中国内地白牌电视窜起

LCDs Utilizing FPGAs and New Technologies to Enter HDTV Market
Tam Do, Altera Corporation, Senior Technical Marketing Manager,
Broadcast/Consumer Applications Business Unit
High definition TV (HDTV) represents the new frontier for liquid crystal display (LCD) technology, requiring higher resolution than previous LCD standards which, in turn, increases data rate and power consumption. As the data rate accelerates, faster moving video requires special image processing algorithms. These algorithms can be implemented into field programmable gate arrays (FPGAs) in order to properly convert and map the digital video signal onto the display panel.
FPGAs give LCD designers the flexibility required to reconfigure image processing algorithms, accommodating the increasing data rate for different LCD sizes while maintaining the same hardware platform for all products. Specifically in the digital consumer market, FPGAs can provide an effective blend of cost, performance and flexibility for digital televisions and displays. Manufacturers of LCD TVs leverage FPGAs for time-to-market benefits, as the competition to get products into retail outlets quickly is particularly fierce.
An LCD system can be designed around an FPGA in which the FPGA co-processor, running a real-time embedded operating system, controls the complete display apparatus. Besides the central control of the display, designers can use FPGAs in the data path for specific processing. For instance, FPGAs are ideal for optional display features, where they perform real-time image scaling on the video stream.
The newer generations of FPGAs include optimized hard-coded digital signal processing (DSP) blocks, which form the basic elements of video and image processing. DSP blocks possess high-speed parallel processing capabilities ideal for implementing DSP applications, such as image processing, that require high data throughput.
The most commonly used DSP functions include finite impulse response (FIR) filters, complex FIR filters, fast Fourier transform (FFT), discrete cosine transform (DCT), and correlators. These functions are the building blocks for HDTV and other complex LCD applications.
System designers also benefit from incorporating FPGAs into their LCD systems because they can be reprogrammed throughout the life of the product. This critical ability allows designers to add features from one generation to the next without having to redesign the whole system.
New Technologies Overcome HDTV Obstacles
As HDTV continues to move into the mainstream of commercial television, key industry players have introduced specialized technologies that help incorporate LCD into the HDTV application.
National Semiconductor introduced low voltage differential signaling (LVDS) to reduce the amount of power and electromagnetic interference (EMI) associated with the high speed LCD interface. Flat panel display (FPD) is a National Semiconductor-defined LVDS-based link between a host panel and display panel in an LCD HDTV and monitor platform.
Reduced swing differential signaling (RSDS) is also a National Semiconductor-defined signaling standard primarily used for display applications with resolutions between VGAs and ultra extended graphic arrays UXGAs.
Texas Instruments also introduced a similar interface standard called mini-LVDS with the same objectives of reducing power and EMI. Flat link is a TI-defined LVDS-based link between a host panel and display panel in an LCD HDTV and monitor platform. The requirements for mini-LVDS interfaces are identical to that of RSDS, except that mini-LVDS assumes a center-aligned output clock under the AC timing requirements.

This interface is similar to that of the FPD link and is primarily used by LG, Philips, and Thomson for their LCD HDTV products. With the consumer appetite for larger and larger TV displays, current interface technology may still have its limitations when designers try to design circuit boards and traces in order to meet signal integrity. The latest interface called PPDS by National Semiconductor is aimed at the larger LCD display. Table 1 summaries the differences between the display panel technologies.

Fig. 1 shows a typical digital LCD TV block diagram. The tuner module either can be a satellite, terrestrial or cable demodulator, followed by a MPEG2 decoder. Besides the signal from the digital TV tuner, a typical LCD TV also provides external video input such as DVI (Digital Visual Interface) or HDMI (High Definition Multimedia Interface), analog RGB, CVBS, S-video, and component video.
The LCD HDTV monitor must be able to handle various video input formats. Some formats may directly be mapped into the display while others must be rescaled for proper viewing.

