Patent ID: 8384307

Claim:
A light emitting diode (LED) lamp, comprising: an LED cluster comprising a plurality of LED groups arranged in series; a power source configured to provide an input power to the LED cluster; and a driving unit configured to adjust a number of the LED groups connected to a current path of the LED cluster in series based on the input power to the LED cluster, wherein the plurality of LED groups comprise: a first LED group connected to the power source; and a second LED group connected to the first LED group in series; wherein the driving unit comprises: a plurality of switches, comprising: a first switch coupled between an output of the first LED group and ground; and a second switch coupled between an output of the second LED group and ground; and a controller configured to turn on one of the first and second switches individually based on the input power to the LED cluster; wherein the controller comprises: a first input connected to the power source to detect the input power; a first output connected to the first switch to turn on or off the first switch; and a second output connected to the second switch to turn on or off the second switch; wherein the controller is further configured to compare the input power to a first threshold level for turning on the first LED group only and a second threshold level for turning on the first and second LED groups simultaneously; and wherein the controller is further configured to turn on the first switch only when the input power is equal to or larger than the first threshold level and less than the second threshold level, and turn off the first switch and turn on the second switch when the input power is greater than the second threshold level.