| 摘要 |
PROBLEM TO BE SOLVED: To reduce a peak value of a starting voltage, alleviate stress to a circuit element, and prevent the occurrence of acoustic resonance phenomena by a bridge circuit provided with a high-frequency driving circuit and a low-frequency driving circuit in opposite being a half bridge during a starting period and being a full bridge at a normal illumination period. SOLUTION: Via a bridge circuit consisting of switching elements 24 and 26 provided with a high-frequency driving circuit 62 and switching elements 28 and 30 provided with a low-frequency driving circuit 64 and a resonance circuit consisting of an inductor 50 and a capacitor 52, power is supplied to a discharge lamp 44, and lighting is performed. In such a case, the high-frequency circuit 62 and the low-frequency driving circuit 64 are controlled via a control circuit 68, and an output mode of the bridge circuit is controlled. In a mode of the starting period of the discharge lamp 44, the switching elements 24 and 26 are employed as a half bridge at a high frequency, and at the normal illumination period the whole is employed as a full bridge of a low frequency. |
