High-density gas discharge lamp starting and operating circuit - gives optimum matching of lamp operating voltage during both initial heating and subsequent operating phases

The circuit has a DC/AC converter coupled to the DC inputs employing a transistor switch, a transformer with respective capacitors across its primary and secondary windings and a pulse width modulator with a HF generator providing an operating signal for the transistor switch. A blocking delay element uses a diode, a filter capacitor and a second transformer its primary connected in series with the secondary capacitor of the first transformer via a diode. The output of the blocking delay element is fed to the input of the AC/AC converter. The latter coupled to a power control sum amplifier receiving a pair of control signals dependent on the sampled current and voltage. A heating control allowing the lamp to be operated at a higher power level during an initial heating phase is coupled to the secondary windings of a third transformer with its primary in series with the transistor switch and a fourth transformer in series with the primary capacitor of the first transformer. USE - For miniature metal halogen lamps e.g. headlights used in automobiles.