A driving method of an OLED display panel

Abstract

The application discloses a kind of driving method of OLED display panel, the OLED display panel includes 8T1C LTPO drive circuit, the driving method includes: S1: two-dimensional look-up table is established by experiment in advance;S2: when receiving the display image information sent by host computer in the N frame, the display image information is obtained gray scale statistical value, according to the gray scale statistical value and the display brightness level by the two-dimensional look-up table corresponding DVH reset voltage value is inquired;S3: when the N+1 frame to the N+m frame, host computer does not send display image information, whether the display brightness level is changed is judged.The two-dimensional look-up table established in advance, in low-frequency display mode, the DVH reset voltage value of current frame picture of current display brightness level is selected, the problem of response time difference can be improved, avoid trailing and color deviation phenomenon and the shaking screen phenomenon when low frequency, when picture and DBV do not change, maintain the DVH reset voltage value unchanged to reduce calculation, reduce energy consumption.

Description

Technical Field

[0001] The present invention relates to the field of OLED display driving, and in particular to a driving method for an OLED display panel. Background Art

[0002] Currently, in the OLED display field (consumer mobile phones, wearables, notebooks, and automotive), array units generally use 7T1C LTPS or 8T1C LTPO pixel circuits (with Vth compensation function) as the driving circuit of OLED display panels to eliminate Vth differences caused by process fluctuations (Vth differences will cause display mura).

[0003] like Figure 1 As shown, taking 7T1C as an example, initialization is performed at time T1, the gate of the switch tube M3 is reset, and the circuit node N4, i.e., the anode of the OLED, is reset; at time T2, the display data data is written to the circuit node N1 of the switch tube M3, and Vth compensation is performed at the same time; at time T3, light is emitted.

[0004] like Figure 2 As shown, taking the 8T1C LTPO pixel circuit as an example, during compensation and skip frames, the DVH signal is used to reset the N2 node. Figure 3 As shown, at time T1: the DVH signal resets the N2, N3, and N1 nodes; at time T2: Vref resets the N1 node; at time T3: Vref resets the N3 and N2 nodes; at time T4: data performs threshold compensation; at time T5: a fixed DVH reset, followed by a high potential being brushed into the N1 node, and M3 has PBS for a period of time; at low frequency, only SP* works.

[0005] At low AOD frequencies, the 7T1C pixel circuit will have poor low grayscale detection due to the large Ioff of the LTPS process, 10e-13A. Figure 4 As shown in the figure, for the 8T1C LTPO pixel circuit, LTPO has a relatively good frame rate due to its leakage current being less than 10e-15A compared to LTPS. However, for the driver tube, OBS is still required to eliminate the influence of bias voltage. The frame rate is significantly improved, as shown by the red line in the figure.

[0006] It is found that different bias of N2 has different contribution to the frame retention curve, and the current data bias has the best effect. At different brightness, the data value is different, and the phenomenon of trailing and screen shaking is more obvious at low brightness. However, the current technology basically uses one voltage for refresh frame and one voltage for skip frame, and does not dynamically adjust according to the data voltage, because if the dvh signal is dynamically adjusted according to the voltage of each frame, the fluctuation is too large, and the power consumption of ddic will increase.

[0007] As shown in Figure 5 , because the switch tube M3 is in the light-emitting state, there is different Vth offset due to different bias, and the pTFT is in the PBS state, the Vth will be positively shifted, resulting in more serious Vth positive shift at low gray scale. Therefore, when the screen is in black in the previous frame and white in the next frame, the brightness of the white area will not be enough, resulting in visual trailing. As shown in Figure 6 , when the display effect of a specific display screen is taken as an example, when 1:05 switches to 1:06 at 1Hz display standby time, the brightness of the first frame when black is switched to white does not reach the normal brightness, so in the first second, the corresponding black-to-white position of the number 6 appears obvious darkening problem.

[0008] The further principle of the above phenomenon is shown in Figure 7 , when the screen is in black, the potential of the circuit node N1 is high, and Vth1 is positively shifted. When black is switched to white, the TFT characteristic cannot quickly change to the white TFT characteristic 3. The Vth2 of the corresponding Vth compensation is positively shifted from the normal white characteristic curve Vth, so the display brightness is lower. When the next frame continues to be white, because the previous 1 frame has been biased for 1 frame of white, the curve characteristic is characteristic 3, so the brightness of the second frame is relatively normal white brightness. This phenomenon is called TFT hysteresis effect.

