| 摘要 |
PROBLEM TO BE SOLVED: To restrain the occurrence of a fault due to connection abnormality in a solid light-emitting element and also simplify circuit configuration and cut down costs.SOLUTION: When abnormality in a state of connection between a connector 5 and a light source 6 (non-loaded or loose contact) occurs, a ratio of an ON period ton and an OFF period toff of a switching element Q1 changes from normal time. Therefore, when the ratio of the ON period ton and the OFF period toff of the switching element Q1 goes out of a prescribed range, a control circuit 2 restrains output of a switching power supply circuit 1. For this reason, unlike in a conventional case, a circuit for detecting abnormality in a state of connection between a connector 5 and a light source 6 is unnecessary, except the control circuit 2, making it possible to simplify circuit configuration and cut down costs while also restraining the occurrence of a fault due to connection abnormality in a solid light-emitting element. |
