A charger includes a power supply generating a direct current power supply potential, an output transistor, a USB connector, a controller, and a resistor bridge circuit. The controller has a potential setting circuit which sets the potentials of the first and second connection nodes of the resistor bridge circuit to a middle potential between a power supply potential and a ground potential in a first mode, and sets the potentials of the first and second connection nodes to the power supply potential in a second mode.