An LED display control method and chip

Abstract

The LED display control chip provided by the present invention includes a storage module and a plurality of output channels. Each output channel includes a digital module, a blanking module, an analog clamping module, and a constant current output module. Among them, the input end of the digital module is connected to the storage module. The output ends of the digital module are respectively connected to the input end of the blanking module and the input end of the analog clamping module. The output end of the analog clamping module is connected to the input end of the constant current output module. The output end of the blanking module is connected to the input end of the constant current output module. The output end of the constant current output module serves as the output end of the LED display control chip. The storage module is used to store the grayscale data to be displayed for each frame of the LED display. This chip has a low cost and a simple structure, can improve the display defects of the LED display caused by the coupling effect, and enhance the picture quality.

Description

Technical Field

[0001] The present invention belongs to the technical field of integrated circuits, and particularly relates to an LED display control method and a chip. Background Art

[0002] Due to the advantages of high refresh rate, high gray scale, wide viewing angle, low power consumption, long service life, and customizable shape, LED displays are widely used in commercial advertising, information dissemination, sports broadcast, security monitoring and other fields. With the continuous expansion of the application fields of displays and the development of display technologies, the pitch of displays is getting smaller and smaller, and the requirements for the performance and display effect of display systems are getting higher and higher. Therefore, the tasks borne by the constant current IC, which most intuitively reflects the display effect, are becoming more and more arduous.

[0003] The coupling problem of the display has always been an important factor restricting the improvement of the display effect. The coupling phenomenon is mainly affected by various parasitic parameters on the PCB, board-end wiring, lamp bead parameters, etc. To solve the coupling problem of the display, the existing method is to fix the end time of the display in a sub-frame and display the gray-scale data in a reverse scanning manner, so that the opening positions of each channel are staggered, avoiding the superposition of coupling effects caused by all channels opening at the same moment, and the coupling effect is more serious.

[0004] Although the above method can solve the display problems caused by the coupling effect of the LED display to a certain extent, it will also bring problems such as uneven gray-scale gradient, color deviation, and bright spots in the first row. When the refresh rate is relatively high, the improvement effects of problems such as medium contrast, high contrast, and cross-board coupling in the coupling effect of the LED display will also be greatly reduced.

[0005] The cross-board coupling phenomenon is as Figure 1 shown. On small-pitch modules, due to the large number of dots, when the area of the PCB board is slightly larger, a row of lamp beads often needs to be powered by two or even more row transistors, so the same row of lamp beads will be divided into two or several segments; or when the modules are spliced into a cabinet, when displaying a color bar with a gradual change from the darkest to the brightest at the physical splicing position between two adjacent modules, a vertical line with an obvious brightness boundary will be formed at the place where the row line is disconnected or at the physical splicing position. This phenomenon is called the cross-board coupling phenomenon.

[0006] The essence of cross-board coupling is that the subsequent gray scale continuously couples with the previous stage, continuously raising the clamping voltage of the previous stage. The coupling effect is more minor for the subsequent gray scale and more serious for the previous gray scale. This will cause the part with lower brightness to become even lower, so an obvious brightness boundary can be seen at the place where the row transistor is disconnected and at the physical splicing position of the module.

[0007] The cause of color deviation is as Figure 2As shown, the LED display screen has the display characteristics of high brightness and high gray levels, and the displayed images sometimes have a very high contrast. Therefore, when a brighter or darker image is superimposed on the low-gray background of the display screen module, phenomena such as color cast, a certain color being brighter (dark and bright), or a certain row being brighter (darker) will occur in the low-gray area.

[0008] This is because the LED gray-scale brightness is distributed to different sub-frames, and the LED lights use the cumulative lighting time in each frame period to express the gray scale for image display. Therefore, in some sub-frames, they may not be lit. When the coupling effect caused by the edge is relatively serious when the channel is opened / closed, it may cause the channels that should not be lit to be lit (channel open coupling) or the brightness of the normally lit channels to become lower (channel closed coupling). Summary of the Invention

[0009] Aiming at the defects in the prior art, the present invention provides an LED display screen control method and chip, which are low in cost and simple in structure, can improve the display defects of the LED display screen caused by the coupling effect, and enhance the picture quality.

