| 摘要 |
PURPOSE:To make it possible to thoroughly detect the abnormality of a lamp, and also to perform automatical switching to a normal lamp by switching power feed of a lighting power supply from a lighting side incandescent lamp to a stand-by side incandescent lamp by means of an abnormal signal from an abnormal current detection circuit or zero current detection circuit. CONSTITUTION:When a current which flows through a lamp 3 increases, for example due to a period short circuit of the filament of a lamp 3 on lighting side, and exceeds a set current which is converted and output from a reference voltage generating circuit 10, an abnormal signal 'H' is output to an OR circuit 31 from a comparator circuit 11. Then, a T type flip-flop 12 is reversed and it becomes 'H' state to turn a relay RY on, and feed power is automatically switched, from the lighting side lamp 3 which theretofore has been supplied with the power by a lamp lighting power supply 7, to a stand-by side lamp 2, for making the stand-by side lamp as a new light source. At the same time, a warning lamp 13 lights, thus the abnormality of a lamp can be recognized by a worker. |