[0009] Because the bias effect of drTFT is inconsistent under different pictures and different display brightness value (DBV) occasions, different DVH reset voltage values are needed, and generally the DVH reset voltage value is related to the distribution of the data voltage value of each pixel corresponding to the picture. Therefore, how to quickly adjust the appropriate DVH reset voltage value according to the picture and display brightness level in low-frequency display mode is a problem to be solved. SUMMARY

[0010] The application aims to provide a driving method of an OLED display panel, in a low-frequency display mode, when a host computer switches a picture, data gray scale information of the picture is counted, and the gray scale information mostly falls in which interval, and according to a display brightness value (DBV), a DVH reset voltage value of a current frame picture of a current display brightness level is selected through a pre-established two-dimensional lookup table.

[0011] To achieve the above-mentioned purpose, the application provides a driving method of an OLED display panel, the OLED display panel comprising an 8T1C LTPO driving circuit, and the driving method comprising:

[0012] S1: a two-dimensional lookup table is pre-established through experiments, and the two-dimensional lookup table is used to find an optimal DVH reset voltage value of a corresponding condition through a gray scale value and a display brightness level of the OLED display panel;

[0013] S2: display image information sent by a host computer is received at an Nth frame, a gray scale statistical value is obtained by counting the display image information, a corresponding DVH reset voltage value is found through the two-dimensional lookup table according to the gray scale statistical value and the display brightness level, and the DVH reset voltage value is used to reset a circuit node of the 8T1C LTPO driving circuit, and N is a positive integer;

[0014] S3: the host computer does not send display image information at an N+1th frame to an N+mth frame, and whether the display brightness level changes is determined;

[0015] If the display brightness level does not change, the corresponding DVH reset voltage value is maintained unchanged, and if the display brightness level changes, a corresponding DVH reset voltage value is re-found;

[0016] m is a positive integer.

[0017] Preferably, in the step of counting the display image information to obtain a gray scale statistical value, only a part of the display image information meeting a preset condition is selected.

[0018] Preferably, after the display image information sent by the host computer is received, whether the display image information changes compared with display image information received last time is determined, and if the display image information does not change, the step of counting the display image information to obtain a gray scale statistical value is skipped.

[0019] Preferably, the two-dimensional look-up table is established by experiments in advance, specifically: in the case that the gray scale value of the display image and the display brightness level are unchanged, the screen jitter phenomenon and the trailing phenomenon in the display effect of the display image when a plurality of different DVH reset voltage values are used are tested, the screen jitter phenomenon and the trailing phenomenon are quantified to obtain the display effect evaluation value corresponding to the DVH reset voltage value; the DVH reset voltage value with the best display effect evaluation value is selected as the optimal DVH reset voltage value under the corresponding condition.

[0020] Preferably, the gray scale statistical value is the mode of the gray scale value.

[0021] Preferably, the preset condition is that the gray scale value is not 0 gray scale and is lower than a preset threshold value.

[0022] Compared with the prior art, the present application has the following beneficial effects:

[0023] Through the two-dimensional look-up table established in advance, in the low-frequency display mode, the DVH reset voltage value of the current frame picture of the current display brightness level is selected, the problem of response time difference can be improved, the trailing and color deviation phenomena and the screen jitter phenomenon in low frequency are avoided, when the picture and the DBV do not change, the DVH reset voltage value is maintained unchanged to reduce the calculation and reduce the energy consumption. BRIEF DESCRIPTION OF DRAWINGS

[0024] Figure 1 It is a 7T1C driving circuit diagram in the prior art;

[0025] Figure 2 It is an 8T1C LTPO driving circuit diagram in the prior art;

[0026] Figure 3 It is a timing diagram of the 8T1C LTPO driving circuit in the prior art;

[0027] Figure 4 It is a schematic diagram of the influence of N2 bias voltage on frame retention curve;

[0028] Figure 5 It is a schematic diagram of the first frame brightness not reaching the effect;

