| 摘要 |
A multimode integrated modulation circuit for controlling the fan rotating speed mainly includes a voltage regulating circuit, an integrated modulation circuit and a fan motor driving circuit. The voltage regulating circuit is used to receive an external voltage signal and regulate the external voltage signal to a suitable range of workable voltage and then a first output voltage is generated. The integrated modulation circuit that is electrically connected with the voltage regulating circuit is used to receive a PWM signal with a duty cycle and a second output voltage is accordingly generated depending on the product of the duty cycle of PWM signal and the first output voltage. The fan motor driving circuit is used to receive the second output voltage and decide the fan motor rotating speed depending on the second output voltage. Therefore, the present invention substantially adopts low-price circuit elements to integrate voltage regulating mode and PWM mode for controlling the fan rotating speed.
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