| 摘要 |
PROBLEM TO BE SOLVED: To prevent stresses on switching elements in a lighting device for a high voltage discharge lamp by suppressing an excess current flowing in each switching element when polarity is changed. SOLUTION: This device includes a DC power supply 2 generating the voltage required for a discharge lamp 7 from a DC power supply 1, a control circuit 3 computing the power required for the discharge lamp 7 and performing feedback control of the DC power supply 2, a polarity switching circuit 4 switching polarities so that the output of the DC power supply 2 is applied to the discharge lamp 7 in the form of a low-frequency rectangular wave, an ignitor 6 superimposing a high-voltage pulse on the discharge lamp 7 during startup, and a capacitor C2 constituting a closed circuit together with the ignitor 6. In this case, a control circuit 5 is provided for operating the polarity switching circuit 4 at low frequencies and for putting the same into chopper action at high frequencies in order to suppress an excess charge and discharge current flowing in the capacitor C2 when the polarity of the polarity switching circuit 4 is changed. |
