A flyback converter is comprised of a primary side and a secondary side. The primary side includes a primary winding and a switch both connected in series. The secondary side includes a secondary winding, a tertiary winding, a first resistor, a capacitor, a second resistor, and an MOSFET (metal-oxide-semiconductor field-effect transistor). The first resistor, the capacitor, and the second resistor are connected in series and together connected in parallel with the tertiary winding. The MOSFET is connected in parallel with the first resistor at its gate and source. Accordingly, when the switch is turned on/off, the power energy provided at the primary side can be transferred to the secondary side in a flyback manner.