| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device having a structure capable of being materialized simply and at a low cost and still not impairing a constant current flow even if a load is different.SOLUTION: In the lighting device for lighting a semiconductor light emitting element 4 by using a step-down chopper circuit 3 provided with an inductor L1, a switching element Q1, and a regeneration diode D1, a controlling circuit 5 for turning on/off the switching element Q1 comprises a means (a current detecting resistance R1 and a chopper current detecting terminal CS) for turning off the switching element Q1, when an instantaneous value of a gradually increasing current flowing in the inductor L1 at the ON time of the switching element Q1 on reaches a prescribed value, and a means (a secondary wound wire n2 and a zero-cross detecting terminal ZCD) for turning on the switching terminal Q1 when a gradually decreasing current flowing in the inductor L1 at the OFF time of the switching element Q1 becomes almost zero. |
