An airflow detecting apparatus for a fan includes an amplifier circuit
(100), a comparator circuit (200), a micro control unit (MCU) (U1), and
an indicating circuit (300). The amplifier circuit has an input terminal
receiving a voltage signal from a piezoelectric film (H1) disposed at an
airflow path of the fan, and outputs an amplified voltage signal at an
output terminal. The comparator circuit has an input terminal receiving
the amplified voltage signal from the amplifier circuit and compares the
amplified voltage signal with a reference voltage signal received at
another input terminal of the comparator circuit, and outputs a voltage
level signal at an output terminal. The MCU receives the voltage level
signal from the comparator circuit and processes it to output an
indicating signal. The indicating circuit receives the indicating signal
from the MCU and indicates status of airflow.