Pixel driving circuit and its driving method, display panel

Abstract

This application provides a pixel driving circuit and its driving method, as well as a display panel. Specifically, in the pixel driving circuit, the driving unit and the light-emitting element are connected in series between a first power line and a second power line. A data writing unit is used to output a data voltage, a third power line is used to output a third voltage, a capacitor unit is connected between the third power line and the data writing unit, and the connection point between the capacitor unit and the data writing unit is a first node. A switching unit is connected between the driving unit and the first node. During the data writing stage, the switching unit controls the driving unit to be turned off based on the data voltage at the first node. During the light-emitting stage, the third voltage output by the third power line is pulled down. Based on the pull-down height of the third voltage, the data voltage written to the first node changes accordingly. When the switching unit is in the on state, the switching unit generates a corresponding driving voltage based on the changed data voltage and applies it to the driving unit to drive the light-emitting element to emit light.

Description

Technical Field

[0001] This application relates to the field of display technology, and in particular to a pixel driving circuit and its driving method, and a display panel. Background Technology

[0002] Compared to LCD displays, display devices such as Micro LED (Micro Light Emitting Diode), OLED (Organic Light-Emitting Diode), and AMOLED (Active-matrix Organic Light-Emitting Diode) have advantages such as low power consumption, self-illumination, wide viewing angle, and fast response speed. Currently, they have begun to replace traditional LCD displays in display fields such as mobile phones, tablets, and smart wearables.

[0003] Taking Micro-OLED as an example, due to its inherent characteristics, Micro-OLED has high driving requirements. It needs to control grayscale by digitally controlling the time under constant current driving. Currently, mainstream products control the emission time through subframes or SWEEP ramps. However, the subframe method requires writing the data signal multiple times to select the subframe signal, requiring a high refresh rate; while using ramp signals, because the emission time is more continuous, the flickering phenomenon is more severe in the low and medium grayscale. Furthermore, because the ramp signal is a global signal, it can only be lit after all pixels have been written, thus also resulting in high flickering. Summary of the Invention

[0004] This application provides a pixel driving circuit and its driving method, as well as a display panel. By optimizing the pixel driving circuit, a signal can be written only once in a frame, enabling progressive scanning and solving the flickering problem.

[0005] To solve the above-mentioned technical problems, the first technical solution provided in this application is as follows: a pixel driving circuit is provided, comprising: a driving unit and a light-emitting element, connected in series between a first power line and a second power line; a data writing unit connected to a data line for outputting a data voltage; a third power line for outputting a third voltage; a capacitor unit connected between the third power line and the data writing unit, wherein the connection point between the capacitor unit and the data writing unit is a first node; and a switching unit connected between the driving unit and the first node; wherein, during the data writing phase, the data writing unit writes the data voltage to the first node, and the switching unit controls the driving unit to be turned off based on the data voltage at the first node; during the light-emitting phase, the third voltage output by the third power line is pulled down, and the data voltage written to the first node is changed accordingly based on the pull-down height of the third voltage; the switching unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and when the switching unit is turned on, the switching unit generates a corresponding driving voltage based on the changed data voltage and applies it to the driving unit, so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light.

[0006] In one embodiment, the driving unit includes a driving transistor; the switching unit includes a first switching transistor and a second switching transistor connected to the control terminal of the driving transistor; wherein the driving transistor and the first switching transistor are of the same type, one of the first switching transistor and the second switching transistor is a P-type transistor and the other is an N-type transistor; wherein, during the data writing phase, the data writing unit writes the data voltage to the first node, the first switching transistor is turned off based on the data voltage at the first node, and the second switching transistor is turned on based on the data voltage at the first node, and a high potential voltage or a low potential voltage is written to the control terminal of the driving transistor through the turned-on second switching transistor to control the driving transistor. The driving transistor is cut off; during the light-emitting stage, the third voltage output by the third power line is pulled down. Based on the pull-down height of the third voltage, the data voltage written to the first node changes accordingly. The second switching transistor is cut off based on the changed data voltage at the first node, and the first switching transistor is turned on based on the changed data voltage at the first node. The high potential voltage or the low potential voltage is written to the control terminal of the driving transistor through the turned-on first switching transistor to control the driving transistor to turn on. The first switching transistor generates a corresponding driving voltage based on the changed data voltage and applies it to the control terminal of the driving unit so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light.

[0007] In one embodiment, there is a reference voltage value time period between two adjacent pull-down time periods of the third voltage, during which the pixel driving circuit is in the data writing stage, and during the pull-down time period, the pixel driving circuit is in the light emission stage.

[0008] In one embodiment, the third voltage is uniformly distributed at different pull-down heights.

