POWER CHARGING SYSTEM AND POWER CHARGING METHOD USING ADAPTER WITH BUILT-IN BATTERY

A charging adapter according to an embodiment comprises: a first battery; and a charging circuit configured to charge the first battery with external power and generate first power, wherein in a fast charging mode, the charging circuit is configured to charge a second battery in an electronic device detachably connected to the charging adapter based on the first power generated and the first battery is configured to generate a second power and charge the second battery with the second power while the charging circuit charges the second battery.