Constant-current driving circuit, constant-current driving chip and display screen

Abstract

The invention discloses a constant-current driving circuit, a constant-current driving chip and a display screen. The constant-current driving circuit comprises a PWM (Pulse Width Modulation) generating circuit, a compensation value determining circuit and a PWM width compensating circuit, the PWM generation circuit generates PWM waves of each display group based on the sub-gray levels of the plurality of display groups obtained by scattering the total gray level; the compensation value determination circuit is used for determining a color temperature compensation value corresponding to the to-be-compensated data when the to-be-compensated data is in a preset compensation range; the color temperature compensation value is a specific compensation value corresponding to a gray value of the to-be-compensated data, and the to-be-compensated data is a total gray value or a sub-gray value; the PWM width compensation circuit is used for compensating a preset display group in the plurality of display groups according to a color temperature compensation value corresponding to the total gray scale; or, according to the color temperature compensation value corresponding to each sub-gray scale, compensating the display group corresponding to each sub-gray scale. The problem of color temperature difference between different low gray levels with low gray levels is solved, and the display effect of different gray levels is better.

Description

Technical Field

[0001] The present application relates to the field of display, and more specifically to a constant current drive circuit, a constant current drive chip and a display screen. Background Art

[0002] At present, the development trend of LED display screens is to increase the number of grayscale levels and display refresh rate. With the increase of grayscale levels and display refresh rate, the display clock frequency of the constant current driver chip needs to be higher and higher. In this way, when the grayscale level of the display is relatively low, the PWM wave is turned on for a very short time. Due to the different output currents of the constant current sources of the three primary colors of red, green and blue, and the nonlinearity of the opening and closing of the PWM wave, the color temperature of different low grayscale levels is different. For example, the display effect of some grayscale levels may be cyan, and the display effect of some grayscale levels may be purple.

[0003] At the same time, in the existing color temperature compensation method, different gray values ​​are compensated with the same fixed value. For example, all gray values ​​less than the threshold are compensated by 0.5 clock cycles, and the fixed compensation value is roughly determined only by the overall display effect. However, for different gray values, the energy of the lamp bead light is different as the opening frequency is different. If the existing fixed value compensation method is used, the compensation is not accurate and the display effect is poor.

[0004] The above problems have become issues that need to be solved urgently. Summary of the invention

[0005] The present application is proposed to solve at least one of the above problems. According to the first aspect of the present application, a constant current driving circuit is provided, the constant current driving circuit comprising: a PWM generating circuit, a compensation value determining circuit and a PWM width compensation circuit; wherein the PWM generating circuit generates a PWM wave for each display group based on the sub-grayscales of the multiple display groups obtained by breaking up the total grayscale; the compensation value determining circuit is used to determine the color temperature compensation value corresponding to the data to be compensated when the data to be compensated is in a preset compensation range, the color temperature compensation value is a specific compensation value corresponding to the grayscale value of the data to be compensated, and the data to be compensated is the total grayscale or the sub-grayscale; the PWM width compensation circuit is connected to the PWM generating circuit and the color temperature compensation value determining circuit, and the PWM width compensation circuit is used to: compensate for a preset display group in the multiple display groups according to the color temperature compensation value corresponding to the total grayscale; or, compensate for the display group corresponding to each sub-grayscale according to the color temperature compensation value corresponding to each sub-grayscale.

[0006] In one embodiment of the present application, the PWM wave of the display group after compensation is widened by K compared with the PWM wave of the display group. i / 2 Q clock cycles; where Ki is the color temperature compensation value of the display group, and Q is the number of bits of the color temperature compensation value.

[0007] In one embodiment of the present application, when the data to be compensated is the total grayscale, the preset compensation range is (0, M1]; wherein M1=M0×N, M0 represents a preset threshold, and N represents the maximum number of groups supporting group display.

[0008] In one embodiment of the present application, when the data to be compensated is the total grayscale, the preset compensation range is (0, M2]; wherein M2 is a non-dispersion threshold.

[0009] In one embodiment of the present application, when the data to be compensated is the sub-grayscale, the preset compensation range is (0, M3]; wherein M3 is a non-dispersion threshold.

[0010] In one embodiment of the present application, the preset display group is a display group with the smallest grayscale value among the multiple display groups.

[0011] In one embodiment of the present application, the compensation value determination circuit includes: a comparison module and a compensation value determination module; wherein the comparison module is used to compare the relationship between the data to be compensated and the preset compensation range; the compensation value determination module is connected to the comparison module, and the compensation value determination module is used to: when the comparison result of the comparison module is that the data to be compensated is within the preset compensation range, determine the color temperature compensation value corresponding to the data to be compensated.

[0012] In one embodiment of the present application, the constant current driving circuit also includes: a group judgment circuit and a group compensation value determination circuit; the group judgment circuit is used to: when the data to be compensated is the total grayscale, determine whether each display group is the preset display group; the group compensation value determination circuit is connected to the group judgment circuit, and the group compensation value determination circuit is used to: when the display group is the preset display group, use the color temperature compensation value corresponding to the total grayscale as the color temperature compensation value corresponding to the display group; and, when the display group is not the preset display group, use zero as the color temperature compensation value corresponding to the display group.

[0013] According to the second aspect of the present application, a constant current drive chip is also provided, which comprises: an output channel and any one of the above-mentioned constant current drive circuits; the output channel is connected to the PWM width compensation circuit, and the output channel is used to output a constant current.

[0014] According to a third aspect of the present application, a display screen is also provided, comprising: any one of the above-mentioned constant current drive chips.

