CN114708823B

CN114708823B - LED display screen driving system and LED display screen

Info

Publication number: CN114708823B
Application number: CN202210395898.1A
Authority: CN
Inventors: 王朝; 朱卫强
Original assignee: Shenzhen Zhouming Technology Co Ltd
Current assignee: Shenzhen Zhouming Technology Co Ltd
Priority date: 2022-04-15
Filing date: 2022-04-15
Publication date: 2024-05-28
Anticipated expiration: 2042-04-15
Also published as: CN114708823A

Abstract

The invention discloses an LED display screen driving system and an LED display screen, and belongs to the technical field of display control, wherein the LED display screen driving system comprises: the display control subsystem is used for receiving the gray weight of the display data and generating a refreshing data stream for driving the lamp beads according to a preset gray weight refreshing sequence based on the gray weight; the programmable voltage generator is used for generating corresponding dynamic voltage according to the dynamic current control signal corresponding to the subframe to be refreshed; and the constant current chip is used for driving the lamp beads to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed when receiving the row tube conduction signal corresponding to the lamp beads. According to the embodiment of the invention, the gray scale of the lamp bead is defined in two dimensions of the instantaneous driving current corresponding to the dynamic voltage and the refreshing PWM, so that the driving efficiency of the lamp bead is greatly improved, the time required for realizing the corresponding gray scale is reduced, and the driving data volume burden is reduced.

Description

LED display screen driving system and LED display screen

Technical Field

The invention relates to the technical field of display control, in particular to an LED display screen driving system and an LED display screen.

Background

The LED display screen utilizes direct light emission of the LED lamp beads to display content, and each pixel point on the screen comprises a red lamp bead, a green lamp bead and a blue lamp bead. To realize different brightness and color display of the pixel, the three lamp beads are required to have different brightness ratios. For each lamp bead, different brightness is realized through gray level refreshing, which is also the working basis of a constant current driving chip for driving the LED lamp beads to emit light.

With the increasing pixel density of the LED display screen, the carrying capacity of the constant current chip cannot keep pace with the development speed of the LED display screen. Typically, one constant current chip can carry 512 beads (typical value), and with the development of pixel density, this number is insufficient for the chip to drive the beads of the complete module. I.e. the area on the module is not enough to put down so many driver chips. Further, the refresh rate of the driving chip has to be increased, and on the other hand the driving time for a single lamp bead has to be reduced. Thereby reducing the display effect.

At the same time, the amount of driving data increases with the number of lamp beads, and in higher density display screens, the whole driving system has to be guaranteed to be capable of bearing huge amounts of data by reducing the refresh rate of video. Originally, the video stream of 1080P and 240HZ can be played, and after the screen image quality is improved to 4K, only the video stream of 60HZ or even 24HZ can be played. And the screen loses much gray detail while the refresh frequency is reduced.

Disclosure of Invention

In view of the above, an objective of the embodiments of the present invention is to provide an LED display driving system and an LED display, so as to solve the technical problem that the existing LED display driving system cannot meet the requirements of higher and higher pixel density and driving data amount.

The technical scheme adopted by the invention for solving the technical problems is as follows:

according to a first aspect of an embodiment of the present invention, there is provided an LED display screen driving system, the system comprising:

The display control subsystem is used for receiving the gray weight of the display data, generating a refreshing data stream for driving the lamp beads according to a preset gray weight refreshing sequence based on the gray weight, dividing the refreshing data stream into a plurality of gray weight bits according to different gray weights, and each gray weight bit corresponds to more than one subframe;

The programmable voltage generator is used for generating corresponding dynamic voltage according to the dynamic current control signal corresponding to the subframe to be refreshed;

And the constant current chip is used for driving the lamp beads to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed when receiving the row tube conduction signal corresponding to the lamp beads.

According to a second aspect of embodiments of the present invention, there is provided an LED display comprising the LED display driving system of the first aspect.

The LED display screen driving system provided by the embodiment of the invention comprises the following components: the display control subsystem is used for receiving the gray weight of the display data, generating a refreshing data stream for driving the lamp beads according to a preset gray weight refreshing sequence based on the gray weight, dividing the refreshing data stream into a plurality of gray weight bits according to different gray weights, and each gray weight bit corresponds to more than one subframe; the programmable voltage generator is used for generating corresponding dynamic voltage according to the dynamic current control signal corresponding to the subframe to be refreshed; and the constant current chip is used for driving the lamp beads to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed when receiving the row tube conduction signal corresponding to the lamp beads. Therefore, the means for representing the gray level of the lamp beads is changed from the original mode of adding binary numbers to the instantaneous driving current corresponding to the dynamic voltage by only depending on a string of binary numbers, and the gray level of the lamp beads is defined in two dimensions, so that the driving efficiency of the lamp beads is greatly improved, the time required for realizing the corresponding gray level is reduced, and the load of driving data volume is reduced. The speed of display data transmission can be improved to a plurality of times under the condition of ensuring the same display effect; or the gray scale of the display screen is greatly improved under the condition of not increasing the transmission rate; or more lamp beads are driven to display the content under the same display data quantity.

Drawings

The invention will be further described with reference to the accompanying drawings and examples, in which:

FIG. 1 is a diagram of a prior art LED display screen drive system for driving and controlling light beads;

FIG. 2 is a constant current chip internal register architecture;

FIG. 3 is a schematic diagram of a control loop according to an embodiment of the present invention;

FIG. 4 is a current and period relationship of a prior LED display screen drive system;

FIG. 5 is a dynamic current drive relationship provided by an embodiment of the present invention;

FIG. 6 is a graph of the volt-ampere characteristics of an LED lamp bead;

FIG. 7 shows the brightness of the beads under different current driving conditions;

FIG. 8 is a schematic diagram of an LED display driving system according to an embodiment of the present invention;

FIG. 9 is a diagram of a dynamic current signature signal transmission format according to an embodiment of the present invention;

FIG. 10 is a schematic diagram of a dynamic current marking signal in data transmission according to an embodiment of the present invention;

FIG. 11 is a schematic diagram of a programmable voltage generator connection according to an embodiment of the present invention;

Fig. 12 is a schematic diagram of another LED display driving system according to an embodiment of the present invention.

