Patent ID: 7227315

Claim:
A discharge lamp drive apparatus comprising: an inverter circuit converting a direct-current voltage into an alternating voltage and outputting the converted voltage; a transformer receiving the alternating voltage from said inverter circuit at an input winding thereof and outputting an alternating voltage from an output winding thereof; a plurality of discharge lamp connection terminals to be connected with a plurality of discharge lamps, respectively; a plurality of ballast capacitors each having a first electrode led to the output winding and a second electrode connected with a corresponding one of said discharge lamp connection terminals; a plurality of voltage detection circuits each having first and second voltage detection elements constituting a series circuit, each series circuit having a first end connected with a corresponding one of said discharge lamp connection terminals and a second end connected with a grounding terminal; and a signal processor generating a signal indicating an open state of a discharge lamp by using an average value and a peak value of voltages appearing between connection points of the first and second voltage detection elements and the grounding terminals.