Abstract: An air-core transformer device for supplying a high-frequency, pulsating DC voltage on the secondary side of the transformer. The primary side of the transformer has two windings which are bifilar-wound having a mutual phase relationship of 180.degree., where the end of the first winding is connected in series with the beginning of the second winding at a common junction point. The voltage supply on the primary side is controlled by a time-set or time-variable power control signal at the beginning of the first winding and at the end of the second winding. A DC voltage is supplied to the common junction point. Two oscillatory circuits are formed on the primary side by a frequency control signal supplied over a field effect transistor, and are maintained by two capacitors C1 and C2, C1 being connected in parallel with the first winding and C2 being connected in parallel with the second primary winding.