Gamma adjusting circuit, driving method thereof and display device

Abstract

The invention discloses a gamma adjusting circuit, a driving method thereof and a display device. The gamma adjusting circuit comprises a chip, the chip comprises a plurality of output end sets, each output end set comprises a first output end and a second output end, the first output ends and the second output ends are configured to alternately output gray scale voltage corresponding to the same gray scale to the liquid crystal display panel, the first voltage of the first output ends is larger than the common voltage, and the second voltage of the second output ends is larger than the common voltage. A second voltage of the second output end is smaller than a common voltage, and the common voltage is a voltage accessed by a common electrode of the liquid crystal display panel; in the first stage, the difference value between the first voltage and the common voltage is a first difference value, the difference value between the common voltage and the second voltage is a second difference value, and the first difference value is larger than the second difference value; in the second stage, the difference value between the first voltage and the common voltage is a third difference value, the difference value between the common voltage and the second voltage is a fourth difference value, and the third difference value is smaller than the fourth difference value. The brightness stability of the liquid crystal display panel can be improved.

Description

Technical Field

[0001] This application relates to the field of display technologies, and particularly to a gamma adjustment circuit, a driving method thereof, and a display device. Background Art

[0002] A liquid crystal display includes a liquid crystal display panel for displaying images and a liquid crystal display driving device for applying driving signals to the liquid crystal display panel. Among them, the liquid crystal display panel includes an array substrate and a color filter substrate disposed opposite to each other, and a liquid crystal layer filled in a gap between the array substrate and the color filter substrate.

[0003] Under normal temperature (25°C) conditions, when the liquid crystal display device is powered on and placed for about 30 minutes, and in a state where the liquid crystal temperature is stable, the desired gray-scale - brightness characteristic can be achieved. At the initial stage of power-on of the liquid crystal display device, the liquid crystal temperature is not yet stable, and at the later stage of power-on of the liquid crystal display device, the backlight source (or IC) generates heat, causing the liquid crystal temperature to rise, and the desired gray-scale - brightness characteristic cannot be achieved, easily resulting in unstable display brightness. For a liquid crystal display device used for medical diagnosis, display malfunction is related to human life. Therefore, how to improve the brightness stability of the liquid crystal display device is a technical problem that those skilled in the art are committed to solving. Summary of the Invention

[0004] Embodiments of this application provide a gamma adjustment circuit, a driving method thereof, and a display device, which can improve the brightness stability of a liquid crystal display panel.

[0005] On the one hand, embodiments of this application provide a gamma adjustment circuit, including: a chip configured to output a gray-scale voltage for display to a liquid crystal display panel, the chip including a plurality of output terminal groups, the output terminal group including a first output terminal and a second output terminal, the first output terminal and the second output terminal being configured to alternately output the gray-scale voltage corresponding to the same gray scale to the liquid crystal display panel, and a first voltage of the first output terminal being greater than a common voltage, a second voltage of the second output terminal being less than the common voltage, the common voltage being the voltage accessed by a common electrode of the liquid crystal display panel; the working process of the chip includes a first stage and a second stage; in the first stage, a difference between the first voltage and the common voltage is a first difference, a difference between the common voltage and the second voltage is a second difference, and the first difference is greater than the second difference; in the second stage, a difference between the first voltage and the common voltage is a third difference, a difference between the common voltage and the second voltage is a fourth difference, and the third difference is less than the fourth difference.

[0006] On the other hand, embodiments of this application provide a driving method, including: applied to a gamma adjustment circuit, the gamma adjustment circuit including a chip configured to output a gray-scale voltage for display to a liquid crystal display panel, the chip including a plurality of output terminal groups, the output terminal group including a first output terminal and a second output terminal; the driving method includes:

[0007] The first output terminal and the second output terminal of the control are configured to alternately output voltages corresponding to the same gray level to the liquid crystal display panel, and the first voltage of the first output terminal is greater than the common voltage, and the second voltage of the second output terminal is less than the common voltage. The common voltage is the voltage accessed by the common electrode of the liquid crystal display panel;

[0008] The working process of the control chip includes a first stage and a second stage;

[0009] In the first stage, the difference between the first voltage and the common voltage is the first difference, and the difference between the common voltage and the second voltage is the second difference. The first difference is greater than the second difference;

[0010] In the second stage, the difference between the first voltage and the common voltage is the third difference, and the difference between the common voltage and the second voltage is the fourth difference. The third difference is less than the fourth difference.

[0011] On the other hand, an embodiment of the present application provides a display device, including: a liquid crystal display panel, a temperature sensor, a driving system, and a gamma adjustment circuit as described in the embodiment of the first aspect;

[0012] The temperature sensor is located inside the liquid crystal display panel, and is used to monitor the temperature of the display device and transmit the temperature data to the driving system;

[0013] The driving system is used to control the gamma adjustment circuit to output corresponding gray scale voltages in real time according to the temperature of the display device.

[0014] According to the embodiment of the present application, the chip of the gamma adjustment circuit includes a plurality of output terminal groups. Each output terminal group includes a first output terminal for outputting a positive voltage and a second output terminal for outputting a negative voltage. And the working process of the chip is divided into two stages. In the first stage, only the voltage output by the first output terminal is increased. In the second stage, only the voltage output by the second output terminal is decreased. In this way, in any stage, the voltage change amount applied to the liquid crystal can be reduced, thereby reducing the brightness change of the liquid crystal display panel and improving the brightness stability. Description of the Drawings

[0015] By reading the following detailed description of the non-limiting embodiments with reference to the drawings, other features, objects, and advantages of the present application will become more obvious. Among them, the same or similar reference numerals represent the same or similar features, and the drawings are not drawn to actual scale.

