Pixel circuit and organic light emitting display device

Abstract

The present application provides a pixel circuit and an organic light-emitting display device, wherein the pixel circuit includes: a first transistor to a seventh transistor, a storage capacitor, and an organic light-emitting diode; wherein the first end of the sixth transistor is connected to the first initialization signal line, and the second end thereof is connected to the second node, and the first end of the seventh transistor is connected to the second initialization signal line, and the second end thereof is connected to the anode of the organic light-emitting diode. In the pixel circuit and the organic light-emitting display device provided by the present application, a pixel circuit with a dual initialization signal line design is used to initialize the gate of the driving transistor and the anode of the organic light-emitting diode respectively through two initialization signal lines, thereby reducing the source-drain voltage difference of the sixth transistor, thereby reducing the leakage current of the sixth transistor, and improving the problem of flickering of the display screen of the organic light-emitting display device under low-frequency driving.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a pixel circuit and an organic light-emitting display device. Background Art

[0002] Compared with many display devices, organic light emitting display devices (OLED) have many advantages such as full solid state, self-luminescence, wide viewing angle, wide color gamut, fast response speed, high luminous efficiency, high brightness, high contrast, ultra-thin and ultra-light, low power consumption, wide operating temperature range, ability to produce large-size and flexible panels and simple process. It can realize truly flexible display and best meet people's requirements for future displays.

[0003] Display devices use different refresh rates in different application scenarios. For example, a higher refresh rate drive method is used to display dynamic images to ensure the smoothness of the displayed images; a lower refresh rate drive method is used to display static images to reduce power consumption. In actual use, it is found that when organic light-emitting display devices are displayed at a low refresh rate, flickering will occur, affecting the visual effect. Moreover, the greater the ambient light intensity, the more severe the flickering phenomenon. Summary of the invention

[0004] In view of this, the present application provides a pixel circuit and an organic light emitting display device to solve the problem of flickering of display images of the organic light emitting display device in the prior art under low-frequency driving.

[0005] In order to solve the above technical problem, the present invention provides a pixel circuit, the pixel circuit comprising:

[0006] an organic light emitting diode, connected between the first power source and the second power source;

[0007] A first transistor, a first end of which is connected to the data line, a second end of which is connected to the first node, and a control end of which is connected to the second scan line;

[0008] a second transistor, a first terminal of which is connected to the first node, a second terminal of which is connected to the third node, and a control terminal of which is connected to the second node;

[0009] a third transistor, a first terminal of which is connected to the second node, a second terminal of which is connected to the third node, and a control terminal of which is connected to the second scan line;

[0010] a fourth transistor, a first terminal of which is connected to the first power source, a second terminal of which is connected to the first node, and a control terminal of which is connected to the emission control line;

[0011] a fifth transistor, a first terminal of which is connected to the third node, a second terminal of which is connected to the anode of the organic light emitting diode, and a control terminal of which is connected to the emission control line;

[0012] a sixth transistor, a first end of which is connected to the first initialization signal line, a second end of which is connected to the second node, and a control end of which is connected to the first scan line;

[0013] a seventh transistor, a first end of which is connected to the second initialization signal line, a second end of which is connected to the anode of the organic light emitting diode, and a control end of which is connected to the third scan line;

[0014] A storage capacitor is connected between the first power source and the second node.

[0015] Optionally, in the pixel circuit, the cathode of the organic light emitting diode is connected to the second power supply, the first power supply and the second power supply are used as driving power supplies for the organic light emitting diode, the first power supply is used to provide a first power supply voltage, and the second power supply is used to provide a second power supply voltage;

[0016] The first initialization signal line is used to transmit a first initialization signal, and the first initialization signal is used to initialize the gate voltage of the second transistor;

[0017] The second initialization signal line is used to transmit a second initialization signal, and the second initialization signal is used to initialize the anode voltage of the organic light emitting diode.

[0018] Optionally, in the pixel circuit, the voltage range of the first initialization signal is between -2V and 0V; or

[0019] The voltage of the first initialization signal is dynamically adjusted according to display brightness, so that the leakage current of the sixth transistor is minimized.

[0020] Optionally, in the pixel circuit, the voltage of the second initialization signal is less than or equal to the second power supply voltage provided by the second power supply.

[0021] Optionally, in the pixel circuit, the first initialization signal line and the second initialization signal line are both connected to an external driving chip, the driving chip has a first initialization signal terminal and a second initialization signal terminal, the first initialization signal line is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, and the second initialization signal line is connected to the second initialization signal terminal, the second initialization signal terminal is used to output the second initialization signal.

