A charging circuit employed in an electronic apparatus is operable to charge a portable electronic device. The charging circuit includes a charging control microchip including two control terminals, a southbridge microchip, a logic control circuit, and a basic input/output system (BIOS). The southbridge microchip and the BIOS are both electronically connected to the logic control circuit to control the logic control circuit to set or reset voltage of the two control terminals, then the charging control microchip is switched to a charging mode or a data transmission mode according to the voltage of the two control terminals.