To charge a battery with high efficiency based on a plurality of direct current voltages from different power sources.

A first voltage detection circuit 16 generates a first input detection signal DET_DC that is asserted when a voltage of a first input terminal DC is higher than a predetermined first threshold voltage. A second voltage detection circuit 18 generates a second input detection signal DET_USB that is asserted when a voltage of a second input terminal USB is higher than a predetermined second threshold voltage. An input selector 20 selects one of the voltages of the first input terminal DC and the second input terminal USB on the basis of the first input detection signal DET_DC and the second input detection signal DET_USB. A DC/DC converter 30 generates a system voltage VSYS by stepping down an output voltage VIN of the input selector 30. A linear charger 50 receives the system voltage VSYS and charges a battery 2 in a constant current mode or a constant voltage mode.