LED backlight power protection circuit diagram
description:
LCD TV screens are bigger and brighter, they require more operating voltage and more operating current, and many circuit protection devices can be used to help protect the LCD display from excessive current or excessive voltage transients. Damage caused by the change. Overcurrent protection can be either a fuse or a resettable PPTC (Polymer Positive Temperature Coefficient) device. Which option to choose depends on the design of the LCD, the type of hazard the product may be exposed to and the associated safety requirements.
PPTC devices are generally suitable for circuits that experience large inrush currents during startup. PPTC devices withstand the impact of inrush currents and eliminate the need to replace burned fuses. The fuse is suitable for circuits that do not require self-recovery, or that cause an overcurrent surge only in the event of a system error. A fuse is also a practical solution when a soft-start circuit is used to limit inrush current.
How does TFT work?
TFT is the abbreviation of "Thin Film Transistor", generally refers to thin film liquid crystal displays, but actually refers to thin film transistors (matrix)-can "actively" control each independent pixel on the screen, which is The origin of the so-called active matrix TFT (active matrix TFT). So how exactly is the image produced? The basic principle is very simple: the Display Screen is composed of many pixels that can emit light of any color, and the purpose can be achieved by controlling each pixel to display the corresponding color. In TFT LCD, backlight technology is generally used. In order to accurately control the color and brightness of each pixel, it is necessary to install a shutter-like switch after each pixel. When the "blinds" are opened, light can pass through, and " When the shutters are closed, light cannot pass through. Of course, technically, it is not as simple as the one just mentioned. LCD (Liquid Crystal Display) utilizes the characteristics of liquid crystals (liquid when heated, and crystallized into solid when cooled). Generally, liquid crystals have three forms:
Smectic liquid crystal similar to clay
Nematic liquid crystal resembling a fine matchstick
Cholestic liquid crystal
The liquid crystal display uses filaments, and when the external environment changes, its molecular structure will also change, and thus have different physical properties-it can achieve the purpose of letting light through or blocking light-which is just like the blinds just now.
Everyone knows the three primary colors, so each pixel on the display screen needs three similar basic components described above to control the three colors of red, green, and blue respectively.
The most commonly used one is twisted nematic TFT LCD (Twisted Nematic TFT LCD). Existing technologies vary greatly, and we will cover them in detail in the second part of this article.
There are grooves on the upper and lower layers. The grooves on the upper layer are arranged longitudinally and the grooves on the lower layer are arranged horizontally. When no voltage is applied to the liquid crystal in its natural state, the light emitted from the light emitting layer of the twisted nematic TFT Display working principle diagram of Figure 2a will be twisted by 90 degrees after passing through the interlayer, so that it can pass through the lower layer smoothly.
When a voltage is applied between the two layers, an electric field is generated. At this time, the liquid crystals are aligned vertically, so the light will not be twisted-the result is that the light cannot pass through the lower layer.
(2) TFT pixel structure: The color filter is divided into red, green, and blue according to the color, which are arranged on the glass substrate to form a group (dot pitch) corresponding to a pixel. Each monochromatic filter is called It is a sub-pixel. In other words, if a TFT display supports a maximum resolution of 1280×1024, then at least 1280×3×1024 sub-pixels and transistors are required. For a 15-inch TFT display (1024×768), then a pixel is about 0.0188 inches (equivalent to 0.30mm), for an 18.1-inch TFT display (1280×1024), it is 0.011 inches (equivalent to 0.28mm) .
As we all know, pixels are decisive for the display. The smaller each pixel is, the larger the maximum resolution that the display can achieve. However, due to the limitation of the physical characteristics of the transistor, the size of each pixel of the TFT at this stage is basically 0.0117 inches (0.297mm), so for a 15-inch display, the maximum resolution is only 1280×1024.
Tft Lcd Module,Lcd Liquid Crystal Display Module,Lcd Module,Lcd Screen Module
ESEN Optoelectronics Technology Co., Ltd, , https://www.esenoptoelectronics.com