An exemplary redundant power supply system includes a first power supply, a second power supply, a first sensor, a control circuit, and a relay switch. The control circuit includes a first input terminal connected to the first power supply via a first sensor to receive a status signal of the first power supply, a first NOT gate, a delay circuit connected to the first input terminal via the first NOT gate, a first output terminal sending a first control signal, and a second output terminal sending a second control signal. The relay switch configured to receive the two control signals from the two output terminals of the control circuit, and select the first power supply or the second power supply to supply power to an electronic device according to the two control signals.