OLED pixel circuits and their driving methods, as well as display panels and display devices

Abstract

This invention discloses an OLED pixel circuit and its driving method, as well as a display panel and display device, including a driving module; a threshold voltage compensation module connected to the control terminal of the driving module at a first node and connected to the input terminal of the driving module at a second node; a data voltage input module connected to the output terminal of the driving module at a third node; and a light-emitting module connected to the output terminal of the driving module. The threshold voltage compensation module is configured to store a superimposed signal of the data voltage provided by the data voltage input module and the threshold voltage of the driving module in the first node during the threshold voltage compensation stage, and to drive the light-emitting module to emit light according to the superimposed signal during the light-emitting stage. This not only solves the problem of uneven display caused by the manufacturing process of the display panel, but also solves the problem of difficult low grayscale adjustment, increasing the optical visual adjustment flexibility of the organic light-emitting diode and making it suitable for mass production.

Description

Technical Field

[0001] This invention relates to the field of display technology, and in particular to an OLED pixel circuit and its driving method, as well as a display panel and display device. Background Technology

[0002] OLED (Organic Light-Emitting Diode) is an emerging flat panel display device. Due to its advantages such as self-illumination, high contrast, and wide color gamut, as well as its simple manufacturing process, low cost, low power consumption, and ease of realizing flexible displays, it has broad application prospects.

[0003] In existing technologies, the luminous intensity of an organic light-emitting diode (OLED) is determined by the data voltage VDATA, the power supply voltage VDD, and the threshold voltage Vth of the thin-film transistor. Due to manufacturing process factors, the threshold voltage Vth of thin-film transistors fabricated on a large-area glass substrate varies, resulting in differences in brightness between adjacent pixels even when the same data voltage VDATA is input.

[0004] Existing technologies address the aforementioned issues by compensating for the threshold voltage Vth of organic light-emitting diodes (OLEDs). However, since the voltage range of the data voltage VDATA is typically small, this results in a sharp reduction in the number of bits that can be effectively displayed, making source driver design difficult. Consequently, the flexibility of optical tuning and visual effects is low, which may even affect mass production. Furthermore, optical tuning is difficult at low grayscale levels, requiring complex optical compensation (BC dimming or PWM dimming), which increases development time and difficulty.

[0005] A new OLED pixel circuit needs to be proposed to solve the above problems. Summary of the Invention

[0006] In view of the above problems, the purpose of the present invention is to provide an OLED pixel circuit and its driving method, as well as a display panel and display device, thereby solving the problem of uneven display brightness of the display panel caused by the manufacturing process.

[0007] According to one aspect of the present invention, an OLED pixel circuit is provided, comprising a driving module; a threshold voltage compensation module connected to a control terminal of the driving module at a first node and connected to an input terminal of the driving module at a second node; a data voltage input module connected to an output terminal of the driving module at a third node; and a light-emitting module connected to the output terminal of the driving module, wherein the threshold voltage compensation module is configured to store a superimposed signal of a data voltage provided by the data voltage input module and a threshold voltage of the driving module at the first node during a threshold voltage compensation phase, and the driving module drives the light-emitting module to emit light according to the superimposed signal during a light-emitting phase.

[0008] Optionally, the pixel circuit further includes a reset phase prior to the threshold voltage compensation phase, wherein the threshold voltage compensation module is configured to precharge the first node according to a first voltage signal during the reset phase to enable the driving module.

[0009] Optionally, the data voltage input module includes a fourth thin-film transistor, whose control terminal receives a first scan signal, its first conducting terminal receives the data voltage, and its second conducting terminal is connected to the third node.

[0010] Optionally, the driving module includes a third thin-film transistor, wherein the control terminal of the third thin-film transistor is connected to the first node, the first conducting terminal is connected to the second node, and the second conducting terminal is connected to the third node.

