Thermal consideration in LED array design for LCD backlight unit applications

Thermal effects were investigated in a liquid crystal display (LCD) backlight unit (BLU) that was composed of light emitting diode (LED) arrays. The driving power for a single LED in a BLU is determined by the desired brightness of the LCD panel and the pitch distance between adjacent LEDs. As the pitch distance increases, individual LEDs need to be driven by a higher power in order to maintain the same brightness. Since the junction temperature of an LED plays an important role in LED performance, such as optical efficiency, intensity degradation, and lifetime, the maximum driving power for an LED should be limited by a critical level of the junction temperature. A guideline for designing LED BLU panels taking account of the junction temperature is presented using various parameters of LED arrays.