| 摘要 |
PURPOSE:To exercise stable rotation control by obtaining the best rotational frequency by switching a rotation controlling circuit for a disk motor according to the presence of a synchronizing signal and by adjusting the rotational frequency of the motor when the synchronizing signal is not detected. CONSTITUTION:A signal recorded on a disk is read by a pickup 3 and only a synchronizing signal is extracted from the output of a demodulator 4 by a synchronous separating circuit 5 and inputted to a synchronizing-signal detecting circuit 6 and a speed controlling circuit 8. A motor controlling signal, i.e., the output of an amplifier 9 is inputted to the terminal A of a switch 10 when the synchronizing signal of the detecting circuit 6 is present or to the terminal B when not. Namely, when the synchronizing signal is not present, the output frequency of an oscillator 7 using phase standard is converted into a function voltage waveform through a frequency divider 16 and a waveform shaping circuit 15, and it is added to the rotation detection signal of a motor by a speed detecting circuit 2 to input the sum to the terminal B via an amplifier 14. Thus, the rotational frequency of the motor 2 is adjusted continuously at a low frequency. |
