Color control in RGB driver system applicable to LED of all ageing conditions

Abstract

This paper presents a method of controlling the white color point in red/green/blue (RGB) LED driver system. In contrast to conventional systems where the average driving currents of the primary-color LEDs can become saturated when the LEDs have sufficiently aged, and causes the resulting white color point to go out of regulation, the proposed method avoids this problem by adjusting the color set points when a predefined threshold current is reached by one or more of the primary-color LEDs. It is shown that the method can effectively maintain the white color point of the RGB LED at the desired value when the LEDs are subjected to an accelerated ageing through repetitive current stress cycles.