| 摘要 |
PURPOSE:To use a reproduction synchronizing signal pulse regardless of the injury of a disk and to attain the stable drive of the disk, by providing a majority decision circuit to a rotary driver. CONSTITUTION:A shift register 8 uses as a reference signal pulse into a clock input and a reproduction synchronizing signal pulse 7 as a series input respectively. The output of the register 8 is supplied to a majority decision circuit 12 and used as a phase clock signal 11. In such a way, a phase lock signal is obtained according to a ratio of majority decision which is set previously. For instance, said ratio is set at 5:3 with an 8-step shift register. Therefore, no problem is produced even if three reproduction synchronizing pulses are lost at most owing to the injury of a disk 6 in a reproduction mode. Furthermore the ratio of majority decision is changed by a switching signal 13 for said ratio. In other words, said ratio is increased up to 7:1, for example, in a starting time point. Then the disk 6 is driven stably after the number of revolutions of a disk motor reaches a prescribed level. |
