Pixel circuit and driving method thereof, display panel and display device
By adjusting the level of the reset signal in the pixel circuit and reducing the voltage drop of the reset transistor, the problems of low luminous efficiency and poor stability caused by leakage current are solved, and higher luminous efficiency and stability are achieved.
Patent Information
- Application Number
- CN202311728962.4
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2023-12-15
- Publication Date
- 2025-06-17
AI Technical Summary
There is a leakage current path in the pixel circuit, which leads to a lower luminous efficiency and a decrease in the stability of the luminous current.
By introducing a reset transistor into the pixel circuit and adjusting the level of the reset signal during the light emitting stage, the voltage drop between the first and second poles of the reset transistor is smaller than the voltage drop on the light emitting diode, thereby reducing the leakage current.
The leakage current is reduced, the power consumption is reduced, the luminous efficiency of the pixel circuit is improved, and the stability of the luminous current is enhanced.
Smart Images
Figure CN120164406A_ABST
Abstract
Description
Technical Field
[0001] This application belongs to the field of display technology, and particularly relates to a pixel circuit, a driving method thereof, a display panel, and a display device. Background Art
[0002] In the fields of AM Micro LED (Active Matrix Micro Light-Emitting Diode) and AM Micro OLED (Active Matrix Micro Organic Light-Emitting Diode) displays, at extremely high pixel densities, the luminous current required for a single pixel is relatively small, possibly reaching the nanoampere to femtoampere level. In such application scenarios, the pixel circuit needs to precisely control the luminous current of the light-emitting element. Due to the internal structure of the pixel circuit, there is always a leakage current path in the pixel circuit. During the normal display of AM Micro LED and AM Micro OLED, the existence of the leakage current will lead to a decrease in luminous efficiency and a decline in the stability of the luminous current. Summary of the Invention
[0003] Embodiments of this application provide a pixel circuit, a driving method thereof, a display panel, and a display device, which can solve the problems of low luminous efficiency and decreased stability of the luminous current caused by the leakage current existing in the pixel circuit.
[0004] In a first aspect, embodiments of this application provide a pixel circuit, including:
[0005] A light-emitting diode for emitting light in response to a driving current;
[0006] A driving module electrically connected to the anode of the light-emitting diode for providing a driving current to the light-emitting diode during the light-emitting stage;
[0007] A data writing module for writing a data signal to the control end of the driving module during the non-light-emitting stage;
[0008] A storage module for storing the data signal and the signal at the first end of the driving module during the non-light-emitting stage, and coupling the signal change at the control end of the driving module to the first end of the driving module;
[0009] A light-emitting control module for controlling the output of the driving current to the light-emitting diode during the light-emitting stage;
[0010] A reset transistor, a first pole of the reset transistor is electrically connected to an anode of the light-emitting diode, a cathode of the light-emitting diode is configured to receive a first level, a second pole of the reset transistor is configured to receive a reset signal, and during a light-emitting stage, a level of the reset signal is higher than the first level.
[0011] During the light-emitting stage, a level on the first pole of the reset transistor is a voltage on the anode of the light-emitting diode. Then, a voltage drop between the first pole and the second pole of the reset transistor is equal to a difference between the voltage on the anode of the light-emitting diode and the level of the reset signal. Since the level of the reset signal is higher than the first level, the voltage drop between the first pole and the second pole of the reset transistor is smaller than the voltage drop across the light-emitting diode. In the prior art, during the light-emitting stage, the level of the reset signal is equal to the first level, so the voltage drop between the first pole and the second pole of the reset transistor is equal to the voltage drop across the light-emitting diode. It can be seen therefrom that the voltage drop between the first pole and the second pole of the reset transistor in the present application becomes smaller compared with the prior art. Since the leakage current flowing through the reset transistor is proportional to the voltage drop between the first pole and the second pole of the reset transistor, when the voltage drop between the first pole and the second pole of the reset transistor becomes smaller, the leakage current flowing through the reset transistor will also become smaller. When the leakage current flowing through the reset transistor becomes smaller, the power consumption caused by the leakage current becomes lower, thereby improving the light-emitting efficiency of the pixel circuit. Since the leakage current will shunt the light-emitting current flowing through the light-emitting diode, when the leakage current becomes smaller, the light-emitting current flowing through the light-emitting diode becomes larger, thereby improving the stability of the light-emitting current.
[0012] In a possible implementation manner of the first aspect, during the light-emitting stage, the level of the reset signal is less than or equal to a first preset value, the first preset value is equal to a sum of a minimum conduction voltage of the light-emitting diode and a first voltage, and the first voltage is a voltage generated by a trace resistance.