[0022] Optionally, in the pixel circuit, the voltage range of the second initialization signal is between -4.5V and -3V.

[0023] Optionally, in the pixel circuit, the first initialization signal line and the second initialization signal line are both connected to an external driving chip, the driving chip having a first initialization signal terminal and a low-level signal terminal, the first initialization signal line is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line is connected to the low-level signal terminal, the low-level signal terminal is used to output a low-level signal, and the second initialization signal transmitted by the second initialization signal line is the low-level signal.

[0024] Optionally, in the pixel circuit, the voltage range of the low-level signal is between -6.5V and -5.5V.

[0025] Optionally, in the pixel circuit, the first initialization signal line is connected to an external driving chip, the driving chip has a first initialization signal terminal, the first initialization signal line is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line is connected to the third scan line, and the second initialization signal transmitted by the second initialization signal line is a third scan line signal.

[0026] Optionally, in the pixel circuit, the second scan line signal is an AC signal, a low-state voltage of the AC signal is between -6.5V and -5.5V, and a high-state voltage of the AC signal is between 4V and 6V.

[0027] Correspondingly, the present invention further provides an organic light-emitting display device, which includes the pixel circuit as described above.

[0028] Optionally, the organic light emitting display device further includes: a substrate and a signal line;

[0029] The pixel circuit and the signal line are both formed on the base substrate, and the signal line is electrically connected to the pixel circuit;

[0030] In the pixel circuit, the orthographic projection of the anode of the organic light emitting diode on the base substrate covers the orthographic projections of the second transistor and the sixth transistor on the base substrate; or

[0031] The orthographic projection of the signal line on the substrate covers the orthographic projections of the second transistor and the sixth transistor on the substrate.

[0032] Optionally, in the organic light emitting display device, the signal line is a data line or a second scan line.

[0033] In the pixel circuit and organic light-emitting display device provided by the present invention, a pixel circuit with a dual initialization signal line design is used, and the gate of the driving transistor and the anode of the organic light-emitting diode are initialized respectively through two initialization signal lines, thereby reducing the source-drain voltage difference of the sixth transistor, and then reducing the leakage current of the sixth transistor, thereby improving the problem of flickering of the display screen of the organic light-emitting display device under low-frequency driving. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] The drawings herein are incorporated into the specification and constitute a part of the specification, illustrate embodiments consistent with the present application, and together with the specification are used to explain the principles of the present application. Obviously, the drawings described below are only some embodiments of the present application, and for ordinary technicians in this field, other drawings can be obtained based on these drawings without creative work.

[0035] Figure 1 is an equivalent circuit diagram of a pixel circuit according to the first embodiment of the present invention;

[0036] Figure 2 It is a statistical graph of FMA measurement results under different reset voltages;

[0037] Figure 3 This is the schematic diagram of FMA measurement;

[0038] Figure 4 is an equivalent circuit diagram of a pixel circuit according to a second embodiment of the present invention;

[0039] Figure 5 is an equivalent circuit diagram of a pixel circuit according to the third embodiment of the present invention. DETAILED DESCRIPTION

[0040] Example embodiments will now be described more fully with reference to the accompanying drawings. However, example embodiments can be implemented in a variety of forms and should not be construed as limited to the embodiments set forth herein. Instead, these embodiments are provided so that this application will be comprehensive and complete and fully convey the concepts of the example embodiments to those skilled in the art. The same reference numerals in the figures represent the same or similar structures, and thus their repeated description will be omitted.

[0041] [Example 1]

[0042] Please refer to Figure 1 , which is a schematic diagram of the structure of the pixel circuit of the first embodiment of the present invention. Figure 1As shown, the pixel circuit 10 includes: an organic light emitting diode OLED, connected between a first power source ELVDD and a second power source ELVSS; a first transistor T1, a first end of which is connected to a data line DTAT, a second end of which is connected to a first node N1, and a control end of which is connected to a second scan line Sn; a second transistor T2, a first end of which is connected to the first node N1, a second end of which is connected to a third node N3, and a control end of which is connected to a second node N2; a third transistor T3, a first end of which is connected to the second node N2, a second end of which is connected to the third node N3, and a control end of which is connected to a second scan line Sn; a fourth transistor T4, a first end of which is connected to the first power source ELVDD, and a second end of which is connected to the first node N1. N1 is connected, and its control end is connected to the emission control line EM; a fifth transistor T5, a first end of which is connected to the third node N3, a second end of which is connected to the anode of the organic light emitting diode OLED, and a control end of which is connected to the emission control line EM; a sixth transistor T6, a first end of which is connected to the first initialization signal line Vint1, a second end of which is connected to the second node N2, and a control end of which is connected to the first scan line Sn-1; a seventh transistor T7, a first end of which is connected to the second initialization signal line Vint2, a second end of which is connected to the anode of the organic light emitting diode OLED, and a control end of which is connected to the third scan line Sn+1; a storage capacitor Cs is connected between the first power supply ELVDD and the second node N2.

