Patent ID: 8487553

Claim:
A lighting device which supplies power to an electrode of a discharge lamp to light the discharge lamp, comprising: a converting circuit which includes a pair of first switching elements and a pair of second switching elements to which a direct current is input, and converts the direct current into an alternating current by switching between a state where one of the pair of first switching elements and the pair of second switching elements is turned on and a state where the other of the pair of first switching elements and the pair of second switching elements is turned off; a pulse generating circuit which generates a high voltage pulse from the alternating current input from the converting circuit and applies the generated high voltage pulse to the electrode; and a trigger circuit which causes the pulse generating circuit to generate the high voltage pulse, wherein the pulse generating circuit includes a primary winding connected to the trigger circuit and a secondary winding connected to the converting circuit and generates the high voltage pulse by increasing a current input to the secondary winding based on a current input to the primary winding, and the trigger circuit includes a high pass filter which is connected at a middle point between the first switching elements and the second switching elements, flows the alternating current if the alternating current having a frequency which is equal to or higher than a predetermined frequency is input from the converting circuit, and interrupts the alternating current if the alternating current having a frequency which is lower than the predetermined frequency is input from the converting circuit; a first capacitor which stores and discharges charges input via the high pass filter; and a third switching element which outputs an output current from a second capacitor connected in parallel to the converting circuit to the primary winding if an output voltage from the first capacitor exceeds a threshold.