[0010] In a first aspect, an LED display screen control chip includes a storage module and a plurality of output channels, and each of the output channels includes a digital module, an analog clamping module, a blanking module, and a constant current output module;

[0011] Among them, the input end of the digital module is connected to the storage module, the output ends of the digital module are respectively connected to the input ends of the blanking module and the analog clamping module, the output end of the analog clamping module is connected to the input end of the constant current output module, the output end of the blanking module is connected to the input end of the constant current output module, and the output end of the constant current output module is used as the output end of the LED display screen control chip;

[0012] The storage module is used to store the gray-scale data to be displayed in each frame of the LED display screen.

[0013] Preferably, the output end of the digital module includes a first output end, a second output end, and a third output end, and the input end of the analog clamping module includes a first input end and a second input end;

[0014] Among them, the first output end of the digital module is connected to the first input end of the analog clamping module, and the second output end of the digital module is connected to the second input end of the analog clamping module; the third output end of the digital module is connected to the input end of the blanking module.

[0015] Preferably, the analog clamping module includes a first digital-to-analog conversion circuit, a second digital-to-analog conversion circuit, a clamping voltage generation circuit, and a clamping time generation circuit;

[0016] Among them, the input end of the first digital-to-analog conversion circuit serves as the first input end of the analog clamping module, and the output end of the first digital-to-analog conversion circuit is connected to the first input end of the clamping voltage generation circuit; the input end of the second digital-to-analog conversion circuit serves as the second input end of the analog clamping module, and the output end of the second digital-to-analog conversion circuit is connected to the second input end of the clamping voltage generation circuit;

[0017] The output end of the clamping voltage generation circuit is connected to the input end of the clamping time generation circuit, and the output end of the clamping time generation circuit serves as the output end of the analog clamping module.

[0018] Preferably, a register control module is further included;

[0019] The register control module is respectively connected to the control end of the clamping voltage generation circuit and the control end of the clamping time generation circuit.

[0020] Preferably, the voltage value output by the first digital-to-analog conversion circuit is different from the voltage value output by the second digital-to-analog conversion circuit.

[0021] In a second aspect, an LED display control method runs on the LED display control chip described in the first aspect, and includes the following steps:

[0022] When the digital module receives an external blanking instruction, it outputs a blanking signal and transmits it to the blanking module;

[0023] The blanking module drives the constant current output module to output a first signal according to the blanking signal and transmits it to the LED display;

[0024] When the digital module detects that there is no PWM waveform in the grayscale data to be displayed in the next frame, it generates a no-PWM clamping signal and transmits it to the analog clamping module;

[0025] The analog clamping module drives the constant current output module to output a second signal according to the no-PWM clamping signal and transmits it to the LED display;

[0026] When the digital module detects that there is a PWM waveform in the grayscale data to be displayed in the next frame, it generates a with-PWM clamping signal and transmits it to the analog clamping module;

[0027] The analog clamping module drives the constant current output module to output a third signal according to the with-PWM clamping signal and transmits it to the LED display;

[0028] Among them, the voltage value of the first signal is greater than the voltage value of the second signal, and the voltage value of the second signal is greater than the voltage value of the third signal.

[0029] Preferably, the priorities of the no-PWM clamping signal and the with-PWM clamping signal are both greater than the blanking signal.

[0030] Preferably, the width of the second signal is greater than or equal to the width of the falling edge at the output end in the constant current output module.

[0031] Preferably, the width of the third signal is greater than or equal to the width of the rising edge at the output end in the constant current output module.

[0032] As can be seen from the above technical solutions, an LED display control method and a chip provided by the present invention have low cost and simple structure, can improve the display defects caused by the coupling effect of the LED display, and enhance the picture quality. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the specific embodiments of the present invention or the technical solutions in the prior art, the following will briefly introduce the drawings required for the description of the specific embodiments or the prior art. In all the drawings, similar elements or parts are generally identified by similar reference numerals. In the drawings, the elements or parts do not necessarily draw to actual scale.