The heart of the LCD HDTV is its image processing and timing control block. The image processing block typically includes functions such as scan rate converter, frame rate converter, color decoder, motion detection, scalar and de-interlacing. Fig. 2 shows a typical LCD TV interface block diagram.
The color response time of the LCD is slower and depends on the color content, which presents a challenge in designing an image processing algorithm that can eliminate any viewing artifact. FPGAs offer a critical time-to-market advantage with their design flexibility, allowing designers to re-design the algorithm within the device without having to re-program it.
Display manufacturers can differentiate from their competitors’ products by adding their own proprietary algorithms for true color and motion performance. There are two methods of proprietary video enhancement used for creating a true video performance from a LCD panel.
The first, a technique called temporal dithering, generates a true gray scale for different colors by rapidly switching the pixels between on and off over a certain time period. The second, spatial dithering, generates the exact amount of color intensity scale. Spatial dithering can cause spatial noise, or error diffusion; further filtering and fine tuning are required to correct this type of noise.
Conclusion
LCDs, originally designed for steady computer data text and graphics, now display fast moving video content over much larger display panels. This capability requires special image processing algorithms that can be implemented with FPGAs. LCD designers using FPGAs can also reconfigure these algorithms based on panel size within a standard hardware platform, which can help reduce manufacturing cost and speed time to market.
Major manufacturers have introduced technologies that help incorporate LCDs into HDTV commercial applications by overcoming power and electromagnetic obstacles. National Semiconductor’s low voltage differential signaling and reduced swing differential signaling, and Texas Instruments’ mini-LVDS, are two such technologies.
y utilizing FPGA flexibility for dynamic image processing and new technologies to help overcome power and EMI obstacles associated with HDTV, designers are well equipped to take LCD even further into leading-edge commercial TV and display applications.
SYSTEM BLOCK DIAGRAMS
TV: LCD/Digital

CCFL Backlight Converter - CCFL Backlight Unit
DC/DC Converters (Integrated Switch)
Inductorless DC/DC Regulators (Charge Pumps)
DC / DC Buck Controller - Analog / Digital I/O
DC/DC Converters (Integrated Switch)
Single Channel LDO
DC / DC Controller - LED Supply
DC/DC Converters (Integrated Switch)
Inductorless DC/DC Regulators (Charge Pumps)
Dual Output LDO
Analog & Mixed-Signal
Power Management Multi-Channel IC (PMIC) Solutions
Gamma Correction Buffer
High Speed Amplifiers (Greater than equal to 50MHz)
LCD Gamma Buffers
Op-Amp stereo line-in L
Line Drivers / Receivers
Precision Amplifiers
Op-Amp stereo line-in R
Line Drivers / Receivers
Precision Amplifiers
Speaker Amplifier
Audio Amplifiers
Digital Audio Power Amplifiers
Speaker Amplifier
Audio Amplifiers
Digital Audio Power Amplifiers
Stereo Audio Codec
Audio Processors
CODECs
USB
USB Peripherals
USB Power Switches
USB Transient Voltage Suppressor
Digital television (DTV) broadcasts and receives digitally in contrast to the analog signals used in traditional TV. DTV, which can be received in standard-definition or high-definition formats, uses digital modulation data, which is digitally compressed and requires decoding by a specially designed television set or a standard receiver with a set-top box. DTV s rapid growth in popularity is spurred by the high-definition video quality as well as the availability of a variety of new features/services including video on demand (VoD), gaming, security, PVR, interactive TV, merchandising and Web browser capabilities. Texas Instruments has a long history of providing expertise and superior products to video market. TI s comprehensive solutions cover the entire video chain,everything from the initial capture of video content to the final viewing experience. TI provides a variety of products for DTV designs including DLP®, LCD and plasma formats which offer superior image, audio quality and better reception over analog.
Core Subsystem include:
DSP - performs MPEG encoder/decoder, video, voice/AC3/MPEG audio processing. RF Demodulation - performs COFDM/QAM/QPSK demodulation, Forward Error Correction (FEC) and video mux. MCU - controls system electronic, network, and user interface. Memory - stores executing code and data/parameters. Video Interface - selects video source to be decoded/encoded by ADC/DAC and DSP. Audio Interface - allows audio to be digitized by the audio codec and processed by DSP to provide high-quality audio for MPEG/AC3 requirements. LCD Interface - parallel digital video is converted into serial data for transmitting to the TFT (Thin Film Transistor) controller via the LVDS (Low-Voltage Differential Signaling) transmitters and receivers. The LCD display is controlled by the CCFL (Cold-Cathode Fluorescent Lamp) backlight and the TFT gate/source drivers. Power Conversion - converts the input power from the AC adaptor to run various functional blocks.Digital Power Solutions
Learn About LCD TV and TFT LCD Displays
TFT LCD TV - What is TFT LCD?
History of TFT LCD
Liquid crystal was discovered by the Austrian botanist Fredreich Rheinizer in 1888. "Liquid crystal" is neither solid nor liquid (an example is soapy water).
In the mid-1960s, scientists showed that liquid crystals when stimulated by an external electrical charge could change the properties of light passing through the crystals.
The early prototypes (late 1960s) were too unstable for mass production. But all of that changed when a British researcher proposed a stable, liquid crystal material (biphenyl).
Today‘s color LCD TVs and LCD Monitors have a sandwich-like structure (see figure below).

