| 摘要 |
PROBLEM TO BE SOLVED: To reduce a noise caused by dimming control.SOLUTION: A drive circuit comprises: a DC/DC converter 2 generating a DC drive current for driving a semiconductor light-emitting element on the basis of a battery voltage; and a control circuit 5 controlling a switching operation of a first switching element SWc included in the DC/DC converter on the basis of a comparison result between a level of the drive current and a reference level so that the level of the drive current is accorded with the reference level. The control circuit comprises a reference level switching part 5A switching the reference level between a first level and a second level on the basis of a PWM signal Spwm. Unlike the conventional art that PWM-drives a switch turning on/off the drive current to perform dimming, no time period in which the drive current becomes at a zero level is generated at dimming, and thereby, a noise can be reduced. |
