[list] [*]Regards, [*] Power Supply. They generally operate with a preset output voltage, both with and without connected load. [*] Driver. Constant current drivers are usually used, the output voltage varies slightly depending on the number of connected LEDs. [*] Driver variable . It allows to adjust the level of output intensity, then working the LED with different powers. [*] Constant voltage. This solution, in LED lighting, reduces the overall system performance. It is not recommended. [*] Constant current . The LED works with a fixed current, within an acceptable range. When it varies, the power varies. This output current is fixed and independent of the number of connected LEDs, within the capacity and power of the driver. [*] Direct voltage (without external driver). Only some LEDs use this technology. It has advantages but also disadvantages. [/list]