| 摘要 |
PROBLEM TO BE SOLVED: To provide an apparatus and a method for controlling the rotational speed of a direct-current motor, based on the pulse width modulation, where the speed of a direct-current motor is controlled by two or more different stages of pulse frequencies and a fixed frequency PWM control method is modified to remedy drawbacks, such as noise and lowering of efficiency. SOLUTION: The apparatus and the method involves a sensor, which is electrically connected with a motor and generates a first sensor signal, corresponding to a feedback signal outputted from the motor; and a controller which is electrically connected with the sensor and the motor and receives the first sensor signal. When the motor is rotating at a low speed, the controller generates a first control signal of a first frequency, based on the first sensor signal and outputs the first control signal to the motor. When the motor is rotating at a high speed, the controller generates a second control signal of a second frequency, based on the first sensor signal and outputs the second control signal to the motor. The first frequency of the first control signal is higher than the second frequency of the second control signal. |
