Discharge lamp lighting device, method of driving discharge lamp, and projector

A discharge lamp lighting device comprising:

• a discharge lamp driving unit that drives a discharge lamp by supplying an AC driving current to the discharge lamp;
• a memory unit configured to store driving parameters for the AC driving current;
• and
• a control unit configured to control the discharge lamp driving unit based on the driving parameters stored in the memory unit,
• wherein the driving parameters comprise a range of duty ratio values, each duty ratio value corresponding to a duty ratio of the AC driving current, the duty ratio being a ratio of a length of a first polarity section of the AC driving current and a length of one cycle of the AC driving current, and
• wherein at a predetermined time condition, the control unit selects one of the duty ratio values corresponding to the duty ratio based on a predetermined probability and controls the discharge lamp driving unit based on the selected duty ratio.