[0016] Figure 1 It is a change trend diagram of liquid crystal driving voltage - transmittance;

[0017] Figure 2 It shows a schematic structural diagram of a gamma adjustment circuit provided by an embodiment of the present application;

[0018] Figure 3 Shows the timing diagram of an output signal of the gamma adjustment circuit in the comparative example;

[0019] Figure 4 Shows Figure 3 The corresponding schematic diagram of a brightness compensation result;

[0020] Figure 5 Shows the relationship diagram between the gray-scale voltage adjustment step and the brightness change rate of the display panel;

[0021] Figure 6 Shows the timing diagram of an output signal of the gamma adjustment circuit provided by the embodiment of the present application;

[0022] Figure 7 Shows Figure 6 The corresponding schematic diagram of a brightness compensation result;

[0023] Figure 8 Shows the schematic diagram of a structure of the liquid crystal display panel provided by the embodiment of the present application;

[0024] Figure 9 Shows the schematic diagram of a circuit structure of a sub-pixel in the liquid crystal display panel provided by the embodiment of the present application;

[0025] Figure 10 Shows the timing diagram of another output signal of the gamma adjustment circuit provided by the embodiment of the present application;

[0026] Figure 11 Shows the timing diagram of yet another output signal of the gamma adjustment circuit provided by the embodiment of the present application;

[0027] Figure 12 Shows the schematic diagram of a structure of the display device provided by the embodiment of the present application;

[0028] Figure 13 Shows the schematic diagram of a gamma curve provided by the embodiment of the present application. Detailed implementation manners

[0029] The features and exemplary embodiments of various aspects of the present application will be described in detail below. To make the objectives, technical solutions and advantages of the present application clearer, the present application will be further described in detail below with reference to the accompanying drawings and specific embodiments. It should be understood that the specific embodiments described herein are only configured to explain the present application and are not configured to limit the present application. For those skilled in the art, the present application can be implemented without some of these specific details. The following description of the embodiments is only provided to provide a better understanding of the present application by showing examples of the present application.

[0030] It should be noted that in this text, relational terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any actual relationship or order between these entities or operations. Moreover, the terms "include", "comprise" or any other variant thereof are intended to cover non-exclusive inclusion, such that a process, method, article or device comprising a series of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article or device. Without further limitation, an element defined by the statement "comprising..." does not exclude the presence of additional identical elements in the process, method, article or device comprising the said element.

[0031] It should be understood that the term "and / or" used herein is merely a description of the associative relationship of associated objects, indicating that three relationships can exist. For example, A and / or B can represent three situations: A exists alone, A and B exist simultaneously, and B exists alone. Additionally, the character " / " in this text generally indicates that the associated objects before and after are in an "or" relationship.

[0032] Without departing from the spirit or scope of the present application, various modifications and variations can be made to the present application, which will be obvious to those skilled in the art. Therefore, the present application is intended to cover modifications and variations of the present application that fall within the scope of the corresponding claims (the claimed technical solutions) and their equivalents. It should be noted that the embodiments provided in the embodiments of the present application can be combined with each other without contradiction.

[0033] Figure 1 is a graph showing the change trend of the liquid crystal driving voltage - transmittance. There are many reasons for the brightness change in a liquid crystal display device. For example, in the initial stage when the liquid crystal display device is powered on, since the temperature of the liquid crystal display device has not yet stabilized, the desired gray scale - brightness characteristic cannot be achieved. Another example is that due to the heat generation of the backlight (and the driving IC), as the temperature of the liquid crystal becomes higher, the dielectric constant, refractive index, and viscosity of the liquid crystal decrease, resulting in a decrease in the liquid crystal transmittance. Please refer to Figure 1 , Figure 1 in which the solid line is the relationship change curve between the liquid crystal driving voltage and the transmittance under ideal conditions, and the dashed line is the relationship change curve between the liquid crystal driving voltage and the transmittance when the liquid crystal temperature increases. From Figure 1 it can be seen that when the liquid crystal temperature increases, when the same liquid crystal driving voltage is applied, compared with the ideal situation, the transmittance of the liquid crystal decreases when the temperature increases.

[0034] In view of the above situation, it is necessary to adjust the voltage applied to the liquid crystal according to the temperature change to compensate for the loss of the liquid crystal transmittance.

[0035] The liquid crystal in the liquid crystal display panel is driven by alternating current. Therefore, for the same gray scale, a positive voltage and a negative voltage need to be applied to the liquid crystal. As Figure 2 shown, the chip 100 of the gamma adjustment circuit includes multiple output terminal groups. Two output terminals of the same output terminal group are respectively used to output the positive voltage and the negative voltage corresponding to the same gray scale. For example, the output terminals OUT1 and OUT14 are an output terminal group, the output terminals OUT2 and OUT13 are an output terminal group, the output terminals OUT3 and OUT12 are an output terminal group, the output terminals OUT4 and OUT11 are an output terminal group, the output terminals OUT5 and OUT10 are an output terminal group, the output terminals OUT6 and OU9 are an output terminal group, and the output terminals OUT7 and OUT8 are an output terminal group. The gray scale voltages output by the output terminals OUT1 to OUT7 are positive voltages, and the gray scale voltages output by the output terminals OUT8 to OUT14 are negative voltages. Here, the positive voltage and the negative voltage are relative to the common voltage COM. The positive voltage is greater than the common voltage COM, and the negative voltage is less than the common voltage COM. The negative voltage is not necessarily less than 0. The common voltage COM refers to the voltage connected to the common electrode of the liquid crystal display panel.

[0036] The minimum value of the voltage change when the liquid crystal voltage is switched is limited by the gray scale voltage adjustment step of the gamma adjustment circuit. For example, as Figure 3 shown, Figure 3 the solid line in shows the timing diagrams of the voltages Vout4 and Vout11 output by the output terminals OUT4 and OUT11 of the chip without compensation, and the dashed line shows the timing diagrams of the voltages Vout4' and Vout11' output by the output terminals OUT4 and OUT11 of the chip after compensation.

[0037] For example, the gray scale voltage adjustment step of the gamma adjustment circuit is approximately 0.013V, Vout4'≈Vout4 + 0.013(V), and Vout11'≈Vout11 - 0.013(V). In this case, the voltage applied to the liquid crystal increases by approximately 0.013V.

[0038] Figure 4 shows the brightness compensation result when the voltage applied to the liquid crystal increases by approximately 0.013V in the related art. Figure 4 In, the horizontal axis represents time, and the vertical axis represents the change in brightness. As Figure 4 shown, the change in brightness between the two dashed lines is about 3%. The brightness that can be recognized by the human eye is about 3%. Therefore, the gamma adjustment circuit operating according to the Figure 3 shown working timing will cause a brightness change that can be recognized by the human eye, which is not conducive to the brightness stability of the liquid crystal display panel. Figure 4The brightness change curves corresponding to 128 gray levels (G128), 256 gray levels (G256), 512 gray levels (G512), and 1023 gray levels (G1023) are shown. Additionally, USL represents the upper spec limit, and LSL represents the lower spec limit.