[0009] In one embodiment, the driving transistor and the first switching transistor are P-type transistors, and the second switching transistor is an N-type transistor. When the first switching transistor is in the off state and the second switching transistor is in the on state, the high potential voltage is written to the control terminal of the driving transistor through the on-state second switching transistor to control the driving transistor to be off. When the first switching transistor is in the on state and the second switching transistor is in the off state, the low potential voltage is written to the control terminal of the driving transistor through the on-state first switching transistor to control the driving transistor to be on and generate a corresponding driving current to drive the light-emitting element to emit light.

[0010] In one embodiment, the first terminal of the second switching transistor is connected to a high-potential power line to receive the high-potential voltage output by the high-potential power line, the second terminal of the second switching transistor is connected to the control terminal of the driving transistor and the first terminal of the first switching transistor, the second terminal of the first switching transistor is connected to a low-potential power line to receive the low-potential voltage output by the low-potential power line, and the control terminals of the first switching transistor and the second switching transistor are connected to the first node.

[0011] In one embodiment, the data writing unit includes a writing transistor, a first terminal of which is connected to the first node, a second terminal of which is connected to a data line to receive the data voltage output by the data line, and a control terminal of which is connected to a scan signal line.

[0012] In one embodiment, the light-emitting element is one of a first light-emitting element, a second light-emitting element, and a third light-emitting element, wherein the first light-emitting element, the second light-emitting element, and the third light-emitting element have different operating voltages; the first power line is a first type power line connected to the first light-emitting element, a second type power line connected to the second light-emitting element, or a third type power line connected to the third light-emitting element, wherein the first type power line, the second type power line, and the third type power line are used to output the operating voltage corresponding to the first light-emitting element, the second light-emitting element, and the third light-emitting element.

[0013] To solve the above-mentioned technical problems, the second technical solution provided by this application is: to provide a display panel, the display panel including the pixel driving circuit described in any one of the above claims.

[0014] To solve the above-mentioned technical problems, the third technical solution provided in this application is: a driving method for a pixel driving circuit, wherein the driving method is applied to the pixel driving circuit described in any of the above claims, and the driving method includes: in the data writing stage, the data writing unit writes the data voltage into the first node, and the switching unit controls the driving unit to be turned off based on the data voltage at the first node; in the light emission stage, the third voltage output by the third power line is pulled down, and the data voltage written into the first node is changed accordingly based on the pull-down and pull-down height of the third voltage, and the switching unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and in the state where the switching unit is turned on, the switching unit generates a corresponding driving voltage based on the changed data voltage and applies it to the driving unit, so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light.

[0015] Unlike existing technologies, the beneficial effects of this application are that the pixel driving circuit and its driving method, and the display panel provided in this application, the pixel driving circuit includes a driving unit, a light-emitting element, a data writing unit, a third power line, a capacitor unit, and a switching unit. The driving unit and the light-emitting element are connected in series between the first power line and the second power line. The data writing unit is connected to a data line and is used to output a data voltage. The third power line is used to output a third voltage. The capacitor unit is connected between the third power line and the data writing unit, and the connection point between the capacitor unit and the data writing unit is the first node. The switching unit is connected between the driving unit and the first node. Specifically, during the data writing stage, the switching unit controls the driving unit to be turned off based on the data voltage at the first node. During the light-emitting stage, the third voltage output by the third power line is pulled down. Based on the pull-down height of the third voltage, the data voltage written to the first node changes accordingly. The switching unit controls the driving unit to be turned on or off based on the changed data voltage at the first node. When the switching unit is on, the switching unit generates a corresponding driving voltage based on the changed data voltage and applies it to the driving unit, so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light. With the above settings, the signal only needs to be written once in a frame, enabling line-by-line scanning and solving the flickering problem. Attached Figure Description

[0016] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort, wherein:

[0017] Figure 1 A schematic diagram of a circuit module for an embodiment of the pixel driving circuit provided in this application;

[0018] Figure 2 A schematic diagram of the circuit structure of an embodiment of the pixel driving circuit provided in this application;

[0019] Figure 3 A timing diagram of an embodiment of the pixel driving circuit provided in this application;

[0020] Figure 4 for Figure 2 The equivalent circuit diagram of the pixel driving circuit during the data writing stage is shown.

[0021] Figure 5 for Figure 2 The diagram shows an equivalent circuit diagram of one embodiment of the pixel driving circuit in the light-emitting stage.

[0022] Figure 6 for Figure 2 The equivalent circuit diagram of another embodiment of the pixel driving circuit in the light-emitting stage is shown.

[0023] Figure 7 A schematic flowchart of an embodiment of the driving method for the pixel driving circuit provided in this application;

[0024] Figure 8 A schematic diagram of the structure of an embodiment of the display panel provided in this application. Detailed Implementation

[0025] The terms "first," "second," and "third" in this application are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Therefore, a feature defined as "first," "second," or "third" may explicitly or implicitly include at least one of that feature. In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. All directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of this application are only used to explain the relative positional relationships and movement of components in a specific posture (as shown in the figures). If the specific posture changes, the directional indications also change accordingly. Furthermore, the terms "comprising" and "having," and any variations thereof, are intended to cover non-exclusive inclusion.