What is TFT LCD?
TFT LCD (Thin Film Transistor Liquid Crystal Display) has a sandwich-like structure with liquid crystal filled between two glass plates.

TFT Glass has as many TFTs as the number of pixels displayed, while a Color Filter Glass has color filter which generates color. Liquid crystals move according to the difference in voltage between the Color Filter Glass and the TFT Glass. The amount of light supplied by Back Light is determined by the amount of movement of the liquid crystals in such a way as to generate color.
TFT LCD - Electronic Aspects of LCD TVs and LCD Monitors
Electronic Aspects of AMLCDs
The most common liquid-crystal displays (LCDs) in use today rely on picture elements, or pixels, formed by liquid-crystal (LC) cells that change the polarization direction of light passing through them in response to an electrical voltage.
As the polarization direction changes, more or less of the light is able to pass through a polarizing layer on the face of the display. Change the voltage, and the amount of light is changed.
There are two ways to produce a liquid-crystal image with such cells: the segment driving method and the matrix driving method.
The segment driving method displays characters and pictures with cells defined by patterned electrodes.
The matrix driving method displays characters and pictures in sets of dots.
Direct vs. multiplex driving of LCD TVs.

The segment drive method is used for simple displays, such as those in calculators, while the dot-matrix drive method is used for high-resolution displays, such as those in portable computers and TFT monitors.
Two types of drive method are used for matrix displays. In the static, or direct, drive method, each pixel is individually wired to a driver. This is a simple driving method, but, as the number of pixels is increased, the wiring becomes very complex. An alternative method is the multiplex drive method, in which the pixels are arranged and wired in a matrix format.
To drive the pixels of a dot-matrix LCD, a voltage can be applied at the intersections of specific vertical signal electrodes and specific horizontal scanning electrodes. This method involves driving several pixels at the same time by time-division in a pulse drive. Therefore, it is also called a multiplex, or dynamic, drive method.
Passive and Active Matrix LCDs
There are two types of dot-matrix LCDs.
Passive-matrix vs. active-matrix driving of LCD Monitors.

