Discharge lamp igniting apparatus

摘要

When a light level of a discharge lamp (104) is smaller than or equal to a predetermined value, first and second reference voltage (108a,108b) are switched by a two-stage switching circuit (109). A comparator (107) compares a detection voltage (106) of the discharge lamp with the first reference voltage, or the detection voltage with the second reference voltage. When the voltage of the discharge lamp becomes high, a control circuit (110) supplies to a high frequency power supply (102), a control signal (112) for interrupting, or reducing an output of the high frequency power supply. Accordingly, it is possible to more correctly discriminate the discharge lamp being operated under normal condition from the discharge lamp being operated in the final lifetime stage over the entire range of the light level. As a consequence, the discharge lamp can be used in the proper manner, and further the electrical damage of the discharge lamp igniting apparatus can be avoided in advance.