| 摘要 |
PROBLEM TO BE SOLVED: To reduce the stress to a component caused by the increase of a resonance current when a high voltage is generated in a non-discharge period before start of discharging a discharge lamp and in a prescribed period after the start of discharging. SOLUTION: This device is provided with a load circuit 11 comprising inductors L1, L2, capacitors C1, C2 and a discharge lamp DL, and a high-frequency electric power source circuit 12 for supplying electric power to the circuit 11. The device is also provided with a control circuit 13, for the power source circuit 12, for detecting, for example, a frequency f4 by detecting a peak value of a lamp voltage Vla corresponding to the frequency f4 which is a higher value when the reactance of the load circuit 11 comes to zero, based on a detected result of the lamp voltage Vla, for keeping a peak value of a current flowing in the inductance L1 when the frequency f4 is brought in, and for changing, in a non-discharge period, a switching frequency to FETs Q1, Q1 from a prescribed frequency higher than the frequency f4 upto a frequency lower than the frequency f4 to bring the peak value of the current hereinbefore. |
