LIGHTING CIRCUIT OF LIGHTING FIXTURE FOR VEHICLE, LIGHT SOURCE UNIT OF LIGHTING FIXTURE FOR VEHICLE, AND LIGHTING FIXTURE FOR VEHICLE

摘要

PROBLEM TO BE SOLVED: To solve a problem of a conventional lighting fixture system for a vehicle, which semiconductor light-emitting elements may turn off when emitting right.SOLUTION: This invention comprises three semiconductor light-emitting elements 21 to 23, an input voltage monitoring and detecting part 4, a switching element SW, and a linear IC 5. If an input voltage is decreased to or lower than a predetermined voltage (11 V), the input voltage monitoring and detecting part 4 outputs a first detection signal to both the switching element SW and the linear IC 5 at the same time. The switching element SW decreases the number of the semiconductor light-emitting elements that are emitting right from three (21 to 23) to two (21, 22). The linear IC 5 increases current supplied to the semiconductor light-emitting elements from 667 mA to 1000 mA. As the result, if the input voltage is within a voltage variation range (9 to 16 V) of the battery's operation guarantee, this invention maintains the right emission of the semiconductor light-emitting elements 21, 22.