Patent ID: 8294390

Claim:
A discharge lamp lighting apparatus for lighting a discharge lamp (Ld) in which a pair of electrodes (E 1 , E 2 ) for main discharge are arranged so as to face each other, the discharge lamp lighting apparatus comprising: a power supply circuit (Ux) that supplies electric power to the discharge lamp (Ld); an electric supply control circuit (Fx) that controls the power supply circuit (Ux); an inverter (Ui) that is provided in a downstream side of the power supply circuit (Ux) and that performs polarity reversals of voltage applied to the discharge lamp (Ld); a periodic driving circuit (Uj) that generates an inverter driving signal (Sj) that is a periodic signal for periodically driving the inverter (Ui); a resonant circuit (Nh), which is made up of a resonance inductor (Lh) and a resonant capacitor (Ch) arranged in a downstream side of the inverter (Ui), and which increases voltage supplied to the discharge lamp (Ld) at start-up time of the discharge lamp (Ld) by a boosting action accompanying a resonance phenomenon, wherein in a starting sequence of the discharge lamp (Ld), while the frequency control circuit (Uf) generates the inverter driving signal (Sj) corresponding to resonance frequency of the resonant circuit (Nh), the electric supply control circuit (Fx) performs control so that the power supply circuit (Ux) outputs non-load open circuit voltage (Vop) that is sufficient voltage to maintain the electric discharge of the discharge lamp (Ld), even when the boosting action accompanying a resonance phenomena in the resonant circuit (Nh) disappears due to starting of electric discharge of the discharge lamp (Ld), wherein after that, the periodic drive circuit (Uj) generates the inverter driving signal (Sj) so as to gradually decrease a frequency of the inverter (Ui) from a frequency corresponding to the resonance frequency of the resonant circuit (Nh), until the frequency of the inverter (Ui) reaches a first threshold frequency (fj 1 ), and wherein when the frequency of the inverter (Ui) reaches the first threshold frequency (fj 1 ), while the periodic drive circuit (Uj) generates the inverter driving signal (Sj) so that the frequency of the inverter (Ui) turns into stable lighting frequency (fstb), the electric supply control circuit (Fx) performs control so that the power supply circuit (Ux) outputs current which is sufficient to maintain the electric discharge of the discharge lamp (Ld).