Patent ID: 8860319

Claim:
A lighting device comprising: a series circuit of an inductor and a switching element which is connected between output terminals of a DC power source, wherein the switching element operates for switching an input from the DC power source; a diode which regenerates and supplies an energy of the inductor to solid state light emitting elements when the switching element is turned off; and a control circuit which controls on/off of the switching element, wherein the control circuit includes a drive signal generator which outputs a high frequency drive signal as a pulse signal to determine an amplitude of a load current flowing through the solid state light emitting elements; and a drive control section which turns on and off the switching element based on the high frequency drive signal and a PWM signal with a frequency lower than that of the high frequency drive signal, an on-duty of the PWM signal being changed according to a dimming level, and wherein the drive signal generator changes an ON time of the high frequency drive signal such that, after the PWM signal is changed from OFF to ON, a peak value of the load current gradually drops along an envelope of a specific slope, and the specific slope of the envelope is changed based on a duty ratio of the PWM signal.