[0043] Specifically, the pixel circuit 10 is a 7T1C circuit structure, including 7 transistors (ie, a first transistor T1 to a seventh transistor T7 ), a storage capacitor Cs, and an organic light emitting diode OLED.

[0044] The organic light emitting diode OLED is connected between the first power supply ELVDD and the second power supply ELVSS, the first power supply ELVDD is used to provide a first power supply voltage (high level), the second power supply ELVSS is used to provide a second power supply voltage (low level), the first power supply ELVDD and the second power supply ELVSS are used as driving power supplies for the organic light emitting diode OLED, the organic light emitting diode OLED includes an anode and a cathode, the anode of the organic light emitting diode OLED is connected to the second end of the fifth transistor T5 and the second end of the seventh transistor T7, the cathode of the organic light emitting diode OLED is connected to the second power supply ELVSS, and the organic light emitting diode OLED emits light of corresponding brightness according to the driving current flowing therethrough.

[0045] The first end of the first transistor T1 is connected to the data line DATA, and the data line DATA is used to load the data signal. The control end of the first transistor T1 and the control end of the third transistor T3 are both connected to the second scan line Sn, and the control end of the seventh transistor T7 is connected to the third scan line Sn+1, the second scan line Sn is used to provide a second scan signal, and the third scan line Sn+1 is used to provide a third scan signal. The control end of the sixth transistor T6 is connected to the first scan line Sn-1, and the first scan line Sn-1 is used to provide a first scan signal. The control end of the fourth transistor T4 and the control end of the fifth transistor T5 are both connected to the emission control line EM, and the emission control line EM is used to provide a light emission control signal. The first end of the sixth transistor T6 is connected to the first initialization signal line Vint1, and the first initialization signal line Vint1 is used to transmit a first initialization signal, and the first initialization signal is used to initialize the second node N2, that is, to reset the gate voltage of the second transistor T2. The first end of the seventh transistor T7 is connected to a second initialization signal line Vint2 , where the second initialization signal line Vint2 is used to transmit a second initialization signal, and the second initialization signal is used to initialize the anode of the organic light emitting diode OLED.

[0046] In this embodiment, the control end of the seventh transistor T7 is connected to the third scan line Sn+1, and the pixel circuit 10 is connected to three scan lines (i.e., the first scan line Sn-1, the second scan line Sn, and the third scan line Sn+1). Among them, the first scan line Sn-1 corresponding to the n-th row of pixel circuits and the second scan line Sn corresponding to the n-1-th row of pixel circuits are the same scan line, the second scan line Sn corresponding to the n-th row of pixel circuits and the third scan line Sn+1 corresponding to the n-1-th row of pixel circuits are the same scan line, and n is an integer greater than or equal to 3.

[0047] In other embodiments, the control end of the seventh transistor T7 may also be selectively connected to the adjacent second scan line Sn depending on the overall circuit layout.