[0034] Figure 1 The circuit diagram of the existing LED display screen proposed for the background technology.

[0035] Figure 2 The coupling schematic diagram of the LED display screen in the existing method proposed for the background technology.

[0036] Figure 3 The timing diagram of the opening of each channel of the LED display screen in the existing method.

[0037] Figure 4 The module schematic diagram of the LED display control chip provided in the first embodiment of the present invention.

[0038] Figure 5 The module schematic diagram of the analog clamping module provided in the first embodiment of the present invention.

[0039] Figure 6 The flowchart of the LED display control method provided in the second embodiment of the present invention. DETAILED DESCRIPTION OF THE EMBODIMENTS

[0040] The following will combine the drawings to describe in detail the embodiments of the technical solutions of the present invention. The following embodiments are only used to illustrate the technical solutions of the present invention more clearly, so they are only examples and cannot be used to limit the protection scope of the present invention. It should be noted that unless otherwise specified, the technical terms or scientific terms used in this application should be the ordinary meanings understood by those skilled in the art to which the present invention belongs.

[0041] It should be understood that, as used in this specification and the appended claims, the terms "comprising" and "including" indicate the presence of the described features, integers, steps, operations, elements, and / or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and / or groups thereof.

[0042] It should also be understood that the terminology used in this specification of the present invention is for the purpose of describing particular embodiments only and is not intended to limit the present invention. As used in this specification of the present invention and the appended claims, unless the context clearly dictates otherwise, the singular forms "a", "an", and "the" are intended to include the plural forms.

[0043] It should be further understood that the term "and / or" used in this specification of the present invention and the appended claims refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.

[0044] As used in this specification and the appended claims, the term "if" can be interpreted as "when", "once", "in response to determining", or "in response to detecting" depending on the context. Similarly, the phrase "if determined" or "if [the described condition or event] is detected" can be interpreted as meaning "once determined", "in response to determining", "once [the described condition or event] is detected", or "in response to detecting [the described condition or event]" depending on the context.

[0045] See Figure 1 , in the existing LED display connection circuit, LED DRIVER1 and LED DRIVER2 are two LED display control chips respectively, and the row lines controlled by these two LED display control chips are powered separately. When the grayscale gradient image is displayed according to the Figure 3 timing, for OUT1 in LED DRIVER1, it will be coupled 15 times, OUT2 will be coupled 14 times, and so on, and OUT16 is not coupled. Similarly, for OUT1 in LED DRIVER2, it will be coupled 15 times, OUT2 will be coupled 14 times ···, and OUT16 is not coupled. Theoretically speaking, the brightness of OUT1 of LED DRIVER2 will be higher than that of OUT16 of LED DRIVER1 because OUT1 of LED DRIVER2 is turned on for a longer time. However, in reality, due to the existence of the coupling effect, the brightness of OUT1 of LED DRIVER2 looks darker to the naked eye.

[0046] When the LED display shows an image with a high contrast, such as when a high-brightness block or a dark block is superimposed on a low-gray area, although the number of couplings is not so large, the amount of coupling will be very large. Due to the different parameters of devices such as the PCB and the lamp beads, different degrees of coupling effect display defects will be caused.

[0047] To solve the above defects, the present invention provides the following control chip and method.

[0048] Embodiment 1:

[0049] An LED display control chip, see Figure 4 , including a storage module and a plurality of output channels. Each output channel includes a digital module, an analog clamping module, a blanking module, and a constant current output module;

[0050] Among them, the input end of the digital module is connected to the storage module. The output ends of the digital module are respectively connected to the input ends of the blanking module and the analog clamping module. The output end of the analog clamping module is connected to the input end of the constant current output module. The output end of the blanking module is connected to the input end of the constant current output module. The output end of the constant current output module is used as the output end of the LED display control chip;

[0051] The storage module is used to store the grayscale data to be displayed for each frame of the LED display.

