Patent ID: 7443106

Claim:
A circuit with a switch-off device for the operation of light sources (Lp), having the following features: a self-commutated half-bridge inverter having a series circuit of an upper electronic switch and a lower electronic switch (T 1 , T 2 ), which are joined at a half-bridge midpoint (M) and are connected between a supply voltage (+) and a ground potential, a start capacitor (C 3 ) which is joined via a trigger element (DIAC) to a control electrode of the lower electronic switch (T 2 ), and a switch-off device having an input (E) and an output, which are configured and connected so that they discharge the start capacitor (C 3 ) if a switch-off signal is applied to the input (E), characterized in that the switch-off device comprises two successively connected transistor stages (T 3 , T 4 ) with bipolar transistors, a first stage (T 3 ) being configured as an emitter circuit and a second stage (T 4 ) being configured as an collector circuit, wherein the collector of the second stage (T 4 ) transistor is not connected to the first stage transistor other than through a ground potential.