Patent Publication Number: US-2012032623-A1

Title: Method of controlling fan speed

Description:
CROSS-REFERENCE TO RELATED APPLICATION 
     This application claims the priority benefit of Taiwan application serial no. 99125759, filed on Aug. 3, 2010. The entirety of the above-mentioned patent application is hereby incorporated by reference herein and made a part of this specification. 
     BACKGROUND OF THE INVENTION 
     1. Field of the Invention 
     The invention relates to a method of controlling speed, and more particularly, to a method capable of controlling fan speed precisely. 
     2. Description of Related Art 
     It is known that internal components (e.g. CPU) and/or apparatuses (e.g. power supply) of conventional computer devices are installed with heat dissipation devices (e.g. heat dissipating sheet, fan, and the like). Among these heat dissipation devices, fans are one of the most essential and important components for their capability of dissipating heat generated by internal components and/or apparatuses in computer devices out of casings of computer devices, so that computer device systems can operate normally. 
     In general, control speed signals used to drive fans can be categorized into direct current (DC) voltage or pulse width modulation signal (PWM signal). The speed of a fan (in units of revolutions per minute/RPM) can be controlled by changing the value of DC voltage or changing the duty cycle of PWM signal. 
     However, identical control speed signals usually lead to the deviation of fan speed (possible deviation of hundreds or even thousands of revolutions) due to different fan specifications and/or deterioration of fans. Consequently, fans with large speed deviations may not be capable of effectively dissipating heat out of casings of computer devices, such that computer device systems can not operate normally. Furthermore, crashes of computer device systems or hardware damages leading to unrecoverable computer device systems may also result. 
     SUMMARY OF THE INVENTION 
     Accordingly, the invention is directed to a method of controlling fan speed. The method is capable of controlling the speed of a fan precisely so as to resolve the issue above. 
     A method of controlling a fan speed in the invention includes: setting a target speed of a fan; providing an actual control speed signal and using the actual control speed signal to drive the fan so as to obtain an actual speed of the fan; determining whether the actual speed of the fan is equal to the set target speed; and when the actual speed of the fan is equal to the set target speed, continuously using the provided actual control speed signal to drive the fan, otherwise, gradually compensating an intensity of the provided actual control speed signal until the actual speed of the fan is equal to the set target speed after the fan is driven by the gradually compensated actual control speed signal. 
     In light of the foregoing, the method of controlling fan speed in the invention mainly adjusts the actual speed of the fan to equal the set target speed through a feedback compensation mechanism. Thus, the problem of identical control speed signals with fan speed deviation caused by different fan specifications and/or deterioration of fans can be improved effectively. 
     It should be understood that the descriptions aforementioned and the following embodiments are merely exemplary and illustrative, and the scope of the invention is not limited thereto. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The accompanying drawings are included to provide further understanding, and are incorporated in and constitute a part of this specification. The drawings illustrate exemplary embodiments and, together with the description, serve to explain the principles of the disclosure. 
         FIG. 1A  illustrates a flow chart of a method of controlling a fan speed according to an embodiment of the invention. 
         FIG. 1B  is a detailed illustration of several steps in  FIG. 1A . 
     
    
    
