CN112967653A - Display panel and display device - Google Patents

Display panel and display device Download PDF

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Publication number
CN112967653A
CN112967653A CN202110259126.0A CN202110259126A CN112967653A CN 112967653 A CN112967653 A CN 112967653A CN 202110259126 A CN202110259126 A CN 202110259126A CN 112967653 A CN112967653 A CN 112967653A
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China
Prior art keywords
driving
initialization
display panel
driving frequency
initialization signal
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CN202110259126.0A
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Chinese (zh)
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CN112967653B (en
Inventor
张蒙蒙
李玥
杨帅
周星耀
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Xiamen Tianma Microelectronics Co Ltd
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Xiamen Tianma Microelectronics Co Ltd
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    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/2007—Display of intermediate tones
    • G09G3/2074—Display of intermediate tones using sub-pixels
    • G—PHYSICS
    • G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
    • G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
    • G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
    • G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
    • G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
    • G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
    • G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
    • G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
    • G09G3/3275—Details of drivers for data electrodes
    • G09G3/3291—Details of drivers for data electrodes in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements

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  • Engineering & Computer Science (AREA)
  • Physics & Mathematics (AREA)
  • Computer Hardware Design (AREA)
  • General Physics & Mathematics (AREA)
  • Theoretical Computer Science (AREA)
  • Control Of Indicators Other Than Cathode Ray Tubes (AREA)
  • Electroluminescent Light Sources (AREA)

Abstract

The embodiment of the invention provides a display panel and a display device. The display panel provided by the embodiment of the invention comprises: a sub-pixel and a pixel driving circuit driving the sub-pixel; the pixel driving circuit comprises a first power supply signal end, a driving transistor, an organic light-emitting element and a second power supply signal end which are connected in series; the initialization transistor is connected between the grid of the driving transistor and the initialization signal end in series; the initialization signal line transmits an initialization signal to the initialization signal terminal; the display panel comprises a first driving frequency mode and a second driving frequency mode; the first driving frequency is less than the second driving frequency; in the first driving frequency mode, the initialization signal is the first initialization signal V1(ii) a At the second driving frequency, the initialization signal is a second initialization signal V2，V1≠V2. The technical scheme of the invention reduces the brightness change caused by leakage current at low frequency.

Description

Display panel and display device
Technical Field
The invention relates to the technical field, in particular to a display panel and a display device.
Background
For wearing products, such as watches or bracelets, minimization of power consumption is an important goal. For convenience of viewing information, these products usually have a continuous display mode, also called aod (always on display) mode, but the power consumption of continuous display at normal driving frequency is very high, so that the display frequency is usually reduced at standby state or some special pictures, such as 15Hz or lower, for reducing the power consumption. However, the display brightness changes due to the leakage current of the driving transistor grid after the frequency is reduced, and even the flicker problem occurs.
In the current design, the problem of dark state brightening may occur due to the increase of the leakage time after the frequency is reduced. If the dark state brightness needs to be reduced, the dark state voltage needs to be increased, which leads to the problem of increased power consumption. This may cause the power consumption in the low frequency mode to be increased rather than the original intention of designing the low frequency display mode. Therefore, there is a need to solve the aforementioned technical problems.
Disclosure of Invention
An embodiment of the present invention provides a display panel, including: a sub-pixel and a pixel driving circuit driving the sub-pixel; the pixel driving circuit comprises a first power supply signal end, a driving transistor, an organic light-emitting element and a second power supply signal end which are connected in series; the initialization transistor is connected between the grid of the driving transistor and an initialization signal end in series; an initialization signal line transmitting an initialization signal to the initialization signal terminal; the display panel comprises a first driving frequency mode and a second driving frequency mode; the first drive frequency is less than the second drive frequency; in the first driving frequency mode, the initialization signal is a first initialization signal V1(ii) a At the second driving frequency, the initialization signal is a second initialization signal V2，V1≠V2。
An embodiment of the present invention provides a display device, including: the display panel is provided.
