| 摘要 |
PURPOSE:To prevent surely runaway of a motor at faulty focus by means of a simple circuit by detecting a fault of focus servo operation and opening electrically a drive coil of a spindle motor while a faulty output is generated. CONSTITUTION:A control switch 20 connected between a drive coil L of the spindle motor 1 and a motor drive amplifier 12 is turned off in response to an output of fault detection circuit 13 and the drive coil L is opened electrically. Through the constitution above, a noise generated at faulty focus is not applied to the motor 1 and the circuit is opened until the focus is locked again, the motor 1 is driven synchronously until the focus servo is unlocked due to external disturbance, the speed decrease from the focus-off to the re-locking is very small thereby locking quickly the motor 1. Thus, the runaway of the spindle motor 1 is prevented surely with a simple circuit. |