[0039] As Figure 5 shown, according to the characteristics of the liquid crystal driving voltage and the liquid crystal transmittance, the brightness change rate caused by the liquid crystal driving voltage is calculated, and the results are as Figure 5 shown. It can be Figure 5 seen that Curve Ⅰ represents the brightness change rate corresponding to a gray level voltage adjustment step of 15 mV, Curve Ⅱ represents the brightness change rate corresponding to a gray level voltage adjustment step of 10 mV, and Curve Ⅲ represents the brightness change rate corresponding to a gray level voltage adjustment step of 7 mV. For Curve Ⅱ, when the gray level voltage adjustment step is 10 mV, in the range of the liquid crystal driving voltage from 1 V to 2.5 V, the brightness change rate exceeds 4%, while the brightness difference distinguishable by the human eye is about 3%. That is to say, when the brightness change rate of the display panel is less than or equal to 3%, the human eye can hardly perceive it. When the brightness change rate of the display panel exceeds 3%, it will cause a visual feeling of unstable brightness of the display panel. If it is desired to reduce the perception of brightness change visually, it is necessary to reduce the voltage change amount applied to the liquid crystal.

[0040] Exemplarily, a dataset of temperature-gray level node voltages can be preset. The dataset includes multiple sets of gray level voltages (also called gamma voltages), and the gray level voltages corresponding to different temperatures can be different. According to the temperature of the liquid crystal display panel, when switching the gray level voltage, for example, the brightness of gray level X under the first set of gray level voltages is L1, and the brightness of gray level X under the second set of gray level voltages is L2. If the brightness change amount between brightness L1 and brightness L2 exceeds 3%, it will attract the attention of the human eye.

[0041] Regarding the above technical problems, the embodiments of the present application provide a gamma adjustment circuit, its driving method, and a display device. The following will describe the embodiments of the present application with reference to the accompanying drawings.

[0042] As Figure 2 shown, the gamma adjustment circuit 1 includes a chip 100. The chip 100 is configured to output gray level voltages for display to the liquid crystal display panel. The chip 100 includes multiple output terminal groups. The output terminal group includes a first output terminal and a second output terminal. The first output terminal and the second output terminal are configured to alternately output the gray level voltages corresponding to the same gray level to the liquid crystal display panel, and the first voltage of the first output terminal is greater than the common voltage, and the second voltage of the second output terminal is less than the common voltage. The common voltage is the voltage accessed by the common electrode of the liquid crystal display panel.

[0043] The first voltage can be referred to as the positive voltage, and the second voltage can be referred to as the negative voltage. It can be understood that the two output terminals of the same output terminal group are respectively used to output the positive voltage and the negative voltage corresponding to the same gray level. Here, the positive voltage and the negative voltage are relative to the common voltage COM. The positive voltage is greater than the common voltage COM, and the negative voltage is less than the common voltage COM. The negative voltage is not necessarily less than 0. The common voltage COM refers to the voltage connected to the common electrode of the liquid crystal display panel.

[0044] As an example, the chip 100 includes 7 output terminal groups. The output terminals OUT1 and OUT14 form an output terminal group, the output terminals OUT2 and OUT13 form an output terminal group, the output terminals OUT3 and OUT12 form an output terminal group, the output terminals OUT4 and OUT11 form an output terminal group, the output terminals OUT5 and OUT10 form an output terminal group, the output terminals OUT6 and OU9 form an output terminal group, and the output terminals OUT7 and OUT8 form an output terminal group. The gray scale voltages output by the output terminals OUT1 to OUT7 are positive voltages, and the gray scale voltages output by the output terminals OUT8 to OUT14 are negative voltages. The output terminals OUT1 to OUT7 are the first output terminals, and the output terminals OUT8 to OUT14 are the second output terminals.

[0045] The working process of the chip 100 includes a first stage and a second stage; in the first stage, the difference between the first voltage and the common voltage is the first difference, and the difference between the common voltage and the second voltage is the second difference, and the first difference is greater than the second difference; in the second stage, the difference between the first voltage and the common voltage is the third difference, and the difference between the common voltage and the second voltage is the fourth difference, and the third difference is less than the fourth difference.

[0046] Please refer to Figure 6 , taking the output terminals OUT4 and OUT11 of the chip as an example, Vout4 represents the voltage value output by the output terminal OUT4 before compensation, Vout4’ represents the voltage value output by the output terminal OUT4 after compensation, Vout11 represents the voltage value output by the output terminal OUT11 before compensation, and Vou11’ represents the second voltage output by the output terminal OUT11 after compensation. In other words, Figure 6 The solid line in represents the voltage value output by the output terminal before compensation, and the dashed line represents the voltage value output by the output terminal after compensation.

[0047] Among them, in the first stage a, Vout4’ is the first voltage, and Vout11 is the second voltage; in the second stage b, Vout4 is the first voltage, and Vout11’ is the second voltage.

[0048] In the first stage a, the difference between Vout4’ and the common voltage COM is the first difference ΔV1, and the difference between the common voltage COM and Vout11 is the second difference ΔV2, and ΔV1 is greater than ΔV2.

[0049] In the second stage b, the difference between Vout4 and the common voltage COM is the third difference ΔV3, and the difference between the common voltage COM and Vout11’ is the fourth difference ΔV4, and ΔV3 is less than ΔV4.

[0050] That is to say, in the first stage a, voltage compensation is only performed on the output voltage of the first output terminal (for example, the output terminal OUT4), and the output voltage of the second output terminal (for example, the output terminal OUT11) remains unchanged. In the second stage b, voltage compensation is only performed on the output voltage of the second output terminal (for example, the output terminal OUT11), and the output voltage of the first output terminal (for example, the output terminal OUT4) remains unchanged.

