Patent ID: 8269424

Claim:
A discharge lamp lighting device comprising: a discharge lamp driving section that supplies a driving current to an electrode of a discharge lamp; a state detecting section that detects a deterioration state of the electrode; and a control unit that controls the discharge lamp driving section, the control unit configured to alternately perform a first DC driving processing and a first AC driving processing in a first section of the driving current; alternately perform a second DC driving processing and a second AC driving processing in a second section of the driving current different from the first section; perform control of supplying a first direct current as the driving current in the first DC driving processing, the first direct current starting from a first polarity and having a first polarity component; perform control of supplying a first alternating current as the driving current in the first AC driving processing, the first alternating current repeating a first polarity component and a second polarity component at a first frequency; perform control of supplying a second direct current as the driving current in the second DC driving processing, the second direct current starting from a second polarity and has a second polarity component; perform control of supplying a second alternating current as the driving current in the second AC driving processing, the second alternating current repeating a first polarity component and a second polarity component at a second frequency; and according to a progress of the deterioration state of the electrode, increase a length of at least one of: (i) a period for which the first DC driving processing is performed, and (ii) a period for which the second DC driving processing is performed.