In passive-matrix LCDs (PMLCDs) there are no switching devices, and each pixel is addressed for more than one frame time. The effective voltage applied to the LC must average the signal voltage pulses over several frame times, which results in a slow response time of greater than 150 msec and a reduction of the maximum contrast ratio. The addressing of a PMLCD also produces a kind of crosstalk that produces blurred images because non-selected pixels are driven through a secondary signal-voltage path. In active-matrix LCDs (AMLCDs), on the other hand, a switching device and a storage capacitor are integrated at the each cross point of the electrodes.
The active addressing removes the multiplexing limitations by incorporating an active switching element. In contrast to passive-matrix LCDs, AMLCDs have no inherent limitation in the number of scan lines, and they present fewer cross-talk issues. There are many kinds of AMLCD. For their integrated switching devices most use transistors made of deposited thin films, which are therefore called thin-film transistors (TFTs).
The most common semiconducting layer is made of amorphous silicon (a-Si).
a-Si TFTs are amenable to large-area fabrication using glass substrates in a low-temperature (300°C to 400°C) process.
An alternative TFT technology, polycrystalline silicon - or polysilicon or p-Si-is costly to produce and especially difficult to fabricate when manufacturing large-area displays.
Nearly all TFT LCDs are made from a-Si because of the technology‘s economy and maturity, but the electron mobility of a p-Si TFT is one or two orders of magnitude greater than that of an a-Si TFT.
This makes the p-Si TFT a good candidate for an TFT array containing integrated drivers, which is likely to be an attractive choice for small, high definition displays such as view finders and projection displays.
Structure of Color TFT LCD TVs and LCD Monitors
A TFT LCD module consists of a TFT panel, driving-circuit unit, backlight system, and assembly unit.
Structure of a color TFT LCD Panel:
LCD Panel
- TFT-Array Substrate
- Color Filter Substrate
Driving Circuit Unit
- LCD Driver IC (LDI) Chips
- Multi-layer PCBs
- Driving Circuits
Backlight & Chassis Unit
- Backlight Unit
- Chassis Assembly
It is commonly used to display characters and graphic images when connected a host system.
The TFT LCD panel consists of a TFT-array substrate and a color-filter substrate.
The vertical structure of a color TFT LCD panel.

The TFT-array substrate contains the TFTs, storage capacitors, pixel electrodes, and interconnect wiring. The color filter contains the black matrix and resin film containing three primary-color - red, green, and blue - dyes or pigments. The two glass substrates are assembled with a sealant, the gap between them is maintained by spacers, and LC material is injected into the gap between the substrates. Two sheets of polarizer film are attached to the outer faces of the sandwich formed by the glass substrates. A set of bonding pads are fabricated on each end of the gate and data-signal bus-lines to attach LCD Driver IC (LDI) chips
Driving Circuit Unit
Driving an a-Si TFT LCD requires a driving circuit unit consisting of a set of LCD driving IC (LDI) chips and printed-circuit-boards (PCBs).
The assembly of LCD driving circuits.

A block diagram showing the driving of an LCD panel.

To reduce the footprint of the LCD module, the drive circuit unit can be placed on the backside of the LCD module by using bent Tape Carrier Packages (TCPs) and a tapered light-guide panel (LGP).
How TFT LCD Pixels Work
A TFT LCD panel contains a specific number of unit pixels often called subpixels.
Each unit pixel has a TFT, a pixel electrode (IT0), and a storage capacitor (Cs).
For example, an SVGA color TFT LCD panel has total of 800x3x600, or 1,440,000, unit pixels.
Each unit pixel is connected to one of the gate bus-lines and one of the data bus-lines in a 3mxn matrix format. The matrix is 2400x600 for SVGA.
Structure of a color TFT LCD panel.

Because each unit pixel is connected through the matrix, each is individually addressable from the bonding pads at the ends of the rows and columns.
The performance of the TFT LCD is related to the design parameters of the unit pixel, i.e., the channel width W and the channel length L of the TFT, the overlap between TFT electrodes, the sizes of the storage capacitor and pixel electrode, and the space between these elements.
The design parameters associated with the black matrix, the bus-lines, and the routing of the bus lines also set very important performance limits on the LCD.
In a TFT LCD‘s unit pixel, the liquid crystal layer on the ITO pixel electrode forms a capacitor whose counter electrode is the common electrode on the color-filter substrate.
Vertical structure of a unit pixel and its equivalent circuit

