The disclosure relates to a flyback converter, a control circuit and a control method therefor. In the control method, a power stage circuit is controlled at a light load to operate alternatively in a pulse width modulation mode (i.e. a constant switching frequency mode) and in a constant on time mode, in accordance with a voltage compensation signal. Thus, output energy may decrease rapidly and smoothly, without need for the control circuit to stop working. The flyback converter has increased efficiency at the light load and decreased output voltage ripple.