| 摘要 |
PURPOSE:To prevent the effect of a drift, etc. and to ensure the stable and assured rotation control of a spindle motor, by controlling a rought adjusting system in response to the duty of a fine adjusting signal for spindle revolution which is based on the phase difference to a reference signal. CONSTITUTION:A bit clock synchronous with a reproduced signal is detected by a PLL 3 and processed by a dividing circuit 12 to be compared with a reference clock in terms of phase by a phase comparator. A phase difference signal gives a fine adjusting to the revolution of a spindle motor 17, and the duty based on this phase difference signal is detected by a duty detecting circuit 14. Then a rough adjusting system is controlled via a gain offset adjusting circuit 9. Thus it is possible to prevent the effect of an evil duty ratio change due to a temperature drift or an offset drift of an amplifier. This ensures good fine adjusting as well as the stable and assured control of revolution of the motor 17. |