Detailed Description

It should be understood that the specific embodiments described herein are for purposes of illustration only and are not intended to limit the scope of the invention.

In the following description, suffixes such as "module", "component", or "unit" for representing elements are used only for facilitating the description of the present invention, and have no specific meaning per se. Thus, "module," "component," or "unit" may be used in combination.

Example 1

In order to solve the technical problem that the existing LED display screen driving system cannot meet the requirements of higher pixel density and driving data volume, the embodiment provides an LED display screen driving system. The system comprises:

The display control subsystem 1 is used for receiving gray weight values of display data, generating a refreshing data stream for driving the lamp beads according to a preset gray weight value refreshing sequence based on the gray weight values, wherein the refreshing data stream is divided into a plurality of gray weight value bits according to different gray weight values, and each gray weight value bit corresponds to more than one subframe;

A programmable voltage generator 2, configured to generate a corresponding dynamic voltage according to a dynamic current control signal corresponding to a subframe to be refreshed;

And the constant current chip 3 is used for driving the lamp beads 4 to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed when receiving the row tube conduction signal corresponding to the lamp beads.

In the embodiment of the present invention, it should be noted that, first, the inventor finds that in the process of developing LED display screen driving, the current LED display screen driving control faces a huge driving problem, the resolution of 4k video is 4096×2160, each pixel is represented by three 256 colors (8 bits) of data of red, blue and green, the video frame number is 60fps, and then the data size of one second of picture is: 4096x2160x3x8x60 ≡11.9Gbps. Further, sound is approximately one tenth of the amount of video data, and thus the amount of data of one second of 4k video is approximately 13gb≡1.6Gb. This is just the amount of audio and video data, and includes transmission redundancy and gamma correction, and typically a 4K LED display screen requires 16Gbps of bandwidth for transmission, i.e., at least 16 wires are required to transmit data to the screen.

The main content of the transmitted data is the gray information of the lamp beads. The pixels of the LED display screen are formed by three lamp beads of red, green and blue, each lamp bead has 256 levels of gray scale, and through different gray scale ratios, the pixels can display 16.77M colors, which is the basis for realizing content display of the screen.

For a single bead, the gray is recorded by an 8-bit binary number, and each bit of the 8-bit binary number can be 0 or 1, so 256 types exist, and the 256 types just correspond to 256 gray levels one by one. This binary number records the gray information of the beads, but does not directly drive the bead display. The beads are current sensitive devices, i.e. small current variations all lead to direct brightness variations. To maintain proper display of the beads, accurate control of the brightness of the beads is required. The current common strategy is constant current driving, i.e. maintaining a constant control current to control the brightness of the lamp beads. The specific constant current mode is to modulate the current for driving the lamp beads through PWM, the lamp beads can flash and blink at extremely high frequency under PWM signals, and the lighting duration of the lamp beads can be adjusted by adjusting pulse width, namely the duty ratio is adjusted.

The constant current driving mode needs to convert the sent light bead gray data into PWM signals for driving the light beads by means of a constant current chip. Specifically, one constant current chip comprises 16 paths of PWM output channels, namely, the chip can drive 16 lamp beads to light at the same time. In order to reduce the number of chips and save the cost, the constant current chips can also be driven in turn and circularly on the lamp bead area array in a dynamic scanning mode. Typically, a constant current chip will control a 16×n LED array (in practice, N is typically 8, 16, 32, etc., configurable), i.e., one OUT channel drives N LEDs. When in display, the display mode of N rows of round-robin display is adopted, and N rows of round-robin logic is realized by an off-chip row tube circuit.

The gray scale of describing a lamp bead is realized by an 8-bit binary number, 16 paths of PWM outputs are arranged on a chip, and 16 PWM signals can be output at the same time to drive the 16 lamp beads to be lighted.

The 8-bit binary numbers have different weights according to the height of the bit number. The basic logic for driving the beads is that the beads can be refreshed 256 times in one frame of time, with the same brightness for each lighting. The number of times the beads are lit corresponds to the gray level of the beads during this frame time.

The constant current chip works by driving the lamp beads to light up according to specific times after receiving the weight number of the 8-bit binary number. In order to improve the processing capability of the chip, the constant current chip is also controlled by an enabling signal, so that the lamp beads do not need to be refreshed 256 times, and the same effect as the above can be achieved only by refreshing 64 times (enabling operation).

The basic working logic of the enabling signal is to cut a PWM signal driving the lamp bead to light, and to invalidate a part of the PWM signal, i.e. to not light the lamp bead.

Based on this, a specific manner of driving and controlling the lamp beads is shown in fig. 1. The beads may be refreshed 64 times in a frame of time, each time, one subframe.

When the constant current chip receives the 8-bit gray scale weight, the lamp beads are driven to light according to the specific weight. In FIG. 1, the 8-bit gray weights are ordered from the highest bit to the lowest bit according to a [7] to a [0 ]. When the constant current chip receives the weight a [7], the lamp beads are driven to light up 32 subframes, when the constant current chip receives the weight a [6], the lamp beads are driven to light up 16 subframes, and so on until the lamp beads receive the weight a [1], only half subframes of the lamp beads need to be lighted up, at this time, an enabling signal works, the chip is in an invalid state under half subframes, so that the lamp beads are not lighted up, and only half subframes of the lamp beads need to be lighted up.

In the simplest driving mode, the constant current chip uniformly drives the lamp beads to light according to the current same weight. The constant current chip has the structure that: taking the constant current chip 2038 as an example, the 2038 constant current driving chip internally comprises 32 registers, and the 32 registers are divided into two types, wherein the first type comprises 16 paths of shift registers, and the second type comprises 16 paths of latch registers. Wherein each shift register is connected in series, and data is transmitted in series on the shift registers. Each latch register is connected in parallel with each shift register, and data can be latched in the form shown in fig. 2. The chip can light 16 lamp beads at the same time, and the transmission mode of the internal data is that the data is written in from the 16 paths of shift registers. Namely, 160 or 1 are written, after the 16 shift registers are filled, the latch signals are operated, and the 16 signals are stored in the latch registers. The constant current chip can drive the lamp beads to refresh according to the data stored in the latch register.