[0048] In this embodiment, the first transistor T1 is used as a switching transistor, and is used to transmit the data signal to the first node N1 (i.e., the first end of the second transistor T2) according to the second scan signal provided by the second scan line Sn. The second transistor T2 is used as a driving transistor, and is used to control the driving current provided to the organic light emitting diode OLED according to the potential of the second node N2. The fourth transistor T4 and the fifth transistor T5 are both used as light emitting control transistors, and the fourth transistor T4 is used to transmit the first power supply voltage to the first node N1 (i.e., the first end of the driving transistor T2) according to the light emitting control signal provided by the emission control line EM, and the fifth transistor T5 is used to transmit the driving current output by the driving transistor T2 to the organic light emitting diode OLED according to the light emitting control signal provided by the emission control line EM. The third transistor T3 is used as a compensation transistor, and is used to electrically connect the second node N2 (i.e., the control end of the driving transistor T2) and the third node N3 (i.e., the second end of the driving transistor T2) according to the second scan signal provided by the second scan line Sn. The sixth transistor T6 is used as an initialization transistor, and is used to transmit an initialization signal provided by the first initialization signal line Vint1 to the second node N2 according to the first scan signal provided by the first scan line Sn-1. The seventh transistor T7 is used as a reset transistor, and is used to transmit the second initialization signal provided by the second initialization signal line Vint2 to the anode of the organic light emitting diode OLED according to the third scan signal provided by the third scan line Sn+1. The first end of the storage capacitor Cs is connected to the first power source ELVDD, and the second end of the storage capacitor Cs is connected to the second node N2. The storage capacitor Cs is used to couple the potential of the first node N1 and the second node N2, thereby maintaining the potential of the second node N2, so that the organic light emitting diode OLED continues to emit light within one frame time.

[0049] The first transistor T1 to the seventh transistor T7 each have a first end, a second end and a control end, the first end is one of a source or a drain, the second end is the other of a source or a drain, and the control end is a gate. In this embodiment, the first end is a source, and the second end is a drain.

[0050] In this embodiment, the seven thin film transistors (ie, the first transistor T1 to the seventh transistor T7) of the pixel circuit 10 are all P-type thin film transistors, which are turned on when the control terminal is at a low level and turned off when the control terminal is at a high level.

[0051] In this embodiment, the source of the sixth transistor T6 is connected to the first initialization signal line Vint1, and the source of the seventh transistor T7 is connected to the second initialization signal line Vint2. The source of the sixth transistor T6 and the source of the seventh transistor T7 are not connected, but are respectively connected to different initialization signal lines. It can be seen that the pixel circuit 10 adopts a dual initialization signal design. The second node N2 and the anode of the organic light emitting diode OLED are provided with initialization signals by different initialization signal lines.

[0052] Correspondingly, the external driver chip is required to support two Vint power supplies at the same time, that is, the driver chip has a first initialization signal terminal and a second initialization signal terminal, the first initialization signal line Vint1 is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line Vint2 is connected to the second initialization signal terminal, the second initialization signal terminal is used to output the second initialization signal, and the first initialization signal line Vint1 and the second initialization signal line Vint2 are connected to the same driver chip.

[0053] The second initialization signal provided by the second initialization signal line Vint2 is used as a reset signal for the anode terminal of the organic light emitting diode OLED. The voltage of the second initialization signal (i.e., the reset voltage) is usually set according to the second power supply voltage provided by the second power supply ELVSS, and is generally required to be less than or equal to the second power supply voltage provided by the second power supply ELVSS. In this embodiment, the voltage range of the second initialization signal is required to be controlled between -4.5V and -3V. Controlling the reset voltage of the anode terminal of the organic light emitting diode OLED in this range can reduce the black state brightness and improve the display contrast.

[0054] In this embodiment, the first initialization signal provided by the first initialization signal line Vint1 is used as a reset signal of the second node N2, and the voltage of the first initialization signal (i.e., the reset voltage) is required to be controlled between -2 V and 0 V. By controlling the reset voltage of the second node N2 within this range, the source-drain voltage difference of the sixth transistor T6 can be reduced, thereby reducing the leakage current of the sixth transistor T6 and improving the flicker phenomenon under low-frequency driving.

[0055] In other embodiments, the reset voltage provided by the first initialization signal line Vint1 may not be a fixed value, but may be dynamically adjusted according to the display brightness, so that the leakage current of the sixth transistor T6 is minimized, which can further improve the flicker phenomenon.

[0056] Accordingly, the present invention further provides an organic light emitting display device, and the organic light emitting display device includes the above-mentioned pixel circuit 10. Please refer to the above for details, which will not be described here.

[0057] In the prior art, due to the higher mobility and stronger driving capability of low temperature polysilicon (LTPS), LTPS thin film transistors are more widely used in OLED display panels as driving transistors of pixel circuits. However, the leakage current of LTPS thin film transistors is relatively large. Especially in low-frequency display, the large leakage current can easily lead to unstable gate voltage, thereby making the gate-source potential difference unstable, resulting in unstable current of the OLED light-emitting element and flickering of the display panel.

[0058] The display device can be partially lit in the lock screen state. This partially lit screen display mode is called the lock screen lighting (full name in English: Always On Display, referred to as AOD) display mode. The pixel circuit of LTPS thin film transistor is selected. In the AOD display mode, the refresh rate is generally set at 15HZ, and the maximum refresh rate is about 10HZ. If the refresh rate is lower, flickering will occur.

