| 摘要 |
PURPOSE:To control the number of rotations of motor only with modification of programs stored in the CPU without changing circuit configuration even for change of the number of poles of motor. CONSTITUTION:A spindle motor control circuit of magnetic disk apparatus comprising a plurality of Hall sensors 6 for detecting rotating angle of a rotor, a frequency divider 2 for dividing an output of only one sensor 1 to 1/2n (n is a natural number), a selector 3 for selecting a plurality of output signals of the frequency divider to determine a dividing ratio and a CPU 4 for obtaining the number of rotations by detecting period of frequency-divided outputs. |