According to the display panel and the display device provided by the embodiment of the invention, the initialization signal is changed in the low-frequency driving mode, the leakage current in the low-frequency driving mode is reduced, the brightness after the leakage current in the low-frequency driving mode is the same as the brightness after the leakage current in the normal-frequency driving mode is realized, and the problems of dimming and flickering of the brightness caused by large leakage current in the low-frequency driving mode are solved.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions in the prior art, the drawings needed to be used in the description of the embodiments or the prior art will be briefly introduced below, and it is obvious that the drawings in the following description are some embodiments of the present invention, and for those skilled in the art, other drawings can be obtained according to these drawings without creative efforts.
Fig. 1 is a schematic diagram of a display panel according to an embodiment of the present invention;
fig. 2 is a schematic diagram of a pixel driving circuit according to an embodiment of the invention;
FIG. 3 is a timing diagram of the pixel driving circuit shown in FIG. 2;
FIG. 4 is a schematic diagram of signal simulation according to an embodiment of the present application;
fig. 5 is a schematic diagram of a display panel according to another embodiment of the invention;
fig. 6 is a schematic diagram of a display panel according to yet another embodiment of the present invention;
FIG. 7 is a schematic diagram of signal simulation for another embodiment of the present application;
FIG. 8 is a schematic diagram of signal simulation for yet another embodiment of the present application;
fig. 9 is a schematic diagram of a display device according to an embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention clearer, the technical solutions in the embodiments of the present invention will be clearly and completely described below with reference to the drawings in the embodiments of the present invention, and it is obvious that the described embodiments are some, but not all, embodiments of the present invention. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The terminology used in the embodiments of the invention is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. As used in the examples of the present invention and the appended claims, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context clearly indicates otherwise.
As described in the background art, a product such as a watch, a bracelet, or a mobile phone needs to display in real time, and the driving frequency of a display panel is reduced in order to reduce power consumption. The time of the next frame at 60Hz is 16.67ms, the time of the next frame at 15Hz is 66.67ms, that is, the time for which the potential of the gate of the driving transistor needs to be maintained in the display mode at 15Hz is 4 times that in the display mode at 60 Hz. Therefore, the leakage continues in the low frequency mode, resulting in an increase in luminance and even flickering of display luminance. The present application provides a display panel and a display device to solve the above technical problems.
Referring to fig. 1 to 4, fig. 1 is a schematic view of a display panel according to an embodiment of the present invention; fig. 2 is a schematic diagram of a pixel driving circuit according to an embodiment of the invention; FIG. 3 is a timing diagram of the pixel driving circuit shown in FIG. 2; FIG. 4 is a schematic diagram of signal simulation according to an embodiment of the present application;
the display panel of the present application includes a subpixel P and a pixel driving circuit C driving the subpixel; the pixel driving circuit C includes a first power signal terminal PVDD, a driving transistor DT, an organic light emitting element OLED, and a second power signal terminal PVEE connected in series; the initialization transistor T1 is connected between the grid electrode (represented by an N1 node) of the driving transistor DT and an initialization signal terminal Vint in series; the initialization signal line Int transmits an initialization signal to the initialization signal terminal Vint; to be provided withThe driving transistor DT is initialized. Taking the PMOS type pixel driving circuit shown in fig. 2 as an example, in order to ensure that the driving transistor DT can be turned on in the data writing phase, the potential of the gate N1 of the driving transistor DT must satisfy Vmin-VN1＜|VthL, wherein VminThe lowest data voltage. Therefore, the potential inputted to the gate N1 of the driving transistor must be lower than the lowest data voltage VminMinus the absolute value of the threshold voltage | VthA smaller potential. That is, the initialization signal line Int is kept at a low potential all the time, and both ends of the initialization transistor T1 are respectively the initialization signal terminal Vint and the N1 node at the time of light emission. Since the voltage difference between the node N1 of the gate of the driving transistor and the voltage on the initialization signal line is large, the initialization transistor T1 generates a leakage current, which causes the voltage on the node N1 of the gate of the driving transistor to change, and finally causes the brightness to change. Referring to fig. 4, taking the first driving frequency as 30Hz and the second driving frequency as 60Hz as an example, one frame under the first driving frequency exactly corresponds to two frames under the second driving frequency. First Frame 1st Frame and second initialization voltage V at 60Hz2The corresponding potential of the node N1 is shown in FIG. 4, and the potential of the node N1 gradually decreases due to the existence of leakage current; after the second Frame 2nd Frame rewrites the data signal, the potential of the N1 node starts to fall from the high level again. If the initialization potential in the first driving frequency mode is the same as that in the second driving frequency mode, i.e. V1' corresponding potential simulation diagram of node N1 shows that in the second half of the first driving frequency mode, the potential of node N1 continuously decreases, resulting in continuous brightness change, and the potential in the second half changes more, the brightness change is also larger, even flicker occurs, and the display effect is affected.
