| 摘要 |
PURPOSE:To accelerate automatic control on prescribed rotating speed and to simplify constitution, by controlling the rotating speed of a driving motor by comparing the time length of the signal part with specific pulse width of a DCM signal with a reference time length. CONSTITUTION:A pulse having the maximum pulse width is detected out of digital signals from a disk D by a frame pulse detection circuit FPD, and it is compared with the reference time length at a decision circuit FLJ, and different signals based on the size of the difference are outputted. When the difference of the time length is large, the signal to increase the rotating speed of the driving motor Md steeply is supplied to a motor driving circuit MDSS, then, the rotating speed of the driving motor Md is controlled, and also, when the difference of the time length is small, the signal to decrease the rotating speed of the driving motor Md is supplied, then, the rotating speed of the driving motor Md is controlled with the output signal of a frame phase servo FSCS by the motor driving circuit MDC.
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