| 摘要 |
PURPOSE:To enhance servo characteristics and to shorten the time required for a tracking servo to become stable after rough search by switching arbitrarily output impedance of a drive circuit of an actuator drive coil to more than two values if and when necessary. CONSTITUTION:When a tracking servo is on, a changeover switch 22 is set to a side I , which causes output impedance of a drive circuit to be a high current drive type. As a result an actuator drive device with a good servo characteristic can be realized without effected by adverse influence of impedance of a drive coil 14. At the time of rough search, the switch 22 is set to a II side, which causes output impedance of a drive circuit to be a low-voltage drive type, and drive impedance at both ends of the drive coil 14 becomes a resistance of a current detecting resistance 21. Vibration of an actuator 13 is clamped by counter electromotive force of the drive circuit 14, and therefore it is substantially reduced. Thus the time required for a tracking servo to become stable after rough search is substantially shortened. |