[0026] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0027] The technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only a part of the embodiments of this application, and not all of the embodiments. Based on the embodiments of this application, all other embodiments obtained by those of ordinary skill in the art without creative effort are within the scope of protection of this application.

[0028] See Figure 1 , Figure 1 This is a schematic diagram of a circuit module of an embodiment of the pixel driving circuit provided in this application. This application provides a pixel driving circuit 100, including a driving unit 10, a light-emitting element 20, a data writing unit 30, a third power line L3, a capacitor unit 40, and a switching unit 50. The driving unit 10 and the light-emitting element 20 are connected in series between a first power line L1 and a second power line L2, wherein the first power line L1 is used to output VDD voltage, and the second power line L2 is used to output VSS voltage; the data writing unit 30 is connected to a data line L4 and is used to output a data voltage Vdata; the third power line L3 is used to output a third voltage SP; the capacitor unit 40 is connected between the third power line L3 and the data writing unit 30, and the connection point between the capacitor unit 40 and the data writing unit 30 is a first node n1; the switching unit 50 is connected between the driving unit 10 and the first node n1.

[0029] During the data writing phase, the data writing unit 30 writes the data voltage Vdata to the first node n1, and the switching unit 50 controls the driving unit 10 to be turned off based on the data voltage Vdata at the first node n1. During the light emission phase, the third voltage SP output by the third power line L3 is pulled down. Based on the pull-down height of the third voltage SP, the data voltage Vdata written to the first node n1 is changed accordingly. Based on the changed data voltage Vdata at the first node n1, the switching unit 50 controls the driving unit 10 to be turned on or off. When the switching unit 50 is turned on, the switching unit 50 generates a corresponding driving voltage based on the changed data voltage Vdata and applies it to the driving unit 10 so that the driving unit 10 generates a corresponding driving current I to drive the light-emitting element 20 to emit light.

[0030] Understandably, due to the different pull-down heights of the third voltage SP and the bootstrap effect of the capacitor unit 40, the data voltage Vdata at the first node n1 also has different pull-down heights, resulting in different conduction levels of the switching unit 50 in the on state. This further leads to different conduction levels of the switching unit 50 controlling the driving unit 10, and consequently, different driving currents I generated by the driving unit 10, thus achieving different grayscale displays.

[0031] Specifically, the pixel driving circuit 100 provided in this application writes a data voltage Vdata at the first node n1 during the data writing stage. During the light emission stage, the data voltage Vdata at the first node n1 changes accordingly based on the pull-down and pull-down height of the third voltage SP. This causes the switching unit 50 to control the driving unit 10 to be turned on or off based on the changed data voltage Vdata at the first node n1. When the switching unit 50 is in the on state based on the changed data voltage Vdata at the first node n1, the switching unit 50 generates a corresponding driving voltage based on the changed data voltage Vdata and applies it to the driving unit 10, so that the driving unit 10 generates a corresponding driving current I (corresponding to different gray levels) to drive the light-emitting element 20 to emit light. Through the above settings, only one signal needs to be written in one frame, and the line-by-line scanning function can be realized. Moreover, compared with using ramp control to control the light emission time of the light-emitting element 20, this application can solve the flickering problem of the light-emitting element 20.

[0032] Combination Figure 1 and Figure 2 , Figure 2This is a schematic diagram of the circuit structure of an embodiment of the pixel driving circuit provided in this application. In one embodiment, the driving unit 10 includes a driving transistor DTFT; the switching unit 50 includes a first switching transistor T1 and a second switching transistor T2 connected to the control terminal of the driving transistor DTFT; wherein the driving transistor DTFT is of the same type as the first switching transistor T1, and one of the first switching transistor T1 and the second switching transistor T2 is a P-type transistor and the other is an N-type transistor.

[0033] Understandably, a P-type transistor is in the off state based on a high-level voltage received at its control terminal and in the on state based on a low-level voltage received at its control terminal; an N-type transistor is in the on state based on a high-level voltage received at its control terminal and in the off state based on a low-level voltage received at its control terminal.

[0034] In this embodiment, during the data writing stage, the data writing unit 30 writes the data voltage Vdata into the first node n1. The first switching transistor T1 is turned off based on the data voltage Vdata at the first node n1, and the second switching transistor T2 is turned on based on the data voltage Vdata at the first node n1. The high potential voltage VGH or the low potential voltage VGL is written to the control terminal of the driving transistor DTFT through the turned-on second switching transistor T2 to control the driving transistor DTFT to be turned off.