[0015] According to the constant current drive circuit, constant current drive chip and display screen provided by the embodiments of the present application, by setting a compensation value determination circuit and a PWM width compensation circuit, the compensation value determination circuit is used to determine the color temperature compensation value corresponding to the data to be compensated when the data to be compensated is within a preset compensation range; the PWM width compensation circuit is used to: compensate a preset display group in multiple display groups according to the color temperature compensation value corresponding to the total grayscale; or compensate a display group corresponding to each sub-grayscale according to the color temperature compensation value corresponding to each sub-grayscale. The present application has the following effects:

[0016] 1. When the displayed grayscale level is relatively low, by compensating the PWM wave generated by the PWM generating circuit, the problem of different color temperatures between different low grayscale levels caused by the different output currents of the constant current sources of the three primary colors of red, green and blue, as well as the nonlinearity of the opening and closing of the PWM wave can be solved, thereby making the display effect of different grayscale levels better.

[0017] 2. When the gray is low, different gray values ​​are compensated differentially. The compensation value is related to the size of the gray value. It can solve the problem that the conventional compensation method is not accurate enough and the compensation effect is poor due to different gray values ​​and different opening frequencies and different luminous energy of the lamp beads. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] In order to more clearly illustrate the technical solutions in the embodiments of the present invention, the accompanying drawings required for use in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings in the following description are only some embodiments of the present invention. For ordinary technicians in this field, other accompanying drawings can be obtained based on these accompanying drawings without paying creative labor.

[0019] Figure 1 A schematic block diagram of a constant current driving circuit provided by an embodiment of the present invention;

[0020] Figure 2 A schematic block diagram of a constant current driving circuit provided by another embodiment of the present invention;

[0021] Figure 3 A schematic block diagram of a constant current driving circuit provided by another embodiment of the present invention;

[0022] Figure 4 A schematic block diagram of a constant current driving circuit provided by another embodiment of the present invention;

[0023] Figure 5 A schematic block diagram of a constant current drive chip provided by another embodiment of the present invention;

[0024] Figure 6 A schematic block diagram of a display screen provided in accordance with another embodiment of the present invention. DETAILED DESCRIPTION

[0025] In order to make the purpose, technical scheme and advantages of the present invention more obvious, the exemplary embodiments according to the present invention will be described in detail with reference to the accompanying drawings. Obviously, the described embodiments are only part of the embodiments of the present invention, rather than all the embodiments of the present invention, and it should be understood that the present invention is not limited to the exemplary embodiments described herein. Based on the embodiments of the present invention described in the present invention, all other embodiments obtained by those skilled in the art without creative work should fall within the protection scope of the present invention.

[0026] In the following description, a large number of specific details are provided to provide a more thorough understanding of the present invention. However, it is apparent to those skilled in the art that the present invention can be implemented without one or more of these details. In other examples, in order to avoid confusion with the present invention, some technical features well known in the art are not described.

[0027] It should be understood that the present invention can be implemented in different forms and should not be interpreted as limited to the embodiments set forth herein. On the contrary, these embodiments are provided to make the disclosure thorough and complete and to fully convey the scope of the present invention to those skilled in the art.

[0028] The purpose of the terms used herein is only to describe specific embodiments and is not intended to be limiting of the present invention. When used herein, the singular forms "one", "an" and "said / the" are also intended to include plural forms, unless the context clearly indicates otherwise. It should also be understood that the terms "consisting of" and / or "comprising", when used in this specification, confirm the presence of the features, integers, steps, operations, elements and / or parts, but do not exclude the presence or addition of one or more other features, integers, steps, operations, elements, parts and / or groups. When used herein, the term "and / or" includes any and all combinations of the relevant listed items.

[0029] In order to fully understand the present invention, a detailed structure will be proposed in the following description to illustrate the technical solution proposed by the present invention. The optional embodiments of the present invention are described in detail as follows, but in addition to these detailed descriptions, the present invention may also have other implementations.

[0030] In mid-to-high-end display screens, constant current source driver chips that can output high-refresh PWM (Pulse Modulation) are usually used. Many PWM displays of such chips use the SSPWM (Symmetrical and Scrambled Pulse Width Modulation) method, which divides the data into high gray (High Gray, HG) and low gray (Low Gray, LG) during display, where high gray data (HG) is displayed in groups, and low gray data (LG) is displayed in low gray without breaking up. For example, when the frame rate of the input video source = 60HZ, if the number of groups = 64 groups, the LED display refresh rate = 3840HZ (64*60).

[0031] As the number of grayscale levels and refresh rates increase, the display clock frequency of the constant current driver chip needs to be higher and higher. In this way, when the grayscale level is low, the PWM wave is turned on for a short time. Due to the different output currents of the constant current sources of the three primary colors of red, green and blue, and the nonlinearity of the opening and closing of the PWM wave, the color temperature of different low grayscale levels is different. For example, the display effect of some grayscale levels may be cyan, and the display effect of some grayscale levels may be purple. There is currently no effective adjustment method to solve this technical problem.

[0032] To solve at least some of the technical problems in the above-mentioned related technologies, the present application proposes the following embodiments.

[0033] Some embodiments of the present invention are described in detail below in conjunction with the accompanying drawings. In the absence of conflict, the following embodiments and features in the embodiments can be combined with each other.

[0034] First, the application scenario of the constant current drive circuit shown in the example of this application is introduced. The constant current drive circuit is applied to the PWM wave modulation scenario of the constant current source drive circuit.

