Thermal management of active LEDs in consumer TV LED-LCD display

High end consumer-TVs use active LEDs in direct lit LCD-LED displays to enhance the viewing experience of the end customers. In direct-lit displays, 2D dimming and boosting are used to actively adapt the light from the display LEDs to the brightness distribution of the picture content, enabling the display of high dynamic range contrast video with brighter lights and darker blacks. The solder joint reliability and lifetime of the LEDs is an ongoing concern, therefore the dimming and boosting algorithms need to incorporate protective measures. In this work thermal management of active LEDs in a consumer TV LCD-LED display is discussed. Transient LED temperatures are investigated for different typical timescales and picture loads. The cycle time dependent temperature is subsequently applied to a simplified solder fatigue model (described elsewhere) incorporating the effect of short creep times, resulting in a typical solder joint damage expression as a function of boost time. This damage function is applied to a database of timescales typical for video picture loads, and different protection strategies are assessed as to their effect on the total damage over long viewing times. This enables the use of the time scale differences between the optical response of the LED, the thermal response of the LED and the resulting effect on the solder creep mechanism, to ensure an enhanced consumer viewing experience at no additional cost to the display LED solder joints lifetime.