| 摘要 |
PROBLEM TO BE SOLVED: To prevent an abnormal speed rotary control signal from being generated when switching duty after soft start is made and rotational speed reaches a target value. SOLUTION: An up/down counter 38 is counted up by a first clock signal in activation, a rotary speed control signal DSfan is generated following slope that is gradually increased, and a PWM signal is generated by a PWM output circuit 44 for increasing the speed. After a target speed that is determined by a rotational speed target value signal Dfan is reached, the up/down counter 38 is counted up or down by a second clock signal, and the rotational speed control signal DSFan that is changed with a slope of 100%/second is generated for controlling the speed. |
