| 摘要 |
PURPOSE:To drive a disk motor at high efficiency and lower power consumption by switching and selecting high level driving voltage when an AFC signal that controls servo driving together with an AFC signal is deviated from the normal value. CONSTITUTION:An APC signal and an AFC signal through PLL 15 and a CLV servo circuit 16 are added by an adder circuit 17 and converted to a PWM signal by a PWM conversion circuit 18. The level of the PWM signal is controlled according to low level voltage V1 from a change-over switch 24 and duty ratio is enlarged, and a disk motor 12 is servo driven efficiently. On the other hand, when the signal AFC become above a specified value deviating from servo drawing, the switch 24 is changed by a detecting circuit 25, and the level of the PWM signal is heightened by high voltage V2 higher than voltage V1, and drawing to the servo state is made effectively by high gain. Thus, the disk motor is driven at high efficiency according to the state, and power consumption is lowered.
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