Abstract: An inverter circuit, comprising a control circuit for improving the switching off of transistors (1 and 2). The control circuit includes a secondary winding (16) for an inductive winding (7) included in a load circuit, said secondary winding being connected in series with a winding (17) for a base control transformer (3) of transistors (1 and 2). The control circuit closes itself by way of a diode (21 or 20) and transistor (1 or 2). Thus, a voltage induced in secondary winding (16) indicating the rate of decrease of the collector current of transistor (1 or 2) improves or accelerates the switching off of transistor (1 or 2) when the hazard of simultaneous conduction of transistors increases e.g. as a result of the reversal of loading state or variation of individual characteristics (such as storage time) of transistors.

Abstract: An electronic ballast for a discharge lamp (8) for restricting and stabilizing the lamps current. The ballast comprises a high frequency oscillator for connection to a D.C. supply which consists of two transistors (1,2) connected in series, with a base drive transformer (3) coupled between them to bring the transistors (1,2) into alternating phase operation. A resonance circuit connected in series with the primary winding (4) of the transformer (3), comprises an inductor (7), resonance capacitors (10 and 11) and a capacitor (9) coupled in parallel with the lamp (8). The lamp (8) is, in turn, connected in series with the resonance circuit. In addition, a filter capacitor (c) having a high charging ability is coupled between the terminals of the D.C. supply. The resonance capacitors (10 and 11) are connected in series between the terminals of the D.C.

Abstract: A means for limiting and regulating the current of a discharge lamp. The problem is in particular making the power control of a thin fluorescent lamp easy to manage and in a universally applicable manner. The starting point chosen for the solving of this problem is a conventional supply voltage regulator, for instance one which when the luminous power is controlled clips part of the leading or trailing front of the supply voltage wave. Between such a control (1) and the lamp (8) has been connected an electronic ballast means (7) having after a filtering circuit (L,C1,C2) and a rectifier (5), a high frequency oscillator consisting of two series-connected transistors (V6, V5), a transformer (T1) connected betweem them, a choke (L1,L2) connected in series with the transformer's primary winding, and a capacitor (C6,C7) in the last-mentioned series circuit between the lamp and the current source.