Drum servo system using a PLL with frequency divided reference clock signals as an input

摘要

A drum servo system is provided with a rotation control device for controlling the rotation of a drum on the basis of a phase comparison signal obtained as a result of comparing the phase of an angle-of-rotation information signal obtained according to an angle of rotation of the drum with the phase of a control signal. The system also includes a detection device for determining the existence of a large data block or a small path block and outputting the result to a reference signal generator. The frequency of the reference signal is higher than that of the control signal, and is altered based on the output of the detection device. Frequency division is performed on the reference signal after it has been acted on by a phase locked loop, and the result is compared to the phase of the angle-of-rotation information signal in the rotation control device. Thus, a radical change in the control signal which occurs when the phase or frequency of the control signal is changed due to an abrupt external disturbance can preferably be absorbed in the comparison control device. Thereby, the rotation control device can always stably follow an abrupt change occurring in the control signal.