[0035] For example, such as Figure 4 As shown, Figure 4 for Figure 2 The equivalent circuit diagram of the pixel driving circuit during the data writing stage is shown. When the first switching transistor T1 and the driving transistor DTFT are P-type transistors and the second switching transistor T2 is an N-type transistor, the first terminal of the second switching transistor T2 is connected to the high-potential power line L5 to receive the high-potential voltage VGH output by the high-potential power line L5. The second terminal of the second switching transistor T2 is connected to the control terminal of the driving transistor DTFT and the first terminal of the first switching transistor T1. The second terminal of the first switching transistor T1 is connected to the low-potential power line L6 to receive the low-potential voltage VGL output by the low-potential power line L6. The control terminals of the first switching transistor T1 and the second switching transistor T2 are connected to the first node n1. The first switching transistor T1 is turned off based on the data voltage Vdata at the first node n1 being a high-level voltage. The second switching transistor T2 is turned on based on the data voltage Vdata at the first node n1 being a high-level voltage. The high-potential voltage VGH is written to the control terminal of the driving transistor DTFT through the turned-on second switching transistor T2 to control the driving transistor DTFT to turn off.

[0036] For example, when the first switching transistor T1 and the driving transistor DTFT are N-type transistors, and the second switching transistor T2 is a P-type transistor, the first terminal of the second switching transistor T2 is connected to the high-potential power line L5 to receive the high-potential voltage VGH output by the high-potential power line L5. The second terminal of the second switching transistor T2 is connected to the control terminal of the driving transistor DTFT and the first terminal of the first switching transistor T1. The second terminal of the first switching transistor T1 is connected to the low-potential power line L6 to receive the low-potential voltage VGL output by the low-potential power line L6. The control terminals of the first switching transistor T1 and the second switching transistor T2 are connected to the first node n1. The first switching transistor T1 is turned on based on the data voltage Vdata at the first node n1 being a high-level voltage, and the second switching transistor T2 is turned off based on the data voltage Vdata at the first node n1 being a high-level voltage. The low-potential voltage VGL is written to the control terminal of the driving transistor DTFT through the turned-on first switching transistor T1 to control the driving transistor DTFT to turn off.

[0037] During the light-emitting phase, the third voltage SP output by the third power line L3 is pulled down. Based on the pull-down height of the third voltage SP, the data voltage Vdata written to the first node n1 is changed accordingly. The second switching transistor T2 is turned off based on the changed data voltage Vdata at the first node n1, and the first switching transistor T1 is turned on based on the changed data voltage Vdata at the first node n1. The high potential voltage VGH or the low potential voltage VGL is written to the control terminal of the driving transistor DTFT through the turned-on first switching transistor T1 to control the driving transistor DTFT to turn on. The first switching transistor T1 generates a corresponding driving voltage based on the changed data voltage Vdata and applies it to the control terminal of the driving unit 10 so that the driving unit 10 generates a corresponding driving current I to drive the light-emitting element 20 to emit light.

[0038] Taking the first switching transistor T1 and the driving transistor DTFT as P-type transistors, and the second switching transistor T2 as an N-type transistor as an example, such as Figure 5 and Figure 6 As shown, Figure 5 for Figure 2 The diagram shows an equivalent circuit diagram of one embodiment of the pixel driving circuit in the light-emitting stage. Figure 6 for Figure 2The equivalent circuit diagram of another embodiment of the pixel driving circuit in the light-emitting stage is shown. Due to the different pull-down heights of the third voltage SP and the bootstrap effect of the capacitor unit 40, the data voltage Vdata at the first node n1 also corresponds to different pull-down heights. If the data voltage Vdata at the first node n1 is still at a high level after being pulled down, the first switching transistor T1 is turned off, the second switching transistor T2 is turned on, and the high potential voltage VGH is written to the control terminal of the driving transistor DTFT through the turned-on second switching transistor T2 to control the driving transistor DTFT to be turned off, and the light-emitting element 20 does not emit light (see...). Figure 5 If the data voltage Vdata at the first node n1 is pulled down to a low level, then the first switching transistor T1 is turned on, and the second switching transistor T2 is turned off. The low potential voltage VGL is written to the control terminal of the driving transistor DTFT through the turned-on first switching transistor T1 to control the driving transistor DTFT to turn on. The conduction degree of the first switching transistor T1 is related to the data voltage Vdata after the pull-down, and the conduction degree of the driving transistor DTFT is related to the conduction degree of the first switching transistor T1. This causes the driving unit 10 to generate a corresponding driving current I, thereby enabling the light-emitting element 20 to achieve different grayscale displays (see...). Figure 6 ).

