Abstract: A shut-off device is provided for an inverter which feeds at least one discharge lamp, the shut-off device operable to shut-off the inverter in limiting cases and remaining in this condition until a lamp replacement. The shut-off device flips into its normal condition when a holding current in a monitoring circuit falls below a flyback limit value. In order to keep the losses as low as possible, the monitoring circuit is dimensioned high-resistant and a separate holding circuit is provided, the separate holding circuit having a controlled dependency on the low control current in the monitoring circuit. In the disconnect case, the control current also suffices to hold the shut-off device in the disconnect condition when an electrode is broken.

Abstract: An autoconverter comprises a step-up regulating unit and following inverter so that a charging switch of the step-up regulating unit is synchronously controlled as a function of the voltage at one of the switches of the inverter. With the invention, a particularly simple synchronous control of the charging switch designed as a MOS power transistor is provided.