Electronic apparatus that allows cooling fan to be driven with certainty even at the time of software malfunction/lock-up or at the time of controller failure

Abstract

A voltage for driving a cooling fan is usually output from a fan voltage control circuit. Whether to cause the fan voltage control circuit to output the drive voltage or not is controlled by a system management utility (software) and a bridge controller (hardware) on the basis of temperature data from a temperature sensor. To provide for the occurrence of a failure in the system management utility or the bridge controller, a temperature comparator monitors the temperature data from the temperature sensor and instructs a fan voltage control circuit to output a drive voltage for the cooling fan in the case where the temperature rises above a given value.

1 . A cooling fan drive controlling method of an electronic apparatus including a cooling fan, a fan drive circuit which drive-controls the cooling fan and first and second fan voltage control circuits each of which outputs a drive voltage required for the fan drive circuit to drive the cooling fan, the method comprising: 
 sensing a temperature;    drive-controlling the first fan voltage control circuit to output the drive voltage when the sensed temperature exceeds a first value; and    drive-controlling the second voltage control circuit to output the drive voltage when the sensed temperature exceeds a second value which is higher than the first value.    
   
   
       2 . The cooling fan drive controlling method according to  claim 1 , further comprising indicating the occurrence of an abnormal condition when the second voltage control circuit outputs the drive voltage.  
   
   
       3 . The cooling fan drive controlling method according to  claim 1 , wherein the second voltage control circuit outputs the drive voltage which is higher than the drive voltage output from the first voltage control circuit.  
   
   
       4 . The cooling fan drive controlling method according to  claim 1 , further comprising setting the first value and the second value.  
   
   
       5 . The cooling fan drive controlling method according to  claim 1 , further comprising applying the drive voltage from the first or second fan voltage control circuit to the fan drive circuit, when the drive voltage is output from at least one of the first and second fan voltage control circuits.  
   
   
       6 . The cooling fan drive controlling method according to  claim 5 , wherein the applying the drive voltage includes applying the drive voltage from the second fan voltage control circuit to the fan drive circuit, when both of the first and second fan voltage control circuits output the drive voltage.