[0039] Please continue reading Figure 2 In one embodiment, the data writing unit 30 includes a writing transistor T3, and the capacitor unit 40 includes a capacitor C. Specifically, the first terminal of the writing transistor T3 and the first plate of the capacitor C are connected to the first node n1, the second plate of the capacitor C is connected to the third power line L3, the second terminal of the writing transistor T3 is connected to the data line L4 to receive the data voltage Vdata output by the data line L4, and the control terminal of the writing transistor T3 is connected to the scan signal line L7. Specifically, the scan signal line L7 is used to output a scan control signal Gn to control the writing transistor T3 to be turned on or off. When the writing transistor T3 is a P-type transistor, the scan signal line L7 outputs a low-level scan control signal Gn to control the writing transistor T3 to be turned on, so that the data voltage Vdata output by the data line L4 is written to the first node n1 through the turned-on writing transistor T3; when the writing transistor T3 is an N-type transistor, the scan signal line L7 outputs a high-level scan control signal Gn to control the writing transistor T3 to be turned on, so that the data voltage Vdata output by the data line L4 is written to the first node n1 through the turned-on writing transistor T3.

[0040] Please combine Figure 3 , Figure 3This is a timing diagram of an embodiment of the pixel driving circuit provided in this application. In one embodiment, there is a reference voltage value time period S2 between two adjacent pull-down time periods S1 of the third voltage SP. During the reference voltage value time period S2, the pixel driving circuit 100 is in the data writing stage, and during the pull-down time period S1, the pixel driving circuit 100 is in the light emission stage.

[0041] Specifically, during each reference voltage value time period S2, the data writing unit 30 outputs the data voltage Vdata and writes the data voltage Vdata of that row.

[0042] Taking the first switching transistor T1 and the driving transistor DTFT as P-type transistors and the second switching transistor T2 as an N-type transistor as an example, the reference voltage corresponding to the reference voltage value time period S2 is less than the minimum data voltage Vdata output by the data writing unit 30. This makes it so that during the data writing stage, since the data voltage Vdata is greater than the reference voltage, the second switching transistor T2 is turned on based on the data voltage Vdata at the first node n1 being a high-level voltage, and the first switching transistor T1 is turned off based on the data voltage Vdata at the first node n1 being a high-level voltage. The high potential voltage VGL is written to the control terminal of the driving transistor DTFT through the turned-on second switching transistor T2 to control the driving transistor DTFT to be turned off, and the light-emitting element 20 does not emit light.

[0043] During the pull-down period S1 of the third voltage SP, if the pull-down voltage value corresponding to the pull-down height of the third voltage SP is less than the data voltage Vdata, then during the light-emitting stage, the first switching transistor T1 remains off, and the second switching transistor T2 remains on. The high-potential voltage VGH is written to the control terminal of the driving transistor DTFT through the on-state second switching transistor T2 to control the driving transistor DTFT to turn off, and the light-emitting element 20 does not emit light. If the pull-down voltage value corresponding to the pull-down height of the third voltage SP is greater than the data voltage Vdata, then during the light-emitting stage, the first switching transistor T1 changes from the off state to the on state, and the second switching transistor T2 changes from the on state to the off state. The low-potential voltage VGL is written to the control terminal of the driving transistor DTFT through the on-state first switching transistor T1 to control the driving transistor DTFT to turn on. The data voltage Vdata, which changes based on the pull-down, causes the driving unit 10 to generate a corresponding driving current I, thereby enabling the light-emitting element 20 to achieve different grayscale displays.

[0044] Based on the different gray levels of the light-emitting element 20, the data voltage Vdata output by the data writing unit 30 is also different. Taking the data voltage Vdata output by the data writing unit 30 as including a first data voltage V1, a second data voltage V2, a third data voltage V3, a fourth data voltage V4, and a fifth data voltage V5, and the first data voltage V1 < the second data voltage V2 < the third data voltage V3 < the fourth data voltage V4 < the fifth data voltage V5; the pull-down height of the third voltage SP includes a first pull-down height H1, a second pull-down height H2, a third pull-down height H3, a fourth pull-down height H4, and a fifth pull-down height H5, and the voltage value pulled down by the first pull-down height H1 < the voltage value pulled down by the second pull-down height H2 < the voltage value pulled down by the third pull-down height H3 < the voltage value pulled down by the fourth pull-down height H4 < the voltage value pulled down by the fifth pull-down height H5 as an example.

[0045] For details, see Figure 2 and Figure 3 During each reference voltage time period S2, the data writing unit 30 writes the data voltage Vdata for that row at the first node n1. At this time, the data voltage Vdata is relatively high, turning on the second switching transistor T2. The high potential voltage VGH turns off the driving transistor DTFT through the second switching transistor T2. The data writing unit 30 stops writing the data voltage Vdata at the first node n1, and the writing of the data voltage Vdata for that row is completed. The third voltage SP is pulled down. Based on the pull-down height of the third voltage SP and the voltage value corresponding to the data voltage Vdata, it is determined whether the subframe emits light. If the data voltage Vdata written for each subframe is the first data voltage V1, the first data voltage V1 is relatively low. All pull-down height subframes can turn on the first switching transistor T1 and turn off the second switching transistor T2, so that the driving transistor DTFT is turned on, thus achieving a high-brightness image. When the data voltage Vdata written for each subframe is relatively high, such as the fifth data voltage V5, the driving transistor DTFT is turned on only when the pull-down height of the third voltage SP is at its maximum (the fifth pull-down height H5), and the light-emitting element 20 starts to emit light, thereby achieving a low grayscale display. Among them, the third voltage SP needs to be refreshed continuously. As long as the data voltage Vdata is written within the reference voltage value time period S2, one frame can be displayed. Therefore, line-by-line scanning writing can be achieved, greatly reducing flicker.

