CN115762406A - Pixel circuit and organic light emitting display device - Google Patents
Pixel circuit and organic light emitting display device Download PDFInfo
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Abstract
The present application provides a pixel circuit and an organic light emitting display device, wherein the pixel circuit includes: first to seventh transistors, a storage capacitor, and an organic light emitting diode; the first end of the sixth transistor is connected with the first initialization signal line, the second end of the sixth transistor is connected with the second node, the first end of the seventh transistor is connected with the second initialization signal line, and the second end of the seventh transistor is connected with the anode of the organic light emitting diode. In the pixel circuit and the organic light-emitting display device provided by the application, the pixel circuit with a double-initialization signal line design is adopted, and the grid electrode of the driving transistor and the anode of the organic light-emitting diode are respectively initialized through the two initialization signal lines, so that the source-drain voltage difference of the sixth transistor is reduced, the leakage current of the sixth transistor is further reduced, and the problem that a display picture of the organic light-emitting display device flickers under the low-frequency driving is solved.
Description
Technical Field
The present disclosure relates to the field of display technologies, and in particular, to a pixel circuit and an organic light emitting display device.
Background
Compared with many Display devices, an Organic Light Emitting Display (OLED for short) has many advantages of being solid-state, self-luminous, wide in viewing angle, wide in color gamut, fast in reaction speed, high in luminous efficiency, high in brightness, high in contrast, ultra-thin, ultra-Light, low in power consumption, wide in working temperature range, capable of manufacturing large-sized and flexible panels, simple in manufacturing process and the like, can achieve flexible Display in a real sense, and can meet the requirements of people on future displays.
The display device can adopt different refresh rates in different application scenes, for example, a driving mode with higher refresh rate is adopted to display a dynamic picture, so as to ensure the fluency of the displayed picture; the static picture is displayed by adopting a driving mode with a lower refresh rate so as to reduce power consumption. In the actual use process, the organic light-emitting display device is found to have a flicker phenomenon when displaying at a low refresh rate, which affects the visual effect. Also, the larger the ambient light intensity is, the more serious the flicker phenomenon is.
Disclosure of Invention
In view of the above, the present application provides a pixel circuit and an organic light emitting display device to solve the problem of flicker of a display screen under low frequency driving of the organic light emitting display device in the prior art.
To solve the above technical problem, the present invention provides a pixel circuit, including:
an organic light emitting diode connected between a first power source and a second power source;
a first transistor having a first terminal connected to the data line, a second terminal connected to the first node, and a control terminal connected to the second scan line;
a second transistor having a first terminal connected to the first node, a second terminal connected to a third node, and a control terminal connected to a second node;
a third transistor having a first terminal connected to the second node, a second terminal connected to the third node, and a control terminal connected to a second scan line;
a fourth transistor having a first terminal connected to the first power supply, a second terminal connected to the first node, and a control terminal connected to an emission control line;
a fifth transistor having a first terminal connected to the third node, a second terminal connected to an anode of the organic light emitting diode, and a control terminal connected to an emission control line;
a sixth transistor having a first terminal connected to the first initialization signal line, a second terminal connected to the second node, and a control terminal connected to the first scan line;
a seventh transistor having a first terminal connected to the second initialization signal line, a second terminal connected to the anode of the organic light emitting diode, and a control terminal connected to the third scan line;
a storage capacitor connected between the first power source and the second node.
Optionally, in the pixel circuit, a 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 configured to provide a first power supply voltage, and the second power supply is configured to provide a second power supply voltage;
the first initialization signal line is used for transmitting a first initialization signal, and the first initialization signal is used for initializing the grid voltage of the second transistor;
the second initialization signal line is used for transmitting a second initialization signal, and the second initialization signal is used for initializing the anode voltage of the organic light emitting diode.
Optionally, in the pixel circuit, 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 the display brightness, so that the leakage current of the sixth transistor is minimized.
Optionally, in the pixel circuit, a voltage of the second initialization signal is less than or equal to a second power supply voltage provided by the second power supply.
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 end and a second initialization signal end, the first initialization signal line is connected to the first initialization signal end, the first initialization signal end is configured to output the first initialization signal, the second initialization signal line is connected to the second initialization signal end, and the second initialization signal end is configured to output the second initialization signal.
Optionally, in the pixel circuit, the voltage range of the second initialization signal is between-4.5V and-3V.
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 end and a low level signal end, the first initialization signal line is connected to the first initialization signal end, the first initialization signal end is used to output the first initialization signal, the second initialization signal line is connected to the low level signal end, the low level signal end is used to output a low level signal, and a second initialization signal transmitted by the second initialization signal line is the low level signal.