The 16 latching signals can be distinguished according to the transmission order, and the 16 signals latched at one time are under the same weight, and the data with different weights are refreshed in sequence according to time. Namely, the data of 16 a [7] are latched first, then the data of 16 a [6] are latched, and so on. The chip latches the gray data of 16 lamp beads at the same time, and for a single lamp bead, the chip is required to latch 8 times (shifting 8 times) in one output path, so that the gray data of one frame can be clearly displayed.

The data refreshing mode is many, the simplest mode is that according to the weight of 8-bit lamp beads, the lamp beads are transmitted to the constant current chip one by one for latching, the display data of 16 a 7 weights are transmitted first, the lamp beads are refreshed 32 times, wherein some lamp beads need to be refreshed, and some lamp beads do not need to be refreshed (depending on display contents). And then transmitting the display data of 16 a 6 weight values, refreshing the lamp beads for 16 times, and only refreshing needed by display, then transmitting step by step and shifting for 8 times, so that the 8-bit gray scale can be embodied on the lamp beads.

In fact, in the dynamic scanning mode, the constant current chip sends a PWM signal to the lamp beads under the high-speed conduction of the row tube, taking 32 scan as an example, the lamp beads first light up the lamp beads of the first row, then light up the second row and the third row until the 32 th row is lighted up, and then light up the first row again. In one frame time, 8 times of such polling are needed, so that all gray data of the current 16x32 area array of the lamp beads can be displayed. The polling is done once to latch 512 bits, and a total of 4096 bits need to be stored for 8 rounds. Each lamp bead is written with 8 bits of gray data, so that the lamp bead is driven.

Based on this, the bead driving and display data are correlated, and the actual gray scale data of all beads in a certain area for a certain time can be understood. Under a single lamp bead which is lighted at a time, the brightness of the lamp beads is uniform, namely, the current for driving the lamp beads is uniform. Specifically, since the current is constant, in theory, the magnitude of the driving current received by the lamp bead is fixed at each conduction time, which means that the brightness of the lamp bead is constant at each time. The lamp beads need to display different contents, the brightness of the pixel points is changed, the colors are different, and the core thought is to drive the lamp beads to work through PWM. The duty ratio of the lamp beads in unit time is adjusted by adjusting the pulse width, so that the red, green and blue lamp beads on the pixel point can have different gray scales and display different pixels and colors. This is the basic method of LED display drive control at present.

Based on the method, the gray scale of the lamp bead is described by an 8-bit binary number, and finally the gray scale is displayed on the lamp bead, and 256 gray scale expressions are realized by 64 times of refreshing and matching with an enabling signal.

Along with the continuous development of packaging technology, higher requirements are put on the driving of the constant current chip, and the chip can carry more lamp beads at the same time. For example, assuming that the gray level of each bead is 8 bits, one chip can light up 64 beads in a frame time, which means that the chip can output all gray level data of 64 beads to the beads in a frame time, and a total of 512 bits are transmitted. 60 frames are transmitted in one second, i.e. 30720 bits.

Now, under the condition that the same gray effect is ensured, a chip is required to light 512 lamp beads according to the same time of one frame, the gray data of the 512 lamp beads are required to be transmitted to the 512 lamp beads in the same time of one frame, the chip still keeps 16 paths of output, 4096 bits of data are required to be output in the same time of one frame, 245.76Kb of data are required to be output in one second, and compared with the original data, the gray data are increased to 8 times.

The invention is an efficient LED display driving method, so that part of engineering details are simplified in the process of illustration, and only the realization method for improving the display driving efficiency is discussed.

In fact, since the beads can be lit only at a constant magnitude of current at a time, the amount of information that can be expressed by binary numbers describing the gradation information of the beads is limited. Therefore, the key point is that the brightness of the lamp beads can be adjusted in a plurality of modes, and the gray information of the lamp beads can be better expressed, so that the driving efficiency of the lamp beads is improved. Specifically, the most intuitive way to change the brightness information of the lamp beads is to adjust the current. The foregoing describes the current driving method for the lamp beads of the LED display screen, and the current is constant in all the subframes. Through changing the current of lamp pearl in controllable within range to help the better demonstration content of lamp pearl, just can demonstrate the gray information of lamp pearl with more modes. Of course, this control of the current is achieved while maintaining the total brightness value of the lamp beads for one frame time.

Specifically, the LED display screen is formed by LED lamp beads, and the LED lamp beads belong to current sensitive devices, namely, the LED lamp beads show different brightness changes to the change of the current. This is determined by the volt-ampere characteristics of the LED lamp beads. The voltammetric characteristic of the LED lamp beads is shown in fig. 6. As can be seen from fig. 6, the lamp beads do not generate induced current immediately after being connected to the forward voltage, because the external voltage is smaller than the internal barrier voltage of the PN junction, i.e. the on voltage, so that it is impossible to generate current in the external voltage direction. When the voltage continues to increase and reaches point a, the internal balance is broken, the lamp beads are turned on, current starts to be generated, and then the current increases exponentially with the increase of the voltage. Because the current change is exponentially increased along with the continuous increase of the voltage after the lamp beads are conducted, the voltage cannot be infinitely increased, otherwise, the current becomes infinitely large, and then the lamp beads are burnt out due to short circuit. In order to fully ensure the consistency of the driving current of the lamp beads, the driving control mode of the existing LED display screen is realized by adopting constant current driving. In this working interval, a specific current is selected as the calibration current for driving the lamp beads, and the current for driving the lamp beads is controlled to be at the calibration current, which is called constant current driving.

Further, as shown in fig. 7, the lamp beads are current sensitive devices, the brightness of the lamp beads is different under different driving currents, and the brightness variation amplitude of the lamp beads is changed along with the increase of the driving currents. Under high current drive, a series of factors including junction temperature can cause color temperature drift of the lamp beads. Therefore, by intercepting the voltage corresponding to the maximum current that the lamp bead 4 can normally work, the voltage reaches the point a, and in this interval, the voltage is the forward working area of the LED lamp bead 4, and in this interval, the lamp bead 4 can normally work at a specific voltage.

Based on the analysis, in order to improve the carrying capacity of the constant current chip and improve the driving efficiency of the lamp beads and reduce the time and the driving data volume burden required for realizing the corresponding gray scale, the embodiment of the invention provides an LED display screen driving system.