[0046] In one embodiment, the third voltage SP is uniformly distributed at different pull-down heights. Specifically, the uniform distribution of the third voltage SP at different pull-down heights can disperse the emission time, which helps to avoid mid-grayscale flickering.

[0047] Specifically, such as Figure 3As shown, if the third data voltage V3 is written in each subframe, and if the third voltage SP with different pull-down heights is evenly distributed, the driving transistor DTFT will be turned on only when the pull-down height of the third voltage SP is greater than or equal to the third pull-down height H3, and the light-emitting element 20 will start to emit light, thereby realizing the dispersion of light emission time.

[0048] In one embodiment, the light-emitting element 20 is one of a first light-emitting element 20, a second light-emitting element 20, and a third light-emitting element 20, and the first light-emitting element 20, the second light-emitting element 20, and the third light-emitting element 20 include any three of red light-emitting element 20, green light-emitting element 20, blue light-emitting element 20, and white light-emitting element 20. Since the types of light-emitting elements 20 are different, the operating voltages of the first light-emitting element 20, the second light-emitting element 20, and the third light-emitting element 20 are different.

[0049] To achieve constant current control for different types of light-emitting elements 20, a first power line L1 is provided, comprising a first-type power line, a second-type power line, and a third-type power line. Specifically, when the light-emitting element 20 is a first-type light-emitting element 20, the first power line L1 is a first-type power line connected to it; when the light-emitting element 20 is a second-type light-emitting element 20, the first power line L1 is a second-type power line connected to it; and when the light-emitting element 20 is a third-type light-emitting element 20, the first power line L1 is a third-type power line connected to it. Specifically, the first-type, second-type, and third-type power lines are used to output the operating voltage corresponding to the first, second, and third light-emitting elements 20, respectively, to achieve constant current control for the different types of light-emitting elements 20.

[0050] Of course, in other embodiments, if circuits such as 7T1C, 6T1C, and 5T2C are used for constant current control, the driving circuit of this application can also be combined, and no limitation is made here.

[0051] Specifically, in the pixel driving circuit 100 provided in this application, during the data writing stage, the switching unit 50 controls the driving unit 10 to be turned off based on the data voltage Vdata at the first node n1; during the light emission stage, the third voltage SP output by the third power line L3 is pulled down. Based on the pull-down and pull-down height of the third voltage SP, the data voltage Vdata written to the first node n1 changes accordingly. The switching unit 50 controls the driving unit 10 to be turned on or off based on the changed data voltage Vdata at the first node n1. When the switching unit 50 is on, the switching unit 50 generates a corresponding driving voltage based on the changed data voltage Vdata and applies it to the driving unit 10, so that the driving unit 10 generates a corresponding driving current I to drive the light-emitting element 20 to emit light. Through the above settings, only one signal needs to be written in one frame, enabling progressive scan and solving the flickering problem. In addition, by setting the third voltage SP with different pull-down heights to be evenly distributed, the light emission time can be dispersed, which helps to avoid mid-grayscale flickering.

[0052] See Figure 7 , Figure 7 This is a flowchart illustrating an embodiment of the driving method for the pixel driving circuit provided in this application. This application also provides a driving method for a pixel driving circuit 100, applied to the pixel driving circuit 100 provided in any of the above embodiments, the driving method comprising:

[0053] Step S1: During the data writing stage, the data writing unit 30 writes the data voltage Vdata to the first node n1, and the switching unit 50 controls the driving unit 10 to turn off based on the data voltage Vdata at the first node n1.

[0054] Specifically, during each reference voltage value time period S2, the scan signal line L7 controls the write transistor T3 to turn on line by line, and the data write unit 30 outputs the data voltage Vdata, writing the data voltage Vdata for that line.

[0055] Combination Figures 2-4 The following explanation will be based on the example of the first switching transistor T1 and the driving transistor DTFT being P-type transistors, and the second switching transistor T2 being an N-type transistor.

[0056] Furthermore, the first terminal of the second switching transistor T2 is connected to the high-potential power line L5 to receive the high-potential voltage VGH output by the high-potential power line L5, the second terminal of the second switching transistor T2 is connected to the control terminal of the driving transistor DTFT and the first terminal of the first switching transistor T1, the second terminal of the first switching transistor T1 is connected to the low-potential power line L6 to receive the low-potential voltage VGL output by the low-potential power line L6, and the control terminal of the first switching transistor T1 and the control terminal of the second switching transistor T2 are connected to the first node n1.