     DESCRIPTION OF EMBODIMENTS 
     Embodiments of the invention are described in details below, and examples of the embodiments are illustrated in the drawings. Moreover, identical devices/components/steps in the drawings and embodiments are denoted with identical notations to represented identical or similar parts whenever possible. 
       FIG. 1A  illustrates a flow chart of a method of controlling a fan speed according to an embodiment of the invention. Referring to  FIG. 1A , the method includes the following. Firstly, a target speed of a fan is set (step S 101 ). Next, an actual control speed signal is provided (step S 103 ). The actual control speed signal is used to drive the fan so as to obtain an actual speed of the fan (step S 105 ). Thereafter, whether the actual speed of the fan is equal to the target speed set in step S 101  is determined (step S 107 ). Finally, when the actual speed of the fan is equal to the target speed set in step S 101  (that is, “yes” for step S 107 ), the fan is driven by using the actual control speed signal provided in step S 103  continuously; otherwise, (that is, “no” for step S 107 ) an intensity of the actual control speed signal provided in step S 103  is compensated gradually (step S 109 ) until the actual speed of the fan is equal to the set target speed after the fan is driven by the gradually compensated actual control speed signal. 
     More specifically,  FIG. 1B  is a detailed illustration of step S 107  and step S 109  in  FIG. 1A . Referring to  FIGS. 1A and 1B , in the present embodiment, the determining of whether the actual speed of the fan is equal to the target speed set in step S 101  may include determining whether the actual speed of the fan is faster than the target speed set in step S 101  (step S 107 _ 1 ); and determining whether the actual speed of the fan is slower than the target speed set in step S 101  (step S 107 _ 2 ). 
     Thus, when the actual speed of the fan is not faster nor slower than the target speed set in step S 101  (that is, “no” for steps S 107 _ 1  and S 107 _ 2 ), the actual speed of the fan after the fan is driven by the actual control speed signal provided in step S 103  is determined to be equal to the target speed set in step S 101 . Accordingly, the actual control speed signal provided in step S 103  is used continuously to drive the fan, such that the actual speed of the fan is equal to the target speed set in step S 101 . In other words, the intensity of the actual control speed signal provided in step S 103  is sufficient for controlling the actual speed of the fan to equal to the target speed set in step S 101 . 
     In addition, when the actual speed is faster than the target speed set in step S 101  (that is, “yes” for step S 107 _ 1 ), the actual speed of the fan is determined not equal to the target speed set in step S 101  (that is, “no” for step S 107 ). In other words, the intensity of the actual control speed signal provided in step S 103  is sufficient for controlling the actual speed of the fan to be faster than the target speed set in step S 101 . As a result, the compensating of the intensity of the actual control speed signal illustrated in step S 109  includes gradually reducing the intensity of the actual control speed signal provided in step S 103  in a pre-determined ratio (step S 109 _ 1 ) until the actual speed of the fan is equal to the target speed set in step S 101  after the fan is driven by the gradually reduced actual control speed signal. 
     Further, when the actual speed of the fan is slower than the target speed set in step S 101  (that is, “yes” for step S 107 _ 2 ), the actual speed of the fan is determined not equal to the target speed set in step S 101  (that is, “no” for step S 107 ). In other words, the intensity of the actual control speed signal provided in step S 103  is sufficient for controlling the actual speed of the fan to be slower than the target speed set in step S 101 . As a result, the compensating of the intensity of the actual control speed signal illustrated in step S 109  further includes gradually increasing the intensity of the actual control speed signal provided in step S 103  in a pre-determined ratio (step S 109 _ 2 ) until the actual speed of the fan is equal to the target speed set in step S 101  after the fan is driven by the gradually increased actual control speed signal. 
     It should be noted that since the actual control speed signal configured to drive the fan is usually a direct current (DC) voltage or a pulse width modulation signal (PWM) signal, the method of gradually reducing/increasing the intensity of the actual control speed signal provided in step S 103  with a pre-determined ratio as illustrated in steps S 109 _ 1  and S 109 _ 2  may adopt 0.5V (when the actual control speed signal is a DC voltage, but not limited thereto) or 5% (when the actual control speed signal is a PWM signal, but not limited thereto) as the pre-determined ratio to gradually reduce/increase the intensity of the actual control speed signal provided in step S 103 . 
     For example, the target speed set in step S 101  is 5000 revolutions per minute (that is, 5000 RPM) and the actual speed of the fan is 4000 revolutions per minute (that is, 4000 RPM) after the fan is driven by the actual control speed signal provided by step S 103 . As the actual speed of the fan after the fan is driven by the actual control speed signal provided by step S 103  is determined to be slower than the target speed set in step S 101  in step S 107  (4000 RPM&lt;5000 RPM), steps S 105 -S 109  are repeated for using 0.5V (when the actual control speed signal is a DC voltage, but not limited thereto) or 5% (when the actual control speed signal is a PWM signal, but not limited thereto) as the pre-determined ratio to gradually increase the intensity of the actual control speed signal provided in step S 103  (i.e. the original DC voltage 4V is increased 0.5V at a time to 5V, or the original duty cycle 40% is increased 5% at a time to 50%, but the invention is not limited thereto) until the actual speed of the fan is equal to the target speed set in step S 101  after the fan is driven by the gradually increased actual control speed signal. 
     Similarly, in another example, the target speed set in step S 101  is 5000 revolutions per minute (that is, 5000 RPM) and the actual speed of the fan is 6000 revolutions per minute (that is, 6000 RPM) after the fan is driven by the actual control speed signal provided by step S 103 . As the actual speed of the fan after the fan is driven by the actual control speed signal provided by step S 103  is determined to be faster than the target speed set in step S 101  in step S 107  (6000 RPM&gt;5000 RPM), steps S 105 -S 109  are repeated for using 0.5V (when the actual control speed signal is a DC voltage, but not limited thereto) or 5% (when the actual control speed signal is a PWM signal, but not limited thereto) as the pre-determined ratio to gradually reduce the intensity of the actual control speed signal provided in step S 103  (i.e. the original DC voltage 6V is reduced 0.5V at a time to 5V, or the original duty cycle 60% is reduced 5% at a time to 50%, but the invention is not limited thereto) until the actual speed of the fan is equal to the target speed set in step S 101  after the fan is driven by the gradually reduced actual control speed signal. 
     It should be noted that the method of controlling the fan speed in the invention mainly adjusts the actual speed of the fan to equal the set target speed through a feedback compensation mechanism (that is, repeating steps S 105 -S 109 ). Therefore, the problem of identical control speed signals with fan speed deviation caused by different fan specifications and/or deterioration of fans can be improved effectively. 
     On the other hand, in practical application, the method of controlling the fan speed in the invention is at least applied in computer device systems. Accordingly, identical control speed signals do not cause deviations of fan speed due to different fan specifications and/or fan deterioration. Consequently, the fan can effectively dissipate the heat generated by internal components (i.e. CPU) and or devices (i.e. power supply) in computer devices out of casings of computer devices, so that computer device systems can operate normally. Furthermore, crashes of computer device systems or unrecoverable hardware damages are prevented. Obviously, the method of controlling fan speed in the invention is applicable to any electronic device system adopting fans. Thus, the embodiments illustrated above do not limit the application scope of the invention. 
     It will be apparent to those skilled in the art that various modifications and variations can be made to the structure of the disclosed embodiments without departing from the scope or spirit of the disclosure. In view of the foregoing, it is intended that the disclosure cover modifications and variations of this disclosure provided they fall within the scope of the following claims and their equivalents.