[0011] Optionally, the threshold voltage compensation module includes a first thin-film transistor, whose control terminal receives a light emission signal, its first conducting terminal receives the first voltage signal, and its second conducting terminal is connected to the second node; a second thin-film transistor, whose control terminal receives a second scan signal, its first conducting terminal is connected to the second node, and its second conducting terminal is connected to the first node; and a storage capacitor, one end of which is connected to the first node and the other end is grounded.

[0012] Optionally, the light-emitting module includes an organic light-emitting diode (OLED), the anode of which is connected to the third node, and the cathode receives a second voltage signal.

[0013] Optionally, the pixel circuit is configured to, during the reset phase, turn on the first thin-film transistor and the second thin-film transistor, with the first thin-film transistor transmitting the first voltage signal to the first node through the second thin-film transistor to pre-charge the first node, and turning on the third thin-film transistor when the voltage value of the first node is greater than the threshold voltage of the third thin-film transistor, until the voltage value of the first node is equal to the first voltage signal; during the threshold voltage compensation phase, turn on the second thin-film transistor and the fourth thin-film transistor, with the fourth thin-film transistor inputting the data voltage to the second conducting terminal of the third thin-film transistor, and the first node begins to discharge until the voltage value of the first node is equal to the superimposed signal; during the light emission phase, turn on the first thin-film transistor, and the third thin-film transistor drives the organic light-emitting diode to emit light according to the superimposed signal.

[0014] Optionally, the pixel circuit further includes a fifth thin-film transistor, the first conducting terminal of which is connected to the second node, the second conducting terminal of which is connected to the first conducting terminal of the third thin-film transistor, the control terminal receiving a third scan signal, and the fifth thin-film transistor being turned off during the reset phase.

[0015] Optionally, the pixel circuit further includes a fifth thin-film transistor, wherein a first conducting terminal of the fifth thin-film transistor is connected to the third node, a second conducting terminal is connected to the anode of the organic light-emitting diode, a control terminal receives a third scan signal, and the fifth thin-film transistor is turned off during the reset phase and the threshold voltage compensation phase.

[0016] According to another aspect of the present invention, a display panel is provided, comprising a plurality of OLED pixel circuits as described above.

[0017] According to another aspect of the present invention, a display device is provided, comprising a display panel as described above.

[0018] According to another aspect of the present invention, a driving method for an OLED pixel circuit includes a reset phase in which a first thin-film transistor and a second thin-film transistor are turned on, and the first thin-film transistor transmits a first voltage signal to a first node through the second thin-film transistor to precharge the first node. The third thin-film transistor is turned on when the voltage value of the first node is greater than the threshold voltage of the third thin-film transistor, until the voltage value of the first node equals the first voltage signal. A threshold voltage compensation phase in which the second thin-film transistor and a fourth thin-film transistor are turned on, and the fourth thin-film transistor inputs a data voltage to the second on terminal of the third thin-film transistor, causing the first node to discharge, until the voltage value of the first node equals the superimposed signal of the data voltage and the threshold voltage of the third thin-film transistor. A light-emitting phase in which the first thin-film transistor is turned on, and the third thin-film transistor drives an organic light-emitting diode to emit light according to the superimposed signal.

[0019] The OLED pixel circuit and its driving method, as well as the display panel and display device provided in this embodiment of the invention, have a threshold voltage compensation module configured to store the superimposed signal of the data voltage provided by the data voltage input module and the threshold voltage of the driving module in a first node during the threshold voltage compensation stage, and to drive the light-emitting module to emit light according to the superimposed signal during the light-emitting stage, so that the voltage applied to the anode of the organic light-emitting diode is always equal to the data voltage, thus solving the problem of uneven display caused by the manufacturing process of the display panel; the data voltage is input to the second conducting terminal of the third thin film transistor through the fourth thin film transistor, so that the voltage range of the input data voltage is larger, and the voltage range of the corresponding organic light-emitting diode is larger, thereby solving the problem of difficult low grayscale adjustment, suitable for mass production, and increasing the optical visual adjustment flexibility of the organic light-emitting diode.