The display panel of the present application includes a first driving frequency mode and a second driving frequency mode; the first driving frequency is less than the second driving frequency; in the first driving frequency mode, the initialization signal is the first initialization signal V1(ii) a At a second driving frequency, the initialization signal is a second initialization signal V2，V1≠V2. The application is realized by combining a first driving frequency mode and a second frequency modeThe initialization signals are set to be unequal so that the leakage current is reduced although the time of the leakage current is increased in the first driving frequency mode, thereby ensuring that the luminance after the leakage current in the first driving frequency mode is the same as the luminance after the leakage current in the second driving frequency table mode.
Further, fig. 2 and fig. 3 are used to illustrate a pixel driving circuit according to an embodiment of the present application. The pixel driving circuit comprises a driving transistor DT, an initialization transistor T1 connected in series between an initialization signal end Vint and a driving transistor grid N1; a reset transistor T2 connected in series between a reset signal terminal Vreset and the first electrode of the organic light emitting element; a first light emission control transistor T3 connected in series between the first power signal terminal PVDD and the first pole of the driving transistor; a second light emission control transistor T4 connected in series between the second electrode of the driving transistor and the first electrode of the organic light emitting element; a compensation transistor T5 connected in series between the gate and the second pole of the driving transistor; a DATA write transistor T6 connected in series between the DATA signal terminal DATA and the first pole of the driving transistor; and a storage capacitor CST having a first electrode connected to the first power signal terminal PVDD and a second electrode connected to the gate N1 of the driving transistor. The initialization transistor T1 is controlled by a first Scan signal Scan1, the reset transistor T2, the data write transistor T6 and the compensation transistor T5 are controlled by a second Scan signal Scan 2; the first and second light emission control transistors T3 and T4 are controlled by a light emission control signal EMIT.
Referring to fig. 3, the driving timing of the pixel driving circuit includes an initialization phase P1, a threshold capture phase P2, and a light emitting phase P3;
in the initialization phase P1, the first Scan signal Scan1 provides an on level, the second Scan signal Scan2 and the emission control signal EMIT provide an off level, and the initialization transistor T1 is turned on to initialize the driving transistor DT; it should be noted that the active level here refers to a level at which a transistor which can be controlled by the active level is in a conducting state, for example, in the PMOS pixel driving circuit of fig. 2, the active level refers to a low level. The initialization signal is transmitted to the driving transistor DT to reset the driving transistor DT.
In the threshold capture phase P2, the second Scan signal Scan2 provides an on level, the first Scan signal Scan1 and the emission control signal EMIT provide an off level; the data writing transistor T6 and the compensation transistor T5 are turned on, so that the data signal is written into the gate of the driving transistor DT and self-compensation is completed; at the same time, the reset transistor T2 is turned on, and the initialization signal is transmitted to the organic light emitting element OLED to reset the organic light emitting element OLED. The data signal is transmitted to the gate of the driving transistor DT through the first pole of the data writing transistor T6, the driving transistor DT and the compensating transistor T5, and the initialization signal stored at the gate of the driving transistor at the previous time is raised until the potential of the gate of the driving transistor is VDATA-VthThe driving transistor DT is turned off at the moment, and the potential stored by the grid electrode of the driving transistor is V at the momentDATA-VthIn which V isthIs the threshold voltage of the drive transistor. Due to the process of manufacturing transistors, even if the same process parameters are satisfied during the manufacturing of the transistors, the threshold voltages of the transistors on the display panel are different, and the threshold voltages of the transistors drift with the increase of the service time after the transistors age, which causes the brightness of the same written data signals at different positions of the display panel to be different, and the brightness of the same written data signals displayed with the increase of the service time also to be different, which causes the display to be uneven and the color to drift. Therefore, the present embodiment grasps and stores the threshold voltage of the driving transistor DT to the gate of the driving transistor in order to eliminate the influence of the threshold voltage on the light emission luminance.
