VEHICLE LAMP TOOL AND LIGHTING CIRCUIT

摘要

PROBLEM TO BE SOLVED: To provide a vehicle lamp tool capable of varying luminance at a high speed.SOLUTION: The lighting circuit 20 is used together with a semiconductor light source 10 and constitutes a vehicle lamp tool 1. A switching converter 30 supplies power to the semiconductor light source 10. A converter roller 32 controls the switching converter 30. A current detection circuit 34 detects a current Isupplied to the semiconductor light source 10 from the switching converter 30. A hysteresis comparator 36 compares a current detected value Vwith an upper threshold voltage Vand a lower threshold voltage V, and generates a control pulse Saccording to the comparison result. A threshold value voltage generation circuit 38 receives a variable control voltage Vinstructing the target amount of a current I, and generates an upper threshold voltage Vand a lower threshold voltage Vaccording to the control voltage V.SELECTED DRAWING: Figure 2