Abstract: In an electronic apparatus comprising a power supply controller, a power supply circuit, a battery, and a host controller, when power is supplied to the apparatus through an AC power supply line, the power supply controller causes the power supply circuit to supply power to the main section and battery of the apparatus and to the power supply line of a serial bus. When no power is supplied to the apparatus through the AC power supply line and power is supplied to the apparatus through the power supply line of the serial bus, the power supply controller determines the amount of power to be consumed by the main section of the apparatus and the amount of power to charge battery with, from the amount of power represented by data supplied from the host controller, which represents the amount of power the power supply line of the serial bus can supply. The power supply controller controls the power supply circuit in accordance with the amount of power thus determined.