In the light emitting period P3, the light emitting control signal EMIT provides an on level, and the first Scan signal Scan1 and the second Scan signal Scan2 provide an off level; the driving transistor DT generates a driving current and causes the organic light emitting element OLED to emit light. The first light emitting control transistor T3 is turned on, and the first power signal VDD is transmitted to the first pole of the driving transistor DT to make the driving transistor DT generate the driving current; the second light emission controlling transistor T4 is turned on to transmit the driving current to the organic light emitting element OLED. Wherein the drive transistor DT generates a drive current Ids＝1/2Coxμ*W/L*(Vsg-Vth)^2＝1/2Coxμ*W/L*(VDD-(VDATA-Vth)-Vth)^2＝1/2Coxμ*W/L*(VDD-VDATA) 2. It can be seen that the light emission current of the present embodiment depends on the written data signal regardless of the threshold voltage of the driving transistor DT through the compensation of the data writing period P3, and thus, the influence of the non-uniformity and the drift of the threshold voltage of the driving transistor DT on the light emission current is eliminated.
In addition, it can be found from the above formula that the higher the data signal, the smaller the driving current, and the lower the brightness. Therefore, the black state voltage is generally close to or equal to the first power supply voltage VDD, and the writing of the black state voltage in the first driving frequency mode is a potential of the node N1 and the initialization signal V1The difference is large, which causes serious leakage current, black state is not black, and even flicker phenomenon. The initialization voltage of the first driving frequency mode is set to be different from the initialization voltage of the second driving frequency mode, so that the leakage current in the first driving frequency mode is reduced, the brightness after leakage is approximately the same as that in the second driving frequency mode, and the technical problem is solved. In addition, the black state of the liquid crystal display is darker without increasing data voltage, and the improvement of power consumption is avoided.
Referring to fig. 1 to 4, in an embodiment of the present application, the driving transistor is a P-type transistor, and the first initialization signal V is1Greater than the second initialization signal V2. On the other hand, referring to the threshold grabbing phase P2, the data signal is transmitted to the gate of the driving transistor DT through the first electrode of the data writing transistor T6, the driving transistor DT and the compensating transistor T5, and the initialization signal stored at the gate of the driving transistor DT at the previous time is raised, but the potential of the node N1 cannot be raised to V completelyDATA-VthCan only be close to VDATA-Vth. In this embodiment, since the first initialization signal is greater than the second initialization signal, the initial state in the first driving frequency mode is higher, and therefore, even if the same data voltage is written, the potential of the node of the driving transistor gate N1 is higher in the first driving frequency mode. On the other hand, since the first initialization voltage is larger than the second initialization voltage, the first initialization voltage is larger than the second initialization voltageThe difference between the potentials of the driving transistor gates in the first driving frequency mode is smaller, and the leakage current is smaller. By combining the two factors, the brightness in the first driving frequency mode and the brightness in the second driving frequency mode after the application are used are the same. Please refer to the first initialization voltage V in fig. 41The potential of the corresponding N1 node changes. The method sets a first initialization signal V1Greater than the second initialization signal V2Average value of potential variation line corresponding to the second voltage and second initialization voltage V2The average values of the potential variation lines of the corresponding N1 nodes are closer, namely, the brightness of the two driving frequency modes is closer at one position. Referring to fig. 4, taking the first driving frequency as 30Hz and the second driving frequency as 60Hz as an example, one frame under the first driving frequency exactly corresponds to two frames under the second driving frequency. First Frame 1st Frame and second initialization voltage V at 60Hz2The corresponding potential of the node N1 is shown in FIG. 4, and the potential of the node N1 gradually decreases due to the existence of leakage current; after the second Frame 2nd Frame rewrites the data signal, the potential of the N1 node starts to fall from the high level again. If the initialization voltage in the first driving frequency mode is larger than that in the second driving frequency mode, i.e. V1The potential simulation diagram of the corresponding N1 node shows that, in the first half of the first driving frequency mode, the potential of the N1 node is itself relatively high, and the leakage current rate in the first half and the second half is very low, so that the average value of the potential of the node N1 of the driving transistor gate is close to or even equal to that in the second driving frequency mode, and the problems of brightness change and flicker in the low frequency mode are solved.