[0051] For example, in the first stage a, if the voltage output from the output terminal OUT4 is compensated by an increase of 0.013V, then Vout4’ = Vout4 + 0.013 (V). In the first stage a, the voltage V applied to the liquid crystal conforms to Equation (1):

[0052] V = (Vout4 - Vout11 + 0.013) / 2 · · · (1)

[0053] If Vout4 - COM = COM - Vout11, that is, Vout11 = -1*(Vout4 - 2*COM) is substituted into Equation (1), then V = Vout4 - COM + 0.0065.

[0054] That is to say, in the first stage a, the change in the voltage applied to the liquid crystal is 0.065V, reducing the change in the voltage applied to the liquid crystal.

[0055] In the second stage b, if the voltage output from the output terminal OUT11 is compensated by a decrease of 0.013V, then Vout11’ = Vout11 - 0.013 (V). Similarly, in the second stage b, the change in the voltage applied to the liquid crystal is 0.065V, reducing the change in the voltage applied to the liquid crystal.

[0056] Figure 7 Shows the brightness compensation result corresponding to the voltage compensation scheme provided by the embodiment of the present application. Figure 7 In the figure, the horizontal axis represents time, and the vertical axis represents the change in brightness. As Figure 7 The change in brightness between the two dashed lines in the figure is about 2% or less, making it difficult for the human eye to visually observe the change in brightness. Figure 7 The figure shows the brightness change curves corresponding to 128 gray levels (G128), 256 gray levels (G256), and 512 gray levels (G512) respectively. In addition, USL represents the upper spec limit, and LSL represents the lower spec limit.

[0057] According to an embodiment of the present application, the chip of the gamma adjustment circuit includes multiple output terminal groups. Each output terminal group includes a first output terminal for outputting a positive voltage and a second output terminal for outputting a negative voltage. The working process of the chip is divided into two stages. In the first stage, only the voltage output by the first output terminal is increased. In the second stage, only the voltage output by the second output terminal is decreased. In this way, in any stage, the voltage change amount applied to the liquid crystal can be reduced, thereby reducing the brightness change of the liquid crystal display panel and improving the brightness stability.

[0058] Exemplarily, within a certain period of time when switching from the first set of gray-scale voltages to the second set of gray-scale voltages, the output voltage based on the second set of gray-scale voltages is compensated. That is, in the first stage, only the voltage output by the first output terminal is increased. In the second stage, only the voltage output by the second output terminal is decreased, so that the brightness change is less than 3%. It can be understood that the "certain period of time" includes at least one first stage and at least one second stage. Exemplarily, after compensating for a certain period of time, the output voltage compensation may no longer be performed subsequently. During the non-compensation process, the amplitude of the voltage output by the first output terminal is equal to the amplitude of the voltage output by the second output terminal. The amplitude of the voltage output by the first output terminal is the absolute value of the difference between the output voltage value of the first output terminal and the common voltage. The amplitude of the voltage output by the second output terminal is the absolute value of the difference between the output voltage value of the second output terminal and the common voltage.

[0059] Exemplarily, as Figure 8 shown, the liquid crystal display panel 200 includes data lines S1 to Sn and scan lines G1 to Gm. Multiple sub-pixels pixel are arranged in m rows and n columns. Each sub-pixel pixel is electrically connected to the data line and the scan line.

[0060] As Figure 9 shown, the sub-pixel includes a thin film transistor TFT, a pixel electrode, and a common electrode. The common electrode is used to access the common voltage COM. The gate of the thin film transistor TFT is electrically connected to the scan line. The first pole of the thin film transistor TFT is electrically connected to the data line. The second pole of the thin film transistor TFT is electrically connected to the pixel electrode.

[0061] As Figure 8As shown, the liquid crystal display panel 200 further includes a source driver circuit S-IC and a gate driver circuit G-IC. The source driver circuit S-IC is electrically connected to the output terminal of the chip in the gamma adjustment circuit, and the source driver circuit S-IC is electrically connected to the data lines S1 to Sn. The source driver circuit S-IC generates data voltages based on the gray-scale voltages output by the chip in the gamma adjustment circuit. The gate driver circuit G-IC is electrically connected to the scan lines, and the gate driver circuit G-IC controls the thin-film transistors TFTs in the sub-pixels to turn on or off. When the thin-film transistor TFT is turned on, the data voltage output by the source driver circuit S-IC is written into the pixel electrode of the sub-pixel. In addition, a common voltage COM is applied to the common electrode, and an electric field is generated between the pixel electrode and the common electrode to control the flipping of the liquid crystal.

[0062] Please refer to Figure 6 and Figure 8 , in the first stage a, the first output terminal and the second output terminal alternately output a positive voltage (Vout4’) and a negative voltage (Vout11), and the positive-polarity voltage and the negative-polarity voltage are alternately written into the sub-pixels to drive the liquid crystal in an alternating current manner. In the second stage b, the first output terminal and the second output terminal alternately output a positive voltage (Vout4) and a negative voltage (Vout11’), and the positive-polarity voltage and the negative-polarity voltage are alternately written into the sub-pixels to drive the liquid crystal in an alternating current manner. Moreover, in the first stage, only the voltage output by the first output terminal is increased, and in the second stage, only the voltage output by the second output terminal is decreased. In this way, in any stage, the voltage change amount applied to the liquid crystal can be reduced, thereby reducing the brightness change of the liquid crystal display panel and improving the brightness stability.

[0063] In some embodiments, as Figure 2 shown, the chip 100 is connected to a reference voltage STATIC_Hi and a reference voltage GND. The ratio of the difference between the reference voltage STATIC_Hi and the reference voltage GND to the maximum gray scale is the gray-scale voltage adjustment step of the chip. The difference between the first difference and the second difference is the fifth difference, and the fifth difference is equal to the gray-scale voltage adjustment step; and / or, the difference between the fourth difference and the third difference is the sixth difference, and the sixth difference is equal to the gray-scale voltage adjustment step.

[0064] For example, if the reference voltage GND is 0 and the maximum gray scale is N, the gray-scale voltage adjustment step can be calculated based on Equation (2);

[0065] Gray-scale voltage adjustment step = STATIC_Hi / N (2)

[0066] Taking 10 bits as an example, N = 1023. The reference voltage STATIC_Hi is determined by the maximum driving voltage of the liquid crystal, and the reference voltage STATIC_Hi is generally above 13V. For example, the gray-scale voltage adjustment step = 13 / 1023 ≈ 12.7mV, and the gray-scale voltage adjustment step is approximately 0.013V.