[0035] refer to Figure 1The embodiment of the present application provides a constant current driving circuit, which includes: a PWM generating circuit, a compensation value determining circuit and a PWM width compensation circuit; wherein the PWM generating circuit generates a PWM wave for each display group based on the sub-grayscales of the multiple display groups obtained by breaking up the total grayscale; the compensation value determining circuit is used to determine the color temperature compensation value corresponding to the data to be compensated when the data to be compensated is in a preset compensation range, the color temperature compensation value is a specific compensation value corresponding to the grayscale value of the data to be compensated, and the data to be compensated is the total grayscale or all sub-grayscales; wherein the color temperature compensation value is a specific compensation value corresponding to the value of the data to be compensated; the PWM width compensation circuit is connected to the PWM generating circuit and the color temperature compensation value determining circuit, and the PWM width compensation circuit is used to: compensate a preset display group in the multiple display groups according to the color temperature compensation value corresponding to the total grayscale; or, compensate a display group corresponding to each sub-grayscale according to the color temperature compensation value corresponding to each sub-grayscale.

[0036] In the above scheme, by setting a compensation value determination circuit and a PWM width compensation circuit, the compensation value determination circuit is used to determine the color temperature compensation value corresponding to the data to be compensated when the data to be compensated is in a preset compensation range; the PWM width compensation circuit is used to: compensate a preset display group in a plurality of display groups according to the color temperature compensation value corresponding to the total grayscale; or, according to the color temperature compensation value corresponding to each sub-grayscale, compensate the display group corresponding to each sub-grayscale. In this way, when the grayscale level displayed is relatively low, by compensating the PWM wave generated by the PWM generation circuit, the color temperature can be adjusted by grayscale or by PWM wave width to solve the problem that the color temperature between different low grayscales with relatively low grayscales is different due to the different output currents of the constant current source of the three primary colors of red, green and blue, and the nonlinearity of the opening and closing of the PWM wave, so that the color temperature display effects of different grayscale levels are basically the same. Specifically, the color temperature is adjusted by compensating the pulse width of the PWM wave of the display group, and a separate color temperature compensation value is set for different grayscale values ​​or different PWM wave pulse widths to improve the display effect of the LED display screen. By selecting and configuring the color temperature compensation value as a specific compensation value corresponding to the value of the data to be compensated, the grayscale values ​​with different values ​​can be compensated differentially and specifically, so as to make up for the problem of inaccurate compensation and poor compensation effect caused by the fixed value compensation method in the prior art.

[0037] The above-mentioned circuit structures are described in detail below in conjunction with the accompanying drawings.

[0038] When setting the PWM generating circuit, the PWM generating circuit generates a PWM wave for each display group based on the sub-grayscales of the multiple display groups obtained by breaking up the total grayscale. The specific implementation method can be multiple methods. For example, the total grayscale level number of the total grayscale can be 256 levels, and specifically, the total grayscale can be any value between 0 and 255.

[0039] Exemplarily, the total grayscale to be displayed by a certain pixel unit can be obtained by reading a storage medium; then the total grayscale obtained is scattered into sub-grayscales of at least one display group, and the specific scattering method can be adopted in a variety of ways. Exemplarily, the total grayscale can be scattered into sub-grayscales of at least one display group by combining parameters such as but not limited to the maximum number of groups supported for group display, non-scattering threshold, preset threshold, etc., and adopting a scattering algorithm such as but not limited to binary search. Afterwards, the PWM generation circuit generates a PWM wave for each display group based on the sub-grayscale of each display group. Exemplarily, the PWM generation circuit generates a PWM wave for each display group based on the clock signal CLK and the sub-grayscale of each display group. Specifically, a grayscale unit can be represented by a clock cycle, and the number of clock cycles contained in the pulse width of the PWM wave is equal to the sub-grayscale of the display group, that is, the width of the sub-grayscale value clock cycles is the width of the PWM pulse corresponding to the sub-grayscale. For example, the sub-grayscale of a display group is R, which refers to R clock cycles. Correspondingly, the sub-grayscale R of the display group is input into the PWM generating circuit, and the pulse width of the PWM wave output of the display group is the width of R clock cycles.

[0040] An example of breaking up is introduced as follows. For example, if the total grayscale value is 10, it is broken up into 3 display groups, for example, it can be broken up into 3, 3, and 4, that is, the sub-grayscale of display group 1 is 3, and the pulse width of the PWM wave of display group 1 is 3 CLK cycles; the sub-grayscale of display group 2 is 3 CLK cycles, and the pulse width of the PWM wave of display group 2 is 3 CLK cycles; the sub-grayscale of display group 3 is 4, and the pulse width of the PWM wave of display group 3 is 4 CLK cycles. The total pulse width of the PWM waves of all display groups is 10 CLK cycles, corresponding to the aforementioned total grayscale value of 10.

[0041] Exemplarily, the PWM wave of the display group after compensation is widened by K compared with the PWM wave of the display group. i / 2 Q clock cycles; where K i is the color temperature compensation value corresponding to the display group, Q is the number of bits of the color temperature compensation value. i is an integer between 0 and R, and R is the maximum number of groups, that is, the maximum number of subframes into which a frame of image is divided. For example, K i is [0, 2 Q-1], thus providing 2 Q Different color temperature compensation value levels are provided to facilitate the selection of a suitable color temperature compensation value. It should be noted that in the present application, a specific color temperature compensation value can be configured in advance for each grayscale level. For example, the color temperature compensation value of grayscale 1 is represented by M1, the color temperature compensation value of grayscale 2 is represented by M2..., the color temperature compensation value of grayscale N is represented by MN, and the color temperature compensation values ​​can be the same or different from each other. Specifically, for example, the color temperature compensation values ​​corresponding to grayscale levels 1, 2, 3, ... N are 3, 2, 1, 1, 1..., 1 respectively.

[0042] In the present application, a color temperature compensation table can be set up first to pre-store specific compensation values ​​corresponding to each data to be compensated. When the compensation value determination circuit determines that a certain grayscale data is within the preset compensation range, the corresponding specific compensation value is searched in the color temperature compensation table according to the size of the grayscale data.