[0013] In a possible implementation manner of the first aspect, during the light-emitting stage, a difference between the first preset value and the level of the reset signal is less than a second preset value.
[0014] In a possible implementation manner of the first aspect, during the light-emitting stage, the reset transistor is controlled to be turned off, and the driving current flows to the light-emitting diode and the reset transistor respectively, and a magnitude of the light-emitting current flowing through the light-emitting diode is determined by a magnitude of the level of the reset signal.
[0015] In a possible implementation manner of the first aspect, the reset signal includes at least two levels, and magnitudes of the levels are adjustable.
[0016] In a possible implementation manner of the first aspect, the reset signal has at least two level change processes.
[0017] In a possible implementation of the first aspect, during the non-emission stage, the level of the reset signal is less than or equal to the first level.
[0018] In a second aspect, an embodiment of the present application provides a driving method, which applies the pixel circuit described in any one of the first aspects, including:
[0019] During the emission stage, control the reset transistor to turn off, and load a reset signal at the second pole of the reset transistor, and load a first level at the cathode of the light-emitting diode, where the level of the reset signal is higher than the first level;
[0020] During the non-emission stage, control the reset transistor to turn on, and load the reset signal at the second pole of the reset transistor, and write the reset signal to the anode of the light-emitting diode, where the level of the reset signal is less than or equal to the first level.
[0021] In a third aspect, an embodiment of the present application provides a display panel, including the pixel circuit described in any one of the first aspects.
[0022] In a fourth aspect, an embodiment of the present application provides a display device, including the display panel described in the third aspect.
[0023] The beneficial effects of the embodiments of the present application compared with the prior art are:
[0024] The embodiments of the present application provide a pixel circuit, including a light-emitting diode for emitting light and displaying in response to a driving current; a driving module electrically connected to the anode of the light-emitting diode for providing a driving current to the light-emitting diode during the emission stage; a data writing module for writing a data signal to the control end of the driving module during the non-emission stage; a storage module for storing the data signal and the signal at the first end of the driving module during the non-emission stage, and coupling the signal change at the control end of the driving module to the first end of the driving module; a light-emitting control module for controlling the output of the driving current to the light-emitting diode during the emission stage; a reset transistor, the first pole of the reset transistor is electrically connected to the anode of the light-emitting diode, the cathode of the light-emitting diode is used to receive the first level, the second pole of the reset transistor is used to receive the reset signal, and during the emission stage, the level of the reset signal is higher than the first level.
[0025] During the light-emitting stage, the level at the first pole of the reset transistor is the voltage at the anode of the light-emitting diode. Then, the voltage drop between the first and second poles of the reset transistor is equal to the difference between the voltage at the anode of the light-emitting diode and the level of the reset signal. Since the level of the reset signal is higher than the first level, the voltage drop between the first and second poles of the reset transistor is smaller than the voltage drop across the light-emitting diode. In the prior art, during the light-emitting stage, the level of the reset signal is equal to the first level, so the voltage drop between the first and second poles of the reset transistor is equal to the voltage drop across the light-emitting diode. It can be seen from this that the voltage drop between the first and second poles of the reset transistor in the present application becomes smaller compared with the prior art. Since the leakage current flowing through the reset transistor is proportional to the voltage drop between the first and second poles of the reset transistor, when the voltage drop between the first and second poles of the reset transistor becomes smaller, the leakage current flowing through the reset transistor will also become smaller. After the leakage current flowing through the reset transistor becomes smaller, the power consumption caused by the leakage current becomes lower, thereby improving the light-emitting efficiency of the pixel circuit. Since the leakage current will shunt the light-emitting current flowing through the light-emitting diode, when the leakage current becomes smaller, the light-emitting current flowing through the light-emitting diode becomes larger, thereby improving the stability of the light-emitting current.
[0026] In summary, the pixel circuit provided by the embodiment of the present application solves the problems of low light-emitting efficiency and decreased stability of the light-emitting current caused by leakage current.
[0027] It can be understood that the beneficial effects of the second to fourth aspects above can refer to the relevant descriptions in the first aspect above, and will not be repeated here. BRIEF DESCRIPTION OF THE DRAWINGS
[0028] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the following will briefly introduce the drawings required for the embodiments or the description of the prior art. Obviously, the drawings in the following description are only some embodiments of the present application. For those of ordinary skill in the art, without creative efforts, other drawings can be obtained based on these drawings.
[0029] Figure 1 is a schematic block diagram of a pixel circuit provided by an embodiment of the present application;
[0030] Figure 2 is a schematic circuit connection diagram of a pixel circuit provided by an embodiment of the present application;
[0031] Figure 3 is a schematic working principle diagram of a pixel circuit provided by an embodiment of the present application;
[0032] Figure 4 is Figure 2 an equivalent circuit diagram of the reset transistor and the light-emitting diode in the pixel circuit shown.
