Patent ID: 7141937

Claim:
A device for lighting a high-pressure discharge lamp, comprising: a DC power supply: a first switching element having one terminal connected to the high pressure side of the DC power supply; a second switching element having one terminal connected to the low-voltage side of the DC power supply; a third switching element having one terminal connected to the high pressure side of the DC power supply; a fourth switching element having one terminal connected to the low-voltage side of the DC power supply; a first inductor having one terminal connected to the other terminals of the first and second switching elements, and the other terminal connected to one terminal of the high-pressure discharge lamp; a first capacitor connected between an intermediate section of a winding of the first inductor and the low-voltage side of the DC power supply, and composing a first series resonant circuit together with the first inductor; a second capacitor having one terminal connected to the one terminal of the first inductor, and the other terminal connected to the other terminal of the high-pressure discharge lamp; a second inductor having one terminal connected to the other terminals of the third and fourth switching elements, and the other terminal connected to the other terminal of the second capacitor; and a control circuit for controlling turning on and off of the first to fourth switching elements, wherein, before the high-pressure discharge lamp is started up, the control circuit performs control in a first control mode which alternately switches between a state in which the first and fourth switching elements are on and the second and third switching elements are off and a state in which the first and fourth switching elements are off and the second and third switching elements are on, at a predetermined switching frequency, in the first control mode, the switching frequency resonates the first series resonant circuit at its harmonic frequency to generate a high voltage for starting up the high-pressure discharge lamp, and the switching frequency is lower than a resonant frequency of the first series resonant circuit and higher than a resonant frequency of a second series resonant circuit including the second inductor and the second capacitor.