[0067] It can be understood that the gray-scale voltage adjustment step is the minimum adjustable voltage of the chip.

[0068] As Figure 6 shown, the difference between ΔV1 and ΔV2 is the fifth difference ΔV5. It can be understood that Vout4’ - Vout4 = ΔV5. That is to say, in this embodiment, in the first stage a, the voltage of the first output terminal (for example, output terminal OUT4) is increased by one gray-scale voltage adjustment step from the initial voltage (for example, Vout4) to obtain the compensated voltage (for example, Vout4’).

[0069] The difference between ΔV4 and ΔV3 is the sixth difference ΔV6. It can be understood that Vout11 - Vout11’ = ΔV6. That is to say, in this embodiment, in the second stage b, the voltage of the second output terminal (for example, output terminal OUT11) is decreased by one gray-scale voltage adjustment step from the initial voltage (for example, Vout11) to obtain the compensated voltage (for example, Vout11’).

[0070] In this embodiment, in the first stage, only the voltage of the first output terminal is increased, and it is increased according to the gray-scale voltage adjustment step; and / or, in the second stage, only the voltage of the second output terminal is decreased, and it is decreased according to the gray-scale voltage adjustment step; compensating the voltage output by the first output terminal and / or the second output terminal with the minimum gray-scale voltage adjustment step can ensure that the voltage change amount applied to the liquid crystal in the first stage and / or the second stage is the smallest, so as to further ensure that the voltage change amount applied to the liquid crystal can be reduced, thereby reducing the brightness change of the liquid crystal display panel and improving the brightness stability.

[0071] In some embodiments, the difference between the first difference and the second difference is the fifth difference, and one-half of the fifth difference is less than or equal to 7mV; and / or, the difference between the fourth difference and the third difference is the sixth difference, and one-half of the sixth difference is less than or equal to 7mV.

[0072] Still taking output terminal OUT4 and output terminal OUT11 as examples, Vout4’ - Vout4 = ΔV5. For example, ΔV5 = 0.013V, 0.013 / 2 = 0.065V, and 0.065V is 6.5mV, and 6.5mV is less than 7mV.

[0073] Vout11 - Vout11’ = ΔV6. For example, ΔV6 = 0.013V, 0.013 / 2 = 0.065V, 0.065V is 6.5mV, and 6.5mV is less than 7mV.

[0074] As Figure 5 shown, when the gray - scale voltage adjustment step is 7mV or less than 7mVd, the corresponding brightness change rate is not greater than 3%, which can avoid visible brightness changes to the human eye.

[0075] In this embodiment, in the first stage, only the voltage of the first output terminal is increased, and half of the increased voltage is less than or equal to 7mV; and / or, in the second stage, only the voltage of the second output terminal is decreased, and half of the decreased voltage is less than or equal to 7mV; this can better avoid visible brightness changes to the human eye and improve brightness stability.

[0076] In some embodiments, the difference between the first difference and the second difference is the fifth difference, and the difference between the fourth difference and the third difference is the sixth difference, and the fifth difference is equal to the sixth difference.

[0077] Please refer to Figure 6 , still taking output terminal OUT4 and output terminal OUT11 as examples, Vout4’ - Vout4 = ΔV5, Vout11 - Vout11’ = ΔV6. Since ΔV5 = ΔV6, that is, Vout4’ - Vout4 = Vout11 - Vout11’.

[0078] The voltage amplitude increased by output terminal OUT4 in the first stage a is equal to the voltage amplitude decreased by output terminal OUT11 in the second stage b. Output terminal OUT4 outputs a positive voltage, and output terminal OUT11 outputs a negative voltage.

[0079] In this embodiment, the voltage amplitude increased by the positive voltage output by the first output terminal is equal to the voltage amplitude decreased by the negative voltage output by the second output terminal. In this way, the positive voltage and the negative voltage can be compensated with the same compensation amplitude, so that the first stage and the second stage can provide a stable AC signal to the liquid crystal as a whole, further improving brightness stability.

[0080] In some embodiments, the second difference is equal to the third difference.

[0081] Please refer to Figure 6, still taking the output terminals OUT4 and OUT11 of the chip as an example, COM - Vout11 = ΔV2, Vout4 - COM = ΔV3, and ΔV2 = ΔV3. That is, COM - Vout11 = Vout4 - COM, that is, -Vout11 = Vout4. Vout4 is a positive voltage and Vout11 is a negative voltage. That is to say, the voltage amplitude output by the output terminal OUT11 in the first stage a is equal to the voltage amplitude output by the output terminal OUT4 in the second stage b, and the voltage amplitude of the output terminal OUT4 without compensation is equal to the voltage amplitude of the output terminal OUT11 without compensation.

[0082] In this embodiment, the voltage amplitude of the first output terminal without compensation is equal to the voltage amplitude of the second output terminal without compensation, further enabling the first stage and the second stage to provide a stable AC signal to the liquid crystal as a whole, and further improving the brightness stability.

[0083] Exemplarily, please refer to Figure 6 , still taking the output terminals OUT4 and OUT11 of the chip as an example, -Vout11 = Vout4, and, -Vout11’ = Vout4’.

[0084] It should be noted that although the accompanying drawings of this application are only described by taking the output terminals OUT4 and OUT11 as examples, the voltage timings of the output terminals that output positive voltages and the output terminals that output negative voltages in other output terminal groups are the same, and will not be elaborated herein one by one.

[0085] Exemplarily, the first output terminal and the second output terminal can alternately output positive voltages and negative voltages in the order of frames. For example, in the first frame, the first output terminal provides a positive voltage to the liquid crystal display panel, in the second frame, the second output terminal provides a negative voltage to the liquid crystal display panel, in the third frame, the first output terminal provides a positive voltage to the liquid crystal display panel, in the fourth frame, the second output terminal provides a negative voltage to the liquid crystal display panel, and so on. In this case, Figure 6 The first stage a shown includes three frames, and the second stage b includes three frames.

