| 摘要 |
<p>PURPOSE:To obtain an electric power supply life with same degree as an incandescent lamp by using an electric discharge lamp to a front light and outputting a detection signal when the voltage level of a direct current power supply becomes below a prescribed level and controlling the output of the front light corresponding to a direct current voltage. CONSTITUTION:A front light 4 is lighted after operating a chopper circuit 1 and an inverter circuit 2 with the direct current voltage of a low voltage battery E1 by making an electric power supply switch SW on. The lamp voltage of the front light 4 is detected by a lamp voltage detection circuit S5. When this detection direct current voltage stays between voltage levels Vth and V2, a control circuit 7 controls to a certain lamp electric power W1. When the voltage of the battery E1 becomes below a voltage level Vth, the output of an operation amplifier OP1 becomes H level and the voltage switched from the lamp voltage detection value to the voltage value of the battery E1 is outputted to the output end D of a control switching circuit 9. Then, the voltage value of the battery E1 is inputted into the control circuit 7.</p> |
