US Patent 7714522 Method and circuit arrangement for operating a discharge lamp

A method and a circuit arrangement operate a discharge lamp, such as a high-intensity discharge lamp (HID) or ultra high performance lamps (UHP). The discharge lamp has first and second operating phases with a higher first or a lower second frequency of the lamp's alternating current (AC). The operating phases are activated alternatively at defined intervals and for defined periods of time, in order to achieve a stable arc discharge and only a low burnout or rise in burning voltage of the lamp during its life by configuring certain forms of electrode tips.