[0033] In the figure: 10, data writing module; 20, storage module; 30, light emission control module; 40, driving module. Specific implementation manners
[0034] In the following description, specific details such as specific system architectures and technologies are presented for the purpose of illustration rather than limitation, so as to thoroughly understand the embodiments of the present application. However, those skilled in the art should clearly understand that the present application can also be implemented in other embodiments without these specific details. In other cases, detailed descriptions of well-known systems, devices, circuits, and methods are omitted to avoid unnecessary details from interfering with the description of the present application.
[0035] It should be understood that when used in the specification and appended claims of the present application, the term "comprising" indicates the presence of the described features, wholes, steps, operations, elements, and / or components, but does not exclude the presence or addition of one or more other features, wholes, steps, operations, elements, components, and / or their combinations.
[0036] It should also be understood that the term "and / or" used in the specification and appended claims of the present application refers to any combination and all possible combinations of one or more of the associated listed items, and includes these combinations.
[0037] As used in the specification and appended claims of the present application, the term "if" can be interpreted as "when", "once", "in response to determining", or "in response to detecting" depending on the context. Similarly, the phrase "if determined" or "if detecting [the described condition or event]" can be interpreted as meaning "once determined", "in response to determining", "once detecting [the described condition or event]", or "in response to detecting [the described condition or event]" depending on the context.
[0038] In addition, in the description of the specification and appended claims of the present application, the terms "first", "second", "third", etc. are only used for distinguishing descriptions and cannot be understood as indicating or implying relative importance.
[0039] The reference to "one embodiment" or "some embodiments" etc. described in the specification of the present application means that a specific feature, structure, or characteristic described in connection with that embodiment is included in one or more embodiments of the present application. Thus, statements such as "in one embodiment", "in some embodiments", "in other some embodiments", "in still other embodiments", etc. that appear in different places in this specification are not necessarily all referring to the same embodiment, but mean "one or more but not all embodiments", unless otherwise specifically emphasized in other ways. The terms "comprising", "including", "having", and their variants all mean "including but not limited to", unless otherwise specifically emphasized in other ways.
[0040] Based on the fields of AM Micro LED and AM Micro OLED displays, at extremely high pixel densities, the luminous current required for a single pixel is relatively small, possibly reaching the nanoampere to femtoampere level. In such application scenarios, the pixel circuit needs to precisely control the luminous current of the light-emitting element. However, in the displays of AM Micro LED and AM Micro OLED, a reset transistor is usually set in the pixel circuit, which will result in a leakage current path always existing in the pixel circuit, leading to a decrease in luminous efficiency and the stability of the luminous current.
[0041] Related technology one proposes to use a low-leakage oxide transistor as the switching element of the leakage path to reduce the leakage current. However, the oxide transistor is sensitive to water and oxygen in the production process, and its mobility does not meet the requirements.
[0042] Related technology two proposes to reduce the leakage current through a special low-leakage process. However, the special low-leakage process will lead to a decrease in the stability of the subthreshold region of the transistor, affecting the working stability of the transistor. At the same time, the special low-leakage process will also increase the cost.
[0043] In view of the above problems, an embodiment of the present application provides a pixel circuit, as Figure 1 shown, the pixel circuit includes a light-emitting diode D1, a driving module 40, a data writing module 10, a storage module 20, a light-emitting control module 30, and a reset transistor T0. The first end of the data writing module 10 is used to receive a Data signal (data signal), the control end of the data writing module 10 is used to receive a WS signal (gate signal), the second end of the data writing module 10 is electrically connected to the control end of the driving module 40 and the first end of the storage module 20 respectively. The second end of the storage module 20 and the first end of the light-emitting control module 30 are both used to receive a VDD voltage. The control end of the light-emitting control module 30 is used to receive a DS signal (light-emitting enable signal). The second end of the light-emitting control module 30 is electrically connected to the third end of the storage module 20 and the first end of the driving module 40 respectively. The second end of the driving module 40 is electrically connected to the first pole of the reset transistor T0 and the anode of the light-emitting diode D1 respectively. The control end of the reset transistor T0 is used to receive an AZ signal (anode clearing signal). The cathode of the light-emitting diode D1 is used to receive a first level VSS_DC. The second pole of the reset transistor T0 is used to receive a reset signal VSS_SCan.