[0057] like Figure 4 As shown, during the data writing stage, the first switching transistor T1 is turned off based on the data voltage Vdata at the first node n1 being a high-level voltage, and the second switching transistor T2 is turned on based on the data voltage Vdata at the first node n1 being a high-level voltage. The high potential voltage VGH is written to the control terminal of the driving transistor DTFT through the turned-on second switching transistor T2 to control the driving transistor DTFT to be turned off.

[0058] Step S2: During the light-emitting stage, the third voltage SP output by the third power line L3 is pulled down. Based on the pull-down and pull-down height of the third voltage SP, the data voltage Vdata written to the first node n1 is changed accordingly. Based on the changed data voltage Vdata at the first node n1, the switching unit 50 controls the driving unit 10 to be turned on or off. When the switching unit 50 is turned on, the switching unit 50 generates a corresponding driving voltage based on the changed data voltage Vdata and applies it to the driving unit 10 so that the driving unit 10 generates a corresponding driving current I to drive the light-emitting element 20 to emit light.

[0059] See Figure 5 and Figure 6 Specifically, during the light-emitting stage, due to the different pull-down heights of the third voltage SP and the bootstrap effect based on capacitor unit 40, the data voltage Vdata at the first node n1 also corresponds to different pull-down heights, such as... Figure 5 As shown, if the data voltage Vdata at the first node n1 remains high after being pulled down, the first switching transistor T1 is turned off, the second switching transistor T2 is turned on, and the high potential voltage VGH is written to the control terminal of the driving transistor DTFT through the turned-on second switching transistor T2, thereby controlling the driving transistor DTFT to turn off, and the light-emitting element 20 does not emit light. Figure 6 As shown, if the data voltage Vdata at the first node n1 is pulled down to a low level, the first switching transistor T1 is turned on and the second switching transistor T2 is turned off. The low potential voltage VGL is written to the control terminal of the driving transistor DTFT through the turned-on first switching transistor T1 to control the driving transistor DTFT to turn on.

[0060] The conduction level of the first switching transistor T1 is related to the data voltage Vdata after pull-down, and the conduction level of the driving transistor DTFT is related to the conduction level of the first switching transistor T1, thereby causing the driving unit 10 to generate a corresponding driving current I, so that the light-emitting element 20 can achieve different grayscale display.

[0061] Combination Figure 3If the data voltage Vdata written to each subframe is the first data voltage V1, and the first data voltage V1 is low, all pull-down height subframes can turn on the first switching transistor T1 and turn off the second switching transistor T2, thus turning on the driving transistor DTFT and achieving a high-brightness image. When the data voltage Vdata written to each subframe is high, such as the fifth data voltage V5, the driving transistor DTFT is turned on only when the pull-down height of the third voltage SP is at its maximum (the fifth pull-down height H5), and the light-emitting element 20 starts to emit light, thereby achieving a low grayscale display.

[0062] Among them, the third voltage SP needs to be refreshed continuously. As long as the data voltage Vdata is written within the reference voltage value time period S2, one frame can be displayed. Therefore, line-by-line scanning writing can be achieved, greatly reducing flicker.

[0063] In one embodiment, the pull-down height of the third voltage SP output by the third power line L3 is uniformly distributed.

[0064] Specifically, if the third data voltage V3 is written in each subframe, and if the third voltage SP with different pull-down heights is evenly distributed, the driving transistor DTFT will be turned on only when the pull-down height of the third voltage SP is greater than or equal to the third pull-down height H3, and the light-emitting element 20 will start to emit light, thereby achieving dispersion of the light emission time.

[0065] Please see Figure 8 , Figure 8 This is a schematic diagram of the structure of one embodiment of the display panel provided in this application. This application also provides a display panel 200, which includes the pixel driving circuit 100 provided in any of the above embodiments.

[0066] Specifically, the display panel 200 can be applied to mobile phones, televisions, tablets, laptops, smartwatches, etc. The display panel includes, but is not limited to, OLED (Organic Light Emitting Diode) display panels, AMOLED (Active Matrix / Organic Light Emitting Diode) display panels, and Micro LED (Micro Light Emitting Diode) display panels.

[0067] The above are merely embodiments of this application and do not limit the scope of this patent application. Any equivalent structural or procedural changes made using the content of this application's specification and drawings, or direct or indirect applications in other related technical fields, are similarly included within the scope of patent protection of this application.