[0052] Specifically, both the digital module and the constant current output module can be implemented by corresponding modules in existing LED display control chips. The storage module can adopt an SRAM module. The grayscale data to be displayed for each frame of the LED display set by the user or received will be stored in the SRAM module. When displaying normally, the digital module will perform a read operation on the SRAM module. For example, all the grayscale data to be displayed for all the points in one row of the LED display will be read out at one time. Then, corresponding signals will be generated and transmitted to the analog clamping module and the blanking module, so that the blanking module and the analog clamping module drive the constant current output module to output signals with different voltage values. For example, the digital module judges the read grayscale data to be displayed. If the grayscale data to be displayed is zero, a non-PWM clamping signal will be generated and transmitted to the analog clamping module. If the grayscale data to be displayed is not zero, a PWM clamping signal will be generated and transmitted to the analog clamping module. This control chip has low cost and simple structure, can improve the display defects caused by the coupling effect of the LED display, and enhance the picture quality.

[0053] Preferably, the output end of the digital module includes a first output end, a second output end, and a third output end. The input end of the analog clamping module includes a first input end and a second input end;

[0054] The first output terminal of the digital module is connected to the first input terminal of the analog clamping module, and the second output terminal of the digital module is connected to the second input terminal of the analog clamping module; the third output terminal of the digital module is connected to the input terminal of the blanking module.

[0055] Specifically, the digital module is controlled by an independent signal line control method, that is, a digital module will have two independent signal lines to control the analog clamping module, and each output channel is independently controlled, so that the mutual influence between different signals can be eliminated and precise control can be achieved.

[0056] See Figure 5 , the analog clamping module includes a first digital-to-analog conversion circuit, a second digital-to-analog conversion circuit, a clamping voltage generation circuit, and a clamping time generation circuit;

[0057] Among them, the input terminal of the first digital-to-analog conversion circuit is used as the first input terminal of the analog clamping module, and the output terminal of the first digital-to-analog conversion circuit is connected to the first input terminal of the clamping voltage generation circuit; the input terminal of the second digital-to-analog conversion circuit is used as the second input terminal of the analog clamping module, and the output terminal of the second digital-to-analog conversion circuit is connected to the second input terminal of the clamping voltage generation circuit;

[0058] The output terminal of the clamping voltage generation circuit is connected to the input terminal of the clamping time generation circuit, and the output terminal of the clamping time generation circuit is used as the output terminal of the analog clamping module. The voltage values output by the first digital-to-analog conversion circuit and the second digital-to-analog conversion circuit are different.

[0059] Specifically, the analog clamping module includes two digital-to-analog conversion circuits, namely the first digital-to-analog conversion circuit and the second digital-to-analog conversion circuit. The first digital-to-analog conversion circuit receives the non-PWM clamping signal, and the second digital-to-analog conversion circuit receives the PWM clamping signal. The two digital-to-analog conversion circuits output different voltages by receiving different signals, so that the clamping voltage generation circuit will generate clamping voltages in different voltage ranges, thereby controlling the output clamping voltage value of the constant current output module. The digital-to-analog conversion circuit, the clamping voltage generation circuit, and the clamping time generation circuit can be implemented by corresponding modules in the existing LED display control chip. The PWM clamping signal and the non-PWM clamping signal in this method are independently generated and will not affect each other.

[0060] Preferably, it further includes a register control module;

[0061] The register control module is respectively connected to the control terminal of the clamping voltage generation circuit and the control terminal of the clamping time generation circuit.