In another embodiment of the present application, referring to fig. 1, the pixel driving circuit C further includes a reset transistor T2 connected in series between the reset signal terminal Vreset and the first electrode of the organic light emitting device; the Reset signal terminal Vreset is electrically connected with a Reset signal line Reset; the Reset signal line Reset is electrically insulated from the initialization signal line Int. When the voltage across the organic light emitting element is the threshold voltage of the organic light emitting element, the organic light emitting element is lit to emit light. In the related art display panel, the same signal is shared for the gate initialization and the reset of the organic light emitting element, that is, the initialization transistor and the reset transistor are connected to the same terminal. Since the voltage transmitted to the first electrode of the organic light emitting element OLED is increased due to the increase of the initialization voltage in the first driving frequency mode, and the voltage difference between the voltage and the second power voltage may approach or even exceed the threshold voltage of the organic light emitting element, which may cause the organic light emitting element to be stolen, the reset signal terminal and the initialization signal terminal are electrically insulated from each other in this embodiment, thereby avoiding the problem of stealing caused by the initialization voltage increase of the initialization signal terminal in the first driving frequency mode.
In another embodiment of the present application, in a display panel with high pixel density, a layout design cannot accommodate a reset signal line and an initialization signal line separately, please refer to fig. 6, where fig. 6 is a schematic diagram of a display panel according to another embodiment of the present invention; the pixel driving circuit C further includes a reset transistor T2 connected in series between a reset signal terminal Vreset and the first electrode of the organic light emitting element OLED; the reset signal terminal Vreset is electrically connected to the initialization signal line Int;
under the first driving frequency mode, the voltage signal of the second power signal terminal is PVEE1(ii) a At the second driving frequency, the voltage signal of the second power signal terminal is PVEE2，V1-PVEE1≤V2-PVEE2＜VoledWherein said V isoledIs the threshold voltage of the organic light emitting element. In the embodiment, the second power voltage is adjusted in the first driving frequency mode and the second driving frequency mode, so that the voltage difference between the potential transmitted to the first electrode of the organic light-emitting element and the second power signal during resetting is smaller than the threshold voltage of the organic light-emitting element, and the organic light-emitting element is prevented from being stolen. Meanwhile, the reset signal end is electrically connected with the initialization signal wire, an independent reset signal wire does not need to be arranged, the pressure of layout is reduced, and the design of a high-pixel-density display panel is facilitated.
In another embodiment of the present application, in the first driving frequency mode, when the display panel displays a dark-state picture, 0.5V ≦ (V ≦ V)black-|Vth|)-V11V or less, wherein V isblackIs a black state data voltage, VthTo drive the threshold of the transistorPressing; the dark-state picture is a picture in which the sub-pixels with the display gray scale less than 16 gray scale account for more than 70% of the total number of the sub-pixels. Here, the black data voltage refers to a data voltage of 0 gray scale. As in the previous analysis, since the darker the picture data voltage is, the larger the difference from the initialization signal is, the more easily the leakage current is caused, resulting in the increase of the luminance. Therefore, when the application displays the dark-state picture, the first initialization voltage V is set1Satisfies the condition that V is less than or equal to 0.5Vblack-|Vth|)-V1The voltage is less than or equal to 1v, and the power consumption is greatly reduced while the brightness fluctuation in a low-frequency mode is reduced. Specifically, the first initialization voltage is increased when the frequency is reduced, and is set to be 0.5-1V lower than the black state voltage- | Vth | when a black picture is displayed in a standby mode. E.g. black state voltage Vblack＝5V，VthWhen the value is-1.5V, V may be set13V. First initialization voltage V1The voltage difference between the source and the gate of the driving transistor is only 2V, the leakage current of the node N1 (the gate of the driving transistor) is very small, and meanwhile, the CST capacitor needs to be charged and discharged in the initialization stage, so that the charging and discharging of CST are greatly reduced. In particular, assume a first initialization voltage V1at-3.5V, storing CST requires a voltage of N1 to the first initialization voltage V every frame1Reset, then write to the N1 potential from the data line, as described above for the data voltage setting, the N1 node changes as follows: 3.5V → 3.5V, the variation range is 7V. To set the first initialization voltage V1Close to Vblack- | Vth | then only a very small amount of charge and discharge is required in the reset phase. If set to the first initialization voltage V1For 3V, the N1 node changes as follows: 3.5V → 3V → 3.5V, the variation range is only 0.5V. The problem of dark state lightening can be reduced while power consumption can be saved.
