Patent Publication Number: US-2011070098-A1

Title: Fan control system

Description:
BACKGROUND OF THE INVENTION  
     1. Field of the Invention 
     The present invention relates to a control system, and more particularly, to a fan control system. 
     2. Description of the Related Art 
       FIG. 1  shows a schematic block diagram of a conventional fan control system. The conventional control system  10  includes a micro controller  11  for providing pulse width modulation (PWM) signals to a fan assembly  12 . The fan assembly  12  includes a plurality of fans for dissipating heat. Because the conventional control system  10  has only a micro controller  11 , when the micro controller  11  malfunctions and cannot provide PWM signals to the fan assembly  12 , the fans in the fan assembly  12  cannot work to dissipate heat from the whole system, causing the whole system to become unstable and fail to work properly. 
     Therefore, it is necessary to provide a fan control system to solve the above problem. 
     SUMMARY OF THE INVENTION  
     The present invention provides a fan control system, comprising: a first micro controller, a second micro controller and a first logic circuit. The first micro controller provides at least one first control signal. The second micro controller is connected to the first micro controller. The second micro controller detects the operational status of the first micro controller, and provides at least one second control signal. The first logic circuit receives the first control signal and the second control signal to process logical operations and to generate at least one driving signal to at least one fan. 
     The fan control system of the invention utilizes two micro controllers. When one of the two micro controllers malfunctions, the first logic circuit allows the other micro controller to continue proper operation of the fan, thereby preventing the problem of insufficient heat dissipation that results from malfunction of the single micro controller of a conventional fan control system. Furthermore, each of the two micro controllers can detect the operational status of the other so that when one of the two micro controllers malfunctions, an alarm is actuated to alert users to the need for repair. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS  
         FIG. 1  is a schematic block diagram of a conventional fan control system; and 
         FIG. 2  is a schematic block diagram of the fan control system according to the present invention. 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION  
       FIG. 2  is a schematic block diagram of the fan control system according to the present invention. The fan control system  20  of the invention comprises: a first micro controller  21 , a second micro controller  22  and a first logic circuit  23 . The first micro controller  21  provides at least one first control signal to the first logic circuit  23 . In this embodiment, the first control signal serves as a first pulse width modulation signal. 
     The second micro controller  22  is connected to the first micro controller  21 . The second micro controller  22  detects the operational status of the first micro controller  21 , and provides at least one second control signal to the first logic circuit  23 . The first logic circuit  23  receives the first and second control signals to process logic operations and to generate at least one driving signal to at least one fan. In this embodiment, the fan is a fan assembly  30  comprising twelve fans. 
     In this embodiment, the first logic circuit  23  is a logic OR circuit to process a logical OR operation on the first and second control signals. The first control signal serves as the first pulse width modulation signal. When the second micro controller  22  detects the first micro controller  21  under normal operating conditions, and the second control signal serves as a low logic level signal (L). After the logical OR operation of the first logic circuit  23 , the driving signal serves as the first pulse width modulation signal. 
     When the second micro controller  22  detects the first micro controller  21  under abnormal operating conditions, the second control signal serves as a high logic level signal (H). After the logical OR operation of the first logic circuit  23 , the driving signal serves as the high logic level signal (H). That is, when the first micro controller  21  malfunctions, the first control signal is unknown. Thus, the second control signal is set to serve as the high logic level signal (H) so that the fans continue to operate in full speed, thus avoiding the problem of insufficient heat dissipation that would otherwise result from fan failure. 
     In another embodiment, the first control signal serves as a first pulse width modulation signal. When the second micro controller  22  detects the first micro controller  21  under normal operating conditions, the second control signal serves as a low logic level signal (L) so that the driving signal serves as the first pulse width modulation signal. When the second micro controller  22  detects the first micro controller  21  under abnormal operating conditions, the second control signal serves as a second pulse width modulation signal so that the driving signal serves as the second pulse width modulation signal. 
     That is, when the first micro controller  21  malfunctions, if the first micro controller  21  cannot work, and cannot provide the first control signal. Thus, the second micro controller  22  replaces the first micro controller  21  to take the control power, and the second control signal serves as the second pulse width modulation signal to make the fans work normally, thus avoiding the problem of insufficient heat dissipation that would otherwise result from fan failure. 
     The fan control system  20  of the invention further comprises a rotating speed detector  26  for detecting the rotating speed of the fan assembly  30  and for generating at least one rotating speed signal to the second micro controller  22 . The second micro controller  22  transmits the rotating speed signal to the first micro controller  21 . According to the rotating speed signal, the first micro controller  21  can adjust the first control signal, or the second micro controller  22  can adjust the second control signal so as to control the rotating speed of the fan assembly  30  to be a predetermined speed. 
     The fan control system  20  of the invention further comprises a second logic circuit  24  and an alarm  25 , wherein the first micro controller  21  further provides at least one first alarm signal to the second logic circuit  24 , the second micro controller  22  further provides at least one second alarm signal to the second logic circuit  24 . The second logic circuit  24  receives the first alarm signal and the second alarm signal to process logic operation and to generate at least one actuating signal to the alarm  25 . 
     In this embodiment, the second logic circuit  24  is a logic OR circuit. When one of the first micro controller  21  or the second micro controller  22  malfunctions, the second logic circuit  24  processes logical OR operation on the first alarm signal and the second alarm signal to generate the actuating signal to actuate the alarm  25 . In this embodiment, the alarm can be a warning light or warning buzzer. 
     The first micro controller  21  further comprises a first communicating interface  211 , and the second micro controller  22  further comprises a second communicating interface  221 , the first communicating interface  211  and the second communicating interface  221  connects to detect the operational status of the other. When the first micro controller  21  detects the second micro controller  22  under abnormal operating conditions, the first micro controller  21  provides the first alarm signal to actuate the alarm  25 . When the second micro controller  22  detects the first micro controller  21  under abnormal operating conditions, the second micro controller  22  provides the second alarm signal to actuate the alarm  25 . 
     Therefore, the fan control system of the invention utilizes two micro controllers. When one of the two micro controllers malfunctions, the first logic circuit allows the other micro controller to continue proper operation of the fan, thereby preventing the problem of insufficient heat dissipation that results from malfunction of the single micro controller of a conventional fan control system. Furthermore, each of the two micro controllers can detect the operational status of the other so that when one of the two micro controllers malfunctions, an alarm is actuated to alert users to the need for repair. 
     While the embodiment of the present invention have been illustrated and described, various modifications and improvements can be made by those skilled in the art. The embodiments of the present invention are therefore described in an illustrative but not restrictive sense. It is intended that the present invention may not be limited to the particular forms as illustrated, and that all modifications that maintain the spirit and scope of the present invention are within the scope as defined in the appended claims.