Analysis of Various Driving Schemes of LED Display Screen

Introduction and comparison of several driving solutionsTlc5941 driver chipTlc5941 chip is the latest product of Ti Texas Instruments. It has the characteristics of point correction, high gray level (PWM control), etc. All internal data registers, gray level registers, point correction registers and error status information of tlc5941 are accessed through serial interface. The maximum serial clock frequency is 30MHz, the inter chip current error is generally within 6%, the inter bit current error is generally within 4%, and the maximum output current of each channel is 80mA.

Analysis of Various Driving Schemes of LED Display Screen 1

Each channel of tlc5941 can use PWM mode to carry out 4096 level gray control according to the value of internal gray register, which is 12 bits. Each channel LED driving circuit is 64 level controlled by the value of 6-point correction register, and the maximum value of driving current can be set through off-chip resistance. The 64 level current control provides the ability of LED point gray correction, and the 4096 level gray adjustment ensures that each point in the dot matrix has up to 256 levels of gray representation even at a lower gray level, so that the red, green and blue full-color screen can have the color expression ability of 16m colors, These two points are particularly important for high-quality color large screen display. Compared with the traditional color large screen display system, PWM is centrally generated for gray control and programmable logic chip (or the high-speed CPU only needs to process the output of cache management, gray level and point correction data, which reduces the design complexity, and because the PWM gray level control has nothing to do with the serial removal of data, it can easily obtain a higher frame rate and achieve a good dynamic display effect.

In order to ensure the reliable operation of large color screen, tlc5941 provides open circuit (LOD) and over temperature detection of each LED (TSD capability. The built-in open collector output circuit is used to alarm when an error occurs. No matter which of the 16 channels has an error, the output pin of the built-in open collector output circuit will be pulled to the low level. You can know which channel has a fault by querying the internal status information of the chip. The output pin of all tlc5941 built-in open collector output circuits in the system Tlc5941 can be connected together and connected to the high level through the pull-up resistor. By monitoring this signal, the system can make self diagnosis during operation. Tlc5941 is suitable for occasions with poor working environment, high requirements for display effect and high requirements for safety performance, such as LED information signs on highways, large outdoor LED TVs, etc.

Mbi5028 driver chipMbi5028 Taiwan MBI Accumulation Technology) A LED screen driver chip with programmable current gain function introduced by the company. It has built-in serial parallel shift register and output latch, and adopts precisiondr technology to obtain better electrical characteristics. The maximum serial clock frequency of mbl5028 is 25MHz, the inter chip current error is generally within 6%, the inter bit current error is generally within 3%, and the maximum output current is 90mA

Mbi5028 has a built-in current gain control logic unit. The programmable current gain function adopts share IO technology without adding additional pins. You can enter the special function mode of mbi5028 - current adjustment mode by inputting a specific sequence signal at the corresponding pin. In this mode, different current gains can be written to the current gain control logic unit through the system microcontroller Data, lock these data, and effectively control the current output through the built-in digital and analog shared converter. Due to the change of working environment and the aging of LED screen, the brightness of LED screen will be reduced. If a fixed forward current is used, the brightness deviation of LED screen will be small. Through the programmable current gain function and precisiondr technology, the current deviation can be adjusted to compensate the LED screen Using precisiondr technology and built-in digital and analog shared converter, under the same accuracy, the relative output current can be obtained by changing the way of digital code, so as to improve the imaging quality of LED screen.

Analysis of Various Driving Schemes of LED Display Screen 2

The current technology can provide 256 current levels for the LED display screen, making it reach 1200% of the total dynamic range and providing 256 output current levels. In terms of electrical characteristics and chip packaging, mbi5026 has good compatibility. Users can obtain the current gain technology with share IO technology without changing the PCB previously designed for the same type of chip, which can greatly reduce the upgrade cost The i5026 is suitable for LED screen driving schemes that are not harsh in working conditions but require high-quality imaging, such as medium and low-end screens such as indoor large LED display screens. At the same time, the mbi5028 is also suitable for the upgrading of old driver chips.

St2221c driver chip

St2221c Taiwan Siti (dot crystal technology) An LED screen driver chip introduced by the company. It has built-in serial parallel shift register unit, output latch unit and current output control unit, with excellent electrical characteristics. The maximum serial clock frequency of st2221c is 25MHz, the inter chip current error is generally within 10%, the inter bit current error is generally within 6%, and the maximum output current is 120mA. St2221c includes 16 channel constant current driver unit, It can drive 16 LEDs at the same time, which is suitable for the drive of some low-end screens, such as indoor information screen and other low-end LED displays.

Existing problemsPower consumption and heating problemsDue to the large output current, the power consumption and heating problem of LED display chip has always been the first factor hindering the development of driving chip. This problem will become particularly prominent in the driving mode of handheld LED display in the future. With the progress of LED device manufacturing technology and the reduction of driving current, the problem will be solved step by step.