[0059] In this embodiment, the pixel circuit 10 also uses LTPS thin film transistors, but the arrangement and driving method of the pixel circuit are more optimized, which can achieve a lower refresh rate.

[0060] Please refer to Figure 2 , which is a statistical diagram of FMA measurement results under different reset voltages. Figure 2 As shown, when the reset voltage VINT provided by the first initialization signal line Vint1 is -3.3V, -2.5V, -1.5V, and -0.5V respectively, the display screen flicker evaluation parameter FMA (Flicker Modulation Amplitude) is tested respectively. From the test results of FMA, the lower the reset voltage VINT provided by the first initialization signal line Vint1, the lower the FMA value, and the milder the flicker.

[0061] For the principle of FMA measurement, please refer to Figure 3 ,like Figure 3 As shown, the brightness change of the display device is a waveform curve, the AC component of the brightness is Vmax-Vmin, and the DC component of the brightness is (Vmax+Vmin) / 2. The calculation formula of FMA is as follows:

[0062] FMA=(Vmax-Vmin) / {(Vmax+Vmin) / 2}×100%.

[0063] [Example 2]

[0064] Please refer to Figure 4 , which is a schematic diagram of the structure of the pixel circuit of the second embodiment of the present invention. Figure 4 As shown, the pixel circuit 20 includes: an organic light emitting diode OLED, connected between a first power source ELVDD and a second power source ELVSS; a first transistor T1, a first end of which is connected to a data line DTAT, a second end of which is connected to a first node N1, and a control end of which is connected to a second scan line Sn; a second transistor T2, a first end of which is connected to the first node N1, a second end of which is connected to a third node N3, and a control end of which is connected to a second node N2; a third transistor T3, a first end of which is connected to the second node N2, a second end of which is connected to the third node N3, and a control end of which is connected to a second scan line Sn; a fourth transistor T4, a first end of which is connected to the first power source ELVDD, and a second end of which is connected to the first A fifth transistor T5, a first end of which is connected to the third node N3, a second end of which is connected to the anode of the organic light emitting diode OLED, and a control end of which is connected to the emission control line EM; a sixth transistor T6, a first end of which is connected to the first initialization signal line VINT, a second end of which is connected to the second node N2, and a control end of which is connected to the first scan line Sn-1; a seventh transistor T7, a first end of which is connected to the second initialization signal line VGL, a second end of which is connected to the anode of the organic light emitting diode OLED, and a control end of which is connected to the third scan line Sn+1; a storage capacitor Cs, connected between the first power supply ELVDD and the second node N2.

[0065] Specifically, the pixel circuit 20 is also a 7T1C circuit structure, including 7 transistors, 1 storage capacitor Cs and 1 organic light emitting diode OLED. Among them, the source of the sixth transistor T6 and the source of the seventh transistor T7 are also not connected, but are respectively connected to different initialization signal lines. That is, the pixel circuit 20 also adopts a dual initialization signal design.

[0066] The difference between this embodiment and the first embodiment is that the third transistor T3 and the sixth transistor T6 are both dual-gate transistors, and the dual-gate transistors have low leakage characteristics, which can suppress the potential change of the second node N2 when the driving transistor T2 drives the organic light emitting diode OLED to emit light, and avoid the potential change of the second node N2 caused by the leakage of the initialization transistor T6 and the compensation transistor T3.

[0067] In addition, the source of the seventh transistor T7 is not connected to the second initialization signal terminal through the second initialization signal line VGL, but is connected to the low-level signal terminal. Accordingly, the second initialization signal transmitted by the second initialization signal line VGL is a low-level signal, and the voltage range of the low-level signal is between -6.5V and -5.5V.

[0068] In this embodiment, the pixel circuit 20 is compatible with a driver chip that only supports one Vint power supply. The external driver chip connected to the pixel circuit 20 has a first initialization signal terminal and a low-level signal terminal, the first initialization signal line VINT is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line VGL is connected to the low-level signal terminal, and the low-level signal terminal is used to output a low-level signal. The first initialization signal is used to initialize the second node N2, that is, to reset the gate voltage of the second transistor T2. The second initialization signal is used to initialize the anode of the organic light emitting diode OLED.

