Ballast for gas-discharge lamps having electrodes which can be heated

摘要

A ballast for gas-discharge lamps having electrodes which can be heated contains a bridge invertor, consisting of two half bridges which are connected to a supply voltage and are controlled by a common control device so that they can optionally be operated in the push-pull mode or in single-ended operation. Connected between the two outputs of the half bridges is a series circuit which is formed from a gas-discharge lamp having a ballast inductor, the ballast inductor carrying two windings which are in each case connected upstream of an electrode of the gas-discharge lamps. In order to heat the gas-discharge lamps, a heating device is provided which is connected to the electrodes of the gas-discharge lamp. In order to prevent a large reactive current occurring when regulating the burning current of the gas-discharge lamp, the heating device contains a transformer having one primary and two secondary windings, of which each secondary winding is connected to the respectively associated lamp electrode and heats said electrode. The primary winding is connected at one end to one of the power supply inputs of the bridge invertor and, at the other end, is connected via in each case one capacitor to each of the lamp electrodes.