Application cost problemA mainstream 16 bit steady-state current LED display driver chip can only drive 16 LED devices. The resolution of one chip is 1024 768 LED display screen must use multiple driver chips to obtain the expected effect, which makes the material cost relatively high. If the driver chip itself adopts the scanning mode, a mainstream driver chip can drive multi-channel LED devices at one time, which will greatly reduce the application cost.Summary

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The Upstream Raw Material Manufacturers of LED Display Screen Have Raised Their Prices One After Ano
Recently, Continental Shengyi technology, the world's second largest copper foil substrate (CCL) factory, announced that the price of key parts in the traditional peak season of the electronics industry has increased by 5% for different materials since September. CCL is a key raw material for printed circuit board PCB and cannot be replaced by other materials. Shengyi led the price rise, revealing that the market demand is strong. The peak season effect of Taiwan CCL Sanxiong Taiwan optoelectronics, Lianmao and Taiyao is expected, and affects the PCB market. Coincidentally, not long ago, as an upstream PCB manufacturer of LED display screen, willion electronics also issued a notice to adjust the price of copper coating. The upstream raw material manufacturers of LED display screen have raised their prices one after another. How should LED screen enterprises deal with it?The strong demand of 5g market drives the rising value of raw materialsIndustry insiders said that this year, the global electronics industry was quite cautious in pulling goods. The key components such as panels, memory and semiconductor silicon wafers sought after in the market last year have lost their popularity in the past, and prices have been callback one after another. It is understood that the rise in the price of 5G is mainly due to the Chinese mainland's infrastructure construction, which has led to a large demand for CCL by Netcom. As the key raw materials of PCB, copper foil substrate and copper clad laminate can not be replaced by other materials, accounting for more than 30% of the production cost of PCB. PCB is known as the "mother of industry", and its market position is self-evident.Since June 6, 2019, the Ministry of industry and information technology has issued 5g commercial licenses to China Telecom, China Mobile, China Unicom and China Radio and television. The issuance of 5g commercial licenses marks China's entry into the first year of 5g commerce. The advent of 5g era has brought a huge market blue ocean to consumer electronics. At the same time, the huge demand for copper foil substrate and copper clad laminate has also been detonated. It can be said that the rise of 5g concept drives the rise of the value of copper foil substrate and copper clad laminate, and then drives the rise of PCB price. This price increase has affected the cost and raw material supply of PCB Factory and attracted great attention in the industry.Environmental protection storm has also become an important reason for the rise in the price of raw materialsIn recent years, people pay more and more attention to the awareness of environmental protection. While based on the steady economic development, people also have more requirements for environmental protection construction. Building an "environment-friendly" society has increasingly become an urgent need. The state has also adapted to the needs of the times and strengthened the rectification of environmental protection. In 2017, China comprehensively strengthened environmental emission restrictions on the manufacturing industry. In this investigation, nearly 100 enterprises were forced to suspend trading for rectification. The environmental protection tax implemented in 2018 also led to an increase in environmental protection expenses of PCB manufacturers.After rectification, some PCB manufacturers who failed to meet the environmental protection requirements were forced to withdraw from the market. Those lucky to survive also had higher requirements for environmental monitoring of raw materials on environmental protection issues. The increase of environmental protection cost is bound to lead to the increase of upstream industrial chain cost. Among PCB manufacturers, some small and medium-sized PCB enterprises are forced to withdraw from the PCB market due to unqualified environmental protection. The original balance of supply and demand in the PCB market is broken. The shortage of supply in the PCB market will inevitably lead to a direct rise in prices. In the environmental protection tax implemented in 2018, the state has legalized environmental protection issues in the form of law, and environmental monitoring of PCB manufacturers will become a normalization, which is also the reason for the continuous growth of material prices of PCB manufacturers.Forcing screen enterprises to raise prices is conducive to benign competitionFor LED display enterprises, this round of price increase is not only caused by the industry force, but also a strategy for enterprises to take the initiative. On the one hand, the price rise of raw materials exceeds the range that manufacturers can bear, and enterprises need to ensure the quality of products by means of price rise; On the other hand, the industry needs to return to the level of rational competition, and taking the initiative to raise prices is undoubtedly a good start. Therefore, the implementation of price increase by LED display enterprises is excusable, and even will promote the price rise of the whole LED market, and promote the LED display industry to get rid of the vicious competition of "low price" and move towards benign price competition. In addition, the "price rise" will also accelerate the reshuffle of the LED display industry. Those enterprises lacking innovation will either be eliminated, or upgrade their products and take the innovative development route.To sum up, several families are happy and several families are sad. This is nothing more than this, especially in shopping malls where the waves are more treacherous than the battlefield. Today, with a sound supply system, it is inevitable that one stone will stir up thousands of waves. Whatever the reason, the price rise of PCB driven by the rise of raw materials is determined by the market. What enterprises can do now is to play the cards in their hands and not passively let the mermaid meat. No one denies that this is a crisis. However, who does not admit that this is not an opportunity?
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