[0043] In one implementation, the data to be compensated is different and the compensation value is different;

[0044] In one implementation, the compensation value shows a trend of step change as the value of the data to be compensated increases. For example, when the data to be compensated is in the range of [1, A1), the compensation value is 3, when the data to be compensated is in the range of [A1, A2), the compensation value is 2, when the data to be compensated is in the range of [A2, A3), the compensation value is 1, ... It should be noted that in this application, according to non-ideal factors such as routing and parasitic capacitance, the compensation value may increase or decrease according to the increase of the data to be compensated. If it is a step change, the step increases or decreases.

[0045] Since the light emitting energy of the lamp beads is different for different grayscale values ​​and the opening frequency is different, the conventional compensation method will not be accurate enough and the compensation effect is poor. By adopting the scheme of the present application, according to the size of different data values ​​to be compensated, a specific compensation value corresponding to the value is configured, which can achieve targeted compensation and increase compensation accuracy.

[0046] For example, K i is greater than or equal to 0 and less than 2 Q An integer such that the PWM wave of the compensated display group is widened by a pulse width less than one clock cycle compared to the PWM wave of the display group. For example, the above Q can be equal to 8, then 2 Q =256, K iIt can be equal to any integer between 0 and 255. It should be understood that the above is only an exemplary way of determining the PWM wave width value of the display group after compensation compared with the PWM wave width value of the display group. In addition, other ways can be used based on the color temperature compensation value to determine the PWM wave width value of the display group after compensation compared with the PWM wave width value of the display group.

[0047] The processing methods of the compensation value determination circuit and the PWM width compensation circuit are specifically related to whether the data to be compensated is the total grayscale or all sub-grayscales. Similarly, the preset compensation range is specifically related to the type of data to be compensated. They are described separately as follows.

[0048] Example 1

[0049] In this embodiment, the data to be compensated is the total grayscale. The compensation value determination circuit is used to determine the color temperature compensation value corresponding to the data to be compensated when the total grayscale is within the preset compensation range; the PWM width compensation circuit is used to: compensate a preset display group among the multiple display groups according to the color temperature compensation value corresponding to the total grayscale.

[0050] That is, in this embodiment, the judgment object is the total grayscale, and specifically, it is judged whether the total grayscale is within the preset compensation range. When the judgment result is that the total grayscale is within the preset compensation range, it is necessary to determine the color temperature compensation value corresponding to the total grayscale. After determining the color temperature compensation value corresponding to the total grayscale, the color temperature compensation is not directly performed on the total grayscale, but one or more display groups of the multiple display groups obtained by breaking up the total grayscale are compensated. The one or more display groups are preset display groups among the multiple display groups. Afterwards, the PWM width compensation circuit compensates the preset display group according to the color temperature compensation value corresponding to the total grayscale.

[0051] In one embodiment, compensation is performed on only one of the display groups.

[0052] When determining the preset display grouping, a variety of methods can be used. Exemplarily, the preset display grouping can be a display grouping with the smallest grayscale value among multiple display groups. For example, the total grayscale is 5, which is within the preset compensation range. The total grayscale needs to be compensated, and the color temperature compensation value corresponding to the total grayscale is determined to be 7, and the number of bits Q of the color temperature compensation value is equal to 8. The total grayscale 5 is scattered into three display groups, and the results of the dispersion can be 1, 2, and 2. Specifically, the sub-grayscale of display group 1 is 1, and the pulse width of the PWM wave of display group 1 is 1 CLK; the sub-grayscale of display group 2 is 2, and the pulse width of the PWM wave of display group 2 is 2 CLK; the sub-grayscale of display group 3 is 2, and the pulse width of the PWM wave of display group 3 is 2 CLK. The preset display group can be display group 1, that is, the PWM width compensation circuit compensates the PWM wave of display group 1 according to the color temperature compensation value 7 corresponding to the total grayscale 5, and the pulse width of the compensated PWM wave is widened from the original 1 CLK to (1+7 / 256) CLK=263 / 256 CLK. The pulse widths of display group 2 and display group 3 are both 2 CLK and remain unchanged.

[0053] It should be noted that in the above example, the number of display groups with the smallest grayscale value among multiple display groups is 1 display group. In the application process, there may be a situation where the number of display groups with the smallest grayscale value among multiple display groups is more than 2, that is, the grayscale values ​​of more than 2 display groups are equal and the smallest. In this case, one display group can be arbitrarily selected from the more than 2 display groups that are equal and the smallest as the preset display group.

[0054] Exemplarily, the total grayscale is 4, which is within the preset compensation range. The total grayscale needs to be compensated. The color temperature compensation value corresponding to the total grayscale is determined to be 11, and the number of bits Q of the color temperature compensation value is equal to 8. The total grayscale 4 is scattered into three display groups, and the scattered results can be 1, 1, and 2. Specifically, the sub-grayscale of display group 1 is 1, and the pulse width of the PWM wave of display group 1 is 1 CLK; the sub-grayscale of display group 2 is 1, and the pulse width of the PWM wave of display group 2 is 1 CLK; the sub-grayscale of display group 3 is 2 CLK, and the pulse width of the PWM wave of display group 3 is 2 CLK. Then the preset display group can be display group 1. At this time, the PWM width compensation circuit compensates the PWM wave of display group 1 according to the color temperature compensation value 11 corresponding to the total grayscale 4. The pulse width of the compensated PWM wave is widened from the original 1 to (1+11 / 256) CLK=267 / 256 CLK. The pulse width of display group 2 is still 1 CLK, unchanged; the pulse width of display group 3 is still 2 CLK, unchanged. Of course, in the above example, the preset display group can also be display group 2. At this time, the PWM width compensation circuit compensates the PWM wave of display group 2 according to the color temperature compensation value 11 corresponding to the total grayscale 4. The pulse width of the compensated PWM wave is widened from the original 1 to (1+11 / 256) CLK=267 / 256 CLK. The pulse width of display group 1 is still 1 CLK, unchanged; the pulse width of display group 3 is still 2 CLK, unchanged.

