| 摘要 |
PROBLEM TO BE SOLVED: To suppress the fluctuation of an average current value flowing through an LED lamp.SOLUTION: The LED lighting device includes: an LED lamp 1 having a plurality of LED elements 1a connected in series; a changeover switch SW1 which changes the number of series of the plurality of LED elements; a step-down converter 2 which includes a switching element NM1, through which a current Iout of the LED lamp flows, and steps down a power supply voltage Vcc by the switching operation of the switching element, to supply to the LED lamp; a first control circuit 3 which switches off the switching element for a constant period, when a current flowing through the switching element which is in an ON state reaches a preset peak current value Ip, and switches on the switching element after the lapse of the constant period; and a second control circuit 5 which makes the constant period shorter as the voltage VLED between both ends of the LED lamp becomes higher.SELECTED DRAWING: Figure 1 |