A storage capacitor (Cs) and liquid-crystal capacitor (CLC) are connected as a load on the TFT.
Applying a positive pulse of about 20V peak-to-peak to a gate electrode through a gate bus-line turns the TFT on. Clc and Cs are charged and the voltage level on the pixel electrode rises to the signal voltage level (+8 V) applied to the data bus-line.
The voltage on the pixel electrode is subjected to a level shift of DV resulting from a parasitic capacitance between the gate and drain electrodes when the gate voltage turns from the ON to OFF state. After the level shift, this charged state can be maintained as the gate voltage goes to -5 V, at which time the TFT turns off. The main function of the Cs is to maintain the voltage on the pixel electrode until the next signal voltage is applied.
Liquid crystal must be driven with an alternating current to prevent any deterioration of image quality resulting from dc stress.
This is usually implemented with a frame-reversal drive method, in which the voltage applied to each pixel varies from frame to frame. If the LC voltage changes unevenly between frames, the result would be a 30-Hz flicker.
(One frame period is normally 1/60 of a second.) Other drive methods are available that prevent this flicker problem.
Polarity-inversion driving methods.

In an active-matrix panel, the gate and source electrodes are used on a shared basis, but each unit pixel is individually addressable by selecting the appropriate two contact pads at the ends of the rows and columns.
Active addressing of a 3x3 matrix

By scanning the gate bus-lines sequentially, and by applying signal voltages to all source bus-lines in a specified sequence, we can address all pixels. One result of all this is that the addressing of an AMLCD is done line by line.
Virtually all AMLCDs are designed to produce gray levels - intermediate brightness levels between the brightest white and the darkest black a unit pixel can generate. There can be either a discrete numbers of levels - such as 8, 16, 64, or 256 - or a continuous gradation of levels, depending on the LDI.
The optical transmittance of a TN-mode LC changes continuously as a function of the applied voltage.
An analog LDI is capable of producing a continuous voltage signal so that a continuous range of gray levels can be displayed.
The digital LDI produces discrete voltage amplitudes, which permits on a discrete numbers of shades to be displayed. The number of gray levels is determined by the number of data bits produced by the digital driver.
Generating Colors
The color filter of a TFT LCD TV consists of three primary colors - red (R), green (G), and blue (B) - which are included on the color-filter substrate.
How an LCD Panel produces colors.

The elements of this color filter line up one-to-one with the unit pixels on the TFT-array substrate.
Each pixel in a color LCD is subdivided into three subpixels, where one set of RGB subpixels is equal to one pixel.
(Each subpixel consists of what we‘ve been calling a unit pixel up to this point.)
Because the subpixels are too small to distinguish independently, the RGB elements appear to the human eye as a mixture of the three colors.
Any color, with some qualifications, can be produced by mixing these three primary colors.
The total number of display colors using an n-bit LDI is given by 23n, because each subpixel can generate 2n different transmittance levels.
TFT LCD - TFT Device Design
TFT Device Design
There are many structures for thin-film transistors (TFTs), with the first major distinction among them being planar CMOS structures vs. staggered amorphous-silicon (a-Si) structures.
Structure of TFT electrodes

The a-Si TFTs are further divided into staggered and inverse-staggered types.
Structural difference between top- and bottom-gate TFTs

In the inverse-staggered type, the ohmic layer (n+ a-Si) in the channel region can either be etched directly (the etch-back method) or etched by forming a protective film on the a-Si thin film (the etch-stopper method).
Each method has its own set of advantages and disadvantages. The inverse-staggered structure offers a relatively simple fabrication process and an electron mobility that is about 30 percent larger than that of the staggered type. These advantages have resulted in the bottom-gate TFT structure becoming more widely adopted in TFT-LCD design, despite the fact that it‘s technically an upside-down structure.
Because a-Si has photoelectric characteristics, the a-Si TFT must be shielded from incident light .The a-Si layer must also be as thin as possible to minimize the generation of photo-induced current, which can cause the TFT to malfunction.
Reduction of photo-induced leakage current in a TFT

