Pixel driving circuit, driving method thereof and display panel

Abstract

The invention provides a pixel driving circuit, a driving method thereof and a display panel, specifically, a driving unit and a light-emitting element in the pixel driving circuit are connected in series between a first power line and a second power line, a data writing unit is used for outputting data voltage, and a third power line is used for outputting third voltage. The capacitor unit is connected between a third power line and the data write-in unit, the connection point of the capacitor unit and the data write-in unit is a first node, and the switch unit is connected between the driving unit and the first node; in a data writing stage, the switch unit controls the driving unit to be cut off based on the data voltage at the first node; in the light-emitting stage, the third voltage output by the third power line is pulled down, the data voltage written into the first node is correspondingly changed based on the pull-down of the third voltage and the pull-down height, and in the switch unit conduction state, the switch unit generates corresponding driving voltage based on the changed data voltage and applies the driving voltage to the driving unit so as to drive the light-emitting element to emit light.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a pixel driving circuit and a driving method thereof, and a display panel. Background Art

[0002] Compared with liquid crystal 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 the advantages of low energy consumption, self-luminescence, wide viewing angle, and fast response speed. They have begun to replace traditional LCD screens in display fields such as mobile phones, tablets, and smart wearables.

[0003] Taking Micro-OLED as an example, due to its own characteristics, Micro-OLED has high requirements for driving, and needs to control the grayscale by digital driving control time under constant current drive. The current mainstream products control the luminous time through sub-frames or SWEEP ramps. However, the sub-frame method requires multiple writing of the Data signal to select the sub-frame signal, which requires a higher refresh frequency; and the use of ramp signals has more serious flickering in the low and medium grayscales because the luminous time is more continuous, and because the ramp signal is a global signal, it needs to be lit after all pixels are written, so high flickering will also occur. Summary of the invention

[0004] The present application provides a pixel driving circuit and a driving method thereof, and a display panel. By optimizing the pixel driving circuit, a signal only needs to be written once in one frame, a line-by-line scanning function can be realized, and the flicker problem can be solved.

[0005] In order to solve the above technical problems, the first technical solution provided by the present application is: to provide a pixel driving circuit, comprising: a driving unit and a light-emitting element, which are connected in series between a first power line and a second power line; a data writing unit, connected to the 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, and the connection point between the capacitor unit and the data writing unit is a first node; a switch unit, connected between the driving unit and the first node; wherein, in the data writing stage, the data writing unit writes the data voltage into the first node, and the switch unit controls the driving unit to be turned off based on the data voltage at the first node; in the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written into the first node changes accordingly, and the switch unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and when the switch unit is in the on state, the switch 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 is of the same type as the first switching transistor, 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, in a data writing phase, the data writing unit writes the data voltage into the first node, the first switching transistor is turned off based on the data voltage at the first node, 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 into the control terminal of the driving transistor through the turned-on second switching transistor to control the driving transistor. the driving transistor is turned off; in the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written into the first node changes accordingly, the second switch transistor is turned off based on the changed data voltage at the first node, and the first switch transistor is turned on based on the changed data voltage at the first node, and the high potential voltage or the low potential voltage is written to the control end of the driving transistor through the turned-on first switch transistor to control the driving transistor to be turned on, and the first switch transistor generates a corresponding driving voltage based on the changed data voltage and applies it to the control end 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. In the reference voltage value time period, the pixel driving circuit is in the data writing stage, and in the pull-down time period, the pixel driving circuit is in the light emitting stage.

[0008] In one embodiment, the third voltages at different pull-down heights are evenly distributed.

[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 an off state and the second switching transistor is in an on state, the high potential voltage is written into the control end of the driving transistor through the turned-on second switching transistor to control the driving transistor to be turned off; when the first switching transistor is in an on state and the second switching transistor is in an off state, the low potential voltage is written into the control end of the driving transistor through the turned-on first switching transistor to control the driving transistor to be turned on and generate a corresponding driving current to drive the light-emitting element to emit light.

