Functions and roles of led display driver ICs
Functions and roles of led display driver ICs
LED display in the work, the role of the driver IC is to receive the display data in line with the protocol (from the receiver card or video processor and other sources of information), in the internal production of PWM and the current time change, the output and the brightness of grayscale refreshing and other related PWM current to light up the LEDs. the driver IC and the logic IC and the peripheral IC composed of MOS switches, the joint role of the full-color LED display screen display function and determine the display effect. The driver IC, logic IC and MOS switch are the peripheral ICs, which work together in the display function of the full color led display screen and determine the display effect it presents.
LED driver chip can be divided into two kinds of general-purpose chip and special chip.
The so-called general-purpose chip, the chip itself is not specifically designed for the LED, but some of the full-color led display part of the logic function of the logic chip (such as series 2 and shift registers).
The special chip is according to the LED light-emitting characteristics and designed specifically for full-color led display driver chip. LED is a current characteristics of the device, that is, under the premise of saturated conduction, its brightness changes with the current changes, rather than by adjusting the voltage on both sides of the change. Therefore, one of the biggest features of the special chip is to provide a constant current source. Constant current source can ensure the stable driving of LED, eliminate the flickering phenomenon of LED, is the full color led display screen to show the premise of high quality picture. Some special chips also add some special features for different industry requirements, such as LED error detection, current gain control and current correction.
The evolution of driver IC:
In the 90s of last century, led display application to single and double color, the use of constant voltage driver IC. 1997, our country appeared the first full-color led display special driver control chip 9701, from 16 levels of grayscale spanning to 8192 levels of grayscale, realizing the video of the WYSIWYG. Subsequently, for the LED light-emitting characteristics, constant current driver has become the first choice of full-color full-color led display driver, at the same time, the higher integration of 16-channel driver instead of 8-channel driver. at the end of the 1990s, Japan Toshiba, the United States, Allegro and Ti and other companies have launched the 16-channel LED constant current driver chip, at the beginning of the 21st century, the driver chip of Chinese Taiwan-based enterprises have also been mass produced and used. Successive mass production and use. Nowadays, in order to solve the problem of small pitch led display PCB wiring, some driver IC manufacturers have launched a highly integrated 48 channel LED constant current driver chip.
The performance index of driver IC:
In the performance index of led display, refresh rate and gray level and image performance is one of the most important indexes. This requires high consistency of current between the channels of the led display driver IC, high speed communication interface rate and constant current response speed. In the past, the refresh rate, gray level and utilization of the three aspects is a kind of relationship between one and the other, to ensure that one or two of the indicators can be more excellent, it is necessary to appropriate sacrifice the remaining has been two indicators. For this reason, many full-color led display in the practical application is difficult to have the best of both worlds, either the refresh is not enough, high-speed camera equipment shooting easily appear black lines, either gray scale is not enough, the color darkness and brightness is not consistent. With the advancement of driver IC manufacturers technology, has now been a breakthrough in the three high problems, has been able to solve these problems.
In the application of led display, in order to ensure the comfort of the user's eyes for a long time, low brightness and high gray has become a test of the performance of the driver IC is a particularly important criterion.
The trend of driver IC:
1, energy saving:
As a green energy, energy saving is the eternal pursuit of led display, but also an important criterion to consider the performance of the driver IC. Driver IC energy saving mainly includes two aspects, one is to effectively reduce the constant current inflection point voltage, and then the traditional 5V power supply to 3.8V operation; the second is to optimize the IC algorithm and design to reduce the driver IC operating voltage and operating current. Currently there are manufacturers have introduced a 0.2V low inflection voltage, enhance the LED utilization rate of more than 15% of the constant current driver IC, the use of conventional products 16% lower supply voltage to reduce heat, so that led display energy efficiency greatly improved.
2, integration:
With the rapid decline in the pixel pitch of the led display, the unit area to be mounted on the packaging device to geometric multiples of the growth, greatly increasing the module drive surface component density. P1.9 small pitch LED, for example, 15 sweep 160 * 90 module requires 180 constant current driver IC, 45 line tube, 2 138. so many devices, so that the PCB available wiring space becomes extremely crowded, increasing the difficulty of circuit design. At the same time, such a crowded arrangement of components, very easy to cause welding problems, but also reduces the reliability of the module. Driver IC less dosage, PCB larger wiring area, the demand from the application side to force the driver IC must be on a highly integrated technology route.