In the top-gate structure, a light-shield layer must first be formed at the region of the TFT channel The formation of this light shield may cause an extra process step. In bottom-gate TFTs, on the other hand, a gate electrode is first formed at the TFT channel region, where it also serves as a light-shield layer.
Light-shielding structures in a TFT-Array

Design Parameters for TFT Arrays
The operational characteristics of a TFT are determined by the sizes of its electrodes, the W/L ratio, and the overlap between the gate electrode and the source-drain .
Design of an a-Si TFT

The parasitic capacitances resulting from the overlap of electrodes can not be avoided in staggered TFT structures, but the parasitic effects must be minimized to maximize the LCD‘s performance.
To reduce the overlap between the electrodes, a self-align process is often implemented .
Minimizing parasitic capacitance in TFTs

It turns out that the characteristics of the a-Si TFTs used in AMLCDs are very similar to the characteristics of the MOSFETs in semiconductor devices.
I-V Characteristics of an a-Si TFT and its operating points

When a TFT panel is operated under real-world conditions, the gate voltage is set at either 20 V for switch-on, or at -5 V for switch-off. Under these operating conditions, the a-Si TFT is a good switching device with an on/off current ratio larger than 106.
The performance of the TFT also depends on fabrication process parameters, such as electron mobility and thickness of the gate insulators. If we wish to increase the current gain of the TFT for better pixel-switching performance, and the process parameters are fixed, the only thing we can do is increase the W/L ratio. But doing this is not without a significant trade-off: The larger W/L results in a lower aperture ratio - less of the pixel‘s area is transparent to light when the pixel is ON - so the display‘s brightness and contrast are reduced.
Storage Capacitor Design
To maintain a constant voltage on a charged pixel over the entire frame cycle, a storage capacitor (Cs) is fabricated at each pixel. A large Cs can improve the voltage holding ratio of the pixel and reduce the kickback voltage, with resulting improvements in contrast and flicker, but a large Cs results in a lower aperture ratio and higher TFT load.
The storage capacitor can be formed by using either an independent storage-capacitor electrode or part of the gate bus-line as a storage-capacitor electrode (Cs-on-gate method)
Example of an independent-Cs design and equivalent circuit

Example of a Cs-on-gate design and equivalent circuit

The advantages of the Cs-on-gate method are that it eliminates the need for modification in the fabrication process; it minimizes the number of processes; and it produces a larger aperture ratio than does the independent Cs method. But few things are free in TFT-LCD design. The trade-off with the Cs-on-gate method is an increase in the RC time constant of the gate bus-line, which reduces the TFT switching performance.
This RC delay problem can have serious effects on the appearance of the display.
RC delay of a gate signal and its effect on a black display

The solution lies in fabricating the gate bus-line with a low-resistance material such as aluminum (Al).
Signal Bus-line Design
The requirement that the gate bus-line must have a small RC time delay is particularly important for larger and higher-resolution LCDs. If the widths of the signal bus-lines are increased to reduce resistance, the aperture ratio of the pixels is reduced, so the preferred approach is to use a low-resistance material for the bus-lines. For this, Al offers advantage over other metals, such as Cr, W, and Ta.
But, in the bottom-gate TFT process, the gate electrodes are first fabricated on the glass substrate and then subjected to high-temperature processes and various chemical etches. So, to use Al as a gate-electrode material, the Al gate electrodes must be protected from damage produced by hillock formation.
Design of low-resistance aluminum gate bus-line

A thin film of an aluminum oxide (Al2O3), formed by anodic oxidation of the Al surface at room temperature, can protect the Al electrodes from the problems associated with hillock formation. Double-metal or clad structures over the Al electrodes - using a relatively stable material such as Cr, Ta, or W - can also be used to protect the Al electrodes. The trade-off is that these approaches require an additional process. Recently, Al alloy (such as Al-Nd), which can suppress hillock formation, has been used as a gate-electrode material to eliminate the additional process.
Aperture Ratio
As implied previously, another important design consideration is maximizing the aperture ratio of the pixel. In the unit cell, TFT electrodes, storage-capacitor electrodes, signal bus-lines, and the black-matrix material constitute opaque areas.
Opaque areas and aperture ratio of a pixel

