Display apparatus and pixel driving circuit therefor

Abstract

Disclosed in the present application are a display apparatus and a pixel driving circuit therefor, which are applied to the technical field of display. The pixel driving circuit comprises a voltage sampling circuit, a driving transistor, a storage capacitor, a threshold value correction circuit, a light emission control circuit and a light-emitting element, wherein the voltage sampling circuit is connected to a data signal line and a first reference voltage signal line, and is configured to write, in a first phase, a first reference voltage into a gate electrode of the driving transistor, and to sample, in a third phase, an incremental voltage related to a data voltage to the gate electrode of the driving transistor; the threshold value correction circuit is switched on in a second phase, so as to write a threshold value voltage of the driving transistor into the storage capacitor, and is switched off in the third phase and a fourth phase; in the fourth phase, the driving transistor provides an output current on the basis of a gate-source voltage difference thereof; and the light emission control circuit is switched on in the fourth phase, so as to provide the output current to the light-emitting element. Applying the solution of the present application is conducive to ensuring the quality of a display picture and the compact size of a pixel driving circuit, and facilitates an improvement in the contrast ratio of a light-emitting element.

Description

Display device and pixel driving circuit thereof

[0001] The present application claims priority to the Chinese patent application No. 202411375657.6, filed on September 29, 2024, and entitled "A display device and pixel driving circuit thereof", the content of which is incorporated herein by reference in its entirety. TECHNICAL FIELD

[0002] The present application relates to the technical field of display, in particular to a display device and pixel driving circuit thereof. BACKGROUND

[0003] At present, in order to obtain better picture quality, the pixel driving circuit used in the OLED (Organic Light Emitting Diode) display device should be as small as possible. The smaller the pixel driving circuit, the more pixel driving circuits can be arranged in the same space, which is conducive to realizing high resolution and making the display screen of the same area present more details.

[0004] In addition, due to the influence of production process and other factors, there will be uniformity problems in the driving transistors in different pixel driving circuits, that is, the threshold voltages of different driving transistors will be different, which will cause the driving transistors in different pixel driving circuits to not provide current output uniformly and stably, thereby causing the display brightness to be uneven, affecting the quality of the display picture.

[0005] In summary, how to effectively guarantee the quality of the display picture and the small volume of the pixel driving circuit is a technical problem that needs to be solved by the technical personnel in the field at present. SUMMARY

[0006] The purpose of the present application is to provide a display device and pixel driving circuit thereof, which can effectively guarantee the quality of the display picture and the small volume of the pixel driving circuit.

[0007] To solve the above technical problems, the present application provides the following technical solutions:

[0008] In a first aspect, the present application provides a pixel driving circuit, comprising a voltage sampling circuit, a driving transistor, a storage capacitor, a threshold correction circuit, a light-emitting control circuit and a light-emitting element.

[0009] The source of the driving transistor is connected with the first end of the storage capacitor and the first power supply line; the drain of the driving transistor is connected with the gate of the driving transistor through the threshold correction circuit, and the drain is connected with the first electrode of the light emitting element through the light emitting control circuit, and the second electrode of the light emitting element is connected with the second power supply line; the second end of the storage capacitor is connected with the gate; the voltage sampling circuit is connected with the data signal line and the first reference voltage signal line, configured to write the first reference voltage transmitted by the first reference voltage signal line to the gate of the driving transistor in the first stage of each working period, and sample the incremental voltage related to the data voltage transmitted by the data signal line to the gate of the driving transistor in the third stage, so that the gate voltage of the driving transistor at this time is related to the threshold voltage of the driving transistor and the data voltage;

[0010] The threshold correction circuit is configured to be turned on in the second stage to write the threshold voltage of the driving transistor to the storage capacitor, and turned off in the third stage and the fourth stage;

[0011] The driving transistor is configured to provide an output current according to the voltage difference between the gate voltage and the source voltage of the driving transistor in the fourth stage; and the light emitting control circuit is configured to be turned on in the fourth stage to provide the output current to the light emitting element.

[0012] In an embodiment, the voltage sampling circuit comprises a first switch tube and a second capacitor;

[0013] The first end of the second capacitor is connected with the data signal line, the second end of the second capacitor is connected with the first end of the first switch tube, and the connection end is connected with the first reference voltage signal line, and the second end of the first switch tube is used as the output end of the data writing circuit to connect the gate of the driving transistor.

[0014] In an embodiment, the voltage sampling circuit further comprises a third capacitor;

[0015] The first end of the third capacitor is connected with the second end of the second capacitor, and the second end of the third capacitor is connected with the first end of the first switch tube.

[0016] In an embodiment, the light emitting control circuit comprises a second switch tube;

[0017] The first end of the second switch tube is used as the first end of the light emitting control circuit to connect the drain of the driving transistor, and the second end of the second switch tube is used as the second end of the light emitting control circuit to connect the first electrode of the light emitting element.

[0018] In an embodiment, the threshold correction circuit comprises a third switch tube;

[0019] The first end of the third switch tube is the first end of the threshold correction circuit to connect the gate of the drive transistor, and the second end of the third switch tube is the second end of the threshold correction circuit to connect the drain of the drive transistor.