In another embodiment of the present application, in the first driving frequency mode, when the display panel displays a non-dark picture, 0.5V ≦ (V)mode-|Vth|)-V11V or less, wherein V ismodeIs the mode of the data voltage in the display panel. Setting a first initialization voltage V1Close to Vmode- | Vth | then only a very small amount of charge and discharge is required in the reset phase. N1 varied as follows: v1→Vdata-|Vth|→V1For most sub-pixels, the variation range is only about 0.5V to 1V, and a few sub-pixels slightly exceed the range. The problem of dark state lightening can be reduced while power consumption can be saved. In addition, when a non-dark state picture is displayed, the difference of the data lines is large, if the first initialization voltage V is set according to the highest data voltage or the lowest data line1This causes a problem that the charging time varies greatly. For example, setting the first initialization voltage according to the black state voltage makes the charging time of the pixel driving circuit corresponding to the black state sub-pixel short, and makes the charging time of the pixel driving circuit corresponding to the white state sub-pixel long, or vice versa. Therefore, the present embodiment sets the initialization voltage using the mode of the voltage of the data line in the frame to be displayed. So that the charge time of most sub-pixels is close. Here, the non-dark-state picture refers to another picture that does not conform to the definition of the dark-state picture.
Further, referring to fig. 5, fig. 5 is a schematic view of a display panel according to another embodiment of the present invention; due to the development of organic light emitting devices, blue organic light emitting devices have low light emitting efficiency and larger driving current, almost twice as large as that of red and green sub-pixels. Formula I according to the drive currentds＝1/2Coxμ*W/L*(VDD-VDATA) 2, i.e., the N1 node is lower for the blue sub-pixel at the same gray level, which results in a smaller leakage current for the blue sub-pixel and a larger leakage current for the red and green sub-pixels at the same initialization voltage. When the leakage current time increases in the first driving frequency mode, the difference of the leakage current is enlarged, which results in not only the brightness change but also the obvious color shift. Therefore, in the present embodiment, referring to fig. 5, the display panel includes a red sub-pixel, a green sub-pixel and a blue sub-pixel; the initialization signal line comprises a first initialization signal line IntRG and a second initialization signal line IntB; a first initialization signal line IntRG for initializing the pixel driving circuits corresponding to the red and green sub-pixels, and a second initialization signal line IntB for initializing the pixel driving circuits corresponding to the blue sub-pixel(ii) a The first initialization signal line provides red and green first initialization signals V11(ii) a The second initialization signal line provides a blue first initialization signal V12；V11＞V12. Because the driving voltage of the red sub-pixel and the green sub-pixel is larger, a larger first initialization signal is set, the driving voltage of the blue sub-pixel is smaller, and a smaller first initialization voltage is set, so that the leakage currents of the red sub-pixel, the green sub-pixel and the blue sub-pixel are close to each other, and color cast is avoided.
In one embodiment of the present application, since only several driving modes are commonly used, for example: standby mode, ultralow frequency drive, low frequency drive and normal drive, so that the drive frequency of the display panel corresponding to the application is in a scattered point change, and the first drive frequency mode comprises a drive frequency of F5(ii) a The second driving frequency mode comprises a driving frequency of F6，F5＜F6. It should be noted that the first driving frequency mode and the second driving frequency mode mentioned in this application do not mean that only two driving frequency modes can be provided in this application, but rather that there is a high frequency driving mode and a low frequency driving mode relatively. For example: the display panel comprises driving frequencies of 60Hz, 30Hz, 15Hz and 1Hz, wherein 1Hz is a first driving frequency mode, and the driving frequencies of 15Hz, 30Hz and 60Hz can be called as a second driving frequency mode compared with the first driving frequency mode of 1 Hz; similarly, 15Hz is the first driving frequency mode, and both 30Hz and 60Hz can be referred to as the second driving frequency mode compared to the first driving frequency mode of 1 Hz;
further, please refer to fig. 7 and 8, fig. 7 is a signal simulation diagram of an initialization signal according to another embodiment of the present application; FIG. 8 is a signal simulation diagram of an initialization signal according to another embodiment of the present application;