[0010] In one embodiment, the first end 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 end of the second switching transistor is connected to the control end of the driving transistor and the first end of the first switching transistor, the second end 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 end of the first switching transistor and the control end of the second switching transistor are connected to the first node.

[0011] In one embodiment, the data writing unit includes a writing transistor, a first end of the writing transistor is connected to the first node, a second end of the writing transistor is connected to a data line to receive the data voltage output by the data line, and a control end of the writing transistor is connected to a scanning 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 operating voltages of the first light-emitting element, the second light-emitting element and the third light-emitting element are different; 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, wherein the first type of power line, the second type of power line and the third type of power line are used to output the operating voltages corresponding to the first light-emitting element, the second light-emitting element and the third light-emitting element.

[0013] In order to solve the above technical problems, the second technical solution provided in the present application is: to provide a display panel, wherein the display panel comprises the pixel driving circuit described in any one of the above rights.

[0014] In order to solve the above technical problems, the third technical solution provided by the present application is: a driving method for a pixel driving circuit is provided, and the driving method is applied to the pixel driving circuit described in any one of the above items, and the driving method includes: in the data writing stage, the data writing unit writes the data voltage into the first node, and the switch unit controls the driving unit to be cut off based on the data voltage at the first node; in the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written into the first node changes accordingly, and the switch unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and when the switch unit is in the on state, the switch 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] Different from the prior art, the beneficial effect of the present application is that, in the pixel driving circuit and the driving method thereof, and the display panel provided by the present 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 switch unit, wherein 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 the data line for outputting 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 a first node; the switch unit is connected between the driving unit and the first node; specifically, in the data writing stage, the switch unit controls the driving unit to be turned off based on the data voltage at the first node; in the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written to the first node changes accordingly, and the switch unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and when the switch unit is in the on state, the switch 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. Through the above settings, it is only necessary to write a signal once in one frame, so that the line-by-line scanning function can be realized and the flicker problem can be solved. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions in the embodiments of the present application, the drawings required for use in the description of the embodiments are briefly introduced below. Obviously, the drawings described below are only some embodiments of the present application. For those skilled in the art, other drawings can be obtained based on these drawings without creative work, among which:

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

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

[0019] Figure 3 A timing diagram of an embodiment of a pixel driving circuit provided by the present application;

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

[0021] Figure 5 for Figure 2 An equivalent circuit diagram of an embodiment of a pixel driving circuit in a light emitting stage is shown;

[0022] Figure 6 for Figure 2 An equivalent circuit diagram of another embodiment of the pixel driving circuit in the light emitting stage shown;

[0023] Figure 7 A schematic diagram of a flow chart of an embodiment of a driving method of a pixel driving circuit provided in the present application;

[0024] Figure 8 A schematic structural diagram of an embodiment of a display panel provided in the present application. DETAILED DESCRIPTION

[0025] The terms "first", "second" and "third" in this application are only used for descriptive purposes and cannot be understood as indicating or implying relative importance or implicitly indicating the number of indicated technical features. Thus, the features defined as "first", "second" and "third" can explicitly or implicitly include at least one of the features. In the description of this application, the meaning of "multiple" is at least two, such as two, three, etc., unless otherwise clearly and specifically defined. All directional indications in the embodiments of the present application (such as up, down, left, right, front, back...) are only used to explain the relative position relationship, movement, etc. between the components under a certain specific posture (as shown in the accompanying drawings). If the specific posture changes, the directional indication also changes accordingly. In addition, the terms "including" and "having" and any of their variations are intended to cover non-exclusive inclusions.

[0026] Reference to "embodiments" herein means that a particular feature, structure, or characteristic described in conjunction with the embodiments may be included in at least one embodiment of the present application. The appearance of the phrase in various locations in the specification does not necessarily refer to the same embodiment, nor is it an independent or alternative embodiment that is mutually exclusive with other embodiments. It is explicitly and implicitly understood by those skilled in the art that the embodiments described herein may be combined with other embodiments.