[0020] In an embodiment, further comprising an initialization circuit, the first end of the initialization circuit is connected to the first electrode of the light emitting element, the second end of the initialization circuit is connected to a second reference voltage line, and the initialization circuit is configured to be turned on before the first phase in each working cycle to initialize the first electrode of the light emitting element to a second reference voltage;

[0021] Wherein, the difference between the second reference voltage and the voltage of the second power supply line is less than the threshold voltage of the light emitting element.

[0022] In an embodiment, the initialization circuit comprises a fourth switch tube;

[0023] The first end of the fourth switch tube is the first end of the initialization circuit, and the second end of the fourth switch tube is the second end of the initialization circuit.

[0024] In any one or more of the first phase, the second phase, and the third phase, the fourth switch tube is turned on.

[0025] In an embodiment, the drive transistor is a PMOS tube, and the light emitting element comprises a light emitting diode.

[0026] The anode of the light emitting diode is the first electrode of the light emitting element, and the cathode of the light emitting diode is the second electrode of the light emitting element.

[0027] In an embodiment, in the fourth phase, the light emitting control circuit remains turned on, or the duty cycle of the light emitting control circuit meets the current setting value.

[0028] In a second aspect, the present application provides a display device comprising the pixel driving circuit as described above.

[0029] In an embodiment, the display device further comprises a source driver connected to the pixel driving circuit through the data signal line, and a first reference voltage source connected to the pixel driving circuit through the first reference voltage line.

[0030] The source driver is configured to provide a fixed voltage to the data signal line in the first stage and the second stage, and to provide the data voltage to the data signal line in the third stage.

[0031] The first reference voltage source is configured to provide a first reference voltage to the first reference voltage line in the first stage, and to float the first reference voltage line in the second stage.

[0032] By the device connection relationship in the pixel driving circuit, the pixel driving circuit has the ability of threshold voltage compensation of the driving transistor according to the technical scheme provided by the embodiment of the application, so that the current is not affected by the threshold voltage deviation of the driving transistor when the light emitting element emits light in the fourth stage, and the display uniformity of the pixel array is facilitated to be realized.

[0033] Specifically, the source of the drive transistor is connected with the first end of the storage capacitor and the first power supply line; the drain of the drive transistor is connected with the gate of the drive transistor through the threshold correction circuit, and the drain is connected with the first electrode of the light emitting element through the light emitting control circuit, and the second electrode of the light emitting element is connected with the second power supply line; the second end of the storage capacitor is connected with the gate; the voltage sampling circuit is connected with the data signal line and the first reference voltage signal line. In the first stage of each working cycle, the voltage sampling circuit is configured to write the first reference voltage transmitted by the first reference voltage signal line to the gate of the drive transistor in the first stage of each working cycle, so that the drive transistor is turned on. In the second stage, the threshold correction circuit is turned on, and the voltage of the first power supply line charges the lower plate of the storage capacitor through the threshold correction circuit and the drive transistor, so that the gate potential of the drive transistor is continuously raised until the gate-source voltage of the drive transistor reaches the threshold voltage, and the charging process stops, and the second stage ends, at this time the voltage of the storage capacitor is the gate-source voltage of the drive transistor, that is, the threshold voltage of the drive transistor. Therefore, in the second stage, the threshold correction circuit writes the threshold voltage of the drive transistor into the storage capacitor. In the third stage, the voltage sampling circuit samples the incremental voltage related to the data voltage transmitted by the data signal line to the gate of the drive transistor, so as to control the light emitting element in the fourth stage in the working cycle. In the fourth stage, the light emitting control circuit provides an output current according to the voltage difference between the gate voltage and the source voltage, so as to provide the output current to the light emitting element. Since the gate-source voltage difference of the drive transistor is fixed as the threshold voltage VTH in the second stage, after the data voltage is written in the third stage, the gate-source voltage difference of the drive transistor becomes VTH superimposed with a change amount, which is related to the data voltage transmitted by the data signal line. For example, in the specific example below, at the end of the third stage, the gate-source voltage difference VGS of the drive transistor is equal to Vdata x [(C2 / C1+C2)]+VTH. In the fourth stage, based on the current formula Ioled=f(VGS-VTH) in the linear state of the drive transistor, the VTH term is cancelled by substituting the gate-source voltage difference VGS of the drive transistor at the end of the third stage, so that the output current is not related to the threshold voltage. That is, the output current provided by the drive transistor in the fourth stage is not related to the threshold voltage of the drive transistor, so that the current of the light emitting element is not affected by the threshold voltage deviation of the drive transistor when the light emitting element emits light in the fourth stage, which is beneficial to realize the display uniformity of the pixel array.

[0034] And, in the pixel driving circuit provided by the application, the pixel driving circuit comprises a voltage sampling circuit, a driving transistor, a storage capacitor, a light-emitting control circuit, a threshold correction circuit and a light-emitting element, and has simple structure and high reliability, and is conducive to miniaturization of the pixel driving circuit. In addition, in the pixel driving circuit provided by the application, the light-emitting control circuit is only needed to be turned on in the fourth stage, and can be turned off in the first stage to the third stage, so that in the first stage to the third stage, no through current flowing to the light-emitting element is generated, and the contrast of the light-emitting element is improved. BRIEF DESCRIPTION OF DRAWINGS

[0035] In order to more clearly illustrate the technical solutions in the embodiments of the present application or the prior art, the drawings needed to be used in the embodiments or the prior art description will be briefly introduced below. Obviously, the drawings in the following description are only some embodiments of the present application, and other drawings can be obtained by those skilled in the art without creative effort on the basis of these drawings.

