Effect of optical design on the thermal management for the Smart TV LED backlight systems

Abstract

Due to recent advances in electronics, lighting and communication technologies, SMART Televisions (TV) have become more affordable, and are rapidly replacing old-fashioned LCD (liquid crystal display) TV technologies. These TVs are nearly ten times thinner; they include much brighter displays, true-color qualities, at least two times faster refresh rates and smart communication features. While providing such advanced features, lighting has become a critical part of technology advancement. While the backlight unit consumes over 50% of total energy in TVs, light emitting diodes (LEDs) have rapidly replaced the conventional CCFL (Cold Cathode Fluorescent Lamp) based LCD backlight units due to their low energy consumption. The present study identifies the impact of optical solutions with high-power LEDs located at the corner of the backlight unit on the optical efficiency for an advanced TV system. Various optical designs are created and impacting metrics for novel LED backlight units are determined. A computational and experimental study has been performed to identify the optical-thermal interactions in a tight-space LED packaging for a slim TV. Optical modeling has been performed via Light Tools optical simulation software, while thermal modeling was performed via Icepak CFD software. Smart optical packaging resulted in an effective light distribution of minimum 75% brightness uniformity, with no MURA effect problem on the panel The thermal challenge was found to be immense; so a smart thermal packaging was vital. An experimental validation of computational models was also performed. While the target is obtaining a uniform light distribution generated by HB (high brightness) LEDs and reduction of cost by having fewer LEDs, optical structure is found to be very critical in terms of both optical efficiency and pattern design of the light guide plate (LGP), which is an essential part of slim LED TVs. The study is concluded with a detailed discussion of the impact on luminance uniformity and cost for advanced SMART TVs.