Multiple discharge lamp ballast with equalizer voltage protection

A circuit arrangement for operating at least two discharge lamps, comprising:

• input terminals for connection to a supply voltage source,
• first means coupled to the input terminals for generating a high-frequency voltage from a supply voltage delivered by the supply voltage source,
• a load branch coupled to the first means and comprising
• a first branch comprising first lamp terminals for accommodating a discharge lamp and a first inductive element,
• a second branch shunting the first branch and comprising further lamp terminals for accommodating a discharge lamp and a second inductive element which is magnetically coupled to the first inductive element and forms an equalizer transformer together with the first inductive element, and
• second means coupled to the first means for adjusting the light output of the discharge lamps, characterized in that the circuit arrangement further comprises third means coupled to the equalizer transformer for comparing a voltage across the equalizer transformer with a reference voltage and for changing the operating condition of the circuit arrangement if the voltage across the equalizer transformer is higher than the reference voltage.