| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device that can suppress occurrence of flickering even when instantaneous power failure or instantaneous voltage drop occurs.SOLUTION: A lighting device having an AC/DC converter 20 for converting an AC voltage Vac to a DC voltage Vdc, a DC/DC converter 40a for converting the DC voltage Vdc to a DC voltage to be applied to LED 14, and a detection circuit 30a for detecting the AC voltage Vac. The DC/DC converter 40a has a switching element 43, and a control circuit 50 for controlling a switching element 43 to repeat ON and OFF in a current critical mode. The control circuit 50 controls the switching element 43 so that an ON time Ton which is a time for which the switching element 43 continues the ON state does not exceed a predetermined upper limit value. When the AC voltage Vac detected by the detection circuit 30a decreases to be smaller than a predetermined value, the upper limit value is changed to a larger value.SELECTED DRAWING: Figure 1 |
