| 摘要 |
PURPOSE:To uniform the response in the increasing and decreasing direction of rotational frequency by superposing a phase difference signal through a prescribed limiter to a phase difference signal smoothed by a time constant circuit to form a disc driving servo controlling signal. CONSTITUTION:The phase difference output betwen a reference signal and a disc linear speed detecting signal is outputted from a phase comparator 19 and smoothed by the time constant circuit 50 in a servo circuit 22. A limiter 52 is controlled through an operational amplifier 53 actuated in accordance with the smoothed average DC voltage VDC and generates a signal obtained by limiting the phase difference output from the circuit 19 by the voltage 2VDC twice the voltage VDC and an adder 51 superposes the output from the limiter 52 to the voltage VDC and outputs the superposed signal as a servo controlling signal for a disc motor 3. If the power voltage is set up to the voltage 2VDC or more, the upper and lower pulse width becomes voltage VDC respectively and symmetrical about the voltage VDC. Consequently, the respenses in the increasing and decreasing driections of the rotational frequency of the motor are uniformed and smooth servo control is attained. |