Specifically, the display control subsystem 1 receives gray weight values of display data, and generates a refreshing data stream for driving the lamp beads 4 according to a preset gray weight value refreshing sequence based on the gray weight values, wherein the refreshing data stream is divided into a plurality of gray weight value bits according to different gray weight values, and each gray weight value bit corresponds to more than one subframe; the programmable voltage generator 2 generates corresponding dynamic voltage according to the dynamic current control signal corresponding to the subframe to be refreshed; and when the constant current chip 3 receives a row tube conduction signal corresponding to the lamp bead 4, the lamp bead 4 is driven to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed. According to the LED display screen driving system provided by the embodiment of the invention, for a single lamp bead 4, the relation of the whole control loop is shown in fig. 3. When the row tube is switched to conduct the lamp beads 4, the current lamp beads 4 are controlled by two parameters of the refresh data flow and the dynamic current corresponding to the dynamic voltage. Thus, the beads 4 perform gray scale display with a dynamic current. The refreshing data stream is used for determining which lamp beads 4 are lighted in the current row and which lamp beads 4 are not lighted; the dynamic voltage output of the programmable voltage generator 2 determines how much current the constant current chip 3 outputs. Optionally, on a display module, all calibration current pins of the constant current chip 3 are connected together, when the module is lightened each time, the module is lightened according to the same current, and in the process of two adjacent lightening, the module can be lightened according to different currents, so that a dynamic current pulse width modulation driving mode is realized. It will be appreciated by those skilled in the art that the values between different dynamic currents are not limited to integer multiples, and that the figures and associated values expressed in the embodiments of the present invention are integer multiples for convenience of description only. In fact, the difference between two adjacent dynamic currents depends on the brightness of the lamp bead and the gamma distribution curve, namely, the difference is taken according to the sensitivity of human eyes to the current brightness.

Optionally, the dynamic voltages are more than two, each subframe corresponds to a different dynamic voltage, or part of subframes corresponds to the same dynamic voltage.

Specifically, in the conventional driving method, the gray level of the lamp beads can be regarded as the accumulation of the brightness over the time period, the brightness corresponds to the current, and the current corresponds to the control voltage (calibration voltage) of the constant current chip. Taking 8-bit gray scale weights as an example, there is a conventional current-period relationship as shown in fig. 4. Fig. 4 shows a periodic distribution of 8-bit gray scale weights refreshed by a single lamp in a frame time. Specifically, the gray level of the lamp beads in one frame time is the sum of brightness in the frame time, the lamp beads maintain constant current, different durations are refreshed (PWM high-frequency on-off) according to different weights, and the lamp beads can be lighted for half of the time at most when the highest position is refreshed. Gradually decreasing gradually until all gray scales are refreshed. The 8-bit gray scale weight corresponds to the square grid region according to the refreshing sequence from the highest bit to the lowest bit, and the highest bit corresponds to the square grid with the largest leftmost area, and the brightness of the lamp beads is required to be the highest in the region, so that the more time the lamp beads occupy in the lighting process.

At each lighting time of this frame, the brightness of the lamp beads corresponds to the current, and the brightness is the same, and the current is the same, except for the lighting time of the lamp beads. The time length for refreshing and lighting the lamp beads is different, and the gray scale is naturally different.

Specifically, when the high weight is refreshed, since the beads are required to be highlighted, the lighting time of the beads has to be prolonged, and the more the beads are lighted in a unit time, the brighter the beads, and the same time is required.

In fact, this refresh has a certain weight, periodic correspondence table as shown in table 1, which is based on fig. 4.

Weight value

a[7]

a[6]

a[5]

a[4]

a[3]

a[2]

a[1]

a[0]

Cycle time

32T

16T

8T

4T

2T

T

T(1/2)

T(1/4)

Table 1 weight and period correspondence table of existing LED display screen driving system

Wherein the highest order refresh is specified to take 32T times, i.e. 32 bead refreshes. Similarly, until the refreshed brightness does not meet the brightness of one time of lighting the lamp beads, the cooperation work, namely the following T (1/2), is needed, which means that half of the subframes can be operated in one subframe of lighting the lamp beads, so that the lighting time of the lamp beads is only half of the original time. The whole working period is 65T, and the time of 65T is refreshed in one frame time.

The LED display driving system of the present invention means that the current for driving the lamp beads 4 to light up may be different at each refresh time of the lamp beads 4. In the case of a current change, the 8-bit gray scale weight is also refreshed, and the time for refreshing the high-weight current can be reduced by increasing the magnitude of the current value of the high weight.

Specifically, taking the above 8-bit gray scale weight as an example, when the highest bit weight is refreshed, the lamp beads 4 need 32T to accumulate to the brightness required by the highest weight, and the current for driving the lamp beads 4 can be increased to 8 times (assuming that the brightness change of the lamp beads 4 is proportional to the current change), so that the brightness of the lamp beads 4 is 8 times of the original brightness when the lamp beads 4 are lightened every time, the lamp beads 4 do not need to be lightened 32 times, the brightness can be realized only by being lightened 4 times, and 4 subframes correspond to the same dynamic current at the moment. Specifically, the currents I1, I2, I3, I4 depicted in fig. 5 correspond to 8 times, 4 times, 2 times, and 1 time, respectively, of the luminance corresponding to the current I in fig. 4.

Based on this, a weight correspondence table based on dynamic current pulse width modulation can be derived, as shown in table 2.

Weight value

a[7]

a[6]

a[5]

a[4]

a[3]

a[2]

a[1]

a[0]

Cycle time

4T

2T

T

T(1/2)

T(1/4)

TABLE 2 dynamic Current weights, periodic Table of correspondence

Based on the above refresh example, the refresh period can be reduced from 65T to 21T, and the time for refreshing one gray level of the lamp beads 4 can be reduced to less than half of the original time. At the same time, the beads 4 can be refreshed twice.

For another example, the driving circuit can drive the lamp beads 4 to display with 8 different currents, each corresponding to an accurate gray value, so that the control system can write 8-bit gray data into the constant current chip 3 through 8T and refresh the data, and at this time, each subframe corresponds to different dynamic currents. Therefore, in the same time, the lamp beads 4 can refresh 8 times of gray scale, so that the refreshing efficiency is greatly improved, and the screen flickering condition is reduced.

