An operating circuit including a system circuit and a power control circuit is provided. The system circuit operates according to the voltage of the node. The power control circuit includes a first connection port, a second connection port, a first always-on switch, a second always-on switch, a first current limiter, and a second current limiter. The first connection port is configured to receive first power provided by a first external device. The second connection port is configured to receive second power provided by a second external device. The first always-on switch is coupled to the first connection port to transmit the first power. The second always-on switch is coupled to the second connection port to transmit the second power. The first current limiter is coupled between the first always-on switch and the node. The second current limiter is coupled between the second always-on switch and the node.