Research Of Dynamic Backlight Technique For Large-scale Lcd Tvs

LED Dynamic Backlight of LCD TV has become the mainstream of research and application for its low energy consumption and high contrast. Especially, 2D white LED dynamic backlight technology has got more and more attention and become the study focus because of its simple circuit structure and high performance.This paper introduced the research significance and its current development status at home and abroad, the principle and methods of the dynamic backlight control technology. Combined with the characteristics of several dynamic backlight methods, 2D white LED dynamic backlight technology had been determined to be the key research points of this paper. Mainly, this paper researched and described the backlight brightness extraction algorithm and the hardware design algorithm for backlight image simulation, and designed the circuit structure of the dynamic backlight control system and completed the simulation and verification.Dynamic backlight brightness extraction algorithm is the core of the entire system and it affects the advantage and disadvantage of LCD TV display quality. This paper introduced the average algorithm, mean square value algorithm, the backlight enhancement algorithm for dark scene image and IMF backlight algorithm mentioned in several papers. A backlight brightness extraction algorithm based on the threshold of image CDF (Cumulative Distribution Function) was proposed in this paper after analyzing these algorithms above-mentioned. Through subjective and objective comparison and analysis, CDF threshold algorithm shows its good stability.Backlight image simulation is the most complex part of the dynamic backlight control system. How to design the hardware circuit to realize the real-time simulation of current LCD TV backlight images affects the feasibility of 2D dynamic backlight technology and is also the most critical part. Through experimental analysis, a hardware design algorithm based on image scaling- convolution was proposed. And it made the real-time backlight image simulation possible using limited hardware resources.Finally, the backlight control system structure was designed in this paper according to the backlight control principle, and the RTL-level hardware description using Verilog HDL language was completed. The Joint Simulation and Verification based on Quartus II, ModelSim and MATLAB were also accomplished. In this paper, the hardware design of the backlight brightness extraction module and the backlight image simulation module were described importantly. And this paper introduced the 2-D convoluter, the bi-linear scaling module, the access controller of image datas, DDR SDRAM controller, the image conpensation module and LVDS interfaces in detail and introduced the verification of every module. The results showed that the circuit designed in this paper was functional and needed the design requirement.