| 摘要 |
PURPOSE: To prevent a metal halide which is evaporated during lighting from condensing and solidifying on an electrode and lower the starting voltage in the case a lamp is turned off from rated lighting on-state, regarding a discharge lamp lighting apparatus to light a metal halide lamp having an electrode. CONSTITUTION: When one end (c) of a resistor 18 is connected with a electric voltage source through a switch S1, a capacitor is gradually charged through the resistor 18 and the duty ratio of a PWM oscillation output E1 to an IC14 becomes small and the supply current to a metal halide lamp 12 lowers gradually based on the constant of charging time as the lapse of time. Following that, the temperature of a light emitting tube of the lamp 12 lowers and the evaporation amount of an iodide lessens and by the time when the lamp 12 is completely extinguished, scarce amount of the iodide is evaporated in the light emitting tube and emits light and then the lamp 12 is extinguished after a lighting state only by mercury. As a result, the iodide can be prevented from adhering to an electrode. |