[0027] The following will be combined with the drawings in the embodiments of the present application to clearly and completely describe the technical solutions in the embodiments of the present application. Obviously, the described embodiments are only part of the embodiments of the present application, not all of the embodiments. Based on the embodiments in the present application, all other embodiments obtained by ordinary technicians in this field without creative work are within the scope of protection of this application.

[0028] See also Figure 1 , Figure 1 A schematic diagram of a circuit module of an embodiment of a pixel driving circuit provided by the present application. The present 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 switch 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 L is used to output a VDD voltage, and the second power line L2 is used to output a VSS voltage; the data writing unit 30 is connected to the 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 switch unit 50 is connected between the driving unit 10 and the first node n1.

[0029] Among them, in the data writing stage, the data writing unit 30 writes the data voltage Vdata into the first node n1, and the switch unit 50 controls the driving unit 10 to be turned off based on the data voltage Vdata at the first node n1; in the light-emitting stage, the third voltage SP output by the third power line L3 is pulled down, and based on the pull-down and pull-down height of the third voltage SP, the data voltage Vdata written into the first node n1 changes accordingly, and the switch 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, and when the switch unit 50 is in the on state, the switch 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] It can be understood that, due to the different pull-down heights of the third voltage SP and based on the bootstrap effect of the capacitor unit 40, the data voltage Vdata at the first node n1 also has different corresponding pull-down heights, which makes the degree of conduction of the switch unit 50 in the on state different, and further makes the degree of conduction of the drive unit 10 controlled by the switch unit 50 different. Correspondingly, the corresponding drive current I generated by the drive unit 10 is also different, thereby realizing different grayscale displays.

[0031] Specifically, the pixel driving circuit 100 provided by the present application writes the data voltage Vdata at the first node n1 in the data writing phase, and in the light emitting phase, 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, so that the switch 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, and when the switch unit 50 is in the on state based on the changed data voltage Vdata at the first node n1, the switch 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 grayscales) to drive the light emitting element 20 to emit light. Through the above settings, it is possible to write a signal only once in one frame, and a line-by-line scanning function can be realized. Compared with using a ramp wave to control the light emitting time of the light emitting element 20, the present application can solve the flickering problem of the light emitting element 20.

[0032] Combination Figure 1 and Figure 2 , Figure 2A schematic diagram of the circuit structure of an embodiment of the pixel driving circuit provided in the present 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] It can be understood that the P-type transistor is in the off state based on the high-level voltage received at its control terminal, and is in the on state based on the low-level voltage received at its control terminal; the N-type transistor is in the on state based on the high-level voltage received at its control terminal, and is in the off state based on the low-level voltage received at its control terminal.

[0034] In this embodiment, in 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, and the high potential voltage VGH or the low potential voltage VGL is written into the control end 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, Figure 4 As shown, Figure 4 for Figure 2 The equivalent circuit diagram of the pixel driving circuit shown in the data writing stage, when the first switch transistor T1 and the driving transistor DTFT are P-type transistors, and the second switch transistor T2 is an N-type transistor, the first end of the second switch 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 end of the second switch transistor T2 is connected to the control end of the driving transistor DTFT and the first end of the first switch transistor T1, the second end of the first switch 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 end of the first switch transistor T1 and the control end of the second switch transistor T2 are connected to the first node n1, the first switch transistor T1 is turned off based on the data voltage Vdata at the first node n1 being a high level voltage, the second switch transistor T2 is turned on based on the data voltage Vdata at the first node n1 being a high level voltage, and the high potential voltage VGH is written to the control end of the driving transistor DTFT through the turned-on second switch transistor T2 to control the driving transistor DTFT to be turned off.