Optionally, in the pixel circuit, the voltage range of the low-level signal is between-6.5V and-5.5V.
Optionally, in the pixel circuit, the first initialization signal line is connected to an external driver chip, the driver chip has a first initialization signal end, the first initialization signal line is connected to the first initialization signal end, the first initialization signal end is used to output the first initialization signal, the second initialization signal line is connected to the third scan line, and a second initialization signal transmitted by the second initialization signal line is a third scan line signal.
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.
Accordingly, the present invention also provides an organic light emitting display device including the pixel circuit as described above.
Optionally, in the organic light emitting display device, the method further includes: a substrate base plate and a signal line;
the pixel circuit and the signal line are both formed on the substrate, and the signal line is electrically connected with the pixel circuit;
in the pixel circuit, an orthographic projection of an anode of an organic light emitting diode on the substrate covers an orthographic projection of the second transistor and the sixth transistor on the substrate; or
The orthographic projection of the signal line on the substrate covers the orthographic projection of the second transistor and the orthographic projection of the sixth transistor on the substrate.
Optionally, in the organic light emitting display device, the signal line is a data line or a second scan line.
In the pixel circuit and the organic light-emitting display device provided by the invention, the pixel circuit designed by double initialization signal lines is adopted, and the grid electrode of the driving transistor and the anode of the organic light-emitting diode are respectively initialized through the two initialization signal lines, so that the source-drain voltage difference of the sixth transistor is reduced, the leakage current of the sixth transistor is further reduced, and the problem of flicker of a display picture of the organic light-emitting display device under low-frequency driving is solved.
Drawings
The accompanying drawings, which are incorporated in and constitute a part of this specification, illustrate embodiments consistent with the present application and together with the description, serve to explain the principles of the application. It is obvious that the drawings in the following description are only some embodiments of the application, and that for a person skilled in the art, other drawings can be derived from them without inventive effort.
Fig. 1 is an equivalent circuit diagram of a pixel circuit according to a first embodiment of the invention;
FIG. 2 is a statistical plot of FMA measurements at different reset voltages;
FIG. 3 is a schematic diagram of FMA measurement;
fig. 4 is an equivalent circuit diagram of a pixel circuit according to a second embodiment of the invention;
fig. 5 is an equivalent circuit diagram of a pixel circuit according to a third embodiment of the present invention.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the embodiments set forth herein. Rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their repetitive description will be omitted.
[ EXAMPLES one ]
Please refer to fig. 1, which is a schematic structural diagram of a pixel circuit according to a first embodiment of the present invention. As shown in fig. 1, the pixel circuit 10 includes: an organic light emitting diode OLED connected between the first power source ELVDD and the second power source ELVSS; a first transistor T1 having a first terminal connected to the data line DTAT, a second terminal connected to the first node N1, and a control terminal connected to the second scan line Sn; a second transistor T2 having a first terminal connected to the first node N1, a second terminal connected to a third node N3, and a control terminal connected to the second node N2; a third transistor T3 having a first terminal connected to the second node N2, a second terminal connected to the third node N3, and a control terminal connected to a second scan line Sn; a fourth transistor T4 having a first terminal connected to the first power source ELVDD, a second terminal connected to the first node N1, and a control terminal connected to an emission control line EM; a fifth transistor T5 having a first terminal connected to the third node N3, a second terminal connected to the anode of the organic light emitting diode OLED, and a control terminal connected to the emission control line EM; a sixth transistor T6 having a first end connected to the first initialization signal line Vint1, a second end connected to the second node N2, and a control end connected to the first scan line Sn-1; a seventh transistor T7 having a first end connected to the second initialization signal line Vint2, a second end connected to the anode of the organic light emitting diode OLED, and a control end connected to the third scan line Sn + 1; and a storage capacitor Cs connected between the first power source ELVDD and the second node N2.
Specifically, the pixel circuit 10 has a 7T1C type circuit structure, and includes 7 transistors (i.e., the first transistor T1 to the seventh transistor T7), 1 storage capacitor Cs, and 1 organic light emitting diode OLED.
The organic light emitting diode OLED is connected between the first power ELVDD and the second power ELVSS, the first power ELVDD is used to provide a first power voltage (high level), the second power ELVSS is used to provide a second power voltage (low level), the first power ELVDD and the second power ELVSS serve as a driving power source 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 ELVSS, and the organic light emitting diode OLED emits light with a corresponding brightness according to a driving current flowing through the organic light emitting diode OLED.
