| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device which prevents an overcurrent at power input, and a luminaire, a vehicular headlight device and a vehicle therewith.SOLUTION: The lighting device includes: a converter circuit 1 having a switching element Q1 and configured to convert an input voltage Vin to a desired output voltage Vo to be supplied to a discharge lamp La1; a control circuit 4 for controlling switching of the switching element Q1; a control power supply circuit 6 for generating a control voltage Vcc; and a protection circuit 9 comprising a switching element Q6 for making or breaking a current path K1, and a control circuit 91a for controlling switching of the switching element Q6. The control circuit 4 performs the switching control when the control voltage Vcc is equal to or higher than a lower limit value Vmin. The control circuit 91a executes a forced off mode of keeping the switching element Q6 in an off state when the control voltage Vcc is lower than a threshold Vc set equal to or higher than the lower limit value Vmin. |
