Fan control unit and method

Abstract

A fan control unit measures the rotating speeds of the first and second fans to calculate the relative work intensities of the two fans. The control unit determines whether a difference between the first work intensity and the second work intensity is within a predetermined range. If the difference between the first work intensity and second work intensity is not in the predetermined range, the control unit adjusts a duty cycle of a pulse signal output to one of the first and second fans to change the rotating speed of one of the first and second fans to bring the difference between the first work intensity and the second work intensity within the predetermined range.

1 . A fan control unit to control a first fan and a second fan, comprising:
 a first pulse output pin connected to the first fan to output a first pulse signal to control the first fan to rotate;   a second pulse output pin connected to the second to output a second pulse signal to control the second fan to rotate;   a first speed receiving pin connected to the first fan to measure a rotating speed of the first fan; and   a second speed receiving pin connected to the second fan to measure a rotating speed of the second fan;   wherein the fan control unit records the maximum possible rotating speeds of the first and second fans, the fan control unit measures the rotating speeds of the first and second fans to calculate a first work intensity of the first fan and a second work intensity of the second fan, the first work intensity of the first fan is a relationship between the speed and the maximum possible speed of the first fan as a percentage, the second work intensity of the second fan is a relationship between the speed and the maximum possible speed of the second fan as a percentage, the fan control unit determines whether a difference in percentages between the first work intensity and the second work intensity is within a predetermined range, if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range, the fan control unit adjusts a duty cycle of the pulse signal output to one of the first and second fans to change the rotating speed of the corresponding one of the first and second fans to bring the difference in percentages between the first work intensity of the first fan and the second work intensity of the second fan within the predetermined range.   
     
     
         2 . The fan control unit of  claim 1 , wherein if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range, and when the first work intensity is greater than the second work intensity, the fan control unit increases the duty cycle of the second pulse signal output to the second fan to increase the rotating speed of the second fan, to bring the difference in percentages between the first work intensity and the second work intensity within the predetermined ranges. 
     
     
         3 . The fan control unit of  claim 1 , wherein if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range, and when the second work intensity is greater than the first work intensity, the fan control unit increases the duty cycle of the first pulse signal output to the first fan to increase the rotating speed of the first fan, to bring the difference in percentages between the first work intensity and the second work intensity within the predetermined ranges. 
     
     
         4 . A fan control method to control a first fan and a second fan, comprising:
 measuring rotating speeds of the first and second fans;   calculating a first work intensity of the first fan and a second work intensity of the second fan through a fan control unit, wherein the first work intensity of the first fan is a relationship between the speed and the maximum possible speed of the first fan as a percentage, the second work intensity of the second fan is a relationship between the speed and the maximum possible speed of the second fan as a percentage;   determining whether a difference in percentage between the first work intensity and the second work intensity is within a predetermined range; and   adjusting a duty cycle of a pulse signal output to one of the first fan and second fans to change the rotating speed of the corresponding one of the first and second fans, to bring the difference between the first work intensity and the second work intensity within the predetermined range, if the difference in percentages between the first work intensity and the second work intensity is not within the predetermined range.   
     
     
         5 . The fan control method of  claim 4 , wherein the adjusting step comprises:
 increasing the duty cycle of the pulse signal output to the second fan to increase the rotating speed of the second fan to bring the difference in percentages between the first and second work intensities within the predetermined range, if the first work intensity is greater than the second work intensity.   
     
     
         6 . The fan control method of  claim 4 , wherein the adjusting step comprises:
 increasing the duty cycle of the pulse signal output to the first fan to increase the rotating speed of the first fan to bring the difference in percentages between the first and second work intensities within the predetermined range, if the second work intensity is greater than the first work intensity.   
     
     
         7 . A fan control method to control a first fan and a second fan, comprising:
 calculating a difference between a duty cycle of a first pulse signal output to the first fan and a duty cycle of a second pulse signal output to the second fan;   determining whether the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal is within a predetermined range; and   adjusting the duty cycle of a corresponding one of the first and second pulse signals output to one of the first and second fans to bring the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal within the predetermined range, if the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal is not within the predetermined range.   
     
     
         8 . The fan control method of  claim 7 , wherein the adjusting step comprises:
 increasing the duty cycle of the second pulse signal to bring the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal within the predetermined range, if the duty cycle of the first pulse signal is greater than the duty cycle of the second pulse signal.   
     
     
         9 . The fan control method of  claim 7 , wherein the adjusting step comprises:
 increasing the duty cycle of the first pulse signal to bring the difference between the duty cycle of the first pulse signal and the duty cycle of the second pulse signal within the predetermined range, if the duty cycle of the second pulse signal is greater than the duty cycle of the first pulse signal.