Energy efficient current control technique for driving high power LEDs

Inhalt:
This paper presents a concept of an energy efficient current controller for high power light emitting diodes (LEDs) and compares it to a typical current regulator employing a series sensing resistance in the main LED path. In contrast to conventional control techniques, the proposed concept supersedes the sensing resistor in the high current path of the power LEDs. In fact, a replica of the LED current is generated in a low power sensing branch. Hence, losses can be minimized and power efficiency increases. A transistor width ratio determining the current replica ratio of about 1:5300 can be achieved while nominal current precision of 1% is maintained. It is shown that the energy losses in the sensing unit can be reduced from approximately 49mW to about 4mW for driving high power LEDs at a maximum drive current of about ILED = 700 mA.