A display driving method and a display driving chip

Abstract

The application relates to a display driving method and a display driving chip, and belongs to the LED display field, and solves the problem of poor LED display screen effect in the prior art. The display driving method comprises the following steps: confirming a first time point t1 in a display area, t0 < t1 < t2, t0 and t2 respectively represent a start time and an end time of the display area; the PWM wave is evenly distributed to both sides of the first time point t1; and a constant current is output based on the PWM wave. The driving method can significantly improve the display effect.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of LED display, in particular to an LED display driving method and display driving chip. BACKGROUND

[0002] In prior art, one frame of image is usually divided into multiple display sub-frames, and one display sub-frame is divided into multiple display groups. The display is performed sub-frame by sub-frame and group by group, so as to complete the display of the whole image.

[0003] For one display group, the display data is allocated to the display area, which is generally allocated from the start position of the display area to the rear (such as Figure 1 ), or from the end position of the display area to the front. However, since the front of the display area involves pre-charge (for example, for eliminating the first row dim problem), and the rear of the display area involves the elimination of the shadow problem, if the display data is directly allocated from the start time or the end time of the display area, that is, the time when the constant current source is turned on is close to the front or the rear of the display area, it will inevitably affect the pre-charge and the elimination of the shadow, resulting in poor display effect.

[0004] The above problems become problems that need to be solved. SUMMARY

[0005] The present application aims to overcome the shortcomings of prior art, and provide a display driving method and display driving chip to significantly improve the LED display effect.

[0006] The first aspect of the present application provides a display driving method, which comprises:

[0007] Confirming a first time point t1 in the display area, t0 < t1 < t2, t0 and t2 respectively represent the start time and the end time of the display area;

[0008] Equally allocating the PWM wave to both sides of the first time point t1;

[0009] Or,

[0010] Allocating the PWM wave to one side of the first time point t1 along the first time point t1, if the allocable area width of the side is less than the PWM wave width, then allocating the part of the PWM wave exceeding the allocable area width to the other side of the first time point t1 along the first time point t1;

[0011] Outputting a constant current based on the PWM wave.

[0012] The present application starts to grow the PWM wave at the middle position of the display area, so as to reduce the influence on the pre-charge and the elimination of the shadow as much as possible, and improve the display effect.

[0013] Optionally, the PWM wave is evenly distributed to both sides of the first time point t1, comprising:

[0014] The gray value corresponding to the PWM wave width distributed to both sides of the first time point t1 is M and N respectively, M=Q0*A+Y, N=Q0*(A+B), wherein A and B are the integer part and the remainder part of X / 2, X and Y are the integer part and the remainder part of Q / Q0, Q is the gray value of the gray data, and Q0 is the first threshold.

[0015] Optionally, the PWM wave is evenly distributed to both sides of the first time point t1, comprising:

[0016] The gray value corresponding to the PWM wave width distributed to both sides of the first time point t1 is M and N respectively, N=M+B; wherein M and B are the integer part and the remainder part of Q / 2 respectively, and Q is the gray value of the gray data.

[0017] Optionally, t1=(t0+t2) / 2.

[0018] Optionally, the PWM wave comprises a spread part, and the spread part is located in front of or behind the PWM wave.

[0019] Optionally, the display driving method further comprises:

[0020] When the gray value distributed in the display area is not 0, pre-charge the column line to the corresponding potential outside the display area in time;

[0021] When the gray value distributed in the display area is 0, pre-charge the column line to the corresponding potential in the display unit in time; wherein the display unit refers to the smallest display grouping of display data in one sub-frame, and the display area is included in the display unit.

[0022] Optionally, the first time point t1 is configurable according to display effect.

