A control device for regulating the constant output current of a flyback converter, the control device adapted to control the on time period and the off time period of a primary winding switch and including a first circuit adapted to multiply a first signal representative of current flowing through the primary winding and a second signal representative of an input voltage and outputting a signal representative of the multiplication, a second circuit adapted to compare the output signal of the first circuit and a third signal representative of the direct output voltage, the control device determining, on the basis of the output signal of the second circuit, the on time period and the off time period of the switch so that the output signal of the first circuit is equal to the signal representative of the direct output signal to have the output current of the flyback converter constant.