[0062] Embodiment 2:

[0063] An LED display control method, which runs on the above-mentioned LED display control chip, includes the following steps:

[0064] When the digital module receives an external blanking instruction, it outputs a blanking signal and transmits it to the blanking module;

[0065] The blanking module drives the constant current output module to output a first signal according to the blanking signal and transmits it to the LED display screen;

[0066] When the digital module detects that there is no PWM waveform in the grayscale data to be displayed in the next frame, it generates a no-PWM clamping signal and transmits it to the analog clamping module;

[0067] The analog clamping module drives the constant current output module to output a second signal according to the no-PWM clamping signal and transmits it to the LED display screen;

[0068] When the digital module detects that there is a PWM waveform in the grayscale data to be displayed in the next frame, it generates a with-PWM clamping signal and transmits it to the analog clamping module;

[0069] The analog clamping module drives the constant current output module to output a third signal according to the with-PWM clamping signal and transmits it to the LED display screen;

[0070] Wherein, the voltage value of the first signal is greater than the voltage value of the second signal, and the voltage value of the second signal is greater than the voltage value of the third signal.

[0071] Specifically, Figure 6 It is the timing diagram of the LED display screen control method provided in the second embodiment. In this method, the priorities of the no-PWM clamping signal and the with-PWM clamping signal are both greater than the blanking signal. The clamping voltage is set to be able to open the channel at a faster speed, and the blanking voltage is set for blanking when the channel is closed. In this embodiment, through the electrical test experiment on the existing LED display screen, it is found that when there is a falling edge of the constant current output module output, if the clamping voltage value of the constant current output module opened by the no-PWM waveform is too low, the coupled negative pulse will cause the lamp that should not be lit to be lit (or the lamp that should be relatively dim to become brighter). When there is a rising edge of the constant current output module output, if the clamping voltage value of the constant current output module opened by the no-PWM waveform is too high, the coupled positive pulse will cause the lamp bead that should be lit to go out (or the lamp that should be relatively bright to become darker). Therefore, a higher clamping voltage is required at the falling edge, and a lower clamping voltage is required at the rising edge. So in this method, the voltage value of the first signal is greater than the voltage value of the second signal, and the voltage value of the second signal is greater than the voltage value of the third signal.

[0072] This method introduces the concepts of non-PWM clamping and PWM clamping. When the digital module detects that there is no PWM waveform in the grayscale data to be displayed in the next frame (i.e., the grayscale data to be displayed in the next frame is 0), it will generate a non-PWM clamping signal, causing the constant current output module to output a second signal and setting this channel to the non-PWM clamping state. When the digital module detects that there is a PWM waveform in the grayscale data to be displayed in the next frame (i.e., the grayscale data to be displayed in the next frame is not 0), it will generate a PWM clamping signal, causing the constant current output module to output a third signal and setting this channel to the PWM clamping state. In this way, the clamping mode of the channel can be controlled.

[0073] The display process of this method is blanking - non-PWM clamping - display - PWM clamping - blanking. All channels in this method follow the above logic. For the channels with non-PWM waveforms turned on, first the non-PWM clamping takes effect. When the time of non-PWM clamping ends, the channel is in a high-impedance state or the PWM clamping state.

[0074] This method can configure different states according to the display conditions of each channel, so as to better handle the display problems caused by various couplings on the display screen. Therefore, whether it is first-level coupling (channel-channel) or second-level coupling (channel - row line - channel), it will not have a very significant impact on the display system, thus greatly improving the display effect.

[0075] Preferably, the width of the second signal is greater than or equal to the width of the falling edge at the output end in the constant current output module. The width of the third signal is greater than or equal to the width of the rising edge at the output end in the constant current output module.

[0076] Specifically, the widths of the second signal and the third signal do not need to be set too long, as long as they can offset the pulses coupled out when the channel is turned on. The width of the second signal (i.e., the non-PWM clamping time), the width of the third signal (i.e., the PWM clamping time), the blanking time, the voltage value of the second signal, and the voltage value of the third signal can all be freely configured through registers. Due to the existence of the non-PWM and PWM clamping signals, the adjustable range between the PWM clamping signal and the blanking signal can become wider, which is more beneficial for blanking and resisting coupling interference, and is also simpler and more effective for debugging the display effect of the display screen.