[0044] In the embodiment of the present application, the light-emitting diode D1 is used to emit light in response to a driving current. The driving module 40 is used to provide a driving current to the light-emitting diode D1 during the light-emitting stage. The data writing module 10 is used to write a data signal to the control end of the driving module 40 during the non-light-emitting stage. The storage module 20 is used to store the data signal and the signal at the first end of the driving module 40 during the non-light-emitting stage, and couple the signal change at the control end of the driving module 40 to the first end of the driving module 40. The light-emitting control module 30 is used to control the output of the driving current to the light-emitting diode D1 during the light-emitting stage.
[0045] During the light-emitting stage, the level of the reset signal VSS_Scan is higher than the first level VSS_DC.
[0046] During the light-emitting stage, the voltage at the first pole of the reset transistor T0 is the voltage at the anode of the light-emitting diode D1. Then, the voltage drop between the first pole and the second pole of the reset transistor T0 is equal to the difference between the voltage at the anode of the light-emitting diode D1 and the voltage of the reset signal VSS_Scan. Since the level of the reset signal VSS_Scan is higher than the first level VSS_DC, the voltage drop between the first pole and the second pole of the reset transistor T0 is smaller than the voltage drop across the light-emitting diode D1. In the prior art, during the light-emitting stage, the level of the reset signal VSS_Scan is equal to the first level VSS_DC, so the voltage drop between the first pole and the second pole of the reset transistor T0 is equal to the voltage drop across the light-emitting diode D1. It can be seen that the voltage drop between the first pole and the second pole of the reset transistor T0 in the present application becomes smaller compared with the prior art. Since the leakage current flowing through the reset transistor T0 is proportional to the voltage drop between the first pole and the second pole of the reset transistor T0, when the voltage drop between the first pole and the second pole of the reset transistor T0 becomes smaller, the leakage current flowing through the reset transistor T0 also becomes smaller. When the leakage current flowing through the reset transistor T0 becomes smaller, the power consumption caused by the leakage current becomes lower, thereby improving the light-emitting efficiency of the pixel circuit. Since the leakage current will shunt the light-emitting current flowing through the light-emitting diode D1, when the leakage current becomes smaller, the light-emitting current flowing through the light-emitting diode D1 becomes larger, thereby improving the stability of the light-emitting current.
[0047] In summary, the pixel circuit provided by the embodiment of the present application solves the problems of low light-emitting efficiency and decreased stability of the light-emitting current caused by leakage current.
[0048] During the light-emitting stage, on the basis of reducing the leakage current, it is also necessary to ensure that the light-emitting diode D1 can emit light normally. Therefore, the level of the reset signal VSS_Scan is set to be less than or equal to a first preset value, and the first preset value is equal to the sum of the minimum conduction voltage of the light-emitting diode D1 and a first voltage, where the first voltage is the voltage generated by the trace resistance.
[0049] When setting the maximum value of the level of the reset signal VSS_Scan, it is necessary to consider the fluctuation of the turn-on voltage of the light-emitting diode D1 and the voltage generated by the trace resistance during the routing of the reset signal VSS_Scan. The above setting of the maximum value of the level of the reset signal VSS_Scan only satisfies the pixel circuit to which it is applied. If the reset signal VSS_Scan is to satisfy all pixel circuits in the entire display panel during the light-emitting stage, then the level of the reset signal VSS_Scan should be less than or equal to the sum of the minimum turn-on voltage of the light-emitting diode with the smallest turn-on voltage among all light-emitting diodes and the maximum voltage generated by the trace resistance.
[0050] In order to minimize the leakage current as much as possible, in the light-emitting stage of this application, it is limited that the difference between the first preset value and the level of the reset signal VSS_Scan is less than the second preset value. The second preset value is very small and can be set to 0.6V, 0.5V, 0.4V, 0.3V, etc. When the second preset value is smaller, it means that the level of the reset signal VSS_Scan is closer to the voltage on the anode of the light-emitting diode D1. Then the voltage drop between the first pole and the second pole of the reset transistor T0 is smaller. Since the leakage current flowing through the reset transistor T0 is proportional to the voltage drop between the first pole and the second pole of the reset transistor T0, when the voltage drop between the first pole and the second pole of the reset transistor T0 is smaller, the leakage current will also be smaller, which can further improve the light-emitting efficiency of the pixel circuit and the stability of the light-emitting current.
[0051] In the light-emitting stage, the reset transistor T0 is controlled to be turned off, and the drive current flows to the light-emitting diode D1 and the reset transistor T0 respectively. The magnitude of the light-emitting current flowing through the light-emitting diode D1 is determined by the magnitude of the level of the reset signal VSS_Scan.