A first terminal of the first transistor T1 is connected to a DATA line DATA for loading a DATA signal. A control end of the first transistor T1 and a control end of the third transistor T3 are both connected to a second scan line Sn, a control end of the seventh transistor T7 is connected to a third scan line Sn +1, the second scan line Sn is used for providing a second scan signal, and the third scan line Sn +1 is used for providing a third scan signal. The control end of the sixth transistor T6 is connected to a first scan line Sn-1, and the first scan line Sn-1 is used for providing a first scan signal. A control terminal of the fourth transistor T4 and a control terminal of the fifth transistor T5 are both connected to an emission control line EM for providing an emission control signal. A first end of the sixth transistor T6 is connected to a first initialization signal line Vint1, the first initialization signal line Vint1 is configured to transmit a first initialization signal, and the first initialization signal is configured to initialize a second node N2, that is, reset a gate voltage of the second transistor T2. A first end of the seventh transistor T7 is connected to a second initialization signal line Vint2, the second initialization signal line Vint2 is configured to transmit a second initialization signal, and the second initialization signal is configured to initialize an anode of the organic light emitting diode OLED.
In this embodiment, the control terminal 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). The first scanning line Sn-1 corresponding to the pixel circuit in the nth row and the second scanning line Sn +1 corresponding to the pixel circuit in the (n-1) th row are the same scanning line, the second scanning line Sn corresponding to the pixel circuit in the nth row and the third scanning line Sn +1 corresponding to the pixel circuit in the (n-1) th row are the same scanning line, and n is an integer greater than or equal to 3.
In other embodiments, the control terminal of the seventh transistor T7 may also be selectively connected to the adjacent second scan line Sn according to the overall circuit layout.
In this embodiment, the first transistor T1 is used as a switching transistor for transmitting a 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 functions as a driving transistor for controlling a driving current supplied to the organic light emitting diode OLED according to a potential of the second node N2. The fourth transistor T4 and the fifth transistor T5 are both used as light emitting control transistors, the fourth transistor T4 is configured to transmit the first power voltage to the first node N1 (i.e., the first terminal 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 configured 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 for electrically connecting 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 configured 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 configured 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, the second end of the storage capacitor Cs is connected to the second node N2, and the storage capacitor Cs is configured to couple potentials of the first node N1 and the second node N2, so as to maintain the potential of the second node N2, and the organic light emitting diode OLED continuously emits light within one frame time.
The first to seventh transistors T1 to T7 each have a first end, a second end, and a control end, wherein the first end is one of a source or a drain, the second end is the other of the source or the drain, and the control end is a gate. In this embodiment, the first terminal is a source and the second terminal is a drain.
In this embodiment, the 7 thin film transistors (i.e., the first transistor T1 to the seventh transistor T7) of the pixel circuit 10 are all P-type thin film transistors, and the P-type thin film transistors are turned on when the control terminal is at a low level and turned off when the control terminal is at a high level.
In this embodiment, the source of the sixth transistor T6 is connected to the first initialization signal line Vint1, the source of the seventh transistor T7 is connected to the second initialization signal line Vint2, and 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 is designed using a dual initialization signal. The second node N2 and the anode of the organic light emitting diode OLED are supplied with initialization signals by different initialization signal lines, respectively.
Correspondingly, an external driving chip is required to simultaneously support two Vint power supplies, namely the driving chip is provided with a first initialization signal end and a second initialization signal end, a first initialization signal line Vint1 is connected with the first initialization signal end, the first initialization signal end is used for outputting the first initialization signal, a second initialization signal line Vint2 is connected with the second initialization signal end, the second initialization signal end is used for outputting the second initialization signal, and the first initialization signal line Vint1 and the second initialization signal line Vint2 are connected with the same driving chip.
The second initialization signal provided by the second initialization signal line Vint2 is used as a reset signal of the anode terminal of the organic light emitting diode OLED, and the voltage (i.e., the reset voltage) of the second initialization signal is generally set according to the second power voltage provided by the second power ELVSS, and is generally required to be less than or equal to the second power voltage provided by the second power ELVSS. In this embodiment, the voltage range of the second initialization signal is required to be controlled between-4.5V and-3V. The reset voltage of the anode end of the organic light emitting diode OLED is controlled in the interval, so that the black state brightness can be reduced, and the display contrast is improved.
In this embodiment, the first initialization signal provided by the first initialization signal line Vint1 is used as the reset signal of the second node N2, and the voltage (i.e., the reset voltage) of the first initialization signal is required to be controlled between-2V and 0V. The reset voltage of the second node N2 is controlled in this interval, so that 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.
In other embodiments, the reset voltage provided by the first initialization signal line Vint1 may not be a fixed value, but is 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.
Accordingly, the present invention also provides an organic light emitting display device including the pixel circuit 10 as described above. Please refer to the above, which is not described herein.