[0036] Fig. 1 is a structural schematic diagram of a pixel driving circuit provided by a specific embodiment of the present application;

[0037] Fig. 2 is a structural schematic diagram of a pixel driving circuit provided by another specific embodiment of the present application;

[0038] Fig. 3 is a schematic diagram of current direction of the pixel driving circuit provided by a specific embodiment of the present application in the first stage;

[0039] Fig. 4 is a schematic diagram of current direction of the pixel driving circuit provided by a specific embodiment of the present application in the second stage;

[0040] Fig. 5 is a schematic diagram of current direction of the pixel driving circuit provided by a specific embodiment of the present application in the third stage;

[0041] Fig. 6 is a schematic diagram of current direction of the pixel driving circuit provided by a specific embodiment of the present application in the fourth stage;

[0042] Fig. 7 is a structural schematic diagram of a pixel driving circuit provided by another specific embodiment of the present application. DETAILED DESCRIPTION

[0043] The core of the present application is to provide a pixel driving circuit, which is conducive to guaranteeing display picture quality and small size of the pixel driving circuit, and improving contrast of a light-emitting element.

[0044] For those skilled in the art, the present application can be further understood based on the following description in combination with the accompanying drawings and specific embodiments. It is obvious that the described embodiments are only a part of the embodiments of the present application, but not all the embodiments. Based on the embodiments in the present application, all other embodiments obtained by those skilled in the art without creative work fall within the scope of the present application.

[0045] Please refer to FIG. 1, which is a structural schematic diagram of a pixel driving circuit provided by an embodiment of the present application. The pixel driving circuit can include a voltage sampling circuit 10, a driving transistor TD, a storage capacitor C1, a light-emitting control circuit 20, a threshold correction circuit 30, and a light-emitting element 40.

[0046] The source of the driving transistor TD is connected with the first end of the storage capacitor C1 and a first power supply line; the drain of the driving transistor TD is connected with the gate of the driving transistor TD through the threshold correction circuit 30, and is connected with the first electrode of the light-emitting element 40 through the light-emitting control circuit 20, and the second electrode of the light-emitting element 40 is connected with a second power supply line; the second end of the storage capacitor C1 is connected with the gate; the voltage sampling circuit 10 is connected with a data signal line and a first reference voltage signal line, and is configured to write the first reference voltage transmitted by the first reference voltage signal line to the gate of the driving transistor TD in the first stage of each working cycle, and sample an incremental voltage related to the data voltage transmitted by the data signal line to the gate of the driving transistor TD in the third stage;

[0047] The threshold correction circuit 30 is configured to be turned on in the second stage to write the threshold voltage of the driving transistor TD to the storage capacitor C1, and is turned off in the third stage and the fourth stage;

[0048] The driving transistor TD is configured to provide an output current according to the voltage difference between the gate voltage and the source voltage thereof in the fourth stage; and the light-emitting control circuit 20 is configured to be turned on in the fourth stage to provide the output current to the light-emitting element 40.

[0049] Specifically, in the present application, in the first stage of each working cycle, the voltage sampling circuit 10 writes the first reference voltage transmitted by the first reference voltage signal line to the gate of the driving transistor TD, that is, applies the first reference voltage to the gate of the driving transistor TD, so that the driving transistor TD is turned on.

[0050] The specific configuration of the voltage sampling circuit 10 can be set and adjusted according to actual needs, but it can be understood that the function requirements of the voltage sampling circuit 10 in the application scheme can be realized, for example, in a specific embodiment of the application, the structure of the pixel driving circuit provided by another specific embodiment of the application is shown in FIG. 2. In the specific embodiment of FIG. 2, the voltage sampling circuit 10 specifically includes a first switch tube Q1 and a second capacitor C2;

[0051] The first end of the second capacitor C2 is connected with the data signal line, the second end of the second capacitor C2 is connected with the first end of the first switch tube Q1 and the connection end is connected with the first reference voltage signal line, and the second end of the first switch tube Q1 is used as the output end of the data writing circuit to connect the gate of the driving transistor TD.

[0052] In this embodiment, the voltage sampling circuit 10 is specifically composed of the first switch tube Q1 and the second capacitor C2, and the structure is simple. The voltage sampling circuit 10 receives the data voltage Vdata through the data voltage end connected with the data signal line and receives the first reference voltage Vref through the reference voltage end connected with the first reference voltage signal line. In addition, the first switch tube Q1 in FIG. 2 is a PMOS tube, the source thereof is used as the second end of the first switch tube Q1, the drain thereof is used as the first end of the first switch tube Q1, and the gate thereof is used as the control end of the first switch tube Q1.

[0053] The four stages in each working period will be described below taking the embodiment of FIG. 2 as an example.

