Discharge lamp lighting circuit

摘要

A discharge lamp lighting circuit 1 includes an electric power supply part and a control part. The control part generates a control signal (Sc) for controlling the magnitude of electric power based on a lamp voltage (VL) of a discharge lamp. The electric power supply part supplies the electric power based on the control signal (Sc) from the control part to the discharge lamp. The control part has a differential computation part for differentiating a lamp voltage corresponding signal (VS) with respect to time and generating a first differential signal Sd₁ (=dVS/dt), and an integral computation part for integrating a second differential signal (Sd₂) which monotonously increases and decreases as the first differential signal (Sd₁) increases and decreases with respect to time and generating a first integral signal (Si₁), and generates the control signal (Sc) so that the electric power decreases with an increase in the first integral signal (Si₁).