Patent ID: 7943890

Claim:
A discharge lamp lighting device including a switching circuit that controls power supplied to a discharge lamp, in which, in the switching circuit, a switching frequency is controlled in response to a state of the discharge lamp, energy stored in an inductance component when a switching element is turned on is released when the switching element is turned off, and the switching element is controlled to turn on at a timing when a current for releasing the energy turns to substantial zero, the discharge lamp lighting device comprising: a load voltage detector that detects a load voltage; a switching frequency counting unit that performs time measurement for setting the switching frequency based on the voltage detected from the load voltage detector so that predetermined power of the discharge lamp can be achieved; a current detector that detects that the current flowing through the switching circuit has reached a predetermined reference value; a reference arithmetic unit that sets the predetermined reference value based on the voltage detected from the load voltage detector so that the switching element can be turned on and after the timing when the current for releasing the energy turns to substantial zero at the switching frequency set by the switching frequency counting unit; and a drive controller that controls the switching element to turn on upon receiving a signal of the switching frequency counting unit, and controls the switching element to turn off upon receiving an output signal of the current detector.