the inventors found that the brightness perceived by the human eye is the average brightness per unit time. Then human eye perceives luminance L ═ L (T) dt/T; while the potential at node N1 is current dependent and the current is luminance dependent. The inventor analyzes by a infinitesimal method that the potential and the brightness of the N1 node are basically linear in the range of the voltage difference delta V caused by the leakage current of the N1 node. And ^ L (t) dt actually representsArea and T represents time, and L ═ L (T) dt/T represents the average of the areas. Please refer to fig. 7, S1It represents an area of the second driving frequency pattern that is more than the area of the first driving frequency pattern if the initialization voltage is not adjusted. This results in a difference in brightness. Referring to FIG. 8, if we adjust the first initialization voltage to make it have more area S than the area S without adjusting the initialization voltage2Approach S1The luminance in the first driving frequency mode and the luminance in the second driving frequency mode can be considered to be similar or even identical at this time. Wherein S1Drop to value (K/F) of node voltage N16)*1/F6，＝K/F62, where K is the leakage rate. S2 area ≈ DeltaV similar to trapezoid1+(△V1+K/F5-K’/F5))/2F5＝△V1/F5+K-K’/2F5And 2, wherein K' is the leakage rate after the first initialization voltage is adjusted. To make S2Approach S1Then Δ V1/F5+(K-K’)/2F5^2＝＝K/F6^2, then Δ V1＝K*F5/F6^2+(K-K’)/2F5. It is apparent that the leakage rate at the second initialization voltage is greater than the leakage rate at the first initialization voltage, and thus K-K' > 0. In addition, as mentioned above, when the first initializing potential is higher than the second initializing potential, the potential of the node N1 cannot be pulled up by V1-V2I.e. V1-V2＞△V1. Thus, in another embodiment of the present application, V1-V2＞K*F5/F62. Further, K' > 0, so V can be set1-V2＜K*F5/F6^2+K/2F5According to the embodiment, the brightness of the first driving frequency mode and the brightness of the second driving frequency mode can be close to or equal to each other, and the problem of brightness is avoided.
Further, in an embodiment of the present application, the driving frequency of the display panel is continuously varied, and the first driving frequency mode includes that the driving frequency is at F1～F2A drive frequency in between; the second drive frequency mode comprises a drive frequency at F3～F4A drive frequency in between; f1～F2Maximum value in between is less than F3～F4The minimum value in between.
First average driving frequency FmIs F1And F2Average value of (F), second average driving frequency FnIs F3And F4Average value of (1), K x Fm/Fn^2＜V1-V2＜K*Fm/Fn^2+K/2FmWhere K is the leakage rate. The problem of increased leakage current time and brightness change can occur only when the frequency difference is large, and compensation can be performed according to the average value in a small frequency range, so that the brightness of the first driving frequency mode and the brightness of the second driving frequency mode are close to or equal to each other according to the embodiment, and the problem of brightness is avoided.
Further, the present application also discloses a display device, which further includes an initialization voltage adjustment unit 20, wherein the initialization voltage adjustment unit 20 includes a frequency identifier 201 and an initialization voltage generator 202, the frequency identifier 201 is used for identifying the driving frequency of the display panel, and the initialization voltage generator 202 is used for generating a corresponding initialization voltage according to the driving frequency identified by the frequency identifier. The display device of the present application includes, but is not limited to, a cellular phone 1000, a tablet computer, a display of a computer, a display applied to an intelligent wearable device, a display applied to a vehicle such as an automobile, and the like. As long as the display device includes the organic light emitting display panel included in the display device disclosed in the present application, it is considered to fall within the scope of protection of the present application.
The above description is only for the purpose of illustrating the preferred embodiments of the present invention and is not to be construed as limiting the invention, and any modifications, equivalents, improvements and the like made within the spirit and principle of the present invention should be included in the scope of the present invention.
Finally, it should be noted that: the above embodiments are only used to illustrate the technical solution of the present invention, and not to limit the same; while the invention has been described in detail and with reference to the foregoing embodiments, it will be understood by those skilled in the art that: the technical solutions described in the foregoing embodiments may still be modified, or some or all of the technical features may be equivalently replaced; and the modifications or the substitutions do not make the essence of the corresponding technical solutions depart from the scope of the technical solutions of the embodiments of the present invention.