[0077] For the method provided in the embodiments of the present invention, for the sake of brief description, for the parts not mentioned in the embodiment part, reference can be made to the corresponding content in the foregoing product embodiments.

[0078] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit them; although the present invention has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that they can still modify the technical solutions described in the foregoing embodiments, or perform equivalent replacements on some or all of the technical features; and these modifications or replacements do not cause the essence of the corresponding technical solutions to deviate from the scope of the technical solutions of the various embodiments of the present invention, and they should all be covered by the scope of the claims and the description of the present invention.

Claims

1. An LED display control chip, characterized in that, It includes a storage module and several output channels, and each of the output channels includes a digital module, a blanking module, an analog clamping module, and a constant current output module; Among them, the storage module is connected to the input end of the digital module, the output ends of the digital module are respectively connected to the input end of the blanking module and the input end of the analog clamping module, the output end of the analog clamping module is connected to the input end of the constant current output module, the output end of the blanking module is connected to the input end of the constant current output module, and the output end of the constant current output module serves as the output end of the LED display control chip; The storage module is used to store the grayscale data to be displayed for each frame of the LED display; The output end of the digital module includes a first output end, a second output end, and a third output end, and the input end of the analog clamping module includes a first input end and a second input end; Among them, the first output end of the digital module is connected to the first input end of the analog clamping module, and the second output end of the digital module is connected to the second input end of the analog clamping module; the third output end of the digital module is connected to the input end of the blanking module; among them, the digital module is provided with two independent signal lines to control the analog clamping module; The analog clamping module includes a first digital-to-analog conversion circuit, a second digital-to-analog conversion circuit, a clamping voltage generation circuit, and a clamping time generation circuit; Among them, the input end of the first digital-to-analog conversion circuit serves as the first input end of the analog clamping module, and the output end of the first digital-to-analog conversion circuit is connected to the first input end of the clamping voltage generation circuit; the input end of the second digital-to-analog conversion circuit serves as the second input end of the analog clamping module, and the output end of the second digital-to-analog conversion circuit is connected to the second input end of the clamping voltage generation circuit; The output end of the clamping voltage generation circuit is connected to the input end of the clamping time generation circuit, and the output end of the clamping time generation circuit serves as the output end of the analog clamping module.

2. The LED display control chip according to claim 1, wherein It also includes a register control module; The register control module is respectively connected to the control end of the clamping voltage generation circuit and the control end of the clamping time generation circuit.

3. The LED display control chip according to claim 1, wherein The voltage value output by the first digital-to-analog conversion circuit is different from the voltage value output by the second digital-to-analog conversion circuit.

4. A method for controlling an LED display screen, characterized in that, When running on the LED display control chip according to any one of claims 1 to 3, it includes the following steps: When the digital module receives an external blanking instruction, it outputs a blanking signal and transmits it to the blanking module; The blanking module drives the constant current output module to output a first signal according to the blanking signal and transmits it to the LED display; When the digital module detects that there is no PWM waveform in the grayscale data to be displayed in the next frame, it generates a no-PWM clamping signal and transmits it to the analog clamping module; The analog clamping module drives the constant current output module to output a second signal according to the no-PWM clamping signal and transmits it to the LED display; When the digital module detects that there is a PWM waveform in the grayscale data to be displayed in the next frame, it generates a with-PWM clamping signal and transmits it to the analog clamping module; The analog clamping module drives the constant current output module to output a third signal according to the with-PWM clamping signal and transmits it to the LED display; Among them, the voltage value of the first signal is greater than that of the second signal, and the voltage value of the second signal is greater than that of the third signal.

5. The LED display control method according to claim 4, characterized in that The priorities of both the non-PWM clamping signal and the PWM clamping signal are greater than that of the blanking signal.

6. The LED display control method according to claim 4, characterized in that The width of the second signal is greater than or equal to the width of the falling edge at the output end in the constant current output module.

7. The LED display control method according to claim 4, characterized in that The width of the third signal is greater than or equal to the width of the rising edge at the output end in the constant current output module.

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