Color control system for RGB LED with application to light sources suffering from prolonged aging

This paper presents a unified approach to controlling the white color point of the red/green/blue (RGB) light-emitting diode (LED) existing in all aging states. In contrast to conventional color control systems where the average driving currents of the primary-color LEDs can become saturated when the LEDs have undergone prolonged aging, which 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 RGB LED at the desired value when the primary-color LEDs are subjected to an accelerated aging through repetitive current stress cycles.