Claims

1. A pixel driving circuit, characterized in that, include: The driving unit and the light-emitting element are connected in series between the first power line and the second power line; The data writing unit, connected to the data line, is used to output data voltage; The third power supply line is used to output the third voltage; A capacitor unit is connected between the third power line and the data writing unit, and the connection point between the capacitor unit and the data writing unit is the first node; A switching unit is connected between the driving unit and the first node; During the data writing phase, the data writing unit writes the data voltage to the first node, and the switching unit controls the driving unit to turn off based on the data voltage at the first node. During the light-emitting phase, the third voltage output by the third power line is pulled down. Based on the pull-down height of the third voltage, the data voltage written to the first node changes accordingly. Based on the changed data voltage at the first node, the switching unit controls the driving unit to be turned on or off. When the switching unit is turned on, the switching unit generates a corresponding driving voltage based on the changed data voltage and applies it to the driving unit, so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light.

2. The pixel driving circuit according to claim 1, characterized in that, The driving unit includes a driving transistor; The switching unit includes a first switching transistor and a second switching transistor connected to the control terminal of the driving transistor; wherein the driving transistor is of the same type as the first switching transistor, and one of the first switching transistor and the second switching transistor is a P-type transistor and the other is an N-type transistor; During the data writing phase, the data writing unit writes the data voltage to the first node. The first switching transistor is turned off based on the data voltage at the first node, and the second switching transistor is turned on based on the data voltage at the first node. A high potential voltage or a low potential voltage is written to the control terminal of the driving transistor through the turned-on second switching transistor to control the driving transistor to turn off. During the light-emitting phase, the third voltage output from the third power line is pulled down. Based on the pull-down height of the third voltage, the data voltage written to the first node changes accordingly. The second switching transistor is turned off based on the changed data voltage at the first node, and the first switching transistor is turned on based on the changed data voltage at the first node. The high potential voltage or the low potential voltage is written to the control terminal of the driving transistor through the turned-on first switching transistor to control the driving transistor to turn on. The first switching transistor generates a corresponding driving voltage based on the changed data voltage and applies it to the control terminal of the driving unit, so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light.

3. The pixel driving circuit according to claim 1, characterized in that, Between two adjacent pull-down time periods of the third voltage, there is a reference voltage value time period. During the reference voltage value time period, the pixel driving circuit is in the data writing stage, and during the pull-down time period, the pixel driving circuit is in the light emission stage.

4. The pixel driving circuit according to claim 3, characterized in that, The third voltage is uniformly distributed at different pull-down heights.

5. The pixel driving circuit according to claim 2, characterized in that, The driving transistor and the first switching transistor are P-type transistors, and the second switching transistor is an N-type transistor; When the first switching transistor is in the off state and the second switching transistor is in the on state, the high potential voltage is written to the control terminal of the driving transistor through the on-state second switching transistor to control the driving transistor to be turned off. When the first switching transistor is in the on state and the second switching transistor is in the off state, the low potential voltage is written to the control terminal of the driving transistor through the on first switching transistor to control the driving transistor to turn on and generate a corresponding driving current to drive the light-emitting element to emit light.

6. The pixel driving circuit according to claim 5, characterized in that, The first terminal of the second switching transistor is connected to a high-potential power line to receive the high-potential voltage output by the high-potential power line. The second terminal of the second switching transistor is connected to the control terminal of the driving transistor and the first terminal of the first switching transistor. The second terminal of the first switching transistor is connected to a low-potential power line to receive the low-potential voltage output by the low-potential power line. The control terminals of the first switching transistor and the second switching transistor are connected to the first node.

7. The pixel driving circuit according to claim 1, characterized in that, The data writing unit includes a writing transistor, a first end of which is connected to the first node, a second end of which is connected to a data line to receive the data voltage output by the data line, and a control end of which is connected to a scan signal line.

8. The pixel driving circuit according to claim 1, characterized in that, The light-emitting element is one of a first light-emitting element, a second light-emitting element, and a third light-emitting element, wherein the first light-emitting element, the second light-emitting element, and the third light-emitting element have different operating voltages; The first power line is a first type of power line connected to the first light-emitting element, a second type of power line connected to the second light-emitting element, or a third type of power line connected to the third light-emitting element. The first type of power line, the second type of power line, and the third type of power line are used to output the working voltage corresponding to the first light-emitting element, the second light-emitting element, and the third light-emitting element.

9. A display panel, characterized in that, The display panel includes the pixel driving circuit described in any one of claims 1 to 8.

10. A driving method for a pixel driving circuit, characterized in that, The driving method is applied to the pixel driving circuit according to any one of claims 1-8, and the driving method includes: During the data writing phase, the data writing unit writes the data voltage to the first node, and the switching unit controls the driving unit to turn off based on the data voltage at the first node; During the light-emitting phase, the third voltage output by the third power line is pulled down. Based on the pull-down height of the third voltage, the data voltage written to the first node changes accordingly. Based on the changed data voltage at the first node, the switching unit controls the driving unit to be turned on or off. When the switching unit is turned on, the switching unit generates a corresponding driving voltage based on the changed data voltage and applies it to the driving unit, so that the driving unit generates a corresponding driving current to drive the light-emitting element to emit light.

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