Abstract: For triggering a discharge lamp powered by a d.c. source and having electrodes disposed in the lamp bulb, a power supply circuit is proposed having a triggering device where, after the start of heating of a cathode (which cathode is in the form of a heated cathode), the triggering device switches a triggering pulse to a discharge path of the lamp, which discharge path is formed by the two electrodes, and initiates a triggering phase, such that the triggering pulse at least partly overlaps in time with the heating phase of the cathode. In this way, reliable triggering of deuterium discharge lamps and hydrogen discharge lamps is possible, particularly in the case of a deuterium lamp having a relatively small opening, e.g. on the order of 0.3 mm.