[0054] In the first stage of each working period, the light emitting control circuit 20 and the threshold value correction circuit 30 can be turned off, and the voltage sampling circuit 10 writes the first reference voltage transmitted by the first reference voltage signal line to the gate of the driving transistor TD, so that the driving transistor TD is turned on. In the specific example of FIG. 2, the first reference voltage received by the voltage sampling circuit 10 from the first reference voltage signal line is denoted as Vref, and Vref is applied to the gate of the driving transistor TD through the first switch tube Q1, that is, in the specific example of FIG. 2, the first switch tube Q1 is in the on state in the first stage, so that the reference voltage can be applied to the gate of the driving transistor TD, that is, to the lower plate of the storage capacitor C1. Referring to FIG. 3, the current flow direction in the first stage is shown by a dashed line in FIG. 3.

[0055] The driving transistor TD in the scheme of the present application can generally be a MOSFET (Metal-Oxide-Semiconductor Field-Effect Transistor), for example, in a specific embodiment of the present application, referring to FIG. 2, the driving transistor TD is specifically a PMOS transistor, the gate of which is denoted as G in FIG. 2, the source of which is denoted as S in FIG. 2, and the drain of which is denoted as D in FIG. 2. In FIG. 2, the voltage of the first power supply line is specifically denoted as VDD, thus, in the first stage, the potential of node G is equal to Vref, and the potential of node S is equal to VDD, and it can be understood that the specific value of the first reference voltage Vref can be set and adjusted according to actual needs, but after the first reference voltage Vref is applied to the gate of the driving transistor TD, the driving transistor TD is in an on state, for example, for the embodiment of FIG. 2, the driving transistor TD is specifically a PMOS transistor, thus the first reference voltage Vref should not be too high, so that VGS (VGS = VG-VS) is lower than the threshold voltage VTH of the driving transistor TD.

[0056] In one embodiment, in the first stage, the source driver provides a fixed voltage through the data signal line, and the first reference voltage source provides the first reference voltage Vref through the first reference voltage line, so that the two plates of the second capacitor C2 are written with the fixed voltage and the first reference voltage Vref respectively; optionally, the fixed voltage can also be the first reference voltage Vref.

[0057] In the second stage in each working cycle, the voltage sampling circuit 10 can be turned off, for the specific embodiment of FIG. 2, the first switch Q1 is controlled to be in an off state in the second stage, and the threshold correction circuit 30 is turned on, so that the threshold voltage of the driving transistor TD can be written into the storage capacitor C1.

[0058] In addition, it needs to be explained that, since the on-off control of the light-emitting control circuit 20 and the threshold correction circuit 30 is required in the scheme of the present application, the light-emitting control circuit 20 and the threshold correction circuit 30 can generally be realized by MOS transistors, which have the advantages of simple structure, low power consumption, small size, etc.

[0059] For example, in a specific embodiment of the present application, the light-emitting control circuit 20 includes a second switch Q2. The first end of the second switch Q2 is connected to the drain of the driving transistor TD as the first end of the light-emitting control circuit 20, and the second end of the second switch Q2 is connected to the first electrode of the light-emitting element 40 as the second end of the light-emitting control circuit 20.

[0060] In the embodiment of FIG. 2, the second switch Q2 is a PMOS transistor, and the first end of the second switch Q2 is the source of the second switch Q2, the second end of the second switch Q2 is the drain of the second switch Q2, and the control end of the second switch Q2 is the gate of the second switch Q2, so that the on-off state of the second switch Q2 is controlled by controlling the gate voltage of the second switch Q2, i.e., the on-off control of the light emitting control circuit 20 is realized.

[0061] In one embodiment of the present application, the threshold correction circuit 30 includes a third switch Q3. The first end of the third switch Q3 is connected to the gate of the drive transistor TD as the first end of the threshold correction circuit 30, and the second end of the third switch Q3 is connected to the drain of the drive transistor TD as the second end of the threshold correction circuit 30.

[0062] In the embodiment of FIG. 2, the third switch Q3 is a PMOS transistor, and the first end of the third switch Q3 is the source of the third switch Q3, the second end of the third switch Q3 is the drain of the third switch Q3, and the control end of the third switch Q3 is the gate of the third switch Q3, so that the on-off state of the third switch Q3 is controlled by controlling the gate voltage of the third switch Q3, i.e., the on-off control of the threshold correction circuit 30 is realized.

[0063] Referring to FIG. 4, the current flow in the second stage is shown by the dashed line. In the second stage, the drive transistor TD is turned on, and the threshold correction circuit 30 is configured to be turned on to write the threshold voltage of the drive transistor TD into the storage capacitor C1. Therefore, in the example of FIG. 4, the voltage VDD of the first power supply line charges the lower plate of the storage capacitor C1 (i.e., the node G) through the drive transistor TD and the third switch Q3, so that the voltage of the node G continuously rises, and when the voltage rises to the gate-source voltage difference VGS (VGS=VG-VS) of the drive transistor TD equal to the threshold voltage VTH of the drive transistor TD, the drive transistor TD is turned off, the charging stops, and the second stage ends.

