| 摘要 |
PURPOSE:To prevent excess lighting and to reduce power consumption by changing the frequency of an excitation circuit in response to an increase in surrounding illuminance and reducing the quantity of light of electric discharge lamps. CONSTITUTION:A DC power supply is switched using semiconductor elements (TR1, TR2) driven by an excitation circuit (4A) to provide a high frequency AC power. A separately-excited inverter electric discharge lamp lighting circuit which uses the high frequency AC power supply to light electric discharge lamps (3, 3A) is organized so that the resistance value of a resistor element (Rx) which determines the oscillation frequency of the excitation circuit (4A) varies in a manner than the frequency is changed and the quantity of light of the electric discharge lamps (3, 3A) being lighted is reduced in response to an increase in surrounding illuminance. |