[0052] In some specific application scenarios, it is necessary to reduce the light-emitting current flowing through the light-emitting diode D1 to achieve a finer gray-scale transition. Since the light-emitting diode D1 and the reset transistor T0 are in parallel for current sharing, the magnitude of the light-emitting current flowing through the light-emitting diode D1 is determined by the magnitude of the level of the reset signal VSS_Scan. Then the magnitude of the level of the reset signal VSS_Scan can be adjusted to reduce the light-emitting current flowing through the light-emitting diode D1, so that under the same gray-scale voltage difference, a smaller current difference can be obtained, thereby achieving fine adjustment of the gray scale.
[0053] In the non-light-emitting stage, in order to ensure that the light-emitting diode D1 does not emit light, this application limits the level of the reset signal VSS_Scan to be less than or equal to the first level VSS_DC.
[0054] The following takes Figure 2 as an example to illustrate in detail the specific structure of the pixel circuit provided by the embodiment of this application.
[0055] As Figure 2 shown, the data writing module 10 includes a first transistor T1, the storage module 20 includes a first capacitor C1 and a second capacitor C2, the light emission control module 30 includes a second transistor T2, and the driving module 40 includes a third transistor T3. The control terminal of the first transistor T1 is used to receive the WS signal, the first pole of the first transistor T1 is used to receive the Data signal, the second pole of the first transistor T1 is electrically connected to the first end of the first capacitor C1 and the control terminal of the third transistor T3 respectively, the substrate terminals of the first transistor T1, the second transistor T2, and the third transistor T3 are all used to receive the VDD voltage, the second end of the first capacitor C1 is electrically connected to the first end of the second capacitor C2, the second pole of the second transistor T2, and the first pole of the third transistor T3 respectively, the second end of the second capacitor C2 and the first pole of the second transistor T2 are used to receive the VDD voltage, the control terminal of the second transistor T2 is used to receive the DS signal, and the second pole of the third transistor T3 is electrically connected to the first pole of the reset transistor T0 and the anode of the light emitting diode D1 respectively.
[0056] Combined with Figure 2 and Figure 3 the working principle of the pixel circuit provided by the embodiment of the present application will be introduced.
[0057] The operation of the pixel circuit provided by the embodiment of the present application is divided into two major stages. The first stage is the programming and non-light-emitting stage, and the second stage is the light-emitting stage.
[0058] In the first stage, it is further divided into three small stages: 1.1 initialization stage, 1.2 self-discharge stage, and 1.3 data writing and threshold compensation stage. During the display process, the time ratio of the second stage is more than 99%, and the time ratio of the first stage is relatively small.
[0059] 1.1 Initialization stage: The DS signal is low, the second transistor T2 is turned on, and the voltage at point S is the VDD voltage. The WS signal is low, the first transistor T1 is turned on, and the initialization voltage Vofs in the Data signal is written into point G of the third transistor T3. The AZ signal is low, the reset transistor T0 is turned on, and the low level V_VSS_L in the reset signal VSS_Scan is written into point D. The voltage drop between the anode and the cathode of the light emitting diode D1 is less than its conduction voltage, and the light emitting diode D1 does not emit light.
[0060] 1.2 Self-discharge stage: The DS signal is high, the second transistor T2 is turned off. Due to the existence of the second capacitor C2, the voltage VDD is temporarily stored at the S point of the third transistor T3. During the continuous conduction of the third transistor T3, the voltage at the S point will gradually decrease. The WS signal is high, the first transistor T1 is turned off, and the initial voltage Vofs at the G point is temporarily stored on the first capacitor C1. As the third transistor T3 continues to conduct, the voltage at the S point drops. Based on the principle that the voltage across a capacitor cannot change abruptly, the voltage at the G point will also drop accordingly. The AZ signal is low, the reset transistor T0 is turned on, and the low level V_VSS_L in the reset signal VSS_Scan is written to the D point. The voltage drop between the anode and cathode of the light-emitting diode D1 is less than its conduction voltage, so the light-emitting diode D1 does not emit light. The Data signal switches to the effective voltage state to prepare for the 1.3 data writing stage.
