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The objective of this study is to design a novel cone-shaped lens cap on LEDs in order to achieve high optical efficiency in an ultra-thin directly lit RGB LED backlight unit (BLU) for large-sized LCD TVs. The use of the novel lens cap could play the role of a diffuser, a low light-efficiency component in a BLU, in order to gain higher efficiency and simultaneously provide satisfactory uniformity in light distribution. The novel cone-shaped lens is coated with aluminum on the outside surface of the cone for mirroring effects to reflect most of the LED emitted light horizontally and then reflect the light at the BLU boundaries, and then, finally to the output plane. In this way, bright spots on the output plane of the BLU can be avoided, leading to increased uniformity. Simulations were conducted to design and optimize varied aspects of the designed lens and BLU, including the cone angle of the proposed lens and the LED spacing (pitch). To further achieve color balance, a known Genetic Algorithm is used to search for the optimal angular placement of each RGB LED, resulting in better color balance. Finally, a prototype BLU for large-sized 37-in. LCD TVs with the proposed lens was built to verify the expected performance. FIGURE 1 -Illustration of directly lit LED backlight units: (a) An ordinary LED BLU; (b) a BLU with the proposed novel cone-shaped LED lenses. Journal of the SID 16/2, 2008FIGURE 7 -Measured intensity profiles for three different novel cone-shaped lenses.FIGURE 8 -The TracePro ray-tracing model for the BLU.FIGURE 9 -Spectrum reflectances of the coated and white reflectors. Journal of the SID 16/2, 2008

The objective of this study is to develop a high color balance thin RGB LED backlight unit (BLU) for large‐Sized LCD‐TVs. Genetic Algorithm is employed to search the optimal angular placement of each RGB LED and gain the condition of better color mixing for achieving high color balance of BLU.

This study presents a universal lighting driver for unknown connected light emitting diode (LED) arrays by using a single-ended primary inductor converter (SEPIC) DC/DC converter and a T-S fuzzy model-based current controller. Driving and lighting an LED array with unknown series and parallel connection is a significant research for universal adaptable applications. To this end, the input voltage of the LED array is up/down adjusted by the SEPIC DC/DC converter, whereas exact LED lighting current control is realised by the proposed T-S fuzzy parallel distributed integral compensation control method. For easier implementation, a linear-simplified fuzzy observer is introduced under output feedback. Asymptotic convergence is guaranteed by strict stability analysis and linear matrix inequality gain design. Moreover, the fuzzy lighting current controller does not require the electrical model and arrangement of the LED array. In addition, even if we take uncertainty, disturbance and rapidly changing reference current into consideration, the high robustness and transient response performance are still assured via robust gain design. Finally, the satisfactory performance is shown from experimental results.