To stably detect disconnection of a light emitting element with a simple structure.
A disconnection detector includes: a first resistance element 23 and a second resistance element 24 connected in parallel to light emitting elements 12, 13; a third resistance element 26 and a fourth resistance element 27 connected in series to each other and having one end connected to a signal input terminal from a vehicle side and the other end connected to a collector of an NPN-type transistor; a PNP-type transistor 28 having a base connected to the intersection of the third and fourth resistance elements and an emitter connected to the signal input terminal; a diode 29 having an anode connected to the collector of the PNP-type transistor; a fifth resistance element 30 having one end connected to a cathode of the diode and the other end connected to an earth terminal; and a capacitative element 31 having one end connected to the cathode of the diode and the other end connected to the connected to the earth terminal.
COPYRIGHT: (C)2011,JPO&INPIT
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Yasuhiko Tanaka
Shigeru Hashidate