| 摘要 |
PURPOSE:To always lead in the control of the linear speed of a motor by rotating the motor in response to the absolute position to the radial direction of a disc of pickup means. CONSTITUTION:The rotation of a motor 5 is excessively slow in the state that the motor 5 starts rotating, and a clock extracting circuit 3 cannot detect the clock signal from the detected output of pickup means 2, and a changeover switch 6 is connected to the (a) side of a contact. The motor 5 is controlled at the rorating speed in response to the traverse position by a speed control loop which is composed of the motor 5, control circuit 10 and motor drive circuit 7 with the oscillating frequency of a variable oscillator 9 as a reference signal. When the rotating speed of the disc 1 becomes the prescribed speed, a changeover switch 6 is switched to the (b) side of the contact by the output of the circuit 3, and the motor control loop is switched to a linear speed control loop which is composed of the disc 1, pickup means 2, clock extracting circuit 3, control circuit 4, motor drive circuit 7 and motor 5. |
