Patent ID: 7944150

Claim:
A discharge lamp lighting apparatus for turning on a discharge lamp having a lighting condition in which a projection is formed at a tip of an electrode for electric discharge, comprising; a power supply circuit which supplies electric power to the discharge lamp; a lamp voltage detection unit which detects a lamp voltage and generates a lamp voltage detection signal; an inverter which inverts an output voltage and passes an output current in form of an alternating current to the discharge lamp; a polarity-reversal mode control circuit which determines a polarity-reversal mode comprising a first mode and a second mode, based on the lamp voltage detection signal; and an inverter control circuit which generates an inverter control signal which specify a polarity-reversal operation of the inverter based on the polarity-reversal mode, wherein in a period of a lighting steady state, excluding an initial lighting period immediately after start up of the discharge lamp, when the polarity-reversal mode is the second mode, the inverter control circuit operates to generate the inverter control signal so that a DC component contained in the output current increases more than that in the first mode, when the polarity-reversal mode is the first mode, and it is detected that the lamp voltage is lower than a predetermined first voltage, the polarity-reversal mode control circuit changes the polarity-reversal mode into the second mode, and when the polarity-reversal mode is the second mode, and it is detected that the lamp voltage is higher than a predetermined second voltage, the polarity-reversal mode control circuit changes the polarity-reversal mode into the first mode.