Claims (12)

1. A display panel, comprising:
a sub-pixel and a pixel driving circuit driving the sub-pixel;
the pixel driving circuit comprises a first power supply signal end, a driving transistor, an organic light-emitting element and a second power supply signal end which are connected in series; the initialization transistor is connected between the grid of the driving transistor and an initialization signal end in series;
an initialization signal line transmitting an initialization signal to the initialization signal terminal;
the display panel comprises a first driving frequency mode and a second driving frequency mode; the first drive frequency is less than the second drive frequency;
in the first driving frequency mode, the initialization signal is a first initialization signal V1(ii) a And in the initialization phase, the first initialization signal V1Writing to the gate of the drive transistor through the initialization transistor; at the second driving frequency, the initialization signal is a second initialization signal V2，V1≠V2。
2. The display panel according to claim 1,
the pixel driving circuit further comprises a reset transistor connected in series between a reset signal end and the first electrode of the organic light-emitting element; the reset signal end is electrically connected with a reset signal wire; the reset signal line is electrically insulated from the initialization signal line.
3. The display panel according to claim 2,
the pixel driving circuit also comprises a reset transistor which is connected in series between a reset signal end and the first electrode of the organic light-emitting element; the reset signal end is electrically connected with the initialization signal line;
in the first driving frequency mode, the voltage signal of the second power signal terminal is PVEE1(ii) a In the second driving frequency mode, the voltage signal of the second power signal terminal is PVEE2，V1-PVEE1≤V2-PVEE2＜VoledWherein said V isoledIs the threshold voltage of the organic light emitting element.
4. The display panel according to claim 1,
the driving transistor is a P-type transistor, and the first initialization signal V1Is greater than the second initialization signal V2。
5. The display panel according to claim 4,
in the first driving frequency mode, when the display panel displays dark picture, 0.5V ≦ (V)black-|Vth|)-V11V or less, wherein V isblackIs a black state data voltage, VthIs the threshold voltage of the drive transistor; the dark-state picture is a picture in which the sub-pixels with the display gray scale smaller than 16 gray scale account for more than 70% of the total number of the sub-pixels.
6. The display panel according to claim 5,
in the first driving frequency mode, when the display panel displays non-dark state picture, 0.5V ≦ (V)mode-|Vth|)-V11V or less, wherein V ismodeIs the mode of the data voltage in the display panel.
7. The display panel according to claim 4,
the display panel comprises a red sub-pixel, a green sub-pixel and a blue sub-pixel; the initialization signal line comprises a first initialization signal line and a second initialization signal line; the first initialization signal line is used for initializing the pixel driving circuits corresponding to the red sub-pixel and the green sub-pixel, and the second initialization signal line is used for initializing the pixel driving circuits corresponding to the blue sub-pixel;
the first initialization signal line provides a red and green first initialization signal V11(ii) a The second initialization signal line provides a blue first initialization signal V12；V11＞V12。
8. The display panel according to claim 1,
the driving frequency of the display panel is continuously changed, and the first driving frequency mode comprises that the driving frequency is F1～F2A drive frequency in between; the second drive frequency mode comprises a drive frequency at F3～F4A drive frequency in between; f1～F2Maximum value in between is less than F3～F4The minimum value in between.
9. The display panel according to claim 8,
first average driving frequency FmIs F1And F2Average value of (F), second average driving frequency FnIs F3And F4Is determined by the average value of (a) of (b),
K*Fm/Fn^2＜V1-V2＜K*Fm/Fn^2+K/2Fmwhere K is the leakage rate.
10. The display panel according to claim 1,
the driving frequency of the display panel is in a scattered point change, and the first driving frequency mode comprises the driving frequencyA rate of F5(ii) a The second driving frequency mode comprises a driving frequency of F6，F5＜F6。
11. The display panel according to claim 10,
K*F5/F6^2＜V1-V2＜K*F5/F6^2+K/2F5where K is the leakage rate.
12. A display device comprising the display panel according to any one of claims 1 to 11,
the display device further comprises an initialization voltage adjusting unit, wherein the initialization voltage adjusting unit comprises a frequency identifier and an initialization voltage generator, the frequency identifier is used for identifying the driving frequency of the display panel, and the initialization voltage generator is used for generating corresponding initialization voltage according to the driving frequency identified by the frequency identifier.
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