[0086] Exemplarily, in the first stage, the first output terminal and the second output terminal alternately output voltages to the liquid crystal display panel. In addition, the first output terminal outputs positive voltages multiple times, and the second output terminal outputs negative voltages at least once, only increasing the voltage output by the first output terminal. In the second stage, the first output terminal and the second output terminal alternately output voltages to the liquid crystal display panel. In addition, the second output terminal outputs negative voltages multiple times, and the first output terminal outputs positive voltages at least once, only reducing the voltage output by the second output terminal. That is to say, after compensating the voltage output by the first output terminal several times, then compensating the voltage output by the second output terminal several times, so as to eliminate the DC component.

[0087] In some embodiments, the refresh rate of the liquid crystal display panel is F Hertz; in the first stage, the number of times the first output terminal outputs the first voltage is n1, and n1 is greater than or equal to F / 2.

[0088] The inventors' research found that in order to better avoid the visible flicker problem for the human eye, it is necessary to control it below 1 Hz where the human eye cannot sense the flicker.

[0089] Exemplarily, as Figure 10 shown, in order for the human eye not to visually perceive flicker, when the refresh rate of the liquid crystal display panel is 60 HZ, within the first stage a, the number of times the first output terminal (such as output terminal OUT4) outputs the first voltage (such as Vout4') is greater than or equal to 30. For another example, when the refresh rate of the liquid crystal display panel is 90 HZ, within the first stage a, the number of times the first output terminal (such as output terminal OUT4) outputs the first voltage (such as Vout4') is greater than or equal to 45. When the refresh rate of the liquid crystal display panel is 120 HZ, within the first stage a, the number of times the first output terminal (such as output terminal OUT4) outputs the first voltage (such as Vout4') is greater than or equal to 60.

[0090] In this embodiment, as the refresh rate of the liquid crystal display panel increases, increasing the number of times the positive voltage is output by the first output terminal within the first stage can reduce the voltage change period within the first stage, making the voltage change period within the first stage not greater than 1 Hz, thereby avoiding the visible flicker problem for the human eye.

[0091] In some embodiments, the refresh rate of the liquid crystal display panel is F Hertz; in the second stage, the number of times the second output terminal outputs the second voltage is n2, and n2 is greater than or equal to F / 2.

[0092] Exemplarily, as Figure 10 shown, in order for the human eye not to visually perceive flicker, when the refresh rate of the liquid crystal display panel is 60 HZ, within the second stage b, the number of times the second output terminal (such as output terminal OUT11) outputs the second voltage (such as Vout11') is greater than or equal to 30. For another example, when the refresh rate of the liquid crystal display panel is 90 HZ, within the second stage b, the number of times the second output terminal (such as output terminal OUT11) outputs the second voltage (such as Vout11') is greater than or equal to 45. When the refresh rate of the liquid crystal display panel is 120 HZ, within the second stage b, the number of times the second output terminal (such as output terminal OUT11) outputs the second voltage (such as Vout11') is greater than or equal to 60.

[0093] In this embodiment, as the refresh frequency of the liquid crystal display panel increases, the number of times the negative voltage output by the second output terminal is increased within the second stage, which can reduce the voltage change period within the second stage, so that the voltage change period within the second stage is not greater than 1 HZ, thereby avoiding the visible flicker problem for the human eye.

[0094] In some embodiments, n1 = n2.

[0095] For example, when the refresh frequency of the liquid crystal display panel is 60 HZ, within the first stage a, the number of times the first output terminal (such as output terminal OUT4) outputs the first voltage (such as Vout4’) is equal to 30, and within the second stage b, the number of times the second output terminal (such as output terminal OUT11) outputs the second voltage (such as Vout11’) is equal to 30.

[0096] For another example, when the refresh frequency of the liquid crystal display panel is 90 HZ, within the first stage a, the number of times the first output terminal (such as output terminal OUT4) outputs the first voltage (such as Vout4’) is equal to 45, and within the second stage b, the number of times the second output terminal (such as output terminal OUT11) outputs the second voltage (such as Vout11’) is equal to 45.

[0097] In this embodiment, the number of times the compensated voltage is output by the first output terminal within the first stage is equal to the number of times the compensated voltage is output by the second output terminal within the second stage, further enabling the first stage and the second stage to provide a stable AC signal to the liquid crystal as a whole, and further improving the brightness stability.

[0098] In some embodiments, the total duration of the first stage is equal to the total duration of the second stage.

[0099] It can be understood that n1 = n2, and the number of times the second output terminal outputs the second voltage within the first stage is equal to the number of times the first output terminal outputs the first voltage within the second stage. That is, the number of times the compensated voltage is output by the first output terminal within the first stage is equal to the number of times the compensated voltage is output by the second output terminal within the second stage, and the number of times the uncompensated voltage is output by the second output terminal within the first stage is equal to the number of times the uncompensated voltage is output by the first output terminal within the second stage. Further enabling the first stage and the second stage to provide a stable AC signal to the liquid crystal as a whole, and further improving the brightness stability.

[0100] In some embodiments, as Figure 11 shown, the working process of the chip includes multiple change cycles T, and each change cycle T includes a first stage a and a second stage b.

[0101] The display periods that need to be compensated can be divided into multiple change cycles. In the first stage of each change cycle, only the voltage output by the first output terminal is compensated. In the second stage of each change cycle, only the voltage output by the second output terminal is compensated. In this way, voltage compensation can be performed in each relatively short change cycle, avoiding overall positive and negative voltage imbalance, and further improving brightness stability.

[0102] Based on the same technical concept, an embodiment of the present application further provides a driving method. The driving method is applied to a gamma adjustment circuit. The gamma adjustment circuit includes a chip, and the chip is configured to output grayscale voltages for display to a liquid crystal display panel. The chip includes multiple output terminal groups, and each output terminal group includes a first output terminal and a second output terminal.

[0103] The driving method includes:

[0104] Controlling the first output terminal and the second output terminal to be configured to alternately output voltages corresponding to the same grayscale to the liquid crystal display panel, and a first voltage of the first output terminal is greater than a common voltage, and a second voltage of the second output terminal is less than the common voltage, where the common voltage is the voltage accessed by the common electrode of the liquid crystal display panel;

[0105] Controlling the working process of the chip includes a first stage and a second stage;

[0106] In the first stage, a difference between the first voltage and the common voltage is a first difference, and a difference between the common voltage and the second voltage is a second difference, and the first difference is greater than the second difference;

[0107] In the second stage, a difference between the first voltage and the common voltage is a third difference, and a difference between the common voltage and the second voltage is a fourth difference, and the third difference is less than the fourth difference.

