Abstract: Device including an input rectifying circuit 2 for effecting a full wave rectification on an AC input, and an output converter which includes a transforming device 11 having a primary winding 11a and a secondary winding 11b, the primary winding being connected through an inductor 16 with paired outputs of the input rectifying circuit, the secondary winding being connected through an output rectifying circuit with a load. Switching element 18 is controlled by a control circuit 20 to operate between ON and OFF states, and capacitor 19 is connected with the input rectifying circuit and the transforming device so as to be charged during the OFF state period of the switching element 18 through a charging circuit including the inductor 16, and to discharge during the ON state period through the primary winding 11a of the transforming device 11. The control circuit 20 controls the switching element to operate in an ON-OFF manner with a frequency faster than the frequency of the AC input.