Abstract: The AC electric power of the commercial AC power supply is safely supplied to an electronic appliance functioning as a load during an occurrence of a power interruption by an auxiliary power supply apparatus. In the auxiliary power supply apparatus, normally usable electric power derived from a diode bridge energized by the commercial AC power supply, and auxiliary electric power produced from a DC/DC converter energized by a cell are selectively conducted to an output connector of this auxiliary power supply apparatus via a selection switch and a load connection switch, which are controlled in response to a detection result of a power-interrupt detecting circuit. When an AC plug of a load set is inserted into this output connector, a switch is turned ON, and then, a DC voltage applied from a voltage divider to this connector is changed, depending upon the types of the power supply circuits employed in the load sets, namely, a transformer type power supply circuit and a switching type power supply circuit.