To normally detect a blown-out filment and a severed wire by preventing misdetection of cutting of the blown-out filament and the severed wire, when the blown-out filament of a signal lamp or the severed wire in an output wiring is detected during a non-operation (lighting-off).
This circuit for detecting the blown-out filament of a signal lamp comprises a power source 7, a diagnosis current supplying circuit 1 for detecting the blown-out filament, a circuit 2 for detecting the diagnosis current, and a voltage detection circuit 3. Switches 13, 14 are set on, and a slight diagnosis current 6 not lightening a signal lamp 4 is flown from the diagnosis current supplying circuit. When the blown-out filament of the signal lamp or the severed output wire 5 is not detected, a voltage applied to the voltage detection circuit is small, so that a photocoupler 17 is switched on, and a photocoupler 15 is switched off. When the blown-out filament of the signal or the severed output wire is detected, the voltage applied to the voltage detection circuit is large, so that both of the photocouplers 17, 15 are switched on. From such a detection pattern, the blown-out filament of the signal lamp or the severed output wiring during a non-operation (lighting-off) is detected.
COPYRIGHT: (C)2005,JPO&NCIPI
Yurifumi Kurisu
Toru Maeda
Nobuyuki Kamata
日立エンジニアリング株式会社
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