Fan rotary speed controlling device

A fan rotary speed controlling device for controlling a rotary speed of a motor, comprising:

• a first signal generating circuit receiving a real frequency signal and a target frequency signal, and generating a first signal according to the real frequency signal and the target frequency signal;
• a second signal generating circuit electrically connected with the first signal generating circuit and generating a second signal according to the first signal;
• a pulse width modulation (PWM) circuit electrically connected with the second signal generating circuit and generating a PWM signal according to the second signal;
• a switching circuit electrically connected with the PWM circuit and, outputting a control signal to control the rotary speed of the motor;
• and
• a fundamental frequency generating circuit for generating a fundamental frequency signal, wherein the PWM circuit generates the PWM signal according to the second signal and the fundamental frequency signal, and outputs the PWM signal to the switching circuit.

A fan rotary speed controlling device for controlling a rotary speed of a motor, comprising:

• a first signal generating circuit receiving a real frequency signal and a target frequency signal, and generating a first signal according to the real frequency signal and the target frequency signal;
• a second signal generating circuit electrically connected with the first signal generating circuit and generating a second signal according to the first signal;
• a pulse width modulation (PWM) circuit electrically connected with the second signal generating circuit and generating a PWM signal according to the second signal;
• a switching circuit electrically connected with the PWM circuit and outputting a control signal to control the rotary speed of the motor;
• an integrated circuit electrically connected with the first signal generating circuit and the switching circuit wherein the integrated circuit comprises an oscillator for outputting a square wave signal;
• and
• a waveform converting circuit electrically connected with the integrated circuit and the PWM circuit, wherein the waveform converting circuit receives the square wave signal and converts the square ware signal to a triangular wave signal so as to be output to the PWM circuit according to the square wave signal.