A power supply comprising: a battery unit; a self-control protector, SCP, connected in series to the battery unit, the SCP being configured to interrupt charge and discharge currents in an abnormal state; a switch configured to connect the SCP to the battery unit; and a control circuit configured to control turning on and off of the switch, wherein the battery unit includes a plurality of battery cells connected in series to one another, the control circuit comprising a voltage detection circuit configured to detect a voltage of the battery unit or one of the plurality of battery cells, the SCP includes: a fuse element connected in series to an output end of the battery unit; and a heater connected to the battery unit, the heater being configured to generate heat by Joule heating to fusion-cut the fuse element, characterized in that the switch includes a plurality of switching elements (10a, 10b, 10c), each of the plurality of switching elements having one terminal connected to the heater and another terminal connected to a corresponding one of different-voltage terminals (11a, 11b, 11c) of the battery unit, the different-voltage terminals having different voltages appearing thereon, the control circuit includes: a selection circuit configured to select, according to the voltage detected by the voltage detection circuit, a switching element out of the plurality of switching elements which is to be turned on, the selection circuit is configured to, in the abnormal state: select the switching element to be turned on: and connect the switching element which is turned on to connect the battery unit to the heater cause so as to fusion-cut the fuse element. a battery unit; a self-control protector, SCP, connected in series to the battery unit, the SCP being configured to interrupt charge and discharge currents in an abnormal state; a switch configured to connect the SCP to the battery unit; and a control circuit configured to control turning on and off of the switch, wherein the battery unit includes a plurality of battery cells connected in series to one another, the control circuit comprising a voltage detection circuit configured to detect a voltage of the battery unit or one of the plurality of battery cells, the SCP includes: a fuse element connected in series to an output end of the battery unit; and a heater connected to the battery unit, the heater being configured to generate heat by Joule heating to fusion-cut the fuse element, characterized in that a fuse element connected in series to an output end of the battery unit; and a heater connected to the battery unit, the heater being configured to generate heat by Joule heating to fusion-cut the fuse element, characterized in that the switch includes a plurality of switching elements (10a, 10b, 10c), each of the plurality of switching elements having one terminal connected to the heater and another terminal connected to a corresponding one of different-voltage terminals (11a, 11b, 11c) of the battery unit, the different-voltage terminals having different voltages appearing thereon, the control circuit includes: a selection circuit configured to select, according to the voltage detected by the voltage detection circuit, a switching element out of the plurality of switching elements which is to be turned on, the selection circuit is configured to, in the abnormal state: select the switching element to be turned on: and connect the switching element which is turned on to connect the battery unit to the heater cause so as to fusion-cut the fuse element. select the switching element to be turned on: and connect the switching element which is turned on to connect the battery unit to the heater cause so as to fusion-cut the fuse element.