| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device having a smaller power supply voltage dependence degree compared with the conventional art, and with which sounding is suppressed.SOLUTION: A lighting device comprises a lighting circuit 10, a drive circuit 20, a dimming control circuit 35, and an LPF 30. In a case that a wave height of an inputted PWM signal is larger than a first threshold and smaller than a second threshold that is larger than the first threshold, the drive circuit 20 increases an ON-time-period that is a time period corresponding to one ON-time-period during an on/off operation repeatedly performed by a switching element 25 in a burst time period as the wave height becomes higher, and in a case that the wave height is the second threshold or more, the drive circuit 20 performs control so that the ON-time-period becomes constant. The LPF 30 generates a smoothed PWM signal having a first time period where the wave height is larger than the first threshold and smaller than the second threshold, and a second time period where the wave height is the second threshold or more, in a signal section indicating a duty ratio, and outputs the generated smoothed PWM signal to the drive circuit 20. |