[0061] 1.3 Data writing and threshold compensation stage: The DS signal is high, and the second transistor T2 is turned off. The WS signal is low, the first transistor T1 is turned on, and the voltage at the G point is rewritten as the VData voltage. Let the voltage difference at the G point from the end of the 1.2 stage to the 1.3 data writing stage be Delta_G. Due to capacitive coupling, the voltage at the S point will be coupled to S + Delta_G * C1 / (C1 + C2). The ratio of the first capacitor C1 and the second capacitor C2 is precisely designed to cancel out the body bias effect introduced by the different voltages at the S point of the third transistor T3 and the substrate of the second transistor T2 during this process. The ratio of the first capacitor C1 and the second capacitor C2 can be obtained through experiments or by using simulation software, which will not be elaborated here. During the period when the WS signal is low, the voltage at the G point always remains at the VData voltage, and the voltage at the S point is still slightly higher than the low level V_VSS_L after being coupled. Therefore, during this stage, the third transistor T3 acts as a source follower. Before the WS signal becomes high, the third transistor T3 slowly turns off until it is completely off. Let the voltage at its S point be S + Delta_G * C1 / (C1 + C2) - V_leak, where V_leak is the voltage drop at the S point. Then the voltage at its G point is S + Delta_G * C1 / (C1 + C2) - V_leak + Vth3. Therefore, the voltage at the G point also stores the threshold information Vth3 of the third transistor T3.
[0062] 2 Emission stage: The DS signal is low, the second transistor T2 is turned on, and the voltage at the S point is VDD. The WS signal is high, the G point is floating, and the VGS3 of the third transistor T3 is S + Delta_G * C1 / (C1 + C2) + V_leak + Vth3 - VDD. According to the saturation region current formula of the MOS transistor, the current ID flowing through the light-emitting diode D1 is obtained.
[0063] ID = K(VGS3 - VTH3)^2 = (S + Delta_G * C1 / (C1 + C2) - V_leak + Vth3 - VDD - Vth3) = K(S + Delta_G * C1 / (C1 + C2) - V_leak - VDD)^2, where K is the current gain coefficient, Vth3 is the threshold information of the third transistor T3, the threshold information is cancelled out, DeltaG contains the VData voltage information, C1 / (C1 + C2) can cancel the body bias effect, and the V_leak voltage can compensate for the difference in the current generation ability due to the mobility of the third transistor T3 and other parameters. When the AZ signal is high, the reset transistor T0 is turned off and no longer affects the voltage at point D. At this time, the reset signal VSS_Scan is at the high level V_VSS_H. At this time, the high level V_VSS_H is close to the turn-on voltage V_Turn ON of the light-emitting diode D1 when it is normally lit. Therefore, the voltage drop between the first pole and the second pole of the reset transistor T0 is small, and the leakage current in this stage will also be small, and more current flows through the light-emitting diode D1. The high level V_VSS_H needs to consider the fluctuation of the turn-on voltage V_Turn_ON of the light-emitting diode D1 and the first voltage Drop due to the trace resistance. Therefore, V_VSS_H ≤ the minimum turn-on voltage of the light-emitting diode D1 + the first voltage. It should be noted that the setting of the maximum value of V_VSS_H here only satisfies the pixel circuit in which it is applied. If it is required to make V_VSS_H satisfy all the pixel circuits in the entire display panel during the light-emitting stage, then V_VSS_H should be less than or equal to the sum of the minimum turn-on voltage of the light-emitting diode with the smallest turn-on voltage among all the light-emitting diodes and the maximum voltage generated by the trace resistance.
[0064] Exemplarily, assume that the first level VSS_DC is 0V, the voltage on the anode of the light-emitting diode D1 is 5V, the drive current is represented by IM3, the leakage current is represented by IM0, and the light-emitting current flowing through the light-emitting diode D1 is represented by ID, where IM3 = ID + IM0. In the prior art, during the light-emitting stage of the pixel circuit, the reset signal VSS_Scan received by the second pole of the reset transistor T0 is the first level VSS_DC, so the reset signal VSS_Scan = 0V. Since the level on the first pole of the reset transistor T0 is the voltage of 5V on the anode of the light-emitting diode D1, the voltage drop between the first pole and the second pole of the reset transistor T0 is 5V. Since the leakage current IM0 is proportional to the voltage drop between the first pole and the second pole of the reset transistor T0, the leakage current IM0 is large at this time, which affects the light-emitting efficiency and also causes the light-emitting current ID flowing through the light-emitting diode D1 to become smaller, affecting the stability of the light-emitting current.
[0065] In the present application, in the light-emitting stage of the pixel circuit, the level of the reset signal VSS_Scan received by the second pole of the reset transistor T0 is higher than the first level VSS_DC, that is, the level of the reset signal VSS_Scan is greater than 0V, then the voltage drop between the first pole and the second pole of the reset transistor T0 is less than 5V, which will reduce the leakage current IM0, and the power consumption caused by the leakage current becomes lower, thereby improving the luminous efficiency of the pixel circuit, and at the same time, the luminous current ID flowing through the light-emitting diode D1 will become larger, thereby improving the stability of the luminous current ID. In order to make the leakage current IM0 smaller, the level of the reset signal VSS_Scan can be set higher, as long as it does not exceed the minimum conduction voltage of the light-emitting diode D1 + the first voltage. Here, it is assumed that the level of the reset signal VSS_Scan is 4.5V, then the voltage drop between the first pole and the second pole of the reset transistor T0 is 0.5V, and the leakage current IM0 becomes smaller. Compared with the prior art, the present application greatly improves the luminous efficiency and the stability of the luminous current ID caused by the leakage current.
