| 摘要 |
PROBLEM TO BE SOLVED: To prevent excessive consumption of one side of filaments in a discharge lamp and to prolong its life by connecting a node between a direct- current blocking capacitor and an inductor to a negative electrode of a direct- current power supply by a resistor and starting to operate a control circuit when the direct-current blocking capacitor is charged to have substantially half the output voltage of the direct-current power supply. SOLUTION: A first resistor 15 is connected in parallel with a switching element 10a connected to the positive electrode side of a direct-current power supply 3, and a node between a direct-current blocking capacitor 13 and an inductor 14 is connected to the negative electrode side of the direct-current power supply 3 via a second resistor 16. In this arrangement, after the direct- current blocking capacitor 13 is charged to have substantially half the output voltage of the direct-current power supply, a control signal is outputted from a control circuit 11, and a fixed period of time after the direct-current power supply 3 turns into an on-state, an output of an inverter is supplied to filaments of a discharge lamp 2. A shift in voltage applied to the discharge lamp 2 can be thereby eliminated during the pre-heating time of the filaments of the discharge lamp 2. |
