| 摘要 |
PURPOSE:To maintain a high and stable moving speed of a magnetic head and to improve the reliability, by turning on and off a power supply of a magnetic head driving source in response to a change of the moving speed of the magnetic head. CONSTITUTION:A rotary shaft 5 of a rotary solenoid 1 starts its revolution after receiving a magnetic head driving signal. Then the pulse-like signals of different intervals are delivered from a photodetecting element 7 in response to the revolving speed of a disk 2, i.e., the moving speed of a magnetic head 4. The pulse-like signal is fed to a frequency dividing circuit 11 to be converted into a signal which shows the time during which the head 4 moves by a prescribed distance. This signal is compared through a comparator 14 with the signal supplied from a timer circuit and showing the reference time. The output of this comparison is led to a switch control circuit 15 to perform an ON/OFF control of a switching circuit 16. As a result, the conduction is controlled to the solenoid 1 to keep the moving speed of the head 4 at a constant level. |
