Abstract: A device to produce alternating electric current of high frequency for power consumers such as fluorescent tubes comprises a transformer with a winding connected in series with an output terminal and active electronic components controlling the output current, said active components being controlled by electric voltages produced by inductive feed back. Magnetic saturation is utilized to modify the induction relationship in such way that the active components cyclically change the direction of the output current. According to the invention the feedback takes place in two magnetic cores, each core being equipped with at least one further electric magnetization winding designated a command winding, as electric current is fed through the command windings whereby magnetic saturation of the magnetic cores is controlled.