| 摘要 |
PURPOSE:To drive a spindle motor in a magnetic disc device with less variation of revolution by controlling spindle motor driving current in accordance with the difference of a current turning speed and a prescribed turning speed in a position detecting period. CONSTITUTION:When the spindle motor 2 of the disc 1 starts, a counter 7 is reset by a microprocessor 21 at the leading edge of a pulse generated by a position detecting circuit 3 and the counter 7 is similarly reset at the leading edge of successive pulses. The period corresponding to the turning speed of the motor 2 is calculated by the counter 7 counting up clocks. The processor 21 calculates the difference between the counted value and a periodical value corresponding to a prescribed rotational frequency and a current limiting circuit 23 is controlled in accordance with the difference value through a D/A converter 22 to feed back and control the driving current of the motor 2. Consequently, a fixed current is applied for one period of a position detecting signal and the spindle motor of the magnetic disc device can be driven with less variation of revolution. |
