Patent ID: 8022642

Claim:
A discharge lamp lighting device comprising: an inverter circuit for converting DC voltage from a DC power source into AC voltage, a plurality of transformers which include a plurality of primary windings and a plurality of secondary windings, each of said primary windings being in parallel connection to output terminals of said inverter circuit, discharge lamps each connected to respective secondary windings, tube current detecting circuits connected between the secondary winding of said transformers and discharge lamps for detecting tube currents through said discharge lamp to produce detection signals of the level corresponding to the detected tube current, a maximum detection circuit for detecting a maximum value of detected signals from the current detector, a minimum detection circuit for detecting a minimum value of detected signals from the current detector, a comparison circuit for computing one or plural values of sum, difference, product and quotient between maximum value from maximum detector and minimum value from minimum detector to generate a cease signal when the computed value exceeds a predetermined value, and a control circuit for halting operation of the inverter circuit when said comparison circuit generates the cease signal.