[0069] In this embodiment, the control end of the seventh transistor T7 is connected to the third scan line Sn+1, and the pixel circuit 10 is connected to three scan lines (i.e., the first scan line Sn-1, the second scan line Sn, and the third scan line Sn+1). Among them, the first scan line Sn-1 corresponding to the n-th row of pixel circuits and the second scan line Sn corresponding to the n-1-th row of pixel circuits are the same scan line, the second scan line Sn corresponding to the n-th row of pixel circuits and the third scan line Sn+1 corresponding to the n-1-th row of pixel circuits are the same scan line, and n is an integer greater than or equal to 3.

[0070] In other embodiments, the control end of the seventh transistor T7 may also be selectively connected to the adjacent second scan line Sn depending on the overall circuit layout.

[0071] Accordingly, the present invention further provides an organic light emitting display device, wherein the organic light emitting display device comprises the above-mentioned pixel circuit 20. Please refer to the above for details, which will not be described in detail here.

[0072] [Example 3]

[0073] Please refer to Figure 5 , which is a schematic diagram of the structure of the pixel circuit of the third embodiment of the present invention. Figure 5As shown, the pixel circuit 30 includes: an organic light emitting diode OLED, connected between a first power source ELVDD and a second power source ELVSS; a first transistor T1, a first end of which is connected to a data line DTAT, a second end of which is connected to a first node N1, and a control end of which is connected to a second scan line Sn; a second transistor T2, a first end of which is connected to the first node N1, a second end of which is connected to a third node N3, and a control end of which is connected to a second node N2; a third transistor T3, a first end of which is connected to the second node N2, a second end of which is connected to the third node N3, and a control end of which is connected to a second scan line Sn; a fourth transistor T4, a first end of which is connected to the first power source ELVDD, and a second end of which is connected to the first scan line Sn; A fifth transistor T5, a first end of which is connected to the third node N3, a second end of which is connected to the anode of the organic light emitting diode OLED, and a control end of which is connected to the emission control line EM; a sixth transistor T6, a first end of which is connected to the first initialization signal line VINT, a second end of which is connected to the second node N2, and a control end of which is connected to the first scan line Sn-1; a seventh transistor T7, a first end of which is connected to the second initialization signal line, a second end of which is connected to the anode of the organic light emitting diode OLED, and a control end of which is connected to the third scan line Sn+1; a storage capacitor Cs, connected between the first power supply ELVDD and the second node N2.

[0074] Specifically, the pixel circuit 30 is also a 7T1C circuit structure, including 7 transistors, 1 storage capacitor Cs and 1 organic light emitting diode OLED. Among them, the source of the sixth transistor T6 and the source of the seventh transistor T7 are also not connected, but are respectively connected to different initialization signal lines. That is, the pixel circuit 30 also adopts a dual initialization signal design.

[0075] The difference between this embodiment and the first embodiment is that the third transistor T3 and the sixth transistor T6 are both dual-gate transistors, and the dual-gate transistors have low leakage characteristics, which can suppress the potential change of the second node N2 when the driving transistor T2 drives the organic light emitting diode OLED to emit light, and avoid the potential change of the second node N2 caused by the leakage of the initialization transistor T6 and the compensation transistor T3.

[0076] In addition, the source of the seventh transistor T7 is not connected to the second initialization signal terminal through the second initialization signal line, but is connected to the third scan line Sn+1. The third scan line signal transmitted by the third scan line Sn+1 is an AC signal, whose low-state voltage is a low-level signal, and its high-state voltage is a high-level signal. The voltage range of the low-level signal is between -6.5V and -5.5V, and the voltage range of the high-level signal is between 4V and 6V.

[0077] In this embodiment, the pixel circuit 20 is also compatible with a driver chip that only supports one Vint power supply. The external driver chip connected to the pixel circuit 20 has a first initialization signal terminal, the first initialization signal line VINT is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line is connected to the third scan line Sn+1, and the second initialization signal transmitted by the second initialization signal line is the third scan signal. Among them, the first initialization signal is used to initialize the second node N2, that is, to reset the gate voltage of the second transistor T2. The second initialization signal (i.e., the third scan signal) is used to initialize the anode of the organic light emitting diode OLED.

[0078] In this embodiment, the control end of the seventh transistor T7 is connected to the third scan line Sn+1, and the pixel circuit 10 is connected to three scan lines (i.e., the first scan line Sn-1, the second scan line Sn, and the third scan line Sn+1). Among them, the first scan line Sn-1 corresponding to the n-th row of pixel circuits and the second scan line Sn corresponding to the n-1-th row of pixel circuits are the same scan line, the second scan line Sn corresponding to the n-th row of pixel circuits and the third scan line Sn+1 corresponding to the n-1-th row of pixel circuits are the same scan line, and n is an integer greater than or equal to 3.

