| 摘要 |
PROBLEM TO BE SOLVED: To provide a lighting device for dimming a semiconductor light emitting element by using a switching power source circuit, in which, even if a load opening abnormality occurs at the time of dimming, a circuit protecting function is made to work like at the time of full lighting.SOLUTION: The lighting device is provided with an output terminal 3 to which a semiconductor light emitting element 4 lighted by a direct current is connected, a switching power source circuit 1 for supplying a dimming output in accordance with a dimming signal to the out put terminal 3, a dimming releasing means (a no-load detecting circuit 2 and a dimming releasing circuit 7) for releasing a dimming work of the switching power source circuit 1 when the voltage of the output terminal 3 exceeds a first voltage, and a protection means (a pseudo-overcurrent generating circuit 6 and an overcurrent protection circuit 51) for changing the output of the switching power source circuit 1 to a suppressing state when the voltage of output terminal 3 exceeds the first voltage. |