[0023] Another aspect of the present application provides a display driving chip. It comprises:

[0024] A storage circuit is configured to configure a first time point t1 in a display area, t0

[0025] A PWM wave generation circuit is configured to:

[0026] The PWM wave is evenly distributed to both sides of the first time point t1;

[0027] Or,

[0028] If the width of the allocable region on one side of the first time point t1 is less than the width of the PWM wave, the part of the PWM wave exceeding the width of the allocable region is allocated to the other side of the first time point t1 along the first time point t1.

[0029] The channel current output module outputs a constant current based on the PWM wave.

[0030] Optionally, the gray scale values corresponding to the widths of the PWM waves allocated to the two sides of the first time point t1 are M and N respectively, M=Q0*A+Y, and N=Q0*(A+B), where A and B are the integer part and the remainder part of X / 2, X and Y are the integer part and the remainder part of Q / Q0, Q is a gray scale value of the gray scale data, and Q0 is a first threshold value.

[0031] Optionally, the gray scale values corresponding to the widths of the PWM waves allocated to the two sides of the first time point t1 are M and N respectively, N=M+B, where M and B are the integer part and the remainder part of Q / 2 respectively, and Q is a gray scale value of the gray scale data.

[0032] Optionally, the PWM wave comprises a widening part, and the widening part is located in front of or behind the PWM wave.

[0033] Optionally, the display driving chip further comprises:

[0034] When the gray scale value allocated to the display region is not 0, the pre-charge circuit pre-charges the column line to a corresponding potential in time outside the display region.

[0035] When the gray scale value allocated to the display region is 0, the pre-charge circuit pre-charges the column line to a corresponding potential in time inside the display unit, wherein the display unit refers to the minimum display grouping of the gray scale data in one sub-frame, and the display region is included in the display unit.

[0036] Optionally, the first time point t1 is configurable according to display effects.

[0037] The application has the following beneficial effects:

[0038] Compared with the prior art, the application provides a display driving method and a display driving chip, which can reduce the influence on front pre-charging and rear image elimination and improve display effects by reasonably allocating display data positions (for example, positions of high levels of PWM waves). BRIEF DESCRIPTION OF DRAWINGS

[0039] Figure 1 is a PWM wave growth method provided by the prior art;

[0040] Figure 2is a schematic diagram of the gray data display provided by the present application;

[0041] Figure 3 is a PWM wave growth method of an embodiment of the present application;

[0042] Figure 4 is a PWM wave growth method of another embodiment of the present application;

[0043] Figure 5 is a display driving chip of an embodiment of the present application. DETAILED DESCRIPTION

[0044] The technical solutions of the present application will be described in further detail below in combination with specific embodiments, but the protection scope of the present application is not limited to the following description.

[0045] Figure 1 A PWM (pulse width modulation) wave growth method of the prior art is shown. The start time and end time of a display region are t0 and t2 respectively, the start time of a PWM wave is t3 (for example, a rising edge), and the end time of the PWM wave is t4 (for example, a falling edge). The prior art tends to grow the PWM wave backward along the start time t0 of the display region (for example, as shown in FIG. 1) or to grow the PWM wave forward along the end time t2 of the display region. Figure 1 At this time, the start time of the display region and the start time of the PWM wave are the same.

[0046] Figure 2 A schematic diagram of the gray data display is provided. A complete display frame is divided into a plurality of subframes (P), and a complete subframe includes a plurality of display groups (a first row display group, a second row display group, …, an mth display group, m being the number of rows of the display screen). The display unit referred to in the present application refers to the minimum display group of the gray data in a display subframe (for example, the display unit refers to the display period of a display group), and the display region refers to the part included in the display unit and used for assigning the gray data or the PWM wave (it should be noted that the display period of a display group includes, in addition to the display region, a pre-charge stage before the display region and a fade-out stage after the display region). Generally, there is a pre-charge before the display region to eliminate the first row darkening, and there is a fade-out operation after the display region. If the PWM growth method shown in FIG. 1 is used, the grown PWM wave is either close to the area before the display region or close to the area after the display region, which will inevitably affect the display effect. Figure 1 Figure 2 ​The principle diagram of gray data display is provided. A complete display frame is divided into multiple subframes (P), and a complete subframe includes multiple display groups (1st row display group, 2nd row display group, …, mth display group, m is the number of rows of the display screen). The display unit in the present application refers to the minimum display group of gray data in a display subframe (for example, the display unit refers to the display period of one display group), the display area is the part included in the display unit, which is used to allocate gray data or PWM wave (it should be noted that the display period of one display group includes the pre-charge stage in front of the display area and the erasing stage behind the display area, in addition to the display area). Generally, there is pre-charge before the display area to eliminate the first row darkening, and there is erasing operation after the display area. If the PWM growth mode shown in the figure is adopted, the grown PWM wave is close to the area in front of the display area or close to the area behind the display area, which will inevitably affect the display effect. Figure 1

