Redundant power supply power loss alarm method and circuit

The invention relates to the technical field of alarm circuits, in particular to a redundant power supply power-losing alarm method and circuit, by means of the characteristic that a power supply indicates that voltages at two ends of an LED light-emitting tube are fixed values, the voltages serve as a reference end + of a voltage comparator, a voltage division circuit is adopted to divide the power supply voltages and then connect the power supply voltages to a negative end-of the comparator to be compared with the reference end +, and the power-losing alarm is achieved. And when the voltage value after voltage division is smaller than the voltage value of the reference voltage, the output of the voltage comparator is invalid, the relay is released, and the voltage is indicated to be abnormal. The power supply voltage is accurately identified, a fixed threshold value is provided, whether power exists or not can be judged, and whether the voltage is in a normal range or not can also be identified; when the po