[0066] according to Figure 3 It can be seen that the reset signal VSS_Scan changes during the operation of the pixel circuit. In the non-luminous phase of the pixel circuit, the level of the reset signal VSS_Scan is less than or equal to the first level VSS_DC. In the luminous phase of the pixel circuit, the level of the reset signal VSS_Scan is higher than the first level VSS_DC. Compared with the prior art that uses the first level VSS_DC as the reset signal VSS_Scan, the present application reduces the leakage current and solves the problem of low luminous efficiency and decreased stability of the luminous current caused by the leakage current.
[0067] It should be noted that the reset signal VSS_Scan includes at least two levels, and the level is adjustable, and the reset signal VSS_Scan has at least two level change processes. Since the reset signal VSS_Scan includes at least two levels, the present application can break through the voltage limit of the device in a short time during the actual display process, while the reset signal in the prior art has only one level, and its bias time is too long, which poses a reliability risk.
[0068] according to Figure 3 It can be seen that the reset signal VSS_Scan includes two levels, V_VSS_H and V_VSS_L, and the sizes of these two levels can be adjusted according to actual conditions to meet actual needs. In order to realize the working principle of the pixel circuit, the reset signal VSS_Scan also needs to have two level change processes, namely, from the V_VSS_H level to the V_VSS_L level, and from the V_VSS_L level to the V_VSS_H level.
[0069] according to Figure 3It can be known that the reset signal VSS_Scan includes three levels: V_VSS_H, V_VSS_L, and V_VSS_N, and the magnitudes of these three levels can be adjusted according to actual situations to meet actual requirements. In order to implement the working principle of the pixel circuit, the reset signal VSS_Scan also needs to have three level change processes, that is, changing from the V_VSS_H level to the V_VSS_L level, from the V_VSS_L level to the V_VSS_N level, and from the V_VSS_N level to the V_VSS_H level.
[0070] In the actual application process, the number of levels and the level change process of the reset signal VSS_Scan can be set according to actual requirements.
[0071] This application can also be applied to certain specific scenarios. Combining Figure 4 , the reset transistor T0 is equivalent to a resistor R_T0_EFF, and the light-emitting diode D1 is equivalent to a resistor R_D1_EFF. The resistor R_T0_EFF and the resistor R_D1_EFF are connected in parallel, which will shunt the drive current IM3 in parallel. In certain specific application scenarios, it is necessary to reduce the light-emitting current ID flowing through the light-emitting diode D1 to achieve a finer gray-scale transition. Then, the magnitude of the level of the reset signal VSS_Scan can be adjusted to increase the leakage current IM0, so that the light-emitting current ID flowing through the light-emitting diode D1 decreases. Under the same gray-scale voltage difference, a smaller current difference can be obtained, thereby achieving fine adjustment of the gray scale.
[0072] The embodiment of this application also provides a driving method, which applies the above-mentioned pixel circuit and includes:
[0073] In the light-emitting stage, control the reset transistor T0 to be turned off, and load the reset signal VSS_Scan at the second pole of the reset transistor T0, and load the first level VSS_DC at the cathode of the light-emitting diode D1. The level of the reset signal VSS_Scan is higher than the first level VSS_DC.
[0074] During the light-emitting stage, the level on the first pole of the reset transistor T0 is the voltage on the anode of the light-emitting diode D1. Then, the voltage drop between the first and second poles of the reset transistor T0 is equal to the difference between the voltage on the anode of the light-emitting diode D1 and the voltage of the reset signal VSS_Scan. Since the level of the reset signal VSS_Scan is higher than the first level VSS_DC, the voltage drop between the first and second poles of the reset transistor T0 is less than the voltage drop across the light-emitting diode D1. In the prior art, during the light-emitting stage, the level of the reset signal VSS_Scan is equal to the first level VSS_DC, so the voltage drop between the first and second poles of the reset transistor T0 is equal to the voltage drop across the light-emitting diode D1. It can be seen from this that the voltage drop between the first and second poles of the reset transistor T0 in the present application becomes smaller compared with the prior art. Since the leakage current flowing through the reset transistor T0 is proportional to the voltage drop between the first and second poles of the reset transistor T0, when the voltage drop between the first and second poles of the reset transistor T0 becomes smaller, the leakage current flowing through the reset transistor T0 will also become smaller. When the leakage current flowing through the reset transistor T0 becomes smaller, the power consumption caused by the leakage current becomes lower, thereby improving the light-emitting efficiency of the pixel circuit. Since the leakage current will shunt the driving current flowing through the light-emitting diode D1, when the leakage current becomes smaller, the light-emitting current flowing through the light-emitting diode D1 becomes larger, thereby improving the stability of the light-emitting current.