[0020] In a preferred embodiment, by placing a fifth thin-film transistor between the second node and the anode of the organic light-emitting diode, the current flowing through the organic light-emitting diode during the reset phase is blocked, thereby solving the problem of the organic light-emitting diode emitting light briefly during the reset phase, so that the OLED pixel circuit can be used in both high brightness mode and high contrast mode. Attached Figure Description

[0021] The above and other objects, features and advantages of the present invention will become more apparent from the following description of embodiments of the invention with reference to the accompanying drawings, in which:

[0022] Figure 1 A circuit connection diagram of an OLED pixel circuit according to a first embodiment of the present invention is shown;

[0023] Figure 2 A signal timing diagram of an OLED pixel circuit according to a first embodiment of the present invention is shown;

[0024] Figure 3 A circuit connection diagram of an OLED pixel circuit according to a second embodiment of the present invention is shown;

[0025] Figure 4 A signal timing diagram of an OLED pixel circuit according to a second embodiment of the present invention is shown;

[0026] Figure 5 A circuit connection diagram of an OLED pixel circuit according to a third embodiment of the present invention is shown;

[0027] Figure 6 A signal timing diagram of an OLED pixel circuit according to a third embodiment of the present invention is shown. Detailed Implementation

[0028] Various embodiments of the invention will now be described in more detail with reference to the accompanying drawings. In the various drawings, the same elements or modules are indicated by the same or similar reference numerals. For clarity, the various parts in the drawings are not drawn to scale.

[0029] It should be understood that, in the following description, "circuit" may include single or combined hardware circuits, programmable circuits, state machine circuits, and / or elements capable of storing instructions executed by the programmable circuit. When an element or circuit is said to be "connected" to another element or "connected" between two nodes, it may be directly coupled or connected to the other element, or there may be intermediate elements; the connection between elements may be physical, logical, or a combination thereof. Conversely, when an element is said to be "directly coupled to" or "directly connected" to another element, it means that there are no intermediate elements between them.

[0030] Furthermore, it should be noted that in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Moreover, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Without further limitations, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0031] Figure 1 A circuit connection diagram of an OLED pixel circuit according to a first embodiment of the present invention is shown, as follows: Figure 1The OLED pixel circuit shown includes a data voltage input module 10, a threshold voltage compensation module 20, a driving module 30, and a light-emitting module 40.

[0032] The output terminals of the data voltage input module 10 and the drive module 30 are connected to node C to receive the scan signal G1 and the data voltage VDATA, and control the data voltage VDATA to be input to node C according to the scan signal G1.

[0033] The threshold voltage compensation module 20 is grounded and connected to the control terminal of the drive module 30 at node A and to the input terminal of the drive module 30 at node B. It is used to receive the light emission signal EM, the first voltage signal ELVDD (emission layer VDD) and the scan signal G2.

[0034] One end of the light-emitting module 40 is connected to the output end of the driving module 30 at node C, and the other end receives the second voltage signal ELVSS (emission layer VSS).

[0035] During the reset phase, the threshold voltage compensation module 20 precharges node A according to the first voltage signal ELVDD to enable the drive module 30.

[0036] During the threshold voltage compensation phase, node A begins to discharge until the voltage Va of node A equals the superposition signal of the data voltage VDATA provided by the data voltage input module 10 and the threshold voltage VTH1 of the drive module 30.

[0037] During the light-emitting stage, the driving module 30 drives the light-emitting module 40 to emit light according to the superimposed signal.

[0038] like Figure 1 As shown, the data voltage input module 10 includes a fourth thin-film transistor T4. The control terminal of the fourth thin-film transistor T4 receives the scan signal G1, the first conducting terminal receives the data voltage VDATA, and the second conducting terminal is connected to node C.

