| 摘要 |
PROBLEM TO BE SOLVED: To provide a system for controlling the rotational speed of a fan, which reduces time and cost. SOLUTION: A system for controlling the rotational speed of a fan, according to the reference clock having reference frequency, is disclosed. The rotational speed corresponds to a fan rotational speed signal. A fan rotational speed control unit compares the reference clock with the fan rotational speed signal and outputs a speed control signal. A voltage-generating circuit generates a level signal, corresponding to the speed control signal. A drive unit generates a drive signal for controlling the rotational speed of the fan, according to the level signal. Several ways of rated rotational speeds of the fan different in specifications can be obtained, by changing the reference frequency of the control system, using only the coils which are the same in the number of coils, when setting the fan to the control system. Since there is no need to stock the coils which differ in the number of coils in one procedure, this system can reduce the time cost and the manufacture cost. |