[0055] Exemplarily, display group 1 (i.e., the first subframe displayed in a frame of image) is often the display group with the smallest grayscale value among multiple display groups, and the preset display group can be set as display group 1. It should be understood that the above is only an exemplary method for determining the preset display group, and other methods can also be used.

[0056] When the data to be compensated is the total grayscale, the preset compensation range may be set in a variety of ways, and several setting methods are exemplarily introduced below.

[0057] Exemplarily, when the data to be compensated is the total grayscale, the preset compensation range may be (0, M1], that is, the minimum grayscale value of the preset compensation range is greater than 0, and the maximum grayscale value is equal to M1. Among them, M1=M0×N, M0 represents the preset threshold, and N represents the maximum number of groups supporting grouped display, that is, the maximum number of subframes into which a subframe can be divided. For example, the preset threshold M0 may be equal to 2, and the maximum number of groups supporting grouped display N may be equal to 5, then the maximum grayscale value M1 of the preset compensation range is equal to 10. When applied, when the total grayscale is used as the judgment object, as long as the total grayscale is less than or equal to 10, it means that the total grayscale is within the preset compensation range, and it is necessary to compensate for the preset display groups in the multiple display groups obtained by breaking up the total grayscale.

[0058] Of course, it should be noted that when the data to be compensated is the total grayscale, the preset compensation range is not limited to the range shown above, and other preset ranges may also be used.

[0059] In other embodiments, when the data to be compensated is the total grayscale, the preset compensation range may be (0, M2], but in this embodiment, the physical meaning of M2 is different. In this embodiment, M2 is the non-dispersed threshold. Exemplarily, the non-dispersed threshold may be, for example, but not limited to, 4, 6, 8, 10, 12, etc.

[0060] It should be noted that the non-dispersion threshold refers to a parameter used in the above-mentioned dispersion algorithm. Usually in the LED display screen driving system, it is assumed that the non-dispersion threshold is L and the grayscale value is Q. When the total grayscale value Q is allocated to each display group, after the allocation is completed, in the display groups to which the grayscale value is allocated (that is, the sub-grayscale value of the display group is not equal to 0), the number of display groups with grayscale values ​​less than L is at most 1. For example, if the total grayscale value Q is 7, L is 3, and the number of subframes is 3, then it can be allocated in the manner of 1, 3, 3, 4, 3, and 3, 4, but not in the manner of 1, 1, 5.

[0061] Exemplary, reference Figure 2 The compensation value determination circuit may further include: a comparison module and a compensation value determination module. The comparison module is used to compare the relationship between the data to be compensated and the preset compensation range; the compensation value determination module is connected to the comparison module, and the compensation value determination module is used to: when the comparison result of the comparison module is that the data to be compensated is within the preset compensation range, determine the color temperature compensation value corresponding to the data to be compensated.

[0062] Specifically, refer to Figure 2The comparison module is used to compare the relationship between the data to be compensated and the preset compensation range. In this embodiment, the judgment object is the total grayscale, and the comparison module is used to compare the relationship between the total grayscale and the preset compensation range to determine whether the total grayscale is within the preset compensation range. The compensation value determination module is connected in communication with the comparison module to determine whether the preset display group obtained by breaking up the total grayscale needs to be further processed according to the comparison result of the comparison module.

[0063] refer to Figure 2 The compensation value determination module is used to determine the color temperature compensation value corresponding to the total grayscale when the comparison result of the comparison module is that the data to be compensated is within a preset partial range. Specifically, a separate color temperature compensation value can be set for each grayscale value, and each grayscale value corresponds to a compensation value M. For example, the color temperature compensation value of grayscale value 1 is represented by M1, the color temperature compensation value of grayscale value 2 is represented by M2, ..., the color temperature compensation value of grayscale value j is represented by Mj, and each color temperature compensation value can be the same or different from each other. When a total grayscale value is displayed, the color temperature compensation value set corresponding to the total grayscale is searched and obtained.

[0064] For example, the total grayscale is 5, the preset compensation range is (0, 10], the comparison module is used to determine whether the total grayscale 5 is within the range of (0, 10], and the judgment result is obviously that the total grayscale 5 is within the range of (0, 10]. The compensation value determination module is used to determine the color temperature compensation value corresponding to the total grayscale 5 when the judgment result of the comparison module is that the total grayscale 5 is within the range of (0, 10]. Exemplarily, the color temperature compensation value corresponding to the total grayscale 5 is determined to be 7.

[0065] Exemplary, reference Figure 3 The constant current driving circuit may further include: a grouping judgment circuit and a grouping compensation value determination circuit. The grouping judgment circuit is used to: when the data to be compensated is the total grayscale, determine whether each display group is a preset display group; the grouping compensation value determination circuit is connected to the grouping judgment circuit, and the grouping compensation value determination circuit is used to: when the display group is the preset display group, use the color temperature compensation value corresponding to the total grayscale as the color temperature compensation value corresponding to the display group; and when the display group is not the preset display group, use zero as the color temperature compensation value corresponding to the display group.

[0066] Specifically, refer to Figure 3The grouping judgment circuit is used to judge whether each display group obtained by breaking up the total grayscale is a preset display group. The judgment result may include: the display group is a preset display group, or the display group is not a preset display group. The grouping compensation value determination circuit is used to assign a color temperature compensation value to each display group according to the judgment result of the grouping judgment circuit. Specifically, when the judgment result of the grouping judgment circuit is that the display group is a preset display group, the color temperature compensation value corresponding to the total grayscale is used as the color temperature compensation value corresponding to the display group; when the judgment result of the grouping judgment circuit is that the display group is not a preset display group, zero is used as the color temperature compensation value corresponding to the display group, that is, no color temperature compensation is performed on the display group.

