A flyback converter includes a primary winding, a main switch, a charging switch, a primary side controller and an energy storage device. The primary winding receives an input power; the primary side controller has a power input terminal and provides a first control signal and a second control signal to the main switch and the charging switch; after the main switch is turned off, the charging switch maintains turned on during a charging period. During the charging period, the input power passes through the primary winding and the charging switch, and stores a first portion of the input power in the energy storage device as a power supply energy; the power input terminal is coupled to the energy storage device, and the primary side controller receives the power supply power from the energy storage device through the power input terminal.