[0064] In one embodiment, in the second stage, the source driver continues to provide a fixed voltage through the data signal line, and the first reference voltage source is floating on the first reference voltage line, and at this time, the voltages of the two plates of the second capacitor C2 are the fixed voltage and VDD+VTH, respectively.

[0065] That is, at the end of the second stage, the threshold voltage VTH of the driving transistor is written into the storage capacitor C1, at this time the charging is completed, and at this time, the potential VG of the node G is VDD+VTH. For the example example of FIG. 2, since the driving transistor TD is a PMOS transistor, VTH is negative. It can be seen that at the end of the second stage, the potential VG of the node G is related to the threshold voltage VTH of the driving transistor TD, and for this reason, in the subsequent fourth stage, when the light emitting element 40 emits light, the current can not be affected by the deviation of the threshold voltage VTH of the driving transistor TD. The specific principle will be described in the stage analysis below.

[0066] In the third stage in each working cycle, it is a data writing stage, at this time, the source driver provides a data voltage through the data signal line, the first reference voltage source floats the first reference voltage line, and the voltage sampling circuit 10 samples the incremental voltage related to the data voltage transmitted by the data signal line to the gate of the driving transistor TD, so that the gate voltage of the driving transistor at this time is related to the threshold voltage of the driving transistor and the data voltage, thereby controlling the luminance of the light emitting element 40 in the fourth stage of the working cycle. Specifically, in the third stage, the light emitting control circuit 20 and the threshold correction circuit 30 are both turned off, and in the example of FIG. 2, specifically, the second switch Q2 and the third switch Q3 are both turned off, and the first switch Q1 is turned on, at this time, the reference voltage end of the voltage sampling circuit 10 can be floating, that is, the first reference voltage signal line is floating, that is, in a high resistance state, and the data voltage received by the data voltage end of the voltage sampling circuit 10 from the data signal line is denoted as Vdata.

[0067] Referring to FIG. 5, the current flow direction in the third stage is shown by a dashed line. Since in the third stage, the storage capacitor C1 and the second capacitor C2 are connected in series, after the data voltage Vdata is divided by the series-connected storage capacitor C1 and second capacitor C2, it is stored in the lower plate of the storage capacitor C1, so that the potential change amount ΔVG of the node G is Vdata×[(C2 / C1+C2)], that is, the voltage sampling circuit 10 samples the incremental voltage related to the data voltage Vdata to the gate of the driving transistor TD.

[0068] As described above, since at the beginning of the third stage, the potential VG of the node G is VDD+VTH, at the end of the third stage, the potential VG of the node G is equal to ΔVG+VDD+VTH, that is, at the end of the third stage, the potential VG of the node G is Vdata×[(C2 / C1+C2)]+VDD+VTH. At this time, the gate-source voltage difference VGS of the driving transistor TD is equal to Vdata×[(C2 / C1+C2)]+VTH.

[0069] In the fourth phase in each working cycle, the driving transistor TD is configured to provide an output current according to the voltage difference between its gate voltage and source voltage. The light emitting control circuit 20 is configured to be turned on in the fourth phase to provide the output current to the light emitting element 40. In addition, in the fourth phase, the threshold correction circuit 30 and the voltage sampling circuit 10 can both be turned off, and in the example of FIG. 2, specifically, the second switch Q2 is turned on, the third switch Q3 is turned off, the first switch Q1 is turned off, and the first reference voltage source continues to float the first reference voltage line. At this time, the output current provided by the driving transistor TD depends on its gate-source voltage difference VGS. Specifically, in the fourth phase, the driving transistor TD is controlled by the gate potential (i.e., the potential of node G, which is also the potential of the lower plate of the storage capacitor C1) to provide an output current to the light emitting element 40 via the second switch Q2, and the value of the current is a function of the gate-source voltage difference VGS and the threshold voltage VTH of the driving transistor TD, which can be simplified as Ioled = f(VGS-VTH).

[0070] Referring to FIG. 6, the current flow in the fourth phase is shown by dashed lines. As can be known from the above analysis, at the end of the third phase, the gate-source voltage difference VGS of the driving transistor TD is equal to Vdata x [(C2 / C1+C2)]+VTH. Therefore, the current Ioled generated in the fourth phase is f(Vdata x [(C2 / C1+C2)]+VTH-VTH) = f(Vdata x [(C2 / C1+C2)]). As can be seen, after the application of the scheme of the present application, in the fourth phase, the current generated by the driving transistor TD is independent of the threshold voltage VTH of the driving transistor TD and is only controlled by the data voltage Vdata in the third phase. Therefore, when a pixel array is established using the pixel driving circuit according to the present application, the threshold voltage offset of different driving transistors TD caused by the process will not cause the output current Ioled to deviate, so that the display product designed based on the pixel driving circuit according to the present application has good display uniformity and can achieve better display effect.

[0071] The specific structure of the light emitting element 40 can be set and adjusted as needed. For example, in one specific embodiment of the present application, referring to FIG. 2, the light emitting element 40 includes a light emitting diode D1. The anode of the light emitting diode D1 serves as the first electrode of the light emitting element 40, and the cathode of the light emitting diode D1 serves as the second electrode of the light emitting element 40. The second electrode of the light emitting element 40 is connected to the second power supply line, which is denoted as VSS in FIG. 2. In this embodiment, the light emitting function is realized by the light emitting diode D1, which has a simple structure and is easy to implement. The light emitting diode D1 may, for example, specifically be an oled type light emitting diode D1.