The combined areas of these elements, along with the area of the pixel aperture through which light can pass, determine the aperture ratio of the pixel. The aperture ratio is given by the area of the pixel aperture divided by the total pixel area (aperture area plus the area of the opaque elements). To increase the aperture ratio as much as possible, the size of the opaque elements must be made as small as possible, while maintaining a design that maximizes the size of the pixel-electrode area.
Unfortunately, one can only go so far in reducing the opaque areas before degrading image quality and yield. As shown in Fig. 12, the light-shield area on the color-filter substrate must be extended to block the light leaking through the gap between the data-line and the pixel ITO. To do this in conventional TFT-LCD cell structures, while simultaneously providing an adequate plate-alignment margin, significantly reduces the aperture.
But far higher aperture ratios can be achieved by switching from a conventional structure to the BM-on-Array structure, regardless of the accuracy of the plate alignment. The aperture ratio of this cell structure is not determined by the BM opening at the color filter substrate, but by the BM-on-Array, which can be formed with a very high positioning accuracy.
Improvement of aperture ratio using a black-matrix-on-TFT-array

In an independent-Cs-electrode design, the aperture ratio can be increased if the storage-capacitor electrode is fabricated using ITO.
Improvement of aperture ratio using an ITO layer as a Cs electrode

Design for Redundancy
Even when the greatest care is taken and sophisticated quality-management procedures are applied, it is not possible to make the TFT-array fabrication process so perfect that it produces only completely defect-free arrays.
Possible line and pixel defects on a TFT array

To improve the production yield in the fabrication process, redundancy design, repairable design, and fault-tolerant designs are often used. Dual-bus-line design or double-metal structure can help recover from problems of line breakage. Dummy-repair-line design can save the defective panel from data-bus-line open failures. While these redundant-design techniques can effectively improve fabrication yield, in some cases they can also reduce the aperture ratio.
The TFT-array must be protected from electrostatic discharge (ESD), which can be generated in the fabrication processes such as during the rubbing of the alignment layer and spin-drying. Design approaches for protecting the TFT-array against ESD include bus-line shorting and ESD protection circuits.
ESD protection using a bus-line shorting method