[0047] In order to solve the above problems, the present application provides a display driving method, which can be specifically a display driving method of an LED display screen. The method comprises:

[0048] Confirming a first time point t1 in the display area, t0 < t1 < t2, t0 and t2 respectively represent the start time and the end time of the display area;

[0049] The PWM wave is evenly distributed to both sides of the first time point t1;

[0050] Or,

[0051] The PWM wave is distributed to one side of the first time point t1 along the first time point t1, and if the allocable area width of the side is less than the PWM wave width, the part of the PWM wave exceeding the allocable area width is distributed to the other side of the first time point t1 along the first time point t1;

[0052] Based on the PWM wave, a constant current is output.

[0053] The display area of the present application refers to the area for allocating display data (i.e. gray data or PWM wave), and the area where the display data (gray data or PWM wave) is allocated is considered as the actual display area, wherein the width of the PWM wave corresponds to the size of the gray data, both of which reflect the lighting time of the lamp beads. Figure 1 、 3 ​As shown, the start time and end time of the display region are t0 and t2 respectively, the region width of the display data that can be allocated is t2-t0, and the high level part is the actual display region, i.e. the part where the gray data or PWM wave is actually allocated. It needs to be understood that the driving chip controls whether the lamp bead is lit according to the PWM wave, for example, it controls the output of a constant current in the above high level stage, thereby lighting the lamp bead, and stops outputting the constant current in the low level stage, and the lamp bead is extinguished. The width of the high level (i.e. the width of the PWM wave) represents the lighting duration of the lamp bead.

[0054] As mentioned before, in the prior art, as shown in Figure 1 , if the PWM wave grows from the start time t0 of the display region to the front or from the end time t2 to the back, it will inevitably have an impact on the pre-charge in front and the image elimination, thereby affecting the low gray display effect.

[0055] Based on this, the present application proposes a method of growing from the middle to both sides. That is, to find a suitable time point t1 (t0 Figures 3-4 .

[0056] It needs to be explained that the PWM wave allocated to the display region in the present application is a continuous segment, as shown in Figure 1 , 3 , 4, the start time (e.g. rising edge time) and end time (e.g. falling edge time) are represented by t3 and t4 respectively, then t3 <= t1 <= t4 (i.e. the PWM wave is high between t3 and t4). And the PWM width represents the size of the gray data, which is used to determine the lighting duration of the LED lamp bead.

[0057] Figure 3 (Vertical axis: gray value of gray data, horizontal axis: time) shows how to grow (allocate) the PWM wave (gray data) evenly to both sides along the first time point t1 as the gray data changes (e.g. increases). By evenly growing, it means that the gray values corresponding to the width of the PWM wave allocated on both sides of t1 are not significantly different, for example, within an allowable threshold range, such as Q0 (first threshold, described in detail below). In one embodiment, the gray value is an integer and Q0 is an integer. In this case, when the gray value is 1, it is allocated to one side, when the gray value is 2, it is allocated to both sides, when the gray value is 3, it is allocated to one side 1 and the other side 2, and when the gray value is 4, it is allocated to both sides 2. At this time Q0 = 1. Of course, Q0 can also be other values, for example, any number greater than 1, or an integer greater than or equal to 2.