[0072] In one embodiment of the present application, an initialization circuit can also be included, the first end of the initialization circuit is connected to the first electrode of the light emitting element 40, the second end of the initialization circuit is connected to the second reference voltage line, and the initialization circuit is configured to be turned on before the first stage in each working cycle to initialize the first electrode of the light emitting element 40 to the second reference voltage.

[0073] In one embodiment of the present application, an initialization circuit can also be included, the first end of the initialization circuit is connected to the first electrode of the light emitting element 40, the second end of the initialization circuit is connected to the second reference voltage line, and the initialization circuit is configured to be turned on before the first stage in each working cycle to initialize the first electrode of the light emitting element 40 to the second reference voltage.

[0074] The initialization of the first electrode of the light emitting element 40 is achieved by the initialization circuit. Specifically, the first electrode of the light emitting element 40 is initialized to the second reference voltage by being turned on before the first stage in each working cycle, i.e. being turned on in the initialization stage before the first stage. It can be understood that, in order to avoid the light emitting element 40 being turned on in the initialization stage, the difference between the second reference voltage and the voltage of the second power supply line is required to be less than the threshold voltage of the light emitting element 40.

[0075] The initialization circuit can also be implemented based on a switch tube in general. For example, in one embodiment of the present application, the initialization circuit includes a fourth switch tube Q4.

[0076] The first end of the fourth switch tube Q4 is the first end of the initialization circuit, and the second end of the fourth switch tube Q4 is the second end of the initialization circuit; the fourth switch tube Q4 is turned on in any one or more of the first stage, the second stage and the third stage.

[0077] Referring to FIG. 2, the first end of the fourth switch tube Q4 is the first end of the initialization circuit, and needs to be connected to the first electrode of the light emitting element 40; the second end of the fourth switch tube Q4 is the second end of the initialization circuit, and is connected to the second reference voltage line. In FIG. 2, the second reference voltage provided by the second reference voltage line is denoted as VAR, and the specific value of VAR can be set as required, but generally is a relatively low voltage value, so that the difference between the second reference voltage and the voltage of the second power supply line is less than the threshold voltage of the light emitting element 40.

[0078] It should be noted that, in the present application, the light emitting control circuit 20 is provided and turned off in the first stage to the third stage, so that no through current flows to the light emitting element 40 in the first stage to the third stage, which is beneficial to improve the contrast of the light emitting element 40. However, in some cases, due to the quality of the device or other convenient reasons, the through current still flows to the light emitting element 40 in the first stage to the third stage. In this embodiment, the fourth switch Q4 is provided, so that when the fourth switch Q4 is turned on in any one or more of the first stage, the second stage and the third stage, the through current flowing to the light emitting diode D1 can be avoided, that is, the black state current of the light emitting diode D1 is too large, and the contrast is improved. It can be understood that, since the fourth stage is a light emitting stage, the fourth switch Q4 needs to be turned off in the fourth stage.

[0079] In one specific embodiment of the present application, in the fourth stage, the light emitting control circuit 20 remains turned on, or the on-duty ratio of the light emitting control circuit 20 meets the current setting value.

[0080] From the above description, it can be seen that in the fourth stage, the output current Ioled provided to the light emitting element 40 is f(Vdata x [(C2 / C1+C2)]), it can be seen that Ioled is controlled by the data voltage Vdata, and in addition to controlling Ioled by Vdata, the size of Ioled can be further controlled by controlling the on-duty ratio of the light emitting control circuit 20 to realize the brightness control of the light emitting element 40. For this, in the fourth stage, the light emitting control circuit 20 can always remain turned on, or can not always remain turned on, but the on-duty ratio is equal to the current setting value, which improves the brightness control flexibility of the present application.

[0081] In one specific embodiment of the present application, referring to FIG. 7, the voltage sampling circuit 10 can further include a third capacitor C3; the first end of the third capacitor C3 is connected with the second end of the second capacitor C2, and the second end of the third capacitor C3 is connected with the first end of the first switch Q1. In one embodiment, the third capacitor C3 can be a parasitic capacitor formed in the circuit layout.

[0082] As can be seen from the above description, the second capacitor C2 provided in the voltage sampling circuit 10 plays a role of voltage division in the third stage, and such a provision is beneficial to improve the range expansion capability of the data voltage Vdata. That is, by means of the series connection of the storage capacitor C1 and the second capacitor C2, the Vdata is divided, so that the difference between the data voltage Vdata required by the maximum brightness (for example, the maximum brightness is 255 gray scale, corresponding to the maximum output current) and the minimum brightness (for example, the minimum brightness is 0 gray scale, corresponding to the minimum output current) is larger, that is, the range of Vdata is large, so that the step between adjacent gray scales is more easily adjusted, thereby reducing the performance requirement of the driving circuit for the output data voltage Vdata.

[0083] The embodiment further takes into account the parasitic capacitance generated in the actual circuit layout, so that the display effect is improved.

