Patent ID: 8786202

Claim:
A lighting device comprising: a rectifier unit configured to rectify an alternation current voltage to supply the rectified voltage to a plurality of light emitting units; the light emitting units configured of a plurality of light emitting diodes (LEDs) connected with each other in series; a plurality of current sources connected with each of the light emitting units to control currents inputted to a corresponding light emitting unit; a control unit configured to control the plurality of current sources and a first switching element based on levels of an input voltage via the rectifier unit; and the first switching element configured to be switched on and off based on the control of the control unit, wherein the control unit controls the plurality of current sources and the first switching element based on the levels of the input voltage; in a first voltage level, switching on the first switching element, controlling to saturate a first current level of the first current source, and controlling to saturate a first current level of the second current source, in a second voltage level, switching on the first switching element, controlling to saturate a second current level of the first current source, and controlling to saturate a second current level of the second current source, and in a third voltage level, switching off the first switching element, turning off the first current source, and controlling to maintain the second current level of the second current source.