[0075] During the non-light-emitting stage, control the reset transistor T0 to conduct, and load the reset signal VSS_Scan on the second pole of the reset transistor T0, and write the reset signal VSS_Scan to the anode of the light-emitting diode D1. The level of the reset signal VSS_Scan is less than or equal to the first level VSS_DC to ensure that the light-emitting diode D1 is not lit.
[0076] The embodiment of the present application also provides a display panel, including the pixel circuit described above. The display panel provided by the embodiment of the present application has the advantages of high light-emitting efficiency and good stability of the light-emitting current. For the specific working principle, please refer to the description of the working principle of the above-mentioned pixel circuit, which will not be elaborated here.
[0077] The embodiment of the present application also provides a display device, including the display panel described above. The display device provided by the embodiment of the present application has the advantages of high light-emitting efficiency and good stability of the light-emitting current. For the specific working principle, please refer to the description of the working principle of the above-mentioned display panel, which will not be elaborated here.
[0078] In the above embodiments, the descriptions of each embodiment have their own focuses. For the parts not detailed or recorded in a certain embodiment, reference can be made to the relevant descriptions of other embodiments.
[0079] The embodiments described above are only used to illustrate the technical solutions of the present application, rather than to limit it; although the present application has been described in detail with reference to the foregoing embodiments, those of ordinary skill in the art should understand that: they can still modify the technical solutions recorded in the foregoing embodiments, or perform equivalent replacements on some of the technical features; and these modifications or replacements do not make the essence of the corresponding technical solutions deviate from the spirit and scope of the technical solutions of the various embodiments of the present application, and should all be included in the protection scope of the present application.
Claims
1. A pixel circuit, characterized in that, Comprising: A light-emitting diode for emitting light in response to a driving current; A driving module electrically connected to the anode of the light-emitting diode for providing a driving current to the light-emitting diode during the light-emitting stage; A data writing module for writing a data signal to the control terminal of the driving module during the non-light-emitting stage; A storage module for storing the data signal and the signal at the first terminal of the driving module during the non-light-emitting stage, and coupling a change in the signal at the control terminal of the driving module to the first terminal of the driving module; A light-emitting control module for controlling the output of the driving current to the light-emitting diode during the light-emitting stage; A reset transistor, the first pole of the reset transistor is electrically connected to the anode of the light-emitting diode, the cathode of the light-emitting diode is used to receive a first level, the second pole of the reset transistor is used to receive a reset signal, and during the light-emitting stage, the level of the reset signal is higher than the first level.
2. The pixel circuit according to claim 1, characterized in that, During the light-emitting stage, the level of the reset signal is less than or equal to a first preset value, the first preset value is equal to the sum of the minimum turn-on voltage of the light-emitting diode and a first voltage, and the first voltage is the voltage generated by the trace resistance.
3. The pixel circuit according to claim 2, characterized in that, During the light-emitting stage, the difference between the first preset value and the level of the reset signal is less than a second preset value.
4. The pixel circuit according to claim 2, characterized in that, During the light-emitting stage, control the reset transistor to be turned off, the driving current flows to the light-emitting diode and the reset transistor respectively, and the magnitude of the light-emitting current flowing through the light-emitting diode is determined by the magnitude of the level of the reset signal.
5. The pixel circuit according to claim 1, characterized in that, The reset signal includes at least two levels, and the magnitude of the level is adjustable.
6. The pixel circuit according to claim 5, characterized in that, The reset signal has at least two level change processes.
7. The pixel circuit according to claim 1, characterized in that, During the non-light-emitting stage, the level of the reset signal is less than or equal to the first level.
8. A driving method, applied to the pixel circuit according to any one of claims 1-7, characterized in that, Comprising: During the light-emitting stage, control the reset transistor to be turned off, load a reset signal at the second pole of the reset transistor, and load a first level at the cathode of the light-emitting diode, and the level of the reset signal is higher than the first level; During the non-light-emitting stage, control the reset transistor to be turned on, load the reset signal at the second pole of the reset transistor, and write the reset signal to the anode of the light-emitting diode, and the level of the reset signal is less than or equal to the first level.
9. A display panel, characterized in that, Comprising the pixel circuit according to any one of claims 1-7.
10. A display device, characterized in that, Comprising the display panel according to claim 9.