[0079] In other embodiments, the control end of the seventh transistor T7 may also be selectively connected to the adjacent second scan line Sn depending on the overall circuit layout.

[0080] Accordingly, the present invention further provides an organic light emitting display device, wherein the organic light emitting display device comprises the above-mentioned pixel circuit 30. Please refer to the above for details, which will not be described in detail here.

[0081] In other embodiments, in order to further improve the flicker phenomenon, the second transistor T2 and the sixth transistor T6 in the above pixel circuit can be covered with opaque metal material to reduce the influence of external light on the thin film transistors, improve the stability of the thin film transistors, and thus improve the display flicker problem.

[0082] Correspondingly, the present invention also provides an organic light-emitting display device, which includes: a base substrate (not shown in the figure), a plurality of signal lines (not shown in the figure) and a plurality of pixel circuits as described above; the plurality of signal lines and the plurality of pixel circuits are both formed on the base substrate, the plurality of pixel circuits are distributed in an array, and the plurality of signal lines are electrically connected to the plurality of pixel circuits; in each pixel circuit, the orthographic projection of the anode of the organic light-emitting diode OLED on the base substrate covers the orthographic projection of the second transistor T2 and the sixth transistor T6 on the base substrate; or the orthographic projection of the signal line on the base substrate covers the orthographic projection of the second transistor T2 and the sixth transistor T6 on the base substrate.

[0083] Preferably, the signal line is a data line DTAT or a second scan line Sn.

[0084] In this embodiment, each transistor in the pixel circuit is a low-temperature polycrystalline silicon (LTPS) thin film transistor, and a metal layer for blocking external light is arranged above the second transistor T2 and the sixth transistor T6. Such an optimized pixel structure can reduce the light-induced hysteresis effect of the second transistor T2 and the leakage current of the sixth transistor T6, thereby improving the flicker phenomenon.

[0085] In the existing technology, low-temperature polycrystalline oxide (LTPO) display technology combines two thin-film transistors, low-temperature polycrystalline silicon (LTPS) and indium gallium zinc oxide (IGZO), so that the display panel has the characteristics of strong driving capability and low power consumption, and is suitable for both high-frequency display and low-frequency display. However, the process complexity of LTPO technology is high, and the number of masks (MASK) is more than that of LTPS technology, usually 5 masks are required, which not only increases the manufacturing cost, but also affects the product qualification rate.

[0086] In this embodiment, the organic light emitting display device is prepared by LTPS technology, and high-frequency display and low-frequency display can be realized without adding MASK like LTPO technology. It has been verified by experiments that the organic light emitting display device provided by this embodiment does not flicker when the refresh rate is 5HZ.

[0087] It should be noted that the various embodiments in this specification are described in a progressive manner, and each embodiment focuses on the differences from other embodiments. The same or similar parts between the various embodiments can be referenced to each other.

[0088] The above drawings are only schematic illustrations of the pixel circuit provided by the present invention. For the sake of clarity, the shapes and numbers of components in the above drawings are simplified and some components are omitted. Those skilled in the art may make changes according to actual needs. These changes are within the protection scope of the present invention and will not be described in detail here.

[0089] In summary, the pixel circuit and organic light-emitting display device provided by the present invention adopt a pixel circuit with a dual initialization signal line design, and initialize the gate of the driving transistor and the anode of the organic light-emitting diode respectively through two initialization signal lines, thereby reducing the source-drain voltage difference of the sixth transistor, thereby reducing the leakage current of the sixth transistor, and improving the problem of flickering of the display screen of the organic light-emitting display device under low-frequency driving. In addition, by adjusting the position of the anode metal layer or other metal layer so that it covers the second transistor and the sixth transistor, the influence of external light on the two transistors is reduced, the hysteresis effect of the second transistor and the leakage current of the sixth transistor are reduced, and the display flicker problem is further improved.

[0090] The above content is a further detailed description of the present application in combination with specific preferred implementation methods, and it cannot be determined that the specific implementation of the present application is limited to these descriptions. For ordinary technicians in the technical field to which the present application belongs, several simple deductions or substitutions can be made without departing from the concept of the present application, which should be deemed to fall within the scope of protection of the present application.