[0108] According to the embodiment of the present application, the chip of the gamma adjustment circuit includes multiple output terminal groups, and each output terminal group includes a first output terminal for outputting a positive voltage and a second output terminal for outputting a negative voltage, and the working process of the chip is divided into two stages. In the first stage, only the voltage output by the first output terminal is increased. In the second stage, only the voltage output by the second output terminal is decreased. In this way, in any one stage, the amount of voltage change applied to the liquid crystal can be reduced, thereby reducing the brightness change of the liquid crystal display panel and improving brightness stability.

[0109] In some embodiments, the chip accesses a reference voltage and a reference voltage. A ratio of a difference between the reference voltage and the reference voltage to the maximum grayscale is the grayscale voltage adjustment step of the chip; a difference between the first difference and the second difference is a fifth difference, and a difference between the fourth difference and the third difference is a sixth difference. The driving method further includes:

[0110] Controlling the fifth difference to be equal to the voltage adjustment step, and / or controlling the sixth difference to be equal to the grayscale voltage adjustment step.

[0111] In some embodiments, the difference between the first difference and the second difference is a fifth difference, and the difference between the fourth difference and the third difference is a sixth difference. The driving method further includes:

[0112] Controlling one-half of the fifth difference to be less than or equal to 7 mV;

[0113] And / or, controlling one-half of the sixth difference to be less than or equal to 7 mV.

[0114] In some embodiments, the difference between the first difference and the second difference is a fifth difference, and the difference between the fourth difference and the third difference is a sixth difference. The driving method further includes:

[0115] Controlling the fifth difference to be equal to the sixth difference.

[0116] In some embodiments, the driving method further includes:

[0117] Controlling the second difference to be equal to the third difference.

[0118] In some embodiments, the refresh frequency of the liquid crystal display panel is F Hz; the driving method further includes:

[0119] In the first stage, controlling the number of times the first output terminal outputs the first voltage to be n1, where n1 is greater than or equal to F / 2.

[0120] In some embodiments, the refresh frequency of the liquid crystal display panel is F Hz; the driving method further includes:

[0121] In the second stage, controlling the number of times the second output terminal outputs the second voltage to be n2, where n2 is greater than or equal to F / 2.

[0122] In some embodiments, the driving method further includes: controlling n1 = n2.

[0123] In some embodiments, the driving method further includes:

[0124] Dividing the working process of the chip into multiple change cycles, and the change cycle includes a first stage and a second stage.

[0125] In some embodiments, the driving method further includes: controlling the total duration of the first stage to be equal to the total duration of the second stage.

[0126] Based on the same technical concept, an embodiment of the present application further provides a display device. As Figure 12As shown in the figure, the display device 300 includes a liquid crystal display panel 200, a temperature sensor 201, a driving system 10, and a gamma adjustment circuit 10 as described in any of the above embodiments. The temperature sensor 201 is located inside the liquid crystal display panel 200 and is used to monitor the temperature of the display device 300 and transmit the temperature data to the driving system 10; the driving system 10 is used to control the gamma adjustment circuit 00 to output corresponding gray-scale voltages in real time according to the temperature of the display device.

[0127] Exemplarily, the liquid crystal display panel 200 includes a backlight source, which is used to provide a light source for the liquid crystal layer in the liquid crystal display panel 200. The display device 300 includes a driving system 10, and the driving system 10 includes at least one main control chip 01. The main control chip 01 has a storage function, and the compensation curve is pre-stored in the main control chip 01. The gamma adjustment circuit 00 is controlled by the main control chip 01; the display device 300 also includes a temperature sensor 201, which is located inside the liquid crystal display panel 200 and is also electrically connected to the main control chip 01 in the driving system 10. The temperature sensor 201 is used to monitor the temperature of the display device 300, that is, it can monitor the temperature of the backlight source or the temperature of the liquid crystal display panel 200 (such as by setting a temperature sensor 201 inside the liquid crystal display panel 200, etc.), and transmit the monitored temperature data to the main control chip 01. The main control chip 01 controls the gamma adjustment circuit 00 as described above to adjust the gray-scale voltage output to the liquid crystal display panel 200 in real time, drive the liquid crystal layer to deflect, and adjust the display brightness of the liquid crystal display panel 200. The driving system 10 is used to control the gamma adjustment circuit 00 to output corresponding gray-scale voltages according to the monitored temperature, drive the liquid crystal layer to deflect. In this way, by setting the gamma adjustment circuit 00 that only compensates the positive voltage output by the first output terminal in the first stage and only compensates the negative voltage output by the second output terminal in the second stage, and setting the temperature sensor 201 for monitoring the temperature inside the liquid crystal display panel 200, the gray-scale voltage output to the liquid crystal display panel 200 can be adjusted in real time according to the temperature of the liquid crystal display device 300, so that the brightness change of the liquid crystal display panel 200 is lower than the recognizable rate of the human eye, and the brightness stability of the liquid crystal display panel 200 is improved.

[0128] Figure 13 For the gray-scale - brightness curve diagram with a gamma value of 2.2, please refer to Figure 12 and Figure 13 , a display device 300 provided by the present disclosure, the driving system 10 pre-stores a dataset of temperature - gray-scale node voltages, and the dataset of temperature - gray-scale node voltages includes the gray-scale voltages corresponding to different temperatures when the gamma value is 2.2.

[0129] Exemplarily, the driving system 10 of the display device 300 pre-stores a grayscale voltage data set corresponding to different temperatures when the gamma value is 2.2. Please refer to Figure 13 , the brightness response curve of most display devices is closest to the brightness perception curve of the human eye when the gamma value is 2.2. The driving system 10 of the display device 300 pre-stores a grayscale-brightness curve graph when the gamma value is 2.2, and needs to collect a data set of temperature-grayscale node voltages in advance, and confirm the change of grayscale voltage corresponding to the temperature change under the condition that the gamma value remains at 2.2. After the temperature sensor 201 detects a temperature change, it feeds back to the main control chip 01, and the main control chip 01 outputs a grayscale voltage according to the data in the temperature-grayscale node voltage data set according to the temperature change, so as to keep the display brightness of the display device 300 stable.