[0036] For another example, when the first switch transistor T1 and the driving transistor DTFT are N-type transistors, and the second switch transistor T2 is a P-type transistor, the first end of the second switch 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 end of the second switch transistor T2 is connected to the control end of the driving transistor DTFT and the first end of the first switch transistor T1, the second end of the first switch 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 end of the first switch transistor T1 and the control end of the second switch transistor T2 are connected to the first node n1. The first switch transistor T1 is turned on based on the data voltage Vdata at the first node n1 being a high level voltage, the second switch transistor T2 is turned off based on the data voltage Vdata at the first node n1 being a high level voltage, and the low potential voltage VGL is written into the control end of the driving transistor DTFT through the turned-on first switch transistor T1 to control the driving transistor DTFT to be turned off.

[0037] In the light-emitting stage, the third voltage SP output by the third power line L3 is pulled down, and based on the pull-down and pull-down height of the third voltage SP, the data voltage Vdata written into the first node n1 changes accordingly, and the second switch transistor T2 is turned off based on the changed data voltage Vdata at the first node n1, and the first switch transistor T1 is turned on based on the changed data voltage Vdata at the first node n1, and the high potential voltage VGH or the low potential voltage VGL is written to the control end of the driving transistor DTFT through the turned-on first switch transistor T1 to control the driving transistor DTFT to turn on, and the first switch transistor T1 generates a corresponding driving voltage based on the changed data voltage Vdata and applies it to the control end 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] For example, the first switch transistor T1 and the driving transistor DTFT are P-type transistors, and the second switch transistor T2 is an N-type transistor. Figure 5 and Figure 6 As shown, Figure 5 for Figure 2 An equivalent circuit diagram of an embodiment of a pixel driving circuit in a light emitting stage is shown; Figure 6 for Figure 2In the equivalent circuit diagram of another embodiment of the pixel driving circuit in the light-emitting stage, due to the different pull-down heights of the third voltage SP and based on the bootstrap effect of the capacitor unit 40, the data voltage Vdata at the first node n1 is also pulled down to different heights. If the data voltage Vdata at the first node n1 is still at a high level voltage after being pulled down, the first switch transistor T1 is turned off, the second switch 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 switch 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 at a low level voltage after being pulled down, the first switch transistor T1 is turned on, the second switch transistor T2 is turned off, and the low potential voltage VGL is written into the control terminal of the driving transistor DTFT through the turned-on first switch transistor T1 to control the driving transistor DTFT to be turned on, wherein the conduction degree of the first switch transistor T1 is related to the data voltage Vdata after being pulled down, and the conduction degree of the driving transistor DTFT is related to the conduction degree of the first switch transistor T1, thereby causing the driving unit 10 to generate a corresponding driving current I, so that the light-emitting element 20 realizes different grayscale display (see Figure 6 ).

[0039] Please continue to see 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 end of the writing transistor T3 and the first electrode plate of the capacitor C are connected to the first node n1, the second electrode plate of the capacitor C is connected to the third power line L3, the second end 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 end of the writing transistor T3 is connected to the scanning signal line L7. Specifically, the scanning signal line L7 is used to output a scanning 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 scanning signal line L7 outputs a low-level scanning 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 scanning signal line L7 outputs a high-level scanning 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 3A timing diagram of an embodiment of the pixel driving circuit provided in the present 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, and in the reference voltage value time period S2, the pixel driving circuit 100 is in the data writing stage, and in the pull-down time period S1, the pixel driving circuit 100 is in the light emitting stage.

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

[0042] Taking the first switch transistor T1 and the driving transistor DTFT as P-type transistors and the second switch 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, so that in the data writing stage, since the data voltage Vdata is greater than the reference voltage, the second switch transistor T2 is turned on based on the data voltage Vdata at the first node n1 being a high-level voltage, and the first switch transistor T1 is turned off based on the data voltage Vdata at the first node n1 being a high-level voltage, and the high potential voltage VGL is written to the control end of the driving transistor DTFT through the turned-on second switch transistor T2 to control the driving transistor DTFT to be turned off, and the light-emitting element 20 does not emit light.

