Patent ID: 7729871

Claim:
An airflow detecting apparatus for a fan, comprising: an amplifier circuit with an input terminal receiving a voltage signal from a piezoelectric film which is disposed at a path of airflow from the fan, and outputting an amplified voltage signal; a comparator circuit with an input terminal receiving the amplified voltage signal from the amplifier circuit and comparing the amplified voltage signal with a reference voltage signal received at another input terminal of the comparator circuit, and outputting a voltage level signal; a micro control unit (MCU) configured for receiving the voltage level signal from the comparator circuit and processing it to output an indicating signal; and an indicating circuit configured for receiving the indicating signal from the MCU and indicating status of the fan according to status of airflow of the wherein the amplifier circuit comprises an amplifier, a non-inverting input terminal of the amplifier acting as the input terminal of the amplifier circuit is coupled to the piezoelectric film, an inverting input terminal of the amplifier is coupled to ground via a first resistor, the inverting input terminal of the amplifier is coupled to an output terminal of the amplifier via a first variable resistor.