[0130] Exemplarily, the temperature-grayscale node voltage data set can be collected separately for each display device 300. The main control chip 01 in the driving system 10 will pre-collect the node voltage versions that the gamma adjustment circuit 00 should output when the gamma standard value is 2.2 at different temperatures. When the main control chip 01 recognizes that the display device 300 rises or falls to these temperatures, it will control the gamma adjustment circuit 00 to change the grayscale voltage it outputs, so that the display brightness remains basically unchanged, and the gamma curve is fixed near the standard value of 2.2. In this way, after receiving the real-time monitored temperature of the display device 300, the driving system 10 can control the gamma adjustment circuit 00 to output the corresponding grayscale voltage according to the pre-stored temperature-grayscale node voltage data set, so that the display brightness of the display panel 200 is as close as possible to the brightness perception of the human eye.

[0131] In accordance with the embodiments of the present application as described above, these embodiments do not describe all the details in detail, nor do they limit the application to only the specific embodiments described. Obviously, according to the above description, many modifications and variations can be made. The present specification selects and specifically describes these embodiments in order to better explain the principles and practical applications of the present application, so that those skilled in the art can make good use of the present application and its modifications based on the present application. The present application is only limited by the claims and their full scope and equivalents.

Claims

1. A gamma adjustment circuit, characterized in that, Comprising: A chip configured to output a grayscale voltage for display to a liquid crystal display panel. The chip includes a plurality of output terminal groups. Each output terminal group includes a first output terminal and a second output terminal. The first output terminal and the second output terminal are configured to alternately output the grayscale voltage corresponding to the same grayscale to the liquid crystal display panel. The first voltage of the first output terminal is greater than the common voltage, and the second voltage of the second output terminal is less than the common voltage. The common voltage is the voltage applied to the common electrode of the liquid crystal display panel. The operation process of the chip includes a first stage and a second stage. In the first stage, the difference between the first voltage and the common voltage is a first difference, and the difference between the common voltage and the second voltage is a second difference. The first difference is greater than the second difference. In the second stage, the difference between the first voltage and the common voltage is a third difference, and the difference between the common voltage and the second voltage is a fourth difference. The third difference is less than the fourth difference.

2. The gamma adjustment circuit according to claim 1, wherein The chip is connected to a reference voltage and a reference voltage. The reference voltage is STATIC_Hi, and the reference voltage is GND. The maximum grayscale of the liquid crystal display panel is N. The grayscale voltage adjustment step = (STATIC_Hi - GND) / N. The difference between the first difference and the second difference is a fifth difference, and the fifth difference is equal to the voltage adjustment step. And / or, the difference between the fourth difference and the third difference is a sixth difference, and the sixth difference is equal to the grayscale voltage adjustment step.

3. The gamma adjustment circuit according to claim 1 or 2, characterized in that, The difference between the first difference and the second difference is a fifth difference, and one-half of the fifth difference is less than or equal to 7 mV. And / or, the difference between the fourth difference and the third difference is a sixth difference, and one-half of the sixth difference is less than or equal to 7 mV.

4. The gamma adjustment circuit according to claim 1 or 2, characterized in that, The difference between the first difference and the second difference is a fifth difference, and the difference between the fourth difference and the third difference is a sixth difference. The fifth difference is equal to the sixth difference.

5. The gamma adjustment circuit according to claim 1, characterized in that, The second difference is equal to the third difference.

6. The gamma adjustment circuit according to claim 1, wherein The refresh frequency of the liquid crystal display panel is F Hertz. In the first stage, the number of times the first output terminal outputs the first voltage is n1, and n1 is greater than or equal to F / 2.

7. The gamma adjustment circuit according to claim 6, wherein In the second stage, the number of times the second output terminal outputs the second voltage is n2, and n2 is greater than or equal to F / 2.

8. The gamma adjustment circuit according to claim 7, wherein n1 = n2.

9. The gamma adjustment circuit according to claim 1, wherein The operation process of the chip includes a plurality of change cycles, and each change cycle includes the first stage and the second stage.

10. The gamma adjustment circuit according to claim 1, wherein The total duration of the first stage is equal to the total duration of the second stage.

11. A driving method, characterized in that, Applied to a gamma adjustment circuit, the gamma adjustment circuit includes a chip configured to output a grayscale voltage for display to a liquid crystal display panel. The chip includes a plurality of output terminal groups, and each output terminal group includes a first output terminal and a second output terminal. The driving method includes: The control is such that the first output terminal and the second output terminal are configured to alternately output voltages corresponding to the same gray scale to the liquid crystal display panel, and a first voltage of the first output terminal is greater than a common voltage, and a second voltage of the second output terminal is less than the common voltage, where the common voltage is the voltage applied to a common electrode of the liquid crystal display panel; The operation process of the control chip includes a first stage and a second stage; In the first stage, a difference between the first voltage and the common voltage is a first difference, and a difference between the common voltage and the second voltage is a second difference, and the first difference is greater than the second difference; In the second stage, a difference between the first voltage and the common voltage is a third difference, and a difference between the common voltage and the second voltage is a fourth difference, and the third difference is less than the fourth difference.

12. The method according to claim 11, wherein The method further includes: In the first stage, the number of times of controlling the first output terminal to output the first voltage is n1, and n1 is greater than or equal to F / 2.

13. The method according to claim 12, wherein The method further includes: In the second stage, the number of times of controlling the second output terminal to output the second voltage is n2, and n2 is greater than or equal to F / 2.

14. A display device, characterized in that, It includes: A liquid crystal display panel, a temperature sensor, a driving system, and a gamma adjustment circuit as described in any one of claims 1 to 10; The temperature sensor is located inside the liquid crystal display panel, and is configured to monitor the temperature of the display device and transmit temperature data to the driving system; The driving system is configured to control the gamma adjustment circuit to output corresponding gray scale voltages in real time according to the temperature of the display device.

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