[0043] In the pull-down time 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 in the light-emitting stage, the first switch transistor T1 is still turned off, the second switch transistor T2 is still turned on, and the high potential voltage VGH is written into the control end of the driving transistor DTFT through the turned-on second switch transistor T2 to control the driving transistor DTFT to be turned 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 in the light-emitting stage, the first switch transistor T1 changes from the off state to the on state, and the second switch transistor T2 changes from the on state to the off state, and the low potential voltage VGL is written into the control end of the driving transistor DTFT through the turned-on first switch transistor T1 to control the driving transistor DTFT to be turned on, and based on the changed data voltage Vdata after the pull-down, the driving unit 10 generates the corresponding driving current I, so that the light-emitting element 20 realizes different grayscale display.

[0044] Among them, based on the different gray scales of the light-emitting element 20, the size of the data voltage Vdata output by the data writing unit 30 is also different. For example, the data voltage Vdata output by the data writing unit 30 includes 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.

[0045] For details, see Figure 2 and Figure 3 In each reference voltage value time period S2, the data writing unit 30 writes the data voltage Vdata of the changed row at the first node n1. At this time, the data voltage Vdata is too large, and the second switch transistor T2 is turned on. The high potential voltage VGH turns off the driving transistor DTFT through the second switch 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 of the changed row is completed. The third voltage SP is pulled down. According to 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. For example, when the data voltage Vdata written in each subframe is the first data voltage V1, the first data voltage V1 is too low, and all the pull-down height subframes can turn on the first switch transistor T1 and turn off the second switch transistor T2, so that the driving transistor DTFT is turned on, and a high-brightness picture can be achieved. When the data voltage Vdata written in each subframe is too high, such as the fifth data voltage V5, only when the pull-down height of the third voltage SP is the largest (the fifth pull-down height H5), the driving transistor DTFT is turned on, and the light-emitting element 20 starts to emit light, thereby achieving low grayscale display. The third voltage SP needs to be continuously refreshed. As long as the data voltage Vdata is written in the reference voltage value time period S2, one frame of display can be realized. Therefore, line-by-line scanning and writing can be realized, which greatly reduces flicker.

[0046] In one embodiment, the third voltages SP of different pull-down heights are evenly distributed. Specifically, the third voltages SP of different pull-down heights are evenly distributed, which can disperse the light-emitting time and help avoid the mid-grayscale flickering phenomenon.

[0047] Specifically, Figure 3As shown, if the third data voltage V3 is written into each subframe, if the third voltages SP with different pull-down heights are evenly distributed, only when the pull-down height of the third voltage SP is greater than or equal to the third pull-down height H3, the driving transistor DTFT is turned on and the light-emitting element 20 starts to emit light, thereby achieving dispersion of the light-emitting 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 a red light-emitting element 20, a green light-emitting element 20, a blue light-emitting element 20 and a white light-emitting element 20, wherein due to the different types of the light-emitting elements 20, 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] In order to realize the constant current control of different types of light-emitting elements 20, the first power line L1 is provided to include a first type of power line, a second type of power line and a third type of power line, wherein when the light-emitting element 20 is the first light-emitting element 20, the first power line L1 is the first type of power line correspondingly connected to the first light-emitting element 20; when the light-emitting element 20 is the second light-emitting element 20, the first power line L1 is the second type of power line correspondingly connected to the second light-emitting element 20; when the light-emitting element 20 is the third light-emitting element 20, the first power line L1 is the third type of power line correspondingly connected to the third light-emitting element 20. Specifically, the first type of power line, the second type of power line and the third type of power line are respectively used to output the working voltage corresponding to the first light-emitting element 20, the second light-emitting element 20 and the third light-emitting element 20, so as to realize the constant current control of different types of light-emitting elements 20.

