 4, on the other hand, are changed according to the detection output of the disk detecting device 7, and the filter 4 is switched to a small time constant for a small-loaded disk or to a large time constant for a large-sized disk, thereby obtaining the playback image in a short time when the disk is loaded. |
