Discharge lamp lighting circuit

摘要

A discharge lamp lighting circuit adapted to control a transient power corresponding to a cooling condition or a light-out time of a discharge lamp without using a capacitor or storage device having a large capacity, thereby reducing a cost and a size. Power control in a steady state of a discharge lamp is carried out in response to a detection signal for a voltage and a current in the discharge lamp, and a power to be transiently applied to the discharge lamp is controlled before a transition to the power control. The power to be transiently applied is set to be higher than the power in the steady state, thereby promoting light emission of the discharge lamp. An increment in the transient applied power which exceeds the power in the steady state is specified corresponding to a voltage applied to the discharge lamp, a variation in the voltage and a time elapsed from a time that the discharge lamp is lighted up or a start of an operation of a lighting circuit. More specifically, a dedicated circuit for detecting the light-out time of the discharge lamp is eliminated to utilize only detection information required for the power control of the discharge lamp.