ESD protection using protection circuits

We would like to express our appreciation to Samsung Electronics for the preceding information.
About LCD TV Technology
What is TFT lcd?
fabricating TFT LCD‘s
TFT LCD device design
LCD precautions and failure
http://www.lcd-tv-reviews.com/pages/tft_device_design.php
中国内地白牌电视窜起 台厂扮要角
（王君毅／台北） 2008-7-17
中国内地继白牌手机后，白牌电视(当地称山寨平板电视)市场亦开始风起云涌，尤其在台系面板厂、IC业者等帮衬下，让当地白牌电视价格较中国内地国产品牌同尺寸机种便宜约4~5成，成为液晶电视厂关注焦点。电视品牌业者对此指出，中国内地白牌电视窜出，对品牌业者销售与市场势必造成冲击，然不同于手机，在产品定位及使用习性等考虑下，中国内地白牌电视市占率短期内欲大幅提升，仍有先天限制。
中国内地白牌电视产业链在广州、深圳等地渐具规模，发展过程与白牌手机如出一辙，中国内地媒体报导指出，目前在广州深圳等地白牌电视组装厂超过200多家，年产能逾150万台，相当于TCL、创维等业者1年出货量，在台厂电视译码驱动技术与板卡制造技术等支持下，配合次级面板与机壳取得，就可组装出薄型电视。白牌电视推出，已对娱乐场所如KTV等电视市场造成冲击，势力并逐渐潮3、4级城市挺进。
由于白牌电视无需支付专利、开发成本等费用，售价更低，平均较当地国产品牌便宜约4~5成，其中，32英寸液晶电视售价人民币2,500~2,950元，40英寸产品则约人民币3,500~4,000元。事实上，白牌电视组装厂风起云涌，与联发科等业者提供标准化且低成本电视芯片，以及南海奇美电子与华映深圳模块厂产能开出，有相当关联性。
不过，白牌电视窜出，是否如白牌手机般大幅冲击正规军产品销售，对此品牌电视业者认为，不同于手机消费模式，由于消费者过去汰换CRT电视平均时间约5~7年，且收看时间长，相对让消费者对电视质量要求较高，因此，较无质量保障的白牌电视欲拿下高市占率，仍有其难度。
此外，尽管白牌电视具有价格优势，但品牌业者电视价格同样快速滑落，且不同于手机除通话外，仍强调造型、新功能(如收看电视、MP3、MP4播放)等特色，消费者对于电视要求多落在画质与质量表现，在产品诉求差异性小，而质量又成为电视购买指针等前提下，是白牌电视先天限制所在。
对中国国产品牌而言，除白牌电视窜出外，国际大厂如Sony、三星电子(Samsung Electronics)等电视售价快速降低，中国国产品牌腹背受敌，后续经营恐将日益困顿。
液晶电视市场版图不变 代工业者忧喜参半
2008年07月08日 10:43
自2008年第2季度因一线液晶电视(LCDTV)品牌业者发动更犀利价格战，让液晶电视市场版图重新洗牌，面板业者指出，以北美市场为例，从渠道及客户端反应得知，第2季度三星电子(SamsungElectronics)与Sony等品牌大厂液晶电视销售量呈现亮丽增长性，但这亦相对挤压其它品牌业者如东芝(Toshiba)、飞利浦(Philips)、LG电子(LGElectronics)等业者出货，而经由液晶电视市占板块消长，也让台系代工厂出现大小程度不等的影响。
终端业者指出，品牌大厂为因应液晶电视价格快速下跌，对外释出代工订单比重逐渐提高，目前除东芝液晶电视下单给仁宝等业者，飞利浦与冠捷等业者配合，Sony有订单下给纬创与鸿海，LG则下单给佳世达等业者。而因应Sony、三星液晶电视价格纷达到甜蜜点，已让其它品牌业者出货量能降低，亦连带使得相对应的台代工厂出现程度不等的冲击。
然终端业者亦强调，目前代工厂订单短期波动，仍未到最后分出胜负阶段，主因在于虽受到品牌大厂发动价格战挤压，短期内让二线品牌业者受创，但随着2008年下半年电视需求旺季到来，二线品牌业者为强化成本实力，对台下单量亦可望增加，如此或许代工厂可因祸得福。
此外，虽然Sony等业者因拉低电视价格而带动出货翻扬，但观察过去Sony在台电视销售，当其32英寸电视压低到新台币2.99万元（约合人民币7475元）新低价位时，虽然引领其于次月冲上台湾电视出货宝座，但渠道业者反应，由于最低价产品性价比过低，难与Sony强势品牌直接连结，加上店头门市服务人员解说推荐，让消费者转买向上1个等级，且同样降价促销的同品牌液晶电视，使得当时Sony主打最低价U系列32英寸电视，销售量不如上1等级产品。
值得注意的是，台厂替品牌大厂代工低价液晶电视扮演双重角色，其一可直接刺激销售动能，其二可提供消费者来店购买电视诱因，且转买相关系列产品，而最低价电视也可能非卖得最好产品，加上其它代工厂抢单更趋积极，杀价抢单情况更严重，此也意味代工厂压力增加。
电视业者认为，液晶电视经由价格快速下滑带动需求起飞，是最近2~3年的事，但全球最大厂三星仍未对台下单，且既有电视业者所拥有制造厂区规模庞大，让短期内台厂投入电视代工仍是1场零和游戏，经济规模未成形前，与配合品牌厂家出货稍有不顺，就可能让代工厂努力白费；同时液晶电视品牌业者迄今能获利者仍在少数，更遑论代工利润能高到哪里，因此，未来台代工厂仍有不少挑战待克服。