Optionally, the brightness value generated by the dynamic voltage control of the lamp beads 4 corresponding to all subframes in a frame time corresponds to the gray value of the lamp beads 4 in the frame. That is, with the LED display driving system of this embodiment, the total brightness value of the lamp beads 4 in one frame corresponds to the gray value of the lamp beads 4 in the frame, so that the lamp beads 4 just complete refreshing of the corresponding gray value in one frame.

Optionally, the preset gray weight refreshing sequence includes: the refreshing is performed according to the sequence from high to low of the gray weights, or according to the sequence from low to high of the gray weights, or according to the non-monotonic ascending and descending sequence.

Specifically, the refreshing is more convenient to realize according to the sequence from high to low or from low to high of the gray weight; refreshing according to a non-monotonic ascending and descending order can enable the brightness of the lamp beads 4 to be more uniform and constant, and alleviate the influence of color temperature drift on display, for example, refreshing according to the law of highest gray weight, lowest gray weight, next highest gray weight and next lowest gray weight in an interlaced manner, or refreshing according to the law of lowest gray weight, highest gray weight, next lowest gray weight and next highest gray weight in an interlaced manner. Those skilled in the art can understand that other gray weight refreshing sequences may be preset, and the gray weight refreshing sequence specifically adopted in this embodiment is not limited.

In one embodiment, the programmable voltage generator 2 is a first programmable voltage generator 21, the first programmable voltage generator 21 is connected to the display control subsystem 1 and the constant current chip 3, and the constant current chip 3 is connected to the lamp bead 4.

In this embodiment, please refer to fig. 8, fig. 8 is a schematic diagram of an LED display driving system according to an embodiment of the present invention. The LED display screen driving system comprises a display control subsystem 1, a first programmable voltage generator 21, a constant current chip 3 and lamp beads 4. Specifically, the gray scale weights of the display data are externally transmitted into the display control subsystem 1. The display control subsystem 1 converts the external gray scale weight into a refresh data stream for the constant current chip 3 to drive the lamp beads 4 to refresh. The purpose of the dynamic current marking is to distinguish between different dynamic currents, so that the constant current chip 3 can drive the lamp beads 4 according to different currents. The first programmable voltage generator 21 is used for generating a dynamic voltage for controlling the current output of the constant current chip 3, so that the current output of the constant current chip 3 can be changed in real time according to the refresh requirement.

In one embodiment, the refresh data stream includes a dynamic current flag signal corresponding to a subframe to be refreshed, and the dynamic current flag signal is used as the corresponding dynamic current control signal.

In this embodiment, the dynamic current flag signal as the dynamic current control signal is included in the refresh data stream, and the first programmable voltage generator 21 may generate a dynamic voltage corresponding to the subframe to be refreshed according to the dynamic current flag signal, so as to control the constant current chip 3 to drive the lamp beads 4 with a corresponding dynamic current.

Optionally, the dynamic current marking signal marks before or after a line display data stream start point of a line where the lamp beads 4 are located.

Specifically, taking an example of marking the dynamic current marking signal corresponding to the subframe to be refreshed after the row display data stream of the row where the lamp bead 4 is located, the data form is shown in fig. 9.

Further optionally, the marking of the dynamic current marking signal before or after the line display data stream start point of the line where the lamp bead 4 is located includes: in the sub-frame to be refreshed, the dynamic current marking signal corresponding to the sub-frame to be refreshed of the module is marked only before, during or after the line display data flow of the first line of the module where the lamp beads 4 are located.

Specifically, a transmission logic diagram is shown in fig. 10. The calibration current pins of all the constant current chips 3 on one display module are connected together, and in one subframe, the driving currents of all the lamp beads 4 on the display module are the same, so that the dynamic currents corresponding to the subframes to be refreshed of the module can be marked only before, during or after the line display data flow of the first line of the module where the lamp beads 4 are located, and the data quantity is reduced.

In one embodiment, the dynamic current mark signal is generated according to the position of the subframe to be refreshed corresponding to the dynamic current mark signal in the frame where the dynamic current mark signal is located.

In this embodiment, the corresponding dynamic current is configured for the sub-frame to be refreshed according to the arrangement order of the sub-frame in the frame. For example, one dynamic current is configured for subframes 1 to 4, another dynamic current is configured for subframes 5 to 8, and so on. Of course, a different current may be configured for each subframe in the arrangement order. The embodiment is not limited to a specific dynamic current configuration mode.

In another embodiment, the dynamic current mark signal is generated according to the gray scale weight bit to be refreshed corresponding to the dynamic current mark signal.

In this embodiment, a corresponding dynamic current is configured for the subframe to be refreshed according to the gray weight corresponding to the gray weight bit to be refreshed. That is, the dynamic currents of the subframes corresponding to the same gray weight bit to be refreshed are the same. When one gray weight bit to be refreshed corresponds to only one subframe, the dynamic current corresponding to the subframe is used for driving the lamp beads 4, and the refreshing of the gray weight corresponding to the gray weight bit to be refreshed can be completed through one subframe.

Specifically, based on the existing LED display screen driving system, the constant current chip drives the lamp beads to display a picture, that is, display data of a frame, through high-speed scanning refreshing. Taking the example that the constant current chip has 16 paths of outputs means that one constant current chip can light 16 lamp beads at the same time. Taking 16 constant current chips as a group, on a group of chips, the constant current chips are connected in series, so that the display data stream for lighting the lamp beads is shifted on the constant current chips in series, 256 clocks are required to be shifted, the display data of all 256 paths of output corresponding lamp beads can be written into each path of output of the 16 constant current chips, and at the moment, the latch signals are reset, and the data are latched and output, so that one row of 256 lamp beads are lighted.

After a row of 256 lamp beads are lighted, an 8-bit clock refreshing line-feed signal is reserved, a line tube can shift a transmission line to the next row, the lamp beads are continuously lighted, 32 rows are lighted in this way, a round of scanning refreshing is completed, and at the moment, a picture of a subframe is displayed on the area of one 256x32 lamp beads from the view of the module.