[0050] Of course, in other embodiments, if circuits such as 7T1C, 6T1C, 5T2C, etc. are used for constant current control, they can also be combined with the driving circuit of the present application, which is not limited here.

[0051] Specifically, in the pixel driving circuit 100 provided by the present application, in the data writing stage, the switch unit 50 controls the driving unit 10 to be turned off based on the data voltage Vdata at the first node n1; in the light-emitting stage, the third voltage SP output by the third power line L3 is pulled down, and 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, and the switch 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, and when the switch unit 50 is in the on state, the switch 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-mentioned setting, it is possible to write a signal only once in one frame, realize the line-by-line scanning function, and solve the flicker problem. In addition, by setting the third voltage SP with different pull-down heights to be evenly distributed, the light-emitting time can be dispersed, which is conducive to avoiding the mid-grayscale flicker phenomenon.

[0052] See also Figure 7 , Figure 7 This is a flow chart of an embodiment of a driving method of a pixel driving circuit provided by the present application. The present application also provides a driving method of a pixel driving circuit 100, which is applied to the pixel driving circuit 100 provided by any of the above embodiments, and the driving method includes:

[0053] Step S1: In the data writing stage, the data writing unit 30 writes the data voltage Vdata into the first node n1, and the switch unit 50 controls the driving unit 10 to be turned off based on the data voltage Vdata at the first node n1;

[0054] Specifically, in each reference voltage value time period S2, the scanning signal line L7 controls the writing transistor T3 to turn on row by row, and the data writing unit 30 outputs the data voltage Vdata, and writes the data voltage Vdata of the row.

[0055] Combination Figure 2-Figure 4 The following description is made by taking the first switch transistor T1 and the driving transistor DTFT as P-type transistors and the second switch transistor T2 as an N-type transistor as an example.

[0056] A first end of the second switch 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, a second end of the second switch transistor T2 is connected to the control end of the driving transistor DTFT and the first end of the first switch transistor T1, a second end of the first switch 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 a control end of the first switch transistor T1 and a control end of the second switch transistor T2 are connected to a first node n1.

[0057] like Figure 4 As shown, in 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, and the high potential voltage VGH is written into the control end 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: In the light-emitting stage, the third voltage SP output by the third power line L3 is pulled down, and based on the pull-down and pull-down height of the third voltage SP, the data voltage Vdata written into the first node n1 changes accordingly. The switch 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, and when the switch unit 50 is in the on state, the switch 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 also Figure 5 and Figure 6 Specifically, in the light emitting stage, due to the different pull-down heights of the third voltage SP and based on the bootstrap effect of the capacitor unit 40, the data voltage Vdata at the first node n1 also has different corresponding pull-down heights, such as Figure 5 As shown, if the data voltage Vdata at the first node n1 is still at a high level voltage after being pulled down, the first switch transistor T1 is turned off, the second switch transistor T2 is turned on, and the high potential voltage VGH is written to the control end of the driving transistor DTFT through the turned-on second switch transistor T2 to control the driving transistor DTFT to be turned 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 at a low level voltage after being pulled down, the first switch transistor T1 is turned on, the second switch transistor T2 is turned off, and the low potential voltage VGL is written into the control end of the driving transistor DTFT through the turned-on first switch transistor T1 to control the driving transistor DTFT to turn on.

[0060] Among them, the conduction degree of the first switch transistor T1 is related to the data voltage Vdata after being pulled down, and the conduction degree of the driving transistor DTFT is related to the conduction degree of the first switch transistor T1, so that the driving unit 10 generates a corresponding driving current I, so that the light-emitting element 20 realizes different grayscale display.

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

[0062] The third voltage SP needs to be continuously refreshed. As long as the data voltage Vdata is written in the reference voltage value time period S2, one frame of display can be realized. Therefore, line-by-line scanning and writing can be realized, which greatly reduces flicker.