[0058] Figure 4Another way to allocate PWM wave to both sides of t1 as the gray data changes (e.g., increases) is shown. When the gray value is small (here, the gray value is less than or equal to 4), the PWM wave can grow along t1 to one side of t1. At this time, as shown in Figure 4 , t0 = < t3 < t1, t4 = t1; if the gray data is large enough (here, the gray value is greater than 4), as shown in Figure 4 , the width of the gray data (PWM wave) that can be allocated to one side of t1 (i.e., the width of the display area on one side of t1) is only 4, then the gray data (PWM wave) except for the part allocated to the side described above (here, the left side is allocated full, i.e., the gray value is 4) grows along t1 to the other side, and the result is that, as shown in Figure 4 , t3 = t0, t1 < t4 <= t2. Taking the high level between t3 and t4 as an example, i.e., the gray data (PWM is high) is allocated to one side of t1 (the left side). Figure 4 The gray data (high level along t1 to the right) is allocated to the other side of t1.

[0059] For the second way, when the gray value of the gray data is small, it is directly allocated to one side of t1, and when the gray data is large, the width of the gray data that can be allocated to the side is not enough, then the remaining gray data that cannot be allocated grows along t1 to the other side.

[0060] In one possible implementation, the PWM wave is evenly allocated to both sides of the first time point t1, and at this time:

[0061] The width of the PWM wave allocated to both sides of the first time point t1 (denoted as W1 and W2) corresponds to the gray value sizes M and N, respectively, M = Q0*A+Y, N = Q0*(A+B), where A and B are the integer part (quotient) and the remainder part (remainder) of X / 2, X and Y are the integer part and the remainder part of Q / Q0, Q is the gray value of the gray data, and Q0 is the first threshold.

[0062] That is, the gray value sizes M and N corresponding to the PWM width on both sides of t1 differ by no more than Q0. Taking Q0 = 2 as an example, if Q = 1, 2, then the gray data is allocated to the left side of t1; if Q = 3, 4, then 2 is allocated to one side and 1, 2 is allocated to the other side; if Q = 5, 6, then 2 is allocated to one side and 3, 4 is allocated to the other side; if Q = 7, 8, then 4 is allocated to one side and 3, 4 is allocated to the other side, and so on.

[0063] In one possible implementation, when the PWM wave is equally distributed to both sides of the first time point t1, the width of the PWM wave distributed to both sides of the first time point t1 corresponds to the gray scale values of M and N respectively, and N=M+B; wherein M and B are the integer part and the remainder part of Q / 2 respectively, and Q is the gray scale value of the gray scale data.

[0064] As shown in Figure 3 , the gray scale data is as evenly distributed as possible to both sides of t1. For example, if Q=1, it is distributed to one side of t1; if Q=2, it is 1 on each side of t1; if Q=3, it is 1 on one side and 2 on the other side; if Q=4, it is 2 on one side and 2 on the other side; and so on.

[0065] In one preferred implementation, t1=(t0+t2) / 2. That is, the first time point t1 is located at the center of the display area. It can be understood that, at this time, the influence of the pre-charge and the elimination of the shadow is compromised, and the display effect is maximized.

[0066] In one preferred implementation, the PWM wave includes a spread part. Assuming that the original gray scale data is Q, and the gray scale data corresponding to the width of the spread part is ADD, then the total gray scale data corresponding to the width of the PWM wave during actual display is Q+ADD. The ADD part has different uses in different scenarios. In some scenarios, it is used to form a gray scale data with higher precision together with Q. For example, the actual gray scale data to be displayed is 3.2T, T represents a clock period, and due to hardware limitations in the prior art, only 3T can be displayed. In order to obtain accurate 3.2T, the PWM of 3T needs to be spread to obtain a PWM wave of 3.2T. In other scenarios, low gray compensation is needed for low gray data, at which time the original gray scale data needs to be compensated to obtain the spread PWM wave. Regardless of the scenario, the PWM wave grown in the manner described above can be such a spread PWM wave.