Claims

1. A pixel circuit, characterized in that: include: an organic light emitting diode, connected between the first power source and the second power source; A first transistor, a first end of which is connected to the data line, a second end of which is connected to the first node, and a control end of which is connected to the second scan line; a second transistor, a first terminal of which is connected to the first node, a second terminal of which is connected to the third node, and a control terminal of which is connected to the second node; a third transistor, a first terminal of which is connected to the second node, a second terminal of which is connected to the third node, and a control terminal of which is connected to the second scan line; a fourth transistor, a first terminal of which is connected to the first power source, a second terminal of which is connected to the first node, and a control terminal of which is connected to the emission control line; a fifth transistor, a first terminal of which is connected to the third node, a second terminal of which is connected to the anode of the organic light emitting diode, and a control terminal of which is connected to the emission control line; a sixth transistor, a first end of which is connected to the first initialization signal line, a second end of which is connected to the second node, and a control end of which is connected to the first scan line; a seventh transistor, a first end of which is connected to the second initialization signal line, a second end of which is connected to the anode of the organic light emitting diode, and a control end of which is connected to the third scan line; the first end of the sixth transistor is not connected to the first end of the seventh transistor; A storage capacitor is connected between the first power source and the second node.

2. The pixel circuit according to claim 1, wherein: The cathode of the organic light emitting diode is connected to the second power supply, the first power supply and the second power supply are used as driving power supplies for the organic light emitting diode, the first power supply is used to provide a first power supply voltage, and the second power supply is used to provide a second power supply voltage; The first initialization signal line is used to transmit a first initialization signal, and the first initialization signal is used to initialize the gate voltage of the second transistor; The second initialization signal line is used to transmit a second initialization signal, and the second initialization signal is used to initialize the anode voltage of the organic light emitting diode.

3. The pixel circuit according to claim 2, characterized in that: The voltage range of the first initialization signal is between -2V and 0V; or The voltage of the first initialization signal is dynamically adjusted according to display brightness, so that the leakage current of the sixth transistor is minimized.

4. The pixel circuit according to claim 2, characterized in that: A voltage of the second initialization signal is less than or equal to a second power supply voltage provided by the second power supply.

5. The pixel circuit according to claim 2, wherein: The first initialization signal line and the second initialization signal line are both connected to an external driving chip, the driving chip has a first initialization signal terminal and a second initialization signal terminal, the first initialization signal line is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line is connected to the second initialization signal terminal, the second initialization signal terminal is used to output the second initialization signal.

6. The pixel circuit according to claim 5, characterized in that: The voltage range of the second initialization signal is between -4.5V and -3V.

7. The pixel circuit according to claim 2, characterized in that: The first initialization signal line and the second initialization signal line are both connected to an external driving chip, the driving chip has a first initialization signal terminal and a low-level signal terminal, the first initialization signal line is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line is connected to the low-level signal terminal, the low-level signal terminal is used to output a low-level signal, and the second initialization signal transmitted by the second initialization signal line is the low-level signal.

8. The pixel circuit according to claim 7, characterized in that: The voltage range of the low level signal is between -6.5V and -5.5V.

9. The pixel circuit according to claim 2, characterized in that: The first initialization signal line is connected to an external driving chip, the driving chip has a first initialization signal terminal, the first initialization signal line is connected to the first initialization signal terminal, the first initialization signal terminal is used to output the first initialization signal, the second initialization signal line is connected to the third scan line, and the second initialization signal transmitted by the second initialization signal line is a third scan line signal.

10. The pixel circuit according to claim 9, characterized in that: The third scan line signal is an AC signal, a low-state voltage of the AC signal is between -6.5V and -5.5V, and a high-state voltage of the AC signal is between 4V and 6V.

11. An organic light emitting display device, characterized in that: include: The pixel circuit according to any one of claims 1 to 10.

12. The organic light emitting display device according to claim 11, wherein: Also includes: Substrate substrate and signal lines; The pixel circuit and the signal line are both formed on the base substrate, and the signal line is electrically connected to the pixel circuit; In the pixel circuit, the positive projection of the anode of the organic light emitting diode on the base substrate covers the positive projections of the second transistor and the sixth transistor on the base substrate; or The orthographic projection of the signal line on the substrate covers the orthographic projections of the second transistor and the sixth transistor on the substrate.

13. The organic light emitting display device according to claim 12, wherein: The signal line is a data line or a second scan line.

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