| 摘要 |
PURPOSE:To prevent a runaway of a spindle servo system for a CLV disk by driving a motor at a constant voltage when the PLL of the spindle servo system after the ending of the searching operation of a pickup is not locked. CONSTITUTION:If none of PLLs 206, 207 and 208 is locked after the fast-forwarding operation of a pickup 203 ends (when a playback signal is disordered temporarily by external intense oscillation after the start of the fast-forwarding operation), the output of a lock detecting circuit 209 for the PLLs is h, and a control circuit 215 holds a switch control signal (k) to (L) and a sweep signal (j) to (H). Therefore, a switch 213 is changed over to the side of a prescribed voltage (f) to drive a motor 202 in a certain state, preventing a runaway. A sweeping circuit 210 allows a VCO208 to start sweeping operation and the PLLs enter into a lock-in state again a certain time later. Consequently, the output of the control circuit 215 is inverted to obtain a stationary servo state. |