[0084] By means of the device connection relationship in the pixel driving circuit, the pixel driving circuit has the ability to compensate the threshold voltage of the driving transistor TD according to the technical solution provided by the embodiment of the present application, so that the current is not affected by the threshold voltage deviation of the driving transistor TD when the light emitting element 40 emits light in the fourth stage, and thus the display uniformity of the pixel array is beneficial to be realized.

[0085] Specifically, the source of the drive transistor TD is connected with the first end of the storage capacitor C1 and the first power supply line; the drain of the drive transistor TD is connected with the gate of the drive transistor TD through the threshold correction circuit 30, and is connected with the first electrode of the light emitting element 40 through the light emitting control circuit 20, and the second electrode of the light emitting element 40 is connected with the second power supply line; the second end of the storage capacitor C1 is connected with the gate; the voltage sampling circuit 10 is connected with the data signal line and the first reference voltage signal line. In the first stage of each working cycle, the voltage sampling circuit 10 is configured to write the first reference voltage transmitted by the first reference voltage signal line to the gate of the drive transistor TD in the first stage of each working cycle, so that the drive transistor TD is turned on. In the second stage, the threshold correction circuit 30 is turned on, and the voltage of the first power supply line charges the lower plate of the storage capacitor C1 through the threshold correction circuit 30 and the drive transistor TD, so that the gate potential of the drive transistor TD is continuously raised, and when the gate-source voltage of the drive transistor TD reaches the threshold voltage, the charging process stops, and the second stage ends, at this time, the voltage of the storage capacitor C1 is the gate-source voltage of the drive transistor TD, that is, the threshold voltage of the drive transistor TD. Therefore, in the second stage, the threshold correction circuit 30 writes the threshold voltage of the drive transistor TD into the storage capacitor C1. In the third stage, the voltage sampling circuit 10 samples the incremental voltage related to the data voltage transmitted by the data signal line to the gate of the drive transistor TD, so as to control the light emitting brightness of the light emitting element 40 in the fourth stage in the working cycle. In the fourth stage, the light emitting control circuit 20 will provide an output current according to the voltage difference between the gate voltage and the source voltage to provide the output current to the light emitting element 40. Since the gate-source voltage difference of the drive transistor TD is fixed as the threshold voltage VTH in the second stage, after writing the data voltage in the third stage, the gate-source voltage difference of the drive transistor TD becomes VTH superimposed with a change amount, which is related to the data voltage transmitted by the data signal line. For example, in the specific example below, at the end of the third stage, the gate-source voltage difference VGS of the drive transistor TD is equal to Vdata x [(C2 / C1+C2)]+VTH. In the fourth stage, based on the current formula Ioled=f(VGS-VTH) in the linear state of the drive transistor TD, the VTH term can be cancelled by substituting the gate-source voltage difference VGS of the drive transistor TD at the end of the third stage, so the output current is not related to the threshold voltage. That is, the output current provided by the drive transistor TD in the fourth stage is not related to the threshold voltage of the drive transistor TD, so that when the light emitting element 40 emits light in the fourth stage, the current is not affected by the threshold voltage deviation of the drive transistor TD, which is beneficial to realize the display uniformity of the pixel array.

[0086] And, in the pixel driving circuit, the voltage sampling circuit 10, the driving transistor TD, the storage capacitor C1, the light emitting control circuit 20, the threshold correction circuit 30 and the light emitting element 40 are arranged, so that the pixel driving circuit has simple structure, high reliability and is conducive to miniaturization. In addition, in the pixel driving circuit, the light emitting control circuit 20 is arranged, and the light emitting control circuit 20 is only turned on in the fourth stage and is turned off in the first stage to the third stage, so that in the first stage to the third stage, no through current flows to the light emitting element 40, and the contrast of the light emitting element 40 is improved.

[0087] Corresponding to the above-mentioned embodiments of the pixel driving circuit, the embodiments of the present application also provide a display device, which can include the pixel driving circuit according to any one of the above-mentioned embodiments.

[0088] It should be noted that the display device further includes a source driver connected to the pixel driving circuit through a data signal line, a first reference voltage source connected to the pixel driving circuit through a first reference voltage line, a scanning circuit connected to the voltage sampling circuit through a scanning line, a first control circuit for controlling the threshold correction circuit to be turned on or turned off, and a second control circuit for controlling the light emitting control circuit to be turned on or turned off.

[0089] In one embodiment, the source driver is configured to provide a fixed voltage to the data signal line in the first stage and the second stage, and provide the data voltage to the data signal line in the third stage.

[0090] The first reference voltage source is configured to provide a first reference voltage to the first reference voltage line in the first stage, and float the first reference voltage line in the second stage. The working modes of the remaining circuits can be mutually corresponding to the description above.

[0091] It should be further noted that in the present application, the relationship terms such as first and second are only used to distinguish one entity or operation from another entity or operation, and do not necessarily require or imply any such actual relationship or order between the entities or operations. Moreover, the terms "include", "contain" or any other variants thereof are intended to cover non-exclusive inclusion, so that the process, method, article or equipment including a series of elements not only includes those elements, but also includes other elements not explicitly listed or inherent to such process, method, article or equipment. Without more limitations, the element defined by the statement "including a" does not exclude the presence of another identical element in the process, method, article or equipment including the element.

