Patent ID: 8400068

Claim:
A discharge lamp lighting device comprising: a discharge lamp driving section that supplies a driving current to drive a discharge lamp having a first and a second electrode, each electrode having different thermal conditions, the driving current including components of a first polarity and a component of a second polarity opposite to the first polarity; 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 the first polarity and having a component of the first polarity; perform control of supplying a first alternating current as the driving current in the first AC driving processing, the first alternating current repeating a component of the first polarity and a component of the second polarity 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 the second polarity and having a component of the second polarity; perform control of supplying a second alternating current as the driving current in the second AC driving processing, the second alternating current repeating a component of the first polarity and a component of the second polarity at a second frequency; and perform the first AC driving processing and the second AC driving processing such that the first frequency and the second frequency have different values, wherein a period of the first direct current is longer than half of a period of the first alternating current, and a period of the second direct current is longer than half of a period of the second alternating current.