| 摘要 |
PROBLEM TO BE SOLVED: To provide a rotational speed controller which controls the start-up/ stop of a motor using a low-resolution D/A converter and which also controls the rotation of the motor with high accuracy in a specified rotational speed range. SOLUTION: At the time of start-up of a polygon motor 4, a CPU 121 controls the output voltage Va to about 5V and the outputs of ports A, B to Hi (5V) and the driving voltage Vd to about 5V. At the steady rotation of the polygon motor 4, the output of the port B is set to Lo (0V) and charging voltage Vc is dropped to a specified value by a voltage dividing circuit which is constituted of resistors R3 and R4 and the output voltage Va from a D/A converter 122 is changed by changing the output count based on the frequency at which SOS signals are generated from an SOS (start of scan) sensor 11. The driving voltage Vd can be controlled with the same resolution as the output Va voltage a first voltage dividing circuit constituted of resistors R1 and R2 in a voltage changing range smaller than that of the output voltage Va and thereby a resolusion in a voltage range which is required for controlling a rotational speed to a specified one can be increased. |