[0067] Exemplarily, the total grayscale 5 is scattered into three display groups, and the scattered results can be 1, 2, and 2. The total grayscale 5 is within the preset compensation range, the preset display group is display group 1, the color temperature compensation value corresponding to the total grayscale 5 is 7, and the number of bits Q of the color temperature compensation value is equal to 8. The grouping judgment circuit is used to judge in turn whether each display group in display group 1, display group 2, and display group 3 is a preset display group, and the grouping compensation value determination circuit is used to assign a color temperature compensation value to each display group according to the judgment result of the grouping judgment circuit. The processing flow is as follows:

[0068] The group judgment circuit first judges whether display group 1 is the preset display group. If the judgment result is that display group 1 is the preset display group, the group compensation value determination circuit uses the color temperature compensation value corresponding to the total grayscale 5 as 7 as the color temperature compensation value corresponding to display group 1, that is, the color temperature compensation value corresponding to display group 1 is 7, so that the PWM wave of display group 1 can be compensated by the PWM width compensation circuit later, and the pulse width of the compensated PWM wave is widened from the original 1 to (1+7 / 256) CLK=263 / 256 CLK.

[0069] The group determination circuit determines whether display group 2 is a preset display group. If the determination result is that display group 2 is not a preset display group, the group compensation value determination circuit uses 0 as the color temperature compensation value corresponding to display group 2, that is, no color temperature compensation is subsequently performed on display group 2. The pulse width of display group 2 is still 2 and remains unchanged.

[0070] The group determination circuit determines whether display group 3 is a preset display group. If the determination result is that display group 3 is not a preset display group, the group compensation value determination circuit uses 0 as the color temperature compensation value corresponding to display group 3, that is, no color temperature compensation is subsequently performed on display group 3. The pulse width of display group 3 is still 2 and remains unchanged.

[0071] Exemplarily, the judgment can be made by display group number. For example, assuming that there are N subframes (display groups) in total, the number of each display group is 0, 1, ..., N-1, and the number of the preset display group is N-2, then the group judgment circuit will judge whether it is the expected display group by identifying whether the number of the current display group is equal to the preset number, that is, N-2.

[0072] Example 2

[0073] In this embodiment, the data to be compensated are all sub-grayscales. The compensation value determination circuit is used to determine the color temperature compensation value corresponding to the sub-grayscale when the sub-grayscale is within the preset compensation range; the PWM width compensation circuit is used to: compensate the display group corresponding to each sub-grayscale according to the color temperature compensation value corresponding to each sub-grayscale; the PWM generation circuit is used to obtain the sub-grayscale value according to the total grayscale value, and generate a PWM wave corresponding to each sub-grayscale value.

[0074] It should be noted that determining whether the sub-grayscale is within the preset compensation range may be performed by directly determining whether the sub-grayscale value is within the preset range; for example, if the sub-grayscale value is 1 and the preset compensation range is (0, 4], it is directly determined whether 1 is within the range of (0, 4];

[0075] Alternatively, it is possible to determine whether the width of the PWM wave corresponding to each sub-grayscale is within the width corresponding to the aforementioned preset range. For example, the sub-grayscale value is 1, the preset compensation range is (0, 4], and it is determined whether the pulse width (width of 1CLK) of the PWM wave corresponding to the sub-grayscale value 1 generated by the PWM generating circuit is within the range of (0, 4CLK].

[0076] The difference between this embodiment and embodiment 1 is that the judgment object is different and the subsequent compensation method is different. Specifically, the judgment object of embodiment 1 is the total grayscale, while the judgment object of this embodiment is each sub-grayscale. The subsequent compensation method of embodiment 1 is: according to the color temperature compensation value corresponding to the total grayscale, the preset display group of multiple display groups is compensated. The subsequent compensation method of this embodiment is: according to the color temperature compensation value corresponding to each sub-grayscale, the display group corresponding to each sub-grayscale is compensated.

[0077] Exemplarily, when the data to be compensated is a sub-grayscale, the preset compensation range can be (0, M3]. That is, when the data to be compensated is a sub-grayscale, the minimum grayscale value of the preset compensation range is greater than 0, and the maximum grayscale value of the preset compensation range is M3. Exemplarily, M3 can also be the aforementioned non-dispersed threshold, that is, in some embodiments, M3=M2. It should be understood that the above only exemplarily shows a method for determining a preset compensation range when the data to be compensated is a sub-grayscale. In addition to this, other determination methods can also be used. Exemplarily, in other embodiments, M3 can also be equal to the above-mentioned preset threshold M0.

[0078] Exemplary, reference Figure 4 The compensation value determination circuit may include: a comparison module and a compensation value determination module; wherein the comparison module is used to compare the relationship between the data to be compensated and the preset compensation range; the compensation value determination module is connected to the comparison module, and the compensation value determination module is used to: when the comparison result of the comparison module is that the data to be compensated is within the preset compensation range, determine the color temperature compensation value corresponding to the data to be compensated.

[0079] Specifically, refer to Figure 4 The comparison module is used to compare the relationship between the data to be compensated and the preset compensation range. In this embodiment, the judgment object is each sub-grayscale, and the comparison module is used to compare the relationship between each sub-grayscale and the preset compensation range to determine whether each sub-grayscale is within the preset compensation range. The compensation value determination module is connected in communication with the comparison module to determine whether the display group corresponding to each sub-grayscale needs to be further processed according to the comparison result of the comparison module.