[0039] The threshold voltage compensation module 20 includes a first thin-film transistor T1, a second thin-film transistor T2, and a storage capacitor Cs. The control terminal of the first thin-film transistor T1 receives a light emission signal EM, the first conducting terminal receives a first voltage signal ELVDD, and the second conducting terminal is connected to the first conducting terminal of the second thin-film transistor T2 at node B. The control terminal of the second thin-film transistor T2 receives a scan signal G2, and the second conducting terminal is connected to one end of the storage capacitor Cs at node A. The other end of the storage capacitor Cs is grounded.

[0040] The driving module 30 includes a third thin-film transistor T3, which is a driving transistor. The control terminal of the third thin-film transistor T3 is connected to node A, which is the connection point between the second conducting terminal of the second thin-film transistor T2 and one end of the storage capacitor Cs. The first conducting terminal of the third thin-film transistor T3 is connected to node B, which is the connection point between the second conducting terminals of the first thin-film transistor T1 and the first conducting terminals of the second thin-film transistor T2. The second conducting terminal of the third thin-film transistor T3 is connected to node C, which is the connection point between the second conducting terminal of the fourth thin-film transistor T4 and the anode of the organic light-emitting diode (OLED). The data voltage VDATA is received through the second conducting terminal of the third thin-film transistor T3, allowing for a wider input range of the data voltage VDATA. This results in better visual adjustment performance of the OLED at low grayscale levels, superior to current-driven adjustment, making it suitable for mass production.

[0041] The light-emitting module 40 includes an organic light-emitting diode (OLED), the anode of which is connected to node C, and the cathode receives the second voltage signal ELVSS.

[0042] Furthermore, the voltage value of the first voltage signal ELVDD is greater than the voltage value of the data voltage VDATA.

[0043] Furthermore, during the light-emitting stage, the voltage Vc of node C is always equal to the data voltage VDATA, that is, the voltage of the anode of the organic light-emitting diode OLED is always equal to the data voltage VDATA, so that the voltage difference between the anode and cathode of the organic light-emitting diode OLED is always equal to the voltage difference between the data voltage VDATA and the second voltage signal ELVSS. Therefore, the organic light-emitting diode OLED can be voltage driven.

[0044] Furthermore, the first thin-film transistor T1, the second thin-film transistor T2, the third thin-film transistor T3, and the fourth thin-film transistor T4 are all NMOS transistors, which are turned on in the high-level state and turned off in the low-level state. The first conducting terminal of the first thin-film transistor T1, the second thin-film transistor T2, the third thin-film transistor T3, and the fourth thin-film transistor T4 can be the source, and the second conducting terminal can be the drain, or vice versa.

[0045] Figure 2 A signal timing diagram of an OLED pixel circuit according to a first embodiment of the present invention is shown.

[0046] This invention also provides a driving method for an OLED pixel circuit, applied to the OLED pixel circuit described above, which is described below in conjunction with... Figure 2 The driving method specifically includes a reset phase, a threshold voltage compensation phase, and a light emission phase.

[0047] During the reset phase, i.e., phase t1, the scan signal G1 is set to low level, the scan signal G2 is set to high level, and the light emission signal EM is set to high level. At this time, the first thin-film transistor T1 and the second thin-film transistor T2 are turned on. The first conducting terminal of the first thin-film transistor T1 receives the first voltage signal ELVDD and transmits the first voltage signal ELVDD to node A through the second thin-film transistor T2, thereby pre-charging node A, i.e., pre-charging the storage capacitor Cs, until the voltage Va of node A is equal to the first voltage signal ELVDD. When the voltage Va of node A is greater than the threshold voltage VTH1 of the third thin-film transistor T3, the third thin-film transistor T3 is turned on. At this time, current flows through the third thin-film transistor T3 and through the organic light-emitting diode (OLED), causing the OLED to emit light briefly. Since the light emission time is relatively short, the impact on the display effect is negligible when the OLED pixel circuit is in high-brightness mode, but the impact on the display effect is relatively large when the OLED pixel circuit is in high-contrast mode.

