The current challenge of how to achieve high performance design of LCD industrial LCD driver circuit is an important and huge challenge. This article analyzes the classification and performance characteristics of industrial LCDs, introduces the key components LDO and white LED selection points, and the design method of charge pump LED driver circuit.
The internal structure of the TFT-LCD color module is a LCD industrial LCD composed of polarizer, glass and liquid crystal, below which are white LEDs and backlight board, including LCD driver IC and low voltage difference regulator (LDO) which provides a stable power supply to the LCD driver IC, 2-8 white LEDs and LED driver boost regulator IC.
TFT-LCD color screen module circuit design structure principle, external power supply Vcc after LDO buck regulator, to provide operating voltage to the LCD driver IC such as S6B33BOA, drive color STN-LCD LCD graphics and text; external power supply Vcc by charge pump boost regulator, to provide constant voltage, constant current white LED such as NACW215 / NSCW335 Power supply, LED white light reflected by the backlight board, so that the LCD 65K color fully expressed, the brightness of the LED directly affects the LCD color of the beautiful degree.
LCD belongs to a kind of flat panel display, according to the drive mode can be divided into static drive (Static), simple matrix drive (Simple Matrix) and active matrix drive (Active Matrix) three. Among them, the simple matrix type can be divided into Twisted Nematic (TN), Super Twisted Nematic (STN), and other passive matrix-driven LCDs. Active matrix type can be broadly distinguished as thin film transistor (ThinFilmTransistor, TFT) and two terminal diode (Metal/Insulator/Metal, MIM) two kinds. The advantages and disadvantages of the difference, so that its application in the product range classification also has obvious differences. In terms of the current scope and level of application of liquid crystal display technology, active matrix drive technology is the mainstream of thin-film transistor type, mostly used in notebook computers and animation, image processing products; simple matrix drive technology is currently based on the twisted nematic and STN, STN liquid crystal display through the color filter (color filter), can display red, green, blue three primary colors The STN LCD can display the red, green and blue primary colors separately through the color filter (colorfilter), and can display the true color in full color mode through the reconciliation of the three primary colors ratio. At present, the application of color STN-LCD is mostly based on cell phones, PDAs, digital cameras and video game consoles consumer products and word processing screens.
The choice of white LED backlight. According to the design requirements of the backlight, the need for front drop voltage (VF) and front drop current (IF) small, high brightness (500- To cell phone LCM, for example, are currently using 3-4 white LEDs, with the increase in LED brightness and cell phone manufacturers require lower costs and power consumption, it is expected that by mid-2004 LCM will choose two high-brightness white LEDs (1200-2000mcd), PDA and smart phones due to the LCD screen will be larger as needed to use 4-8 white LEDs. NACW215/NSCW335 and EL 99-21/215UCW/TR8 are white LEDs with reflectors, EL series whose brightness is divided into T, S, R three levels, T for 720-1000mcd, S for 500-720mcd, are in the cell phone LCD backlight for the list.
