Utilizing an altitude sensor to control fan speed

Abstract

A heat-generating device is characterized to determine the relationship between the speed of a DC cooling fan, and the thermal margin of the heat-generating device. Since the speed of DC fans is substantially linear with respect to their input voltage, the speed of the fan may be adjusted within a system to provide the speed necessary for cooling needs. An altitude is input to a converter which uses the characterization of the heat-generating device to determine a fan speed necessary at that altitude to cool the heat-generating device to a temperature within its operating range. The converter then controls the voltage supplied to the DC fan to result in the needed fan speed.

1 . A device, comprising: 
 a fan configured to run at a variable speed; and    a converter electrically coupled to said fan in such a way as to control a speed of said fan, wherein said converter receives an altitude and outputs a fan speed control signal calculated from said altitude to said fan.    
   
   
       2 . The device of  claim 1 , wherein said converter uses an arithmetic algorithm to calculate said fan speed control signal from said altitude.  
   
   
       3 . The device of  claim 1 , wherein said converter uses a look up table to calculate said fan speed control signal from said altitude.  
   
   
       4 . The device of  claim 1 , wherein said fan speed is controlled by said converter using a digital signal.  
   
   
       5 . The device of  claim 1 , wherein said fan speed is controlled by said converter using an analog signal.  
   
   
       6 . A device, comprising: 
 a fan configured to run at a variable speed;    a fan speed detector, outputting a fan speed;    a converter, electrically coupled with said fan speed detector, wherein said converter receives said fan speed and an altitude and outputs a fan speed control signal calculated from said fan speed and said altitude to said fan.    
   
   
       7 . The device of  claim 6 , wherein said converter uses an arithmetic algorithm to convert said fan speed and said altitude to said fan speed control signal.  
   
   
       8 . The device of  claim 6 , wherein said converter uses a look up table to convert said fan speed and said altitude to said fan speed control signal.  
   
   
       9 . The device of  claim 6 , wherein said fan speed control signal is output by said converter as an analog signal.  
   
   
       10 . The device of  claim 6 , wherein said fan speed control signal is output by said converter as an analog signal.  
   
   
       11 . A method for the setting of a fan speed, comprising the steps of: 
 a) characterizing a thermal margin of a heat-generating device with respect to a fan speed;    b) receiving an altitude;    c) converting said altitude into a required fan speed; and    d) setting a fan to said required fan speed.    
   
   
       12 . The method of  claim 11 , wherein said converting step is performed using an arithmetic algorithm.  
   
   
       13 . The method of  claim 11 , wherein said converting step is performed using a look up table.  
   
   
       14 . A method for the setting of a fan speed, comprising the steps of: 
 a) characterizing a thermal margin of a heat-generating device with respect to a fan speed;    b) receiving an altitude;    c) measuring a fan speed;    d) converting said fan speed and said altitude into a required fan speed; and    e) setting a fan to said required fan speed.    
   
   
       15 . The method of  claim 14 , wherein said measuring a fan speed step is performed by said fan.  
   
   
       16 . The method of  claim 14 , wherein said measuring a fan speed step is performed by an optoelectronic device.  
   
   
       17 . A device, comprising: 
 means for receiving an altitude; and    means for calculating a thermal margin of a heat-generating device from said altitude; and    means for setting a fan speed corresponding to a desired thermal margin.    
   
   
       18 . The device of  claim 16 , further comprising: 
 means for characterizing said thermal margin of a heat-generating device with respect to a fan speed.