| 摘要 |
PURPOSE:To conduct a DC firm preheating by feeding a preheating current of a discharge lamp directly from a power source to the filament of the discharge lamp through a current control circuit and a reverse-current preventing element. CONSTITUTION:When a power switch 1 is turned on, a preheating current of a discharge lamp 11 is sent from a current control circuit 7 to a reverse-current preventing diode 10, the filament of the discharge lamp 11, and a short-circuit preventing diode 12, as a relay contact 501 is on the side of a. Then, by turning a lighting switch 2 on, a transistor 4 is operated to excite a relay 5, and the relay contact 501 is changed from the side of a to the side of b. Therefore, a lighting circuit 8 is operated to generate a high frequency voltage, lighting the discharge lamp 11. At this time, the reverse-current preventing diode 10 prevents the high frequency voltage from applying to the current control circuit 7 or the relay contact 501. The high frequency voltage is fed to the discharge lamp 11 without being short-circuited by the diode 12. Hence, a DC firm preheating can be achieved. |