Further, to display a complete frame of picture, such sub-frame pictures need to be refreshed 65 periods, i.e. 65 times, to realize the picture display of one frame. If a 60 frame video is played, 60 refreshes are performed in a second time. A video stream is played with a data payload that reaches a data stream of (256+8) ×32×65×60=32.94 Mb.

In the LED display driving system according to the embodiment of the present invention, the relationship of the entire control loop described above for a single lamp bead 4 is shown in fig. 3. When the row tube is switched on with the lamp beads 4, the current lamp beads 4 are controlled by two parameters of refreshing data flow and dynamic current. Thus, the beads 4 perform gray scale display with a dynamic current. Wherein the dynamic voltage of the constant current chip 3 is determined by the programmable voltage generator 21. On a display module, all calibration current pins of the constant current chip 3 are connected together, when the module is lightened each time, the module is lightened according to the same current, and in the process of two adjacent lightening, the module can be lightened according to different currents, so that a dynamic current pulse width modulation driving mode is realized.

In the LED display driving system according to the embodiment of the present invention, a plurality of bits of data are used to mark the dynamic current, that is, the data is transmitted to the first programmable voltage generator 21 step by step between the transmission of the line feed signal and the line display data stream, so as to generate the required lighting current.

Then, according to the LED display driving system of the embodiment of the present invention, the lamp beads 4 display a gray scale only by 8 periods (the period is the same as the period duration). Wherein the constant current chip 3 is capable of outputting different currents based on different current magnitude marks. According to the 8-bit gray scale weight transliteration, the lamp beads 4 can be driven to achieve 256 gray scales in the shortest period, namely 256 gray scale display of the lamp beads 4 is achieved under 8 periods through 8 different driving currents.

Further, the first programmable voltage generator 21 may be in the form of fig. 11, and the input terminal thereof includes 3 signal pins, which may be respectively set to high and low, and a 3-bit binary code corresponds to a specific resistor. The specific resistance corresponds to the specific voltage, and the voltage output by the output end of the first programmable voltage generator 21 after passing through the corresponding specific resistance is the calibration voltage of the on-board constant current chip 3. The specific corresponding forms are shown in Table 3.

Binary current signature	Resistor	Calibrated voltage output
			000	R1	U1
001	R2	U2
			010	R3	U3
011	R4	U4
			100	R5	U5
101	R6	U6
			110	R7	U7
111	R8	U8

Table 3 first programmable voltage generator 21 correspondence table

The first programmable voltage generator 21 outputs different voltages according to different marking currents. The first programmable voltage generator 21 is directly connected with the calibration current control pins of all the constant current chips 3 on the board, and inputs the calibration voltage into the constant current chips 3 so that the constant current chips output according to the established calibration current. The driving current is calibrated at each output, so that the lamp beads 4 can be lightened according to different currents.

Based on this, only 3 bits of data bits for marking the current magnitude are sufficient to drive the first programmable voltage generator 21 to control the current output of the constant current chip 3 according to eight different calibration voltages.

The total data carrying capacity, i.e., (256+3+8) ×32×8×60=4.1 Mb, is reduced to 12.45% of the original data amount and the transmission time is reduced to 12.3% of the original data amount. The method means that the same gray effect expression can be realized in a faster time with fewer data streams, and the gray expression efficiency of the system is improved.

In one embodiment, the LED display driving system further includes an accumulator 5, the programmable voltage generator 2 is a second programmable voltage generator 22, the accumulator 5 is connected to the display control subsystem 1 and the second programmable voltage generator 22, and the constant current chip 3 is connected to the second programmable voltage generator 22, the display control subsystem 1 and the lamp beads 4; the accumulator 5 is configured to generate a corresponding dynamic current control signal according to the position of the subframe to be refreshed in the frame where the subframe is located.

In this embodiment, referring to fig. 12, fig. 12 is a schematic diagram of another LED display driving system according to an embodiment of the present invention. The LED display screen driving system comprises a display control subsystem 1, an accumulator 5, a second programmable voltage generator 22, a constant current chip 3 and lamp beads 4. The display control subsystem 1 receives gray weight values of display data, and generates a refreshing data stream for driving the lamp beads 4 according to a preset gray weight value refreshing sequence based on the gray weight values, wherein the refreshing data stream is divided into a plurality of gray weight value bits according to different gray weight values, and each gray weight value bit corresponds to more than one subframe; the accumulator 5 generates a corresponding dynamic current control signal according to the position of the subframe to be refreshed in the frame where the subframe is located; the second programmable voltage generator 22 generates a corresponding dynamic voltage according to the dynamic current control signal; and when the constant current chip 3 receives a row tube conduction signal corresponding to the lamp bead 4, the lamp bead 4 is driven to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed. According to the LED display screen driving system provided by the embodiment of the invention, for a single lamp bead 4, the relation of the whole control loop is shown in fig. 3. When the row tube is switched to conduct the lamp beads 4, the current lamp beads 4 are controlled by two parameters of the refresh data flow and the dynamic current corresponding to the dynamic voltage. Thus, the beads 4 perform gray scale display with a dynamic current. The refreshing data stream is used for determining which lamp beads 4 are lighted in the current row and which lamp beads 4 are not lighted; the dynamic voltage output of the programmable voltage generator 2 determines how much current the constant current chip 3 outputs. Optionally, on a display module, all calibration current pins of the constant current chip 3 are connected together, when the module is lightened each time, the module is lightened according to the same current, and in the process of two adjacent lightening, the module can be lightened according to different currents, so that a dynamic current pulse width modulation driving mode is realized. Wherein, the accumulator 5 generates a corresponding dynamic current control signal according to the position of the subframe to be refreshed in the frame thereof, which comprises: corresponding dynamic currents are configured for the subframes to be refreshed according to the arrangement sequence of the subframes in the frames, for example, one dynamic current is configured for the 1 st to 4 th subframes, another dynamic current is configured for the 5 th to 8 th subframes, and the like. Of course, a different current may be configured for each subframe in the arrangement order. The embodiment is not limited to a specific dynamic current configuration mode.

In one embodiment, the second programmable voltage generator 22 includes a second control signal input pin and a plurality of second output pins, wherein the second control signal input pin is connected to the accumulation signal output pin of the accumulator 5, and each of the second output pins is connected to a voltage regulating resistor corresponding to a position of the second output pin.

