Abnormal detection circuit for detecting three-phase AC power

An abnormal detection circuit is provided. The abnormal detection circuit includes a conversion circuit, a voltage detection circuit and a warning circuit. The conversion circuit receives a three-phase AC power and converts the three-phase AC power into a driving power. The voltage detection circuit detects each phase of the three-phase AC power. When a voltage value of at least one phase AC power of the three-phase AC power is abnormal, the voltage detection circuit uses the driving power to output at least one control signal corresponding to the abnormality. The warning circuit is driven by receiving the driving power and outputs at least one warning signal corresponding to the abnormality in response to the at least one control signal.