| 摘要 |
PURPOSE:To ensure stable and smooth control of a disk motor, by controlling an automatic phase control (APC) signal in case a frequency shift of the signal to be controlled obtained from the disk rotation exceeds a prescribed value. CONSTITUTION:When the frequency shift of a signal to be controlled is larger than + or -10%, the output of a >=10% detecting circuit 151 is set at H level. Then an S-RFF 153 is set and an output terminal Q is set at H level. Therefore the output of a latch circuit 145 is equal to about 1/2 maximum count value of a slanting counter circuit 140 since a control input terminal CI is set at H level. Thus an APC signal is kept at about 1/2 APC voltage range. Then if the frequency shift is within + or -5% owing to an automatic frequency control action, the output of a <5% detecting circuit 152 is set at H level to ensure an APC operation. |