[0048] During the threshold voltage compensation stage, i.e., stage t2, both scan signals G1 and G2 are set to high level, and the light emission signal EM is set to low level. At this time, the first thin-film transistor T1 is turned off, and the second thin-film transistor T2, the third thin-film transistor T3, and the fourth thin-film transistor T4 are turned on. The fourth thin-film transistor T4 transmits the data voltage VDATA to the second conducting terminal of the third thin-film transistor T3. Node A begins to discharge through the second thin-film transistor T2 until the voltage Va of node A is equal to the superposition signal of the data voltage VDATA and the threshold voltage VTH1 of the third thin-film transistor T3.

[0049] During the light-emitting stage, i.e., stage t3, scanning signals G1 and G2 are set to low level, and the light-emitting signal EM is set to high level. The voltage of node A is maintained at Va = VDATA + VTH1. At this time, the second thin-film transistor T2 and the fourth thin-film transistor T4 are turned off, and the first thin-film transistor T1 and the third thin-film transistor T3 are turned on. The first conducting terminal of the third thin-film transistor T3 receives the first voltage signal ELVDD through the first thin-film transistor T1. The voltage of node C is Vc = Va - VTH1 = VDATA. The third thin-film transistor T3 drives the organic light-emitting diode OLED to emit light according to the superimposed signal.

[0050] Furthermore, the timing of the OLED pixel circuit in stages t1, t2, and t3 can be set according to the actual situation.

[0051] According to the formula, the voltage Vc applied to the anode of the OLED, i.e., the voltage at node C, is equal to the data voltage VDATA. The voltage across the anode and cathode of the OLED is equal to the difference between the data voltage VDATA and the second voltage signal ELVSS, and is independent of the threshold voltage VTH1 of the third thin-film transistor T3. This solves the problem of the difference in the distribution of the threshold voltage VTH1 of the driving transistor caused by the manufacturing process, improves the display effect of the display panel, and because the input data voltage VDATA has a large voltage range, the voltage across the anode and cathode of the OLED is also large, which makes the visual adjustment of the OLED highly flexible.

[0052] According to the OLED pixel circuit provided in the embodiment of the present invention, the threshold voltage compensation module 20 is configured to store the superimposed signal of the data voltage VDATA provided by the data voltage input module 10 and the threshold voltage VTH of the driving module 30 in node A during the threshold voltage compensation stage, and to drive the light-emitting module 40 to emit light according to the superimposed signal during the light-emitting stage, so that the voltage applied to the anode of the organic light-emitting diode OLED is always equal to the data voltage VDATA, thus solving the problem of uneven display caused by the manufacturing process of the display panel; the data voltage VDATA is input to the second conducting terminal of the third thin film transistor T3 through the fourth thin film transistor T4, so that the voltage value range of the input data voltage VDATA is larger, and the voltage range of the organic light-emitting diode OLED is larger, thereby solving the problem of difficult low grayscale adjustment, suitable for mass production, and increasing the optical visual adjustment flexibility of the organic light-emitting diode OLED.

[0053] Figure 3 A circuit connection diagram of an OLED pixel circuit according to a second embodiment of the present invention is shown.

[0054] The OLED pixel circuit of the second embodiment of the present invention has a basically the same structure as the OLED pixel circuit of the first embodiment of the present invention. The following only describes the differences between the two.

[0055] The OLED pixel circuit also includes a fifth thin-film transistor T5. The first conducting terminal of the fifth thin-film transistor T5 is connected to node B, and the second conducting terminal is connected to the first conducting terminal of the third thin-film transistor T3. The control terminal receives the scan signal G3. The fifth thin-film transistor T5 is, for example, an NMOS transistor.

[0056] Figure 4 A signal timing diagram of an OLED pixel circuit according to a second embodiment of the present invention is shown.

[0057] like Figure 4As shown, the timing of scanning signal G1, scanning signal G2, and light emission signal EM in the second embodiment is the same as that in the first embodiment, and therefore will not be repeated. The following only uses the timing of scanning signal G3 in the three stages to illustrate the difference between the second embodiment and the first embodiment of the present invention.

