Abstract: The object of the invention in to provide a drive circuit in which a high efficiency can be achieved and with which the voltage spikes reacting on the supply network are virtually zero. For this purpose, the discharge lamp (FL) is connected by its first electrode (E1), by means of a connecting line (VL), to the junction (H) between the emitter resistor (R3) of the first transistor (T1) and the collector of the second transistor (T2) of the high-frequency resonant circuit. The discharge lap (FL) in connected by its second electrode (E2) to the neutral conductor (0). As a result, the supply current with the superimposed control frequency flows via the load. Consequently, voltage spikes are compensated for and the efficiency in considerably increased.

Abstract: For driving gas discharge lamps, a ballast is provided between the positive and the negative output terminals of a rectifier arrangement (D1, D2, D3, D4). The ballast comprises a filter stage (C1, C2, C3, DR1, DR2) with an oscillation voltage build-up circuit (R1, C6, D5, DIAC) and with a high-frequency resonant circuit (R2-R6, T1, T2, D5, D6, C6, I1, I2), and also with a decoupling capacitor (C7), a third inductor (DR3) and a third inductance (I3, I4). This third inductance is wound together with the two abovementioned windings of the high-frequency resonant circuit (I1, I2) onto a common core. The ballast is routed by a connecting line (VL) from the junction (H) between the two transistors (T1, T2) to one electrode (E1) of the discharge lamp (FL), the second electrode (E2) of which is connected to the first electrode (E1) via a resonant capacitance (C12, C13).