To provide a lamp failure detecting device of an automobile which can detect not only disconnection of lamps but also cutting of a power source line and a fuse.
When respective lamps 11 are not disconnected, a difference between reference voltage V2 and voltage V1 is 0, and output of an operation amplifier 15 becomes 0. When the voltage V increases since at least one of the respective lamps 11 is disconnected, output of the operation amplifier 15 is put on a high level. In this case, a switching transistor 16 is turned on, and an electric current flows to the switching transistor 16 from an ignition key switch 17, and a warning lamp 19 is lighted. When a fuse 13 is fused since an overcurrent flows to a line 21, a cutting detecting transistor 2 is turned off. In this case, since the output side of the cutting detecting transistor 2 is opened, the input side of the switching transistor 16 is put on a high level, and this switching transistor 16 is turned on, and this warning lamp 19 is lighted.
SAKAMOTO FUKUMA
SUMITOMO WIRING SYSTEMS
SUMITOMO ELECTRIC INDUSTRIES