| 摘要 |
PURPOSE:To control the dimming of a discharge lamp stably by applying the DC power at the level to maintain the discharge in a low light flux dimming condition to superpose to the high-frequency power, in a discharge lamp dimming device to control the dimming from the arc discharge scope to the glow discharge scope. CONSTITUTION:A discharge lamp lighting device which furnishes a low voltage mercury discharge lamp 1, a high-frequency power source 2 to feed a high-frequency power to the discharge lamp 1, and a dimming control unit 3 to dim the discharge lamp 1 from the arc discharge scope to the glow discharge scope is provided. And a DC power at the level to maintain the discharge of the lowest light flux of the low light flux dimming less than 20% of the light flux at the rating lighting of the discharge lamp is applied to the high-frequency power by a DC power superposing device 4 and applied to superpose to the discharge lamp 1. By providing an impedance element Z2 which consists of a resistance element and a switching element, and ON/OFF controlling the switching element responding to the control signal, the superposing amount of the DC power to the discharge lamp 1 can be controlled. |
