| 摘要 |
PURPOSE:To prevent unnecessary vibration of a moving-coil, while to prevent formation of construction in complexity and in a large type by a method wherein the function to enable to attain self-lock of the moving-coil itself at a fixed position is made to be provided inside. CONSTITUTION:Output of an adder 8 added with a command voltage corresponding to a command value is inputted to a driving circuit 10 through a switch 9, and a moving-coil 5 is driven by the output of the driving circuit 10 thereof. Thus obtained displacement is detected by a displacement detector 11 to be fed back to the adder 8. Moreover displacement of the moving-coil 5 is detected by Hall elements 7a, 7b, output thereof is fed back to an adder 13 which is applied with zero cross level signal output of a differential amplifier 12 as the command voltage, and output of the adder 13 thereof is applied to the driving circuit 10 through the switch 9. |