Specifically, referring to fig. 12, the second programmable voltage generator 22 has a second control signal input pin and a plurality of second output pins, and each time it receives a second accumulation signal, the output end moves down by one cell, and the corresponding output pin jumps from one second output pin to the other output pin, so as to jump to the other voltage regulating resistor. Until the last voltage regulating resistor is jumped, the first voltage regulating resistor is returned, and the cycle is performed. Each second output pin of the output end of the second programmable voltage generator 22 is connected with the current calibration pin of the constant current chip 3 after passing through the corresponding voltage regulating resistor, and is used for controlling the output current of the constant current chip 3. Optionally, the number of the voltage regulating resistors is smaller than or equal to the number of subframes in one frame time, when the number of the voltage regulating resistors is smaller than the number of subframes in one frame time, one voltage regulating resistor corresponds to a plurality of subframes, and when the number of the voltage regulating resistors is equal to the number of subframes in one frame time, one voltage regulating resistor corresponds to one subframe, so that corresponding dynamic voltage and dynamic current are configured for each subframe.

In one embodiment, the accumulator 5 is configured to generate a corresponding dynamic current control signal according to a position of a subframe to be refreshed in a frame thereof, including:

The display control subsystem 1 firstly refreshes the data stream to the constant current chip 3 after being started and then activates the accumulator 5;

the accumulator 5 starts to sample the clock of the display control subsystem 1 after being activated and outputs a first accumulation signal to the second programmable voltage generator 22, so that after receiving the first accumulation signal, the accumulator outputs a dynamic voltage corresponding to a first subframe to be refreshed to the constant current chip 3;

The accumulator 5 outputs a second accumulation signal to the second programmable voltage generator 22 every other preset number of clocks of the display control subsystem 1, so that the second programmable voltage generator 22 moves a second output pin of the second programmable voltage generator downwards by one bit when receiving the second accumulation signal every time, is connected with another voltage regulating resistor, and further outputs dynamic voltage corresponding to a current subframe to be refreshed to the constant current chip 3;

and taking the first accumulated signal and the second accumulated signal as the dynamic current control signal.

In this embodiment, the preset number is the number of clocks of the display control subsystem 1 required for refreshing one sub-frame by one module. The switching sequence of the voltage regulating resistor corresponds to the refreshing sequence of the corresponding sub-frame. Referring to fig. 12, the display control subsystem 1 receives the gray scale weight of the display data, converts the gray scale weight into a refresh data stream for the refresh output of the constant current chip 3, and sends the refresh data stream to the constant current chip 3. One of which is clocked out to the accumulator 5 for sampling. The accumulator 5 is activated after the display control subsystem 1 refreshes the data stream to the constant current chip 3, starts to sample the working clock of the display control subsystem 1 and outputs a first accumulation signal to the second programmable voltage generator 22, and then outputs an accumulation signal to the second programmable voltage generator 22 every specific clock. The constant current chip 3 drives the lamp beads 4 to work, and converts the received digital signals into analog signals (PWM). The working current output of the device depends on the current calibration pin. The lamp beads 4 are driven to display contents, and the driving method comprises the following steps: taking 8-bit gray scale weight value corresponding to 8-gear current driving as an example, the full-page module comprises 16 constant current chips 3 with 32 sweeps, and the display control subsystem 1 firstly refreshes the constant current chips 3 after starting and then activates an accumulator 5 to start sampling the clock of the display control subsystem 1 and outputs a first accumulation signal to the second programmable voltage generator 22; after receiving the first accumulation signal, the second programmable voltage generator 22 outputs a dynamic voltage corresponding to a first subframe to be refreshed to the constant current chip 3, so that the constant current chip outputs a dynamic current corresponding to the first subframe to be refreshed; the accumulator 5 outputs a second accumulated signal to the second programmable voltage generator 22 every 256×32, i.e. 8192 clocks of the display control subsystem 1; the output pin of the second programmable voltage generator 22 moves one bit downwards each time the second accumulation signal is received, and is connected with another voltage regulating resistor, so as to output the dynamic voltage corresponding to the current subframe to be refreshed to the constant current chip 3, and enable the constant current chip to output the dynamic current corresponding to the current subframe to be refreshed.

In one embodiment, the second programmable voltage generator 22 moves its output pin one bit down each time the second accumulated signal is received, and the connection to the other voltage regulating resistor includes:

if the output pin of the second programmable voltage generator 22 is already connected to the last voltage regulator resistor before receiving the second accumulation signal, it is returned to be connected to the first voltage regulator resistor after receiving the second accumulation signal.

Specifically, the second programmable voltage generator 22 has only one signal pin, and the output end moves down one cell to jump to another voltage regulating resistor each time it receives a second accumulated signal. Until the last voltage regulating resistor is jumped, the first voltage regulating resistor is returned, and the cycle is performed.

The LED display screen driving system of the embodiment of the invention comprises: the display control subsystem 1 is used for receiving gray weight values of display data, generating a refreshing data stream for driving the lamp beads 4 according to a preset gray weight value refreshing sequence based on the gray weight values, wherein the refreshing data stream is divided into a plurality of gray weight value bits according to different gray weight values, and each gray weight value bit corresponds to more than one subframe; a programmable voltage generator 2, configured to generate a corresponding dynamic voltage according to a dynamic current control signal corresponding to a subframe to be refreshed; and the constant current chip 3 is used for driving the lamp beads 4 to refresh display data according to the refresh data flow and the dynamic voltage corresponding to the subframe to be refreshed when receiving the row tube conduction signal corresponding to the lamp beads 4. Therefore, the means for representing the gray level of the lamp beads 4 is changed into a mode of adding the binary number to the instantaneous driving current corresponding to the dynamic voltage from the original binary number only, and the gray level of the lamp beads 4 is defined in two dimensions, so that the driving efficiency of the lamp beads 4 is greatly improved, the time for driving the lamp beads 4 is reduced, and the load of driving data volume is reduced. The speed of display data transmission can be improved to a plurality of times under the condition of ensuring the same display effect; or the gray scale of the display screen is greatly improved under the condition of not increasing the transmission rate; or more beads 4 are driven to display the content under the same display data amount.

Example two

The embodiment of the invention also provides an LED display screen, which comprises the LED display screen driving system.

