Abstract: The device comprises a switched-mode power supply (1) equipped with an electronic switching member (T.sub.1), the closing of which controls the power supply to an inductor (L.sub.1) which discharges, when the member reopens, into a capacitor (C.sub.1) at the terminals of which the output voltage of the device appears, characterized in that it comprises (a) storage means for recording a sequence of image numbers of successive segments of the predetermined waveform, (b) a clocked digital counter (2) and (c) means (3) for successively loading this counter (2) with each of the numbers of this sequence considered as a bound of the count performed by the counter (2), the latter cyclically controlling the closing of the switching member (T.sub.1) for a predetermined time interval, each time the count performed reaches the limit thus fixed.