Method for controlling fan start-up and fan

Abstract

A method for controlling a fan in a fan start-up stage including a first time period and a second time period comprises the following steps of: during the first time period, continuously providing a first driving signal to drive the fan; and during the second time period, continuously providing a second driving signal to drive the fan; wherein, during the first time period the signal value (driving energy) of the first driving signal gradually decreases until being equal to the signal value of the second driving signal, and the signal value of the first driving signal is initially greater than the signal value of the second driving signal. A fan is also disclosed.

What is claimed is: 
     
         1 . A method for controlling a fan in a fan start-up stage including a first time period and a second time period, comprising:
 during the first time period, continuously providing a first driving signal to drive the fan; and   during the second time period, continuously providing a second driving signal to drive the fan;   wherein, during the first time period the signal value of the first driving signal gradually decreases until being equal to the signal value of the second driving signal, and the signal value of the first driving signal is initially greater than the signal value of the second driving signal.   
     
     
         2 . The method of  claim 1 , wherein the signal value of the second driving signal is an unchanged value. 
     
     
         3 . The method of  claim 1 , wherein the fan comprises an impeller, a motor and a control circuit, the motor is connected to the impeller and drives the impeller to operate, the motor is electrically connected to the control circuit, the control circuit comprises a control unit and a detection unit, the detection unit detects the current phase or back emf of the motor to output a feedback signal to the control unit, the method further comprises:
 after completing the fan start-up stage, providing a third driving signal to drive the fan according to the feedback signal.   
     
     
         4 . The method of  claim 3 , wherein the first driving signal, the second driving signal and the third driving signal are provided by the control unit. 
     
     
         5 . The method of  claim 3 , wherein the first driving signal, the second driving signal and the third driving signal are PWM signals or DC voltage signals. 
     
     
         6 . The method of  claim 1 , wherein the signal value of the first driving signal linearly decreases or non-linearly decreases. 
     
     
         7 . The method of  claim 1 , wherein the sum of the first time period and the second time period is constant. 
     
     
         8 . A fan, comprising:
 an impeller;   a motor, connected to the impeller and drive the impeller to operate; and   a control circuit, electrically connected to the motor, comprising:
 a control unit, in a fan start-up stage providing a first driving signal and a second driving signal to drive the fan; 
   wherein, the fan start-up stage includes a first time period and a second time period,   during the first time period the control unit continuously provides the first driving signal to drive the fan, and during the first time period the signal value of the first driving signal gradually decreases until being equal to the signal value of the second driving signal,   during the second time period the control unit continuously provides the second driving signal to drive the fan, and the signal value of the first driving signal is initially greater than the signal value of the second driving signal.   
     
     
         9 . The fan of  claim 8 , wherein the signal value of the second driving signal is an unchanged value. 
     
     
         10 . The fan of  claim 8 , wherein the control circuit further comprises:
 a detection unit, detecting the current phase or back emf of the motor and outputting a feedback signal to the control unit,   wherein after completing the fan start-up stage, the control unit provides a third driving signal to drive the fan according to the feedback signal.