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

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

[0065] See also Figure 8 , Figure 8 This is a schematic diagram of the structure of an embodiment of a display panel provided in the present application. The present application further provides a display panel 200, and the display panel 200 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, tablet computers, laptop computers, smart watches, etc. The display panel includes but is not limited to OLED (Organic Light Emitting Diode) display panel, AMOLED (Active Matrix / Organic Light Emitting Diode) display panel, Micro LED (Micro Light Emitting Diode) display panel, etc.

[0067] The above are only implementation methods of the present application, and are not intended to limit the patent scope of the present application. Any equivalent structure or equivalent process transformation made using the contents of the present application specification and drawings, or directly or indirectly applied in other related technical fields, are also included in the patent protection scope of the present 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; A data writing unit, connected to the data line, for outputting a data voltage; A third power line, used for outputting a third voltage; a capacitor unit connected between the third power line and the data writing unit, wherein a connection point between the capacitor unit and the data writing unit is a first node; a switch unit, connected between the driving unit and the first node; Wherein, in the data writing stage, the data writing unit writes the data voltage into the first node, and the switch unit controls the driving unit to be turned off based on the data voltage at the first node; In the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written to the first node changes accordingly. The switch unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and when the switch unit is in the on state, the switch 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 switch unit comprises a first switch transistor and a second switch transistor connected to the control terminal of the driving transistor; wherein the driving transistor is of the same type as the first switch transistor, one of the first switch transistor and the second switch transistor is a P-type transistor, and the other is an N-type transistor; Wherein, in the data writing stage, the data writing unit writes the data voltage into the first node, the first switch transistor is turned off based on the data voltage at the first node, the second switch transistor is turned on based on the data voltage at the first node, and the high potential voltage or the low potential voltage is written into the control terminal of the driving transistor through the turned-on second switch transistor to control the driving transistor to be turned off; In the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written into 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, and the high potential voltage or the low potential voltage is written to the control end of the driving transistor through the turned-on first switching transistor to control the driving transistor to be turned on, and the first switching transistor generates a corresponding driving voltage based on the changed data voltage and applies it to the control end 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: There is a reference voltage value time period between two adjacent pull-down time periods of the third voltage. In the reference voltage value time period, the pixel driving circuit is in the data writing stage, and in the pull-down time period, the pixel driving circuit is in the light emitting stage.

4. The pixel driving circuit according to claim 3, characterized in that: The third voltages of different pull-down heights are evenly distributed.

5. The pixel driving circuit according to any one of claims 1 to 4, characterized in that: The driving transistor and the first switch transistor are P-type transistors, and the second switch transistor is an N-type transistor; When the first switch transistor is in the off state and the second switch transistor is in the on state, the high potential voltage is written into the control terminal of the driving transistor through the on second switch transistor to control the driving transistor to be off; When the first switch transistor is in the on state and the second switch transistor is in the off state, the low potential voltage is written into the control end of the driving transistor through the turned-on first switch 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 end 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 end of the second switching transistor is connected to the control end of the driving transistor and the first end of the first switching transistor, the second end 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 end of the first switching transistor and the control end of 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 comprises a writing transistor, a first end of the writing transistor is connected to the first node, a second end of the writing transistor is connected to a data line to receive the data voltage output by the data line, and a control end of the writing transistor is connected to a scanning 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, wherein the first type of power line, the second type of power line and the third type of power line are used to output operating voltages 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 comprises the pixel driving circuit according to 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 to 8, and the driving method comprises: In the data writing phase, the data writing unit writes the data voltage into the first node, and the switch unit controls the driving unit to be turned off based on the data voltage at the first node; In the light-emitting stage, the third voltage output by the third power line is pulled down, and based on the pull-down and pull-down height of the third voltage, the data voltage written to the first node changes accordingly. The switch unit controls the driving unit to be turned on or off based on the changed data voltage at the first node, and when the switch unit is in the on state, the switch 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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