[0029] Figure 6 It is a schematic diagram of the picture trailing effect of the standby display time;

[0030] Figure 7 It is a schematic diagram of the TFT hysteresis effect principle;

[0031] Figures 8 to 11 It is a schematic diagram of the present application;

[0032] In the figure: N1 / N2 / N3 / N4 circuit nodes; M1 / M2 / M3 / M4 / M5 / M6 / M7 switch tubes; Cst capacitor; S1 / S2 / Vref / Emit / PVDD / PVEE / Vdata voltage signal end; Vth1 / Vth2 / Vth3. DETAILED DESCRIPTION

[0033] The technical solutions in the embodiments of the present application will be clearly and completely described below with reference to the accompanying drawings in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, rather than all the embodiments of the present application. Based on the embodiments in the present application, all other embodiments obtained by those of ordinary skill in the art without creative work fall within the protection scope of the present application.

[0034] Figure 8 The main flow of the present application is shown:

[0035] S1: A two-dimensional lookup table is established in advance through experiments, and the two-dimensional lookup table is used to look up the corresponding optimal DVH reset voltage value of the condition through the gray scale value and the display brightness level of the OLED display panel;

[0036] S2: At the Nth frame, the display image information sent by the upper computer is received, the gray scale statistical value is obtained, the corresponding DVH reset voltage value is looked up through the two-dimensional lookup table according to the gray scale statistical value and the display brightness level, and the DVH reset voltage value is used to reset the circuit nodes of the 8T1C LTPO driving circuit, and N is a positive integer;

[0037] S3: At the N+1th frame to the N+mth frame, the upper computer does not send display image information, and whether the display brightness level changes is judged;

[0038] If no change occurs, the corresponding DVH reset voltage value is maintained unchanged, and if a change occurs, the corresponding DVH reset voltage value is re-looked up; m is a positive integer.

[0039] Further, the two-dimensional lookup table established in advance by experiment can be: in the case that the gray scale value of the display image and the display brightness level are unchanged, the screen jitter phenomenon and the trailing phenomenon in the display effect of the display image when a plurality of different DVH reset voltage values are tested are tested, the screen jitter phenomenon and the trailing phenomenon are quantified to obtain the display effect evaluation value corresponding to the DVH reset voltage value (for example, the ratio of the fluctuation peak and valley value of the picture brightness of the screen jitter phenomenon, the percentage of the brightness of the pixel of the trailing phenomenon compared with the brightness of the expected display effect, or the comprehensive evaluation obtained by adding the quantitative evaluation results of the screen jitter phenomenon and the trailing phenomenon according to the preset weight, etc. A person skilled in the art can set a suitable evaluation method to obtain a comprehensive display effect value according to actual needs, and the specific evaluation method is not limited here) ; select the DVH reset voltage value with the best display effect evaluation value as the best DVH reset voltage value under the corresponding condition, and the tested DVH reset voltage value can be selected within a neighboring range of the data voltage value corresponding to the gray scale value of the pure color picture.

[0040] As shown in Figure 9 , when entering low-frequency display, the skip frame method is usually used, and frame_n Refresh means that the current frame is a refresh frame. The host computer sends new display data. Assuming that the current frame rate is 60hz, the following skip1~m is a skip frame, and the picture is not updated, so the frequency of the picture sent is only 60 / (m+1)Hz.

[0041] For 8T1C, a lookup table needs to be established in advance in the factory. For different designs, different batches, and different brightness information, the influence of screen jitter and response time under different bands (display brightness level interval) and gray scale is recorded in order of influence, and the gray scale information and voltage information are recorded.

[0042] As shown in Figure 10 , as part of an example of a two-dimensional lookup table, wherein 1_5.1V in the figure refers to the experimental results of the influence of screen jitter and response time, and the ranking order of the display effect evaluation value reaches 1 when the DVH reset voltage value is 5.1V, that is, the best effect; band0:A means that the current picture is in band0, and the DBV is in the range A interval (for example, the DBV interval corresponding to the white picture 500~700nit, a person skilled in the art can set the interval of the display brightness level according to the actual situation; since the two-dimensional lookup table is influenced by the model, production batch and performance parameters of the display panel, etc., the specific numerical value has little reference value, Figure 10 , and all data are not listed in the table.