At present, the industry's mainstream driver IC suppliers have launched a highly integrated 48-channel LED constant current driver IC, large-scale peripheral circuits integrated into the driver IC wafers, can reduce the complexity of the application side of the PCB circuit board design, but also to avoid the design capabilities of engineers from various manufacturers or design differences in the problems arising.
LED driver chip can be divided into two kinds of general-purpose chip and special chip.
The so-called general-purpose chip, the chip itself is not specifically designed for the LED, but some of the full-color led display part of the logic function of the logic chip (such as series 2 and shift registers).
The special chip is according to the LED light-emitting characteristics and designed specifically for full-color led display driver chip. LED is a current characteristics of the device, that is, under the premise of saturated conduction, its brightness changes with the current changes, rather than by adjusting the voltage on both sides of the change. Therefore, one of the biggest features of the special chip is to provide a constant current source. Constant current source can ensure the stable driving of LED, eliminate the flickering phenomenon of LED, is the full color led display screen to show the premise of high quality picture. Some special chips also add some special features for different industry requirements, such as LED error detection, current gain control and current correction.
The evolution of driver IC:
In the 90s of last century, led display application to single and double color, the use of constant voltage driver IC. 1997, our country appeared the first full-color led display special driver control chip 9701, from 16 levels of grayscale spanning to 8192 levels of grayscale, realizing the video of the WYSIWYG. Subsequently, for the LED light-emitting characteristics, constant current driver has become the first choice of full-color full-color led display driver, at the same time, the higher integration of 16-channel driver instead of 8-channel driver. at the end of the 1990s, Japan Toshiba, the United States, Allegro and Ti and other companies have launched the 16-channel LED constant current driver chip, at the beginning of the 21st century, the driver chip of Chinese Taiwan-based enterprises have also been mass produced and used. Successive mass production and use. Nowadays, in order to solve the problem of small pitch led display PCB wiring, some driver IC manufacturers have launched a highly integrated 48 channel LED constant current driver chip.
The performance index of driver IC:
In the performance index of led display, refresh rate and gray level and image performance is one of the most important indexes. This requires high consistency of current between the channels of the led display driver IC, high speed communication interface rate and constant current response speed. In the past, the refresh rate, gray level and utilization of the three aspects is a kind of relationship between one and the other, to ensure that one or two of the indicators can be more excellent, it is necessary to appropriate sacrifice the remaining has been two indicators. For this reason, many full-color led display in the practical application is difficult to have the best of both worlds, either the refresh is not enough, high-speed camera equipment shooting easily appear black lines, either gray scale is not enough, the color darkness and brightness is not consistent. With the advancement of driver IC manufacturers technology, has now been a breakthrough in the three high problems, has been able to solve these problems.
In the application of led display, in order to ensure the comfort of the user's eyes for a long time, low brightness and high gray has become a test of the performance of the driver IC is a particularly important criterion.
The trend of driver IC:
1, energy saving:
As a green energy, energy saving is the eternal pursuit of led display, but also an important criterion to consider the performance of the driver IC. Driver IC energy saving mainly includes two aspects, one is to effectively reduce the constant current inflection point voltage, and then the traditional 5V power supply to 3.8V operation; the second is to optimize the IC algorithm and design to reduce the driver IC operating voltage and operating current. Currently there are manufacturers have introduced a 0.2V low inflection voltage, enhance the LED utilization rate of more than 15% of the constant current driver IC, the use of conventional products 16% lower supply voltage to reduce heat, so that led display energy efficiency greatly improved.
2, integration:
With the rapid decline in the pixel pitch of the led display, the unit area to be mounted on the packaging device to geometric multiples of the growth, greatly increasing the module drive surface component density. P1.9 small pitch LED, for example, 15 sweep 160 * 90 module requires 180 constant current driver IC, 45 line tube, 2 138. so many devices, so that the PCB available wiring space becomes extremely crowded, increasing the difficulty of circuit design. At the same time, such a crowded arrangement of components, very easy to cause welding problems, but also reduces the reliability of the module. Driver IC less dosage, PCB larger wiring area, the demand from the application side to force the driver IC must be on a highly integrated technology route.
At present, the industry's mainstream driver IC suppliers have launched a highly integrated 48-channel LED constant current driver IC, large-scale peripheral circuits integrated into the driver IC wafers, can reduce the complexity of the application side of the PCB circuit board design, but also to avoid the design capabilities of engineers from various manufacturers or design differences in the problems arising.