[0058] During the reset phase (t1), the scanning signal G3 is at a low level, and the fifth thin-film transistor T5 is turned off, thereby blocking the current flowing through the organic light-emitting diode (OLED) during the reset phase. This allows the OLED pixel circuit provided in this embodiment of the invention to be applicable to both high-brightness mode and high-contrast mode.

[0059] The scanning signal G3 is at a high level during the threshold voltage compensation stage, i.e., stage t2, and the fifth thin-film transistor T5 is turned on, allowing the data voltage VDATA to be input normally.

[0060] The scanning signal G3 is at a high level during the light emission stage, i.e., stage t3. The fifth thin-film transistor T5 is turned on, and the current flows normally through the organic light-emitting diode (OLED) to make the OLED emit light.

[0061] Figure 5 A circuit connection diagram of an OLED pixel circuit according to a third embodiment of the present invention is shown.

[0062] The OLED pixel circuit of the third embodiment of the present invention has a basically the same structure as the OLED pixel circuit of the first embodiment of the present invention. The following only describes the differences between the two.

[0063] The OLED pixel circuit also includes a fifth thin-film transistor T5. The first conducting terminal of the fifth thin-film transistor T5 is connected to node C, the second conducting terminal is connected to the anode of the organic light-emitting diode OLED, and the control terminal receives the third scan signal G3.

[0064] Figure 6 A signal timing diagram of an OLED pixel circuit according to a third embodiment of the present invention is shown.

[0065] like Figure 6 As shown, the timing of scanning signal G1, scanning signal G2, and light emission signal EM in the second embodiment is the same as that in the first embodiment, and therefore will not be repeated. The following only uses the timing of scanning signal G3 in the three stages to illustrate the difference between the third embodiment and the first embodiment of the present invention.

[0066] The scanning signal G3 is at a low level during the reset phase (t1) and the threshold voltage compensation phase (t2), and the fifth thin-film transistor T5 is turned off, thereby blocking the current flowing through the organic light-emitting diode (OLED) during the reset phase and the threshold voltage compensation phase. This allows the OLED pixel circuit provided in this embodiment of the invention to be applicable to both high brightness mode and high contrast mode.

[0067] The scanning signal G3 is at a high level during the light emission stage, i.e., stage t3. The fifth thin-film transistor T5 is turned on, and the current flows normally through the organic light-emitting diode (OLED) to make the OLED emit light.

[0068] According to the second and third embodiments of the present invention, the OLED pixel circuit provides that by setting a fifth thin-film transistor T5 between the second node B and the anode of the organic light-emitting diode (OLED), the current flowing through the organic light-emitting diode (OLED) during the reset phase is blocked, thereby solving the problem of the organic light-emitting diode (OLED) emitting light briefly during the reset phase, so that the OLED pixel circuit can be used in both high brightness mode and high contrast mode.

[0069] This invention also provides a display panel, including a plurality of OLED pixel circuits arranged in an array as described above.

[0070] This invention also provides a display device, including the display panel as described above.

[0071] As described above, these embodiments of the present invention do not exhaustively describe all details, nor do they limit the invention to specific embodiments. Clearly, many modifications and variations can be made based on the above description. This specification selects and specifically describes these embodiments to better explain the principles and practical applications of the invention, thereby enabling those skilled in the art to effectively utilize the invention and its modifications. The scope of protection of this invention should be determined by the scope defined in the claims and their equivalents.

Claims

1. An OLED pixel circuit, comprising: Driver module; A threshold voltage compensation module is connected to the control terminal of the drive module at a first node and to the input terminal of the drive module at a second node. The data voltage input module is connected to the output of the drive module at the third node; as well as The light-emitting module is connected to the output terminal of the driving module. The driving module includes a third thin-film transistor. The threshold voltage compensation module is configured to store a superimposed signal of the data voltage provided by the data voltage input module and the threshold voltage of the third thin-film transistor in the first node during the threshold voltage compensation stage, and to drive the light-emitting module to emit light according to the superimposed signal during the light-emitting stage. The data voltage input module includes a fourth thin-film transistor, whose control terminal receives a first scan signal, its first conduction terminal receives the data voltage, and its second conduction terminal is connected to the third node. The threshold voltage compensation module includes a second thin-film transistor, whose control terminal receives a second scan signal, a first conducting terminal connected to the second node, and a second conducting terminal connected to the first node; as well as The storage capacitor has one end connected to the first node and the other end grounded.

