| 摘要 |
PROBLEM TO BE SOLVED: To prolong the service life of a lamp farther rather than by the conventional control method, in which lamp voltage has been made to increase gradually in passage of time (passage of years). SOLUTION: It is constituted with a lamp La, which has a pair of electrodes and has the characteristic that impedance changes so that power consumption becomes almost fixed, a direct-current power supply DC, a DC-DC converter 11, which steps-down the direct-current voltage from this direct-current power supply DC, switching elements Q1 to Q4 provided in between this and lamp La, and the like. Furthermore, it is constituted with a DC-AC converter 12, which converts the electric power from the DC-DC converter 11 into alternate current electric power, and supplies it to lamp La by switching operation of the switching elements Q1 to Q4, and a control part 13, which controls operating of the switching elements Q1 to Q4 and the like, so that it becomes an alternate frequency, which makes a metal that is vaporized inside the lamp La at starting and regular lighting adhere to the tip portion of each electrode, and grow up into a projection. |