[0080] refer to Figure 4 The compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale when the comparison result of the comparison module is that the sub-grayscale is within the preset partial range. Specifically, a separate color temperature compensation value can be set for each grayscale value, and each grayscale value is equal to a corresponding compensation value M. For example, the color temperature compensation value of grayscale value 1 is M1 、 The color temperature compensation value of gray value 2 is represented by M2, ..., the color temperature compensation value of gray value j is represented by Mj, and each color temperature compensation value can be the same or different from each other. When a sub-gray value is displayed, the color temperature compensation value corresponding to the sub-gray value is searched and obtained.

[0081] For example, the total grayscale is 10, which is divided into three display groups, namely 3, 3, and 4, that is, the sub-grayscale of display group 1 is 3, and the pulse width of the PWM wave of display group 1 is 3 CLKs; the sub-grayscale of display group 2 is 3, and the pulse width of the PWM wave of display group 2 is 3 CLKs; the sub-grayscale of display group 3 is 4, and the pulse width of the PWM wave of display group 3 is 4 CLKs. The preset compensation range is (0, 4]. The comparison module is used to determine whether each sub-grayscale is within the range of (0, 4] in turn. The compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale when the comparison result of the comparison module is that the sub-grayscale is within the preset compensation range. Then, the PWM width compensation circuit compensates the display group corresponding to each sub-grayscale according to the color temperature compensation value corresponding to each sub-grayscale. The following is a detailed introduction:

[0082] First, the comparison module determines that the sub-grayscale 3 of the display group 1 is within the preset compensation range (0, 4]. The compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale 3 of the display group 1 when the comparison module determines that the sub-grayscale 3 of the display group 1 is within the preset compensation range (0, 4]. Exemplarily, the color temperature compensation value corresponding to the sub-grayscale 3 of the display group 1 is determined to be 5, and the number of bits Q of the color temperature compensation value is equal to 8. Then, the PWM wave of the display group 1 is compensated by the PWM width compensation circuit, and the pulse width of the compensated PWM wave is widened from the original 3 to (3+5 / 256) CLK.

[0083] Next, the comparison module determines that the sub-grayscale 3 of the display group 2 is within the preset compensation range (0, 4], and the compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale 3 of the display group 2 when the comparison module determines that the sub-grayscale 3 of the display group 2 is within the preset compensation range (0, 4]. Exemplarily, the color temperature compensation value corresponding to the sub-grayscale 3 of the display group 2 is determined to be 5, and the number of bits Q of the color temperature compensation value is equal to 8. Then, the PWM wave of the display group 2 is compensated by the PWM width compensation circuit, and the pulse width of the compensated PWM wave is widened from the original 3 to (3+5 / 256) CLK.

[0084] Next, the comparison module determines that the sub-grayscale 4 of the display group 3 is within the preset compensation range (0, 4], and the compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale 4 of the display group 3 when the comparison module determines that the sub-grayscale 4 of the display group 3 is within the preset compensation range (0, 4]. Exemplarily, the color temperature compensation value corresponding to the sub-grayscale 4 of the display group 3 is determined to be 3, and the number of bits Q of the color temperature compensation value is equal to 8. Then, the PWM wave of the display group 3 is compensated by the PWM width compensation circuit, and the pulse width of the compensated PWM wave is widened from the original 4 to (4+3 / 256) CLK.

[0085] It should be understood that in the above example, the sub-grayscale corresponding to each display group is within the preset compensation range. In the application process, there may be a situation where the sub-grayscale of some display groups is within the preset compensation range, while the sub-grayscale of some display groups is not within the preset compensation range. An example situation is introduced as follows.

[0086] For example, the total grayscale is 13, which is broken down into three display groups, namely 4, 4, and 5, that is, the sub-grayscale of display group 1 is 4, and the pulse width of the PWM wave of display group 1 is 4 CLKs; the sub-grayscale of display group 2 is 4, and the pulse width of the PWM wave of display group 2 is 4 CLKs; the sub-grayscale of display group 3 is 5, and the pulse width of the PWM wave of display group 3 is 5 CLKs. The preset compensation range is still (0, 4]. The comparison module is used to determine whether each sub-grayscale is within the range of (0, 4] in turn. The compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale when the comparison result of the comparison module is that the sub-grayscale is within the preset compensation range. After that, the PWM width compensation circuit compensates the display group corresponding to each sub-grayscale according to the color temperature compensation value corresponding to each sub-grayscale. The following is a detailed introduction:

[0087] First, the comparison module determines that the sub-grayscale 4 of the display group 1 is within the preset compensation range (0, 4]. The compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale 4 of the display group 1 when the comparison module determines that the sub-grayscale 4 of the display group 1 is within the preset compensation range (0, 4]. Exemplarily, the color temperature compensation value corresponding to the sub-grayscale 4 of the display group 1 is determined to be 3, and the number of bits Q of the color temperature compensation value is equal to 8. Then, the PWM wave of the display group 1 is compensated by the PWM width compensation circuit, and the pulse width of the compensated PWM wave is widened from the original 4 to (4+3 / 256) CLK.

[0088] Next, the comparison module determines that the sub-grayscale 4 of the display group 2 is within the preset compensation range (0, 4], and the compensation value determination module is used to determine the color temperature compensation value corresponding to the sub-grayscale 4 of the display group 2 when the comparison module determines that the sub-grayscale 4 of the display group 2 is within the preset compensation range (0, 4]. Exemplarily, the color temperature compensation value corresponding to the sub-grayscale 4 of the display group 2 is determined to be 3, and the number of bits Q of the color temperature compensation value is equal to 8. Then, the PWM wave of the display group 2 is compensated by the PWM width compensation circuit, and the pulse width of the compensated PWM wave is widened from the original 4 to (4+3 / 256) CLK.

