Method for controlling fan based on temperature variation trend

A method for controlling a fan based on a temperature variation trend, wherein the method controls increase or decrease of a rotation speed of the fan through a controller so as to ensure temperature of a heating element, wherein the method comprises:

• reading a current temperature value T(i), a temperature value T(i−1) of a previous moment, and a temperature value T(i−2) of a moment immediately prior to the previous moment of the heating element;
• reading a pulse-width modulation (PWM) value PWM(i−1) at the previous moment of the fan;
• determining whether there is an obvious temperature trend based on the current temperature value T(i), the temperature value T(i−1) of the previous moment, and the temperature value T(i−2) of the moment immediately prior to the previous moment;
• (a) when there is an obvious temperature trend, calculating a PWM difference value ΔPWM(i) based on the current temperature value T(i);
• (b) when there is no obvious temperature trend, setting a PWM difference value ΔPWM(i) to be zero;
• calculating a current PWM value PWM(i) based on the PWM value PWM(i−1) at the previous moment and the PWM difference value ΔPWM(i);
• and
• controlling the rotation speed of the fan based on the current PWM value PWM(i).