[0067] In one implementation, the foregoing display driving method further comprises:

[0068] When the gray scale value allocated to the display area is not 0, pre-charge the column line to the corresponding potential in time outside the display area;

[0069] When the gray scale value allocated to the display area is 0, pre-charge the column line to the corresponding potential in time within the display unit; wherein the display unit refers to the smallest display grouping of the gray scale data within one subframe, and the display area is included in the display unit.

[0070] That is, in a display unit, if the display area is assigned a gray value other than 0 (a PWM high stage exists), that is, the LED lamp bead will be lit, then after line feed, the column line is pre-charged to a predetermined potential (for eliminating the first row dimness) before the display area. After the display area end time, before line feed, the column line is pre-charged to eliminate the image. Within the display area, the pre-charging circuit is in the off state; outside the display area, the pre-charging circuit pre-charges the column line in time, and each time period corresponds to a target potential to which the column line is charged. For example, time1 starts, the pre-charging circuit charges the column line to V1, from time2, the pre-charging circuit charges the column line to V2, from time3, the pre-charging circuit is off, from time4, the pre-charging circuit charges the column line to V3. Of course, the pre-charging process does not necessarily have to be as described above, and can also include fewer or more charging stages.

[0071] If the display area is assigned a gray value of 0, indicating that the LED lamp bead will not be lit, the pre-charging operation of the column line can be located within the entire display unit according to the display effect. Within the display unit, the column line is also charged to each predetermined target potential in time. When the gray value is 0 or not 0, the target potential corresponding to each stage can be adjusted according to the display effect.

[0072] In an optional implementation, the first time point t1 is configurable according to the display effect.

[0073] The second aspect of the application provides a display driving chip which can execute the display driving method of the first aspect. As shown in the figure, the display driving chip includes: Figure 5

[0074] A storage circuit configured to configure a first time point t1 in a display area, t0 < t1 < t2, wherein t0 and t2 respectively represent the start time and end time of the display area;

[0075] A PWM wave generation circuit configured to:

[0076] Equally distribute the PWM wave to both sides of the first time point t1;

[0077] Or,

[0078] Distribute the PWM wave to one side of the first time point t1 along the first time point t1, and if the assignable area width on that side is less than the PWM wave width, then distribute the part of the PWM wave that exceeds the assignable area width to the other side of the first time point t1 along the first time point t1;

[0079] A channel current output module configured to output a constant current based on the PWM wave. ​

[0080] The storage circuit can be a register. In one embodiment, t1 can be adjusted according to display effect, and how the PWM wave grows along t1 as the gray data increases.

[0081] The PWM wave generating circuit generates a PWM wave according to the gray data, and the position of the PWM wave grows in the aforementioned two ways, i.e., grows evenly on both sides of t1, or grows on one side of t1 when the gray value of the gray data is small, and grows on the other side when the gray value of the gray data is large.

[0082] The channel current output module can output a constant current according to the PWM wave to light up the LED lamp bead.

[0083] In some embodiments, when the PWM wave is evenly distributed to both sides of the first time point t1, the gray value corresponding to the width of the PWM wave distributed to both sides of the first time point t1 is M and N, respectively, M = Q0*A+Y, and N = Q0*(A+B), where A and B are the integer part and the remainder part of X / 2, X and Y are the integer part and the remainder part of Q / Q0, Q is the gray value of the gray data, and Q0 is the first threshold.

[0084] In some embodiments, when the PWM wave is evenly distributed to both sides of the first time point t1, the gray value corresponding to the width of the PWM wave distributed to both sides of the first time point t1 is M and N, respectively, N = M+B; where M and B are the integer part and the remainder part of Q / 2, respectively, and Q is the gray value of the gray data.

