| 摘要 |
PURPOSE:To set the maximum output power during ordinary lighting low by operating a control circuit for a preset time after a power source is turned on and generating the voltage required to start a discharge lamp. CONSTITUTION:When an AC power source AC is turned on, a timer 21 is operated to count the preset time, and a control signal is inputted to a control circuit 23 until this preset time elapses after the power source is turned on. The control circuit 23 controls the frequencies of switching signals applied to switching transistors 3 and 5 based on the signal from a voltage detecting circuit 19 while the control signal is inputted so that the output voltage of an inverter circuit is kept higher than the voltage required to start a discharge lamp 17. When the preset time elapses, the timer 21 stops the feedback control operation of the control circuit 23, and the inverter circuit performs the preset rated operation thereafter. The output power of a lighting device is not increased even at the terminal stage of the lamp life, and the thermal stress of the lighting device can be reduced. |