The LED display screen of the embodiment of the present invention belongs to the same concept as the system of the first embodiment, and the specific implementation process is detailed in the corresponding system embodiment, and the technical features of the system embodiment are correspondingly applicable to the embodiment of the LED display screen, which is not described herein.

The corresponding technical features in the above embodiments can be used mutually without causing contradiction between schemes or incapacitation.

It should be noted that, in this document, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements does not include only those elements but may include other elements not expressly listed or inherent to such process, method, article, or apparatus. Without further limitation, an element defined by the phrase "comprising one … …" does not exclude the presence of other like elements in a process, method, article, or apparatus that comprises the element.

The foregoing embodiment numbers of the present invention are merely for the purpose of description, and do not represent the advantages or disadvantages of the embodiments.

The embodiments of the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to the above-described embodiments, which are merely illustrative and not restrictive, and many forms may be made by those having ordinary skill in the art without departing from the spirit of the present invention and the scope of the claims, which are to be protected by the present invention.

Claims

1. An LED display screen driving system, comprising:

The display control subsystem is used for receiving the gray weight of the display data of the lamp beads, generating a refreshing data stream for driving the lamp beads according to a preset gray weight refreshing sequence based on the gray weight, dividing the refreshing data stream into a plurality of gray weight bits according to different gray weights, and each gray weight bit corresponds to more than one subframe;

The programmable voltage generator is used for generating corresponding dynamic voltage according to the dynamic current control signal corresponding to the subframe to be refreshed of the lamp bead;

The constant current chip is used for driving the lamp beads to refresh display data according to the refresh data flow and dynamic voltage corresponding to a subframe to be refreshed of the lamp beads when receiving a row tube conduction signal corresponding to the lamp beads, wherein the dynamic voltage is used for determining the output current of the constant current chip;

And the brightness value generated by the dynamic voltage control of the lamp beads corresponding to all subframes in one frame time corresponds to the gray value of the lamp beads in the frame.

2. The LED display screen driving system of claim 1, wherein the programmable voltage generator is a first programmable voltage generator, the first programmable voltage generator is respectively connected with the display control subsystem and the constant current chip, and the constant current chip is connected with the lamp bead.

3. The LED display screen driving system of claim 2, wherein the refresh data stream comprises a dynamic current flag signal corresponding to a subframe to be refreshed, the dynamic current flag signal being taken as the corresponding dynamic current control signal.

4. A LED display screen driving system according to claim 3, wherein the dynamic current marking signal marks before or after a line display data stream start point of a line in which the lamp beads are located.

5. The LED display screen driving system of claim 4, wherein the dynamic current marking signal marking before or after a line display data stream start point of a line in which the light beads are located comprises:

and marking a dynamic current marking signal corresponding to the sub-frame to be refreshed of the module only before, during or after the display data flow of the first row of the module where the lamp beads are positioned in the sub-frame to be refreshed.

6. A LED display screen driving system according to claim 3, wherein the dynamic current mark signal is generated according to the position of the sub-frame to be refreshed corresponding thereto in the frame in which it is located.

7. A LED display screen driving system according to claim 3, wherein the dynamic current signature signal is generated from the gray scale weight bits to be refreshed corresponding thereto.

8. The LED display screen driving system of claim 1, further comprising an accumulator, wherein the programmable voltage generator is a second programmable voltage generator, wherein the accumulator is connected to the display control subsystem and the second programmable voltage generator, respectively, and wherein the constant current chip is connected to the second programmable voltage generator, the display control subsystem, and the lamp beads, respectively;

The accumulator is used for generating a corresponding dynamic current control signal according to the position of the subframe to be refreshed in the frame where the subframe is located.

9. The LED display screen driving system of claim 8, wherein said second programmable voltage generator comprises a second control signal input pin and a plurality of second output pins, said second control signal input pin being connected to an accumulation signal output pin of said accumulator, each of said second output pins being connected to a voltage regulating resistor corresponding to a location of said second output pin.

10. The LED display screen driving system according to claim 9, wherein the number of the voltage regulating resistors is equal to or less than the number of subframes in one frame time.

11. The LED display screen driving system according to claim 9 or 10, wherein the accumulator for generating the corresponding dynamic current control signal according to the position of the sub-frame to be refreshed in the frame in which it is located comprises:

The display control subsystem firstly refreshes the data stream to the constant current chip after being started and then activates the accumulator;

The accumulator starts to sample the clock of the display control subsystem after being activated and outputs a first accumulation signal to the second programmable voltage generator, so that the accumulator outputs a dynamic voltage corresponding to a first subframe to be refreshed to the constant current chip after receiving the first accumulation signal;

The accumulator outputs a second accumulation signal to the second programmable voltage generator every other preset number of clocks of the display control subsystem, so that the second programmable voltage generator moves a second output pin downwards by one bit when receiving the second accumulation signal every time, is connected with another voltage regulating resistor, and further outputs dynamic voltage corresponding to a subframe to be refreshed currently to the constant current chip;

12. The LED display screen driving system of claim 11, wherein the second programmable voltage generator moves its output pin one bit down each time the second accumulation signal is received, and connecting with another voltage regulating resistor comprises:

And if the output pin of the second programmable voltage generator is connected with the last voltage regulating resistor before receiving the second accumulation signal, the output pin of the second programmable voltage generator is connected with the first voltage regulating resistor after receiving the second accumulation signal.

13. The LED display screen driving system of claim 11, wherein the predetermined number is a clock number of the display control subsystem required for a module to refresh one sub-frame.

14. The LED display screen driving system according to claim 11, wherein the switching sequence of the voltage regulating resistors corresponds to the refresh sequence of the sub-frames corresponding thereto.

15. The LED display screen driving system of claim 1, wherein the dynamic voltages are two or more, each of the subframes corresponds to a different dynamic voltage, or a part of the subframes corresponds to the same dynamic voltage.

16. The LED display screen driving system according to claim 1, wherein the preset gray weight refresh sequence comprises: the refreshing is performed according to the sequence from high to low of the gray weights, or according to the sequence from low to high of the gray weights, or according to the non-monotonic ascending and descending sequence.

17. An LED display screen, characterized in that the LED display screen comprises an LED display screen driving system according to any of claims 1-16.