[0085] In some embodiments, the PWM wave includes a widening part. The description of the widening part is as described above and will not be repeated here.

[0086] In some embodiments, the display driving chip further includes:

[0087] The pre-charge circuit pre-charges the column line to the corresponding potential in time outside the display area when the gray value allocated to the display area is not 0.

[0088] The pre-charge circuit pre-charges the column line to the corresponding potential in time inside the display unit when the gray value allocated to the display area is 0; where the display unit refers to the smallest display grouping of the gray data in one sub-frame, and the display area is included in the display unit.

[0089] The time-sharing pre-charging of the column line to the corresponding potential refers to that at different time points, the pre-charging circuit starts to pre-charge the column line to the corresponding target potential set in advance. For example, at time1, the pre-charging circuit charges the column line to V1, at time2, the pre-charging circuit charges the column line to V2, and at time3, the pre-charging circuit charges the column line to V3.

[0090] In some embodiments, the first time point t1 is configurable according to display effects.

[0091] In a preferred embodiment, t1 = (t0+t2) / 2. That is, the first time point is located at the middle of the display area. It can be understood that at this time, the effects of pre-charging and image elimination are compromised, and the display effect is maximally improved.

[0092] The above description is only a preferred embodiment of the present application, and it should be understood that the present application is not limited to the form disclosed herein, and should not be considered as excluding other embodiments, but can be used in various other combinations, modifications and environments, and can be modified within the scope of the concept described herein by the above-mentioned teaching or related technical or knowledge. Any modification and change made by those skilled in the art without departing from the spirit and scope of the present application shall be within the protection scope of the claims attached hereto.

Claims

1. A display driving method, characterized by, The method comprises: confirming a first time point t1 in a display region, t0 < t1 < t2, t0 and t2 respectively represent a start time and an end time of the display region; equally distributing PWM waves to both sides of the first time point t1; outputting a constant current based on the PWM waves; wherein the equally distributing of the PWM waves to both sides of the first time point t1 comprises: a gray value corresponding to a width of the PWM wave distributed to both sides of the first time point t1 is M and N respectively, M = Q0*A+Y, N = Q0*(A+B), wherein A and B are an integer part and a remainder part of X / 2, X and Y are an integer part and a remainder part of Q / Q0, Q is a gray value of the gray data, and Q0 is a first threshold.

2. The method according to claim 1, wherein Q0 = 1, M = A, and N = A+B.

3. The method according to claim 1, wherein t1 = (t0+t2) / 2.

4. The method according to claim 1, wherein the PWM waves comprise a spread part. The method further comprises: when the gray value allocated to the display region is not 0, pre-charging a column line to a corresponding potential outside the display region; when the gray value allocated to the display region is 0, pre-charging the column line to the corresponding potential in a display unit; wherein the display unit refers to a minimum display group of the gray data in one display sub-frame, and the display region is included in the display unit.

5. The display driving method according to claim 1, wherein 6. The method according to any one of claims 1-5, wherein the first time point t1 is configured according to a display effect. The chip comprises: a storage circuit configured to configure a first time point t1 in a display region, t0 < t1 < t2, wherein t0 and t2 respectively represent a start time and an end time of the display region; a PWM wave generation circuit configured to: equally distribute the PWM waves to both sides of the first time point t1; 7. A display driving chip, characterized in that, a channel current output module configured to output a constant current based on the PWM waves; wherein the equally distributing of the PWM waves to both sides of the first time point t1 comprises: a gray value corresponding to a width of the PWM wave distributed to both sides of the first time point t1 is M and N respectively, M = Q0*A+Y, N = Q0*(A+B), wherein A and B are an integer part and a remainder part of X / 2, X and Y are an integer part and a remainder part of Q / Q0, Q is a gray value of the gray data, and Q0 is a first threshold.

8. The chip according to claim 7, wherein Q0 = 1, M = A, and N = A+B. ​ ​ ​ ​ ​

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