2. The OLED pixel circuit according to claim 1, wherein, The pixel circuit also includes a reset phase prior to the threshold voltage compensation phase. The threshold voltage compensation module is configured to precharge the first node according to a first voltage signal during the reset phase to enable the driving module.

3. The OLED pixel circuit according to claim 2, wherein, The control terminal of the third thin-film transistor is connected to the first node, the first conducting terminal is connected to the second node, and the second conducting terminal is connected to the third node.

4. The OLED pixel circuit according to claim 3, wherein, The threshold voltage compensation module further includes: The first thin-film transistor has a control terminal that receives a light-emitting signal, a first conduction terminal that receives the first voltage signal, and a second conduction terminal that is connected to the second node.

5. The OLED pixel circuit according to claim 4, wherein, The light-emitting module includes an organic light-emitting diode (OLED), the anode of which is connected to the third node, and the cathode receives a second voltage signal.

6. The OLED pixel circuit according to claim 5, wherein, The pixel circuit is configured to, during the reset phase, turn on the first thin-film transistor and the second thin-film transistor, so that the first thin-film transistor transmits the first voltage signal to the first node through the second thin-film transistor to precharge the first node, and turn on the third thin-film transistor when the voltage value of the first node is greater than the threshold voltage of the third thin-film transistor, until the voltage value of the first node is equal to the first voltage signal. During the threshold voltage compensation phase, the second thin-film transistor and the fourth thin-film transistor are turned on, and the data voltage is input to the second on terminal of the third thin-film transistor by the fourth thin-film transistor. The first node begins to discharge until the voltage value of the first node is equal to the superimposed signal. During the light-emitting phase, the first thin-film transistor is turned on, and the third thin-film transistor drives the organic light-emitting diode to emit light according to the superimposed signal.

7. The OLED pixel circuit according to claim 6, wherein, The pixel circuit also includes: The fifth thin-film transistor has its first conducting terminal connected to the second node, its second conducting terminal connected to the first conducting terminal of the third thin-film transistor, and its control terminal receiving a third scan signal. The fifth thin-film transistor is turned off during the reset phase.

8. The OLED pixel circuit according to claim 6, wherein, The pixel circuit also includes: The fifth thin-film transistor has a first conducting terminal connected to the third node, a second conducting terminal connected to the anode of the organic light-emitting diode, and a control terminal receiving a third scan signal. The fifth thin-film transistor is turned off during the reset phase and the threshold voltage compensation phase.

9. A display panel comprising a plurality of OLED pixel circuits as described in any one of claims 1-8.

10. A display device comprising the display panel as claimed in claim 9.

11. A driving method for driving an OLED pixel circuit as described in any one of claims 1-8, comprising: During the reset phase, the first thin-film transistor and the second thin-film transistor are turned on. The first thin-film transistor transmits a first voltage signal to the first node through the second thin-film transistor to precharge the first node. When the voltage value of the first node is greater than the threshold voltage of the third thin-film transistor, the third thin-film transistor is turned on until the voltage value of the first node is equal to the first voltage signal. During the threshold voltage compensation phase, the second and fourth thin-film transistors are turned on, and the data voltage is input to the second on terminal of the third thin-film transistor by the fourth thin-film transistor. The first node begins to discharge until the voltage value of the first node is equal to the superposition signal of the data voltage and the threshold voltage of the third thin-film transistor. During the light-emitting phase, the first thin-film transistor is turned on, and the third thin-film transistor drives the organic light-emitting diode to emit light according to the superimposed signal.

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