[0092] Those skilled in the art can further understand that the units and algorithm steps of each example described in combination with the embodiments disclosed in the present application can be realized in electronic hardware, computer software or a combination of both. In order to clearly illustrate the interchangeability of hardware and software, the components and steps of each example have been described in the above description in general terms. Whether the functions are performed in hardware or software depends on the specific application and design constraints of the technical solution. A person skilled in the art can use different methods to implement the described functions for each specific application, but such implementation should not be considered beyond the scope of the present application. The principles and implementation of the present application are described by applying specific examples. The above description of the examples is only to help understand the technical solutions of the present application and its core ideas. It should be noted that for those skilled in the art, without departing from the principles of the present application, a number of improvements and modifications can be made to the present application, and these improvements and modifications also fall within the scope of protection of the present application.

Claims

1. A pixel driving circuit, characterized by comprising: The display element comprises a voltage sampling circuit, a driving transistor, a storage capacitor, a threshold correction circuit, a light emitting control circuit and a light emitting element. The source of the driving transistor is connected with the first end of the storage capacitor and a first power supply line; the drain of the driving transistor is connected with the gate of the driving transistor through the threshold correction circuit, and the drain is connected with the first electrode of the light emitting element through the light emitting control circuit, the second electrode of the light emitting element is connected with a second power supply line; the second end of the storage capacitor is connected with the gate; the voltage sampling circuit is connected with a data signal line and a first reference voltage signal line, and is configured to write the first reference voltage transmitted by the first reference voltage signal line to the gate of the driving transistor in a first stage of each working cycle, and sample an incremental voltage related to the data voltage transmitted by the data signal line to the gate of the driving transistor in a third stage, so that the gate voltage of the driving transistor at this time is related to the threshold voltage of the driving transistor and the data voltage. The threshold correction circuit is configured to be turned on in the second stage to write the threshold voltage of the driving transistor to the storage capacitor, and is turned off in the third stage and the fourth stage. The driving transistor is configured to provide an output current according to the voltage difference between the gate voltage and the source voltage thereof in the fourth stage; and the light emitting control circuit is configured to be turned on in the fourth stage to provide the output current to the light emitting element.

2. The pixel driving circuit according to claim 1, characterized in that, The voltage sampling circuit comprises a first switch tube and a second capacitor. The first end of the second capacitor is connected with the data signal line, the second end of the second capacitor is connected with the first end of the first switch tube, and the connection end is connected with the first reference voltage signal line, and the second end of the first switch tube is used as an output end of the data writing circuit to connect the gate of the driving transistor.

3. The pixel driving circuit of claim 2, wherein, The voltage sampling circuit further comprises a third capacitor. The first end of the third capacitor is connected with the second end of the second capacitor, and the second end of the third capacitor is connected with the first end of the first switch tube.

4. The pixel driving circuit of claim 1, wherein, The light emitting control circuit comprises a second switch tube. The first end of the second switch tube is used as a first end of the light emitting control circuit to connect the drain of the driving transistor, and the second end of the second switch tube is used as a second end of the light emitting control circuit to connect the first electrode of the light emitting element.

5. The pixel driving circuit of claim 1, wherein, The threshold correction circuit comprises a third switch tube. The first end of the third switch tube is used as a first end of the threshold correction circuit to connect the gate of the driving transistor, and the second end of the third switch tube is used as a second end of the threshold correction circuit to connect the drain of the driving transistor.

6. The pixel driving circuit of claim 1, wherein, Further comprising an initialization circuit, the first end of the initialization circuit is connected with the first electrode of the light emitting element, the second end of the initialization circuit is connected with a second reference voltage line, and the initialization circuit is configured to be turned on before the first stage of each working cycle to initialize the first electrode of the light emitting element to the second reference voltage. The second reference voltage is less than a threshold voltage of the light emitting element.

7. The pixel driving circuit of claim 6, wherein, The initialization circuit includes a fourth switch tube; The first end of the fourth switch tube is the first end of the initialization circuit, and the second end of the fourth switch tube is the second end of the initialization circuit. The fourth switch tube is turned on in any one or more of the first stage, the second stage, and the third stage. 8.The pixel driving circuit of claim 1, wherein, The driving transistor is a PMOS tube, and the light emitting element includes a light emitting diode. The anode of the light emitting diode is the first electrode of the light emitting element, and the cathode of the light emitting diode is the second electrode of the light emitting element.

9. The pixel driving circuit according to any one of claims 1 to 8, characterized by, In the fourth stage, the light emitting control circuit is kept on, or the on time duty cycle of the light emitting control circuit meets the current setting value.

10. A display device, characterized by comprising: The pixel driving circuit includes any one of claims 1 to 9.

11. The display device according to claim 10, wherein The pixel driving circuit is connected with a source driver through the data signal line and connected with a first reference voltage source through the first reference voltage line. The source driver is configured to provide a fixed voltage to the data signal line in the first stage and the second stage, and provide the data voltage to the data signal line in the third stage. The first reference voltage source is configured to provide a first reference voltage to the first reference voltage line in the first stage, and float the first reference voltage line in the second stage.

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