| 摘要 |
PROBLEM TO BE SOLVED: To provide the speed control circuit of a DC motor where an oscillation hardly occurs even if the range of a desired target rotation speed and a load fluctuation is large. SOLUTION: When the rotation speed of a DC motor 12 is set to a specific target rotation speed, a reference clock being inputted to a PLL circuit 16 is switched to the reference clock of a frequency corresponding to the target rotation speed by an analog switch circuit 22, and at the same time a reference voltage being applied to the non-inverted input edge of an amplification circuit 36 is switched to a reference voltage corresponding to the target rotation speed, thus setting a phase difference between an encoder pulse signal being inputted to the PLL circuit 16 when the DC motor 12 is stably rotating at the target rotation speed and the reference clock to π radian. |