[0089] Next, the comparison module determines that the sub-grayscale 5 of the display group 3 is not within the preset compensation range (0, 4], and the compensation value determination module does not need to determine the color temperature compensation value corresponding to the sub-grayscale 5 of the display group 3, or directly uses 0 as the color temperature compensation value corresponding to the sub-grayscale 5 of the display group 3. The PWM width compensation circuit does not need to compensate the PWM wave of the display group 3. The pulse width of the PWM wave of the display group 3 remains unchanged at 5 CLK.

[0090] Furthermore, the present application embodiment also provides a constant current driver chip, referring to Figure 5The constant current driving chip includes: an output channel and any one of the above constant current driving circuits; the output channel is connected to the PWM width compensation circuit, and the output channel is used to output a constant current.

[0091] Exemplarily, the number of output channels of the constant current driver chip can be H, where H is a positive integer. When the constant current driver chip displays a certain row, the corresponding H total grayscale data are read out from a storage medium such as but not limited to SRAM. Each total grayscale in the H total grayscale data is processed by the above-mentioned constant current driver circuit to achieve color temperature compensation. Specifically, for each channel in the H output channels, the total grayscale value corresponding to each channel is processed by the above-mentioned constant current driver circuit to perform color temperature compensation. The specific compensation method can adopt the above-mentioned embodiment 1, or the above-mentioned embodiment 2 to complete the color temperature compensation.

[0092] The output channel is connected to the PWM width compensation circuit, which is used to output a constant current according to the PWM wave of the display group processed by the PWM width compensation circuit. For the display group after color temperature compensation, the PWM wave of the compensated display group is output. At this time, the PWM wave of the compensated display group can be called an SPWM wave; for the display group without color temperature compensation, the PWM wave of the display group can be directly output. Thus, the output channel controls the output constant current according to the output PWM wave.

[0093] In addition, the present application also provides a display screen, referring to Figure 6 , the display screen includes: any one of the above constant current driver chips. Exemplarily, the type of the display screen can be such as but not limited to LED display screen, Mini-LED display screen, Micro-LED display screen, etc. Exemplarily, reference Figure 6 The display panel may be provided with pixel units composed of LED lamp beads. There may be multiple constant current drive chips, and each constant current drive chip is connected to the display panel.

[0094] The present invention has been described by the above embodiments, but it should be understood that the above embodiments are only for the purpose of example and description, and are not intended to limit the present invention to the scope of the described embodiments. In addition, it can be understood by those skilled in the art that the present invention is not limited to the above embodiments, and more variations and modifications can be made according to the teachings of the present invention, and these variations and modifications all fall within the scope of the protection claimed by the present invention. The protection scope of the present invention is defined by the attached claims and their equivalents.

Claims

1. A constant current driving circuit, characterized in that: include: A PWM generating circuit generates a PWM wave for each display group based on the sub-grayscales of the plurality of display groups obtained by breaking up the total grayscale; A compensation value determination circuit, used for determining a color temperature compensation value corresponding to the data to be compensated when the data to be compensated is within a preset compensation range, wherein the color temperature compensation value is a specific compensation value corresponding to the grayscale value of the data to be compensated, and the data to be compensated is the total grayscale or sub-grayscale; A PWM width compensation circuit is connected to the PWM generation circuit and the color temperature compensation value determination circuit, and is used to: Compensating a preset display group among the multiple display groups according to the color temperature compensation value corresponding to the total grayscale; or, According to the color temperature compensation value corresponding to each sub-grayscale, the display group corresponding to each sub-grayscale is compensated.

2. The constant current driving circuit according to claim 1, characterized in that: The PWM wave of the display group after compensation is widened by K compared with the PWM wave of the display group. i / 2 Q clock cycles; where K i is the color temperature compensation value of the display group, and Q is the number of bits of the color temperature compensation value.

3. The constant current driving circuit according to claim 1, characterized in that: When the data to be compensated is the total grayscale, the preset compensation range is (0, M1]; wherein M1=M0×N, M0 represents a preset threshold, and N represents the maximum number of groups supporting group display.

4. The constant current driving circuit according to claim 1, characterized in that: When the data to be compensated is the total grayscale, the preset compensation range is (0, M2]; wherein M2 is a non-dispersion threshold.

5. The constant current driving circuit according to claim 1, characterized in that: When the data to be compensated is the sub-grayscale, the preset compensation range is (0, M3]; wherein M3 is a non-dispersion threshold.

6. The constant current driving circuit according to claim 1, characterized in that: The preset display group is a display group with the smallest grayscale value among the multiple display groups.

7. The constant current driving circuit according to claim 1, characterized in that: The compensation value determination circuit comprises: A comparison module, used for comparing the relationship between the data to be compensated and the preset compensation range; The compensation value determination module is connected to the comparison module and is used to determine the color temperature compensation value corresponding to the data to be compensated when the comparison result of the comparison module is that the data to be compensated is within the preset compensation range.

8. The constant current driving circuit according to any one of claims 1 to 7, characterized in that: Also includes: A grouping judgment circuit and a grouping compensation value determination circuit; The group determination circuit is used to: when the data to be compensated is the total grayscale, determine whether each display group is the preset display group; The group compensation value determination circuit is connected to the group judgment circuit and is used to: when the display group is the preset display group, use the color temperature compensation value corresponding to the total grayscale as the color temperature compensation value corresponding to the display group; and when the display group is not the preset display group, use zero as the color temperature compensation value corresponding to the display group.

9. A constant current drive chip, comprising: The constant current drive circuit as claimed in any one of claims 1 to 8; An output channel is connected to the PWM width compensation circuit and is used to output a constant current.

10. A display screen, characterized in that: include: The constant current driver chip as claimed in claim 9.

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