[0043] As shown in Figure 11As shown, as an example of the specific process, when the picture sent by the host computer is in the range A interval of band0, according to the image information of the current frame_n Refresh, the gray scale information of the image is counted, the gray scale statistical table is obtained, and after removing the invalid influence of those gray scale values (a screening condition can be preset by those skilled in the art, for example, in the range greater than 0 gray scale and less than the threshold gray scale, every several gray scales are selected as valid influence gray scale values, the rest are invalid influence, and the gray scale between the valid influence gray scale values is counted on the valid influence gray scale value during counting), the mode of the valid influence gray scale value is selected, that is, the gray scale value with the highest proportion, and the value and band0 are looked up through the two-dimensional lookup table to find the best DVH reset voltage value. The value is output to the driving circuit, and the lookup work is performed again only after the next picture change or the DVH reset voltage is changed. That is, as long as the DBV and the picture do not change, the DVH reset voltage does not change whether it is a refresh frame or a skip frame. For the case where the picture does not change and the DBV changes, the original statistical result can be used to find the best DVH reset voltage value again, saving the energy consumption of statistical calculation.

[0044] It is apparent to those skilled in the art that the present application is not limited to the details of the foregoing exemplary embodiments, and that the present application can be implemented in other specific forms without departing from the spirit or essential characteristics of the present application. Therefore, the embodiments should be considered in all respects as illustrative and not restrictive, the scope of the present application being defined by the appended claims rather than by the foregoing description, and it is intended that all changes which come within the meaning and range of equivalency of the claims are resolvable as permissible variants. Any reference signs in the claims should not be construed as limiting the claims to the figures in which the reference signs are used.

[0045] In addition, it should be understood that although the present specification is described in terms of embodiments, not every embodiment contains only one independent technical solution, and the description of the specification is only for the sake of clarity, and those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can be appropriately combined to form other embodiments that those skilled in the art can understand.

Claims

1. A driving method for an OLED display panel, wherein the OLED display panel includes an 8T1C LTPO driving circuit, characterized in that: The driving method includes: S1: Preliminarily establishing a two-dimensional lookup table through experiments, wherein the two-dimensional lookup table is used to find an optimal DVH reset voltage value corresponding to a condition based on a grayscale value and a display brightness level of the OLED display panel; S2: receiving display image information sent by the host computer at the Nth frame, performing statistics on the display image information to obtain grayscale statistics, and searching the corresponding DVH reset voltage value through the two-dimensional lookup table according to the grayscale statistics and the display brightness level, wherein the DVH reset voltage value is used to reset the circuit nodes of the 8T1C LTPO drive circuit, where N is a positive integer; S3: The host computer does not send display image information from the N+1th frame to the N+mth frame, and determines whether the display brightness level changes; If no change occurs, the corresponding DVH reset voltage value is maintained unchanged; if a change occurs, the corresponding DVH reset voltage value is searched again; m is a positive integer; In the step of obtaining grayscale statistical values ​​by counting the displayed image information, only a portion of the displayed image information that meets a preset condition is selected; the preset condition is used to remove grayscale values ​​with invalid effects; and the grayscale statistical value is the mode of the grayscale values.

2. The driving method according to claim 1, wherein: Step S2 also includes: after receiving the display image information sent by the host computer, determining whether the display image information has changed compared with the display image information received last time; if not, skipping the step of counting the display image information to obtain grayscale statistical values.

3. The driving method according to claim 1, wherein: The two-dimensional lookup table is established in advance through experiments, specifically: when the grayscale value and display brightness level of the displayed image remain unchanged, the screen jitter phenomenon and the smear phenomenon in the display effect of the displayed image are tested when several different DVH reset voltage values ​​are used, the screen jitter phenomenon and the smear phenomenon are quantified to obtain the display effect evaluation value corresponding to the DVH reset voltage value; and the DVH reset voltage value with the best display effect evaluation value is selected as the optimal DVH reset voltage value under the corresponding conditions.

4. The driving method according to claim 1, wherein: The preset condition includes: the grayscale value is not grayscale 0 and is lower than a preset threshold.

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