In the prior art, low Temperature Polysilicon (LTPS) has higher mobility and stronger driving capability, so LTPS thin film transistors are widely applied to OLED display panels as driving transistors of pixel circuits, but the LTPS thin film transistors have larger leakage currents, and gate voltages are easily unstable due to the larger leakage currents particularly in Low-frequency display, so that gate-source potential difference is unstable, current of OLED light emitting elements is unstable, and a flicker phenomenon occurs in the display panel.
The Display device can be partially lighted in a screen lock state, and the screen Display mode of the partial lighting is called as a screen lock lighting (all english is called as Always On Display, AOD for short) Display mode. In the pixel circuit using LTPS TFT, the refresh rate is generally set at 15Hz, the limit refresh rate is about 10Hz, and the flicker will occur when the refresh rate is further decreased in the AOD display mode.
In this embodiment, the pixel circuit 10 also uses LTPS thin film transistors, but the arrangement and driving manner of the pixel circuit are more optimized, so that a lower refresh rate can be achieved.
Please refer to fig. 2, which is a statistical chart of FMA measurement results at different reset voltages. As shown in fig. 2, when the reset voltage Vint provided by the first initialization signal line Vint1 is-3.3V, -2.5V, -1.5V, -0.5V, respectively, the Flicker evaluation parameter FMA (Flicker Modulation Amplitude) is tested, and from the test result of FMA, the lower the reset voltage Vint provided by the first initialization signal line Vint1, the lower the FMA value and the lighter the Flicker.
Referring to fig. 3, as shown in fig. 3, the luminance of the display device varies as a wave curve, the AC component of the luminance is Vmax-Vmin, and the DC component of the luminance is (Vmax + Vmin)/2. The formula for FMA is shown below:
FMA＝(Vmax－Vmin)/{(Vmax+Vmin)/2}×100％。
[ example two ]
Please refer to fig. 4, which is a schematic structural diagram of a pixel circuit according to a second embodiment of the present invention. As shown in fig. 4, the pixel circuit 20 includes: an organic light emitting diode OLED connected between the first power source ELVDD and the second power source ELVSS; a first transistor T1 having a first terminal connected to the data line DTAT, a second terminal connected to the first node N1, and a control terminal connected to the second scan line Sn; a second transistor T2 having a first terminal connected to the first node N1, a second terminal connected to a third node N3, and a control terminal connected to the second node N2; a third transistor T3 having a first terminal connected to the second node N2, a second terminal connected to the third node N3, and a control terminal connected to a second scan line Sn; a fourth transistor T4 having a first terminal connected to the first power source ELVDD, a second terminal connected to the first node N1, and a control terminal connected to an emission control line EM; a fifth transistor T5 having a first terminal connected to the third node N3, a second terminal connected to the anode of the organic light emitting diode OLED, and a control terminal connected to the emission control line EM; a sixth transistor T6 having a first terminal connected to the first initialization signal line VINT, a second terminal connected to the second node N2, and a control terminal connected to the first scan line Sn-1; a seventh transistor T7 having a first terminal connected to the second initialization signal line VGL, a second terminal connected to the anode of the organic light emitting diode OLED, and a control terminal connected to the third scan line Sn + 1; and a storage capacitor Cs connected between the first power source ELVDD and the second node N2.
Specifically, the pixel circuit 20 is also a 7T1C type circuit structure, and includes 7 transistors, 1 storage capacitor Cs, and 1 organic light emitting diode OLED. The source of the sixth transistor T6 and the source of the seventh transistor T7 are not connected to each other, but are connected to different initialization signal lines. That is, the pixel circuit 20 is also designed with a dual initialization signal.
The difference between this embodiment and the first embodiment is that the third transistor T3 and the sixth transistor T6 are dual-gate transistors, and the dual-gate transistors have low leakage characteristics, so that when the driving transistor T2 drives the organic light emitting diode OLED to emit light, the potential variation of the second node N2 can be suppressed, and the potential variation of the second node N2 caused by the leakage of the initialization transistor T6 and the compensation transistor T3 can be avoided.
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 a low level signal terminal. Correspondingly, the second initialization signal transmitted by the second initialization signal line VGL is a low level signal, and the voltage of the low level signal ranges from-6.5V to-5.5V.
In this embodiment, the pixel circuit 20 is compatible with a driver chip supporting only one Vint power supply. The external driving chip connected to the pixel circuit 20 has a first initialization signal terminal VINT connected to the first initialization signal terminal for outputting the first initialization signal, and a low level signal terminal VGL connected to the low level signal terminal for outputting 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 for initializing an anode of the organic light emitting diode OLED.
In this embodiment, the control terminal 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). The first scanning line Sn-1 corresponding to the pixel circuit in the nth row and the second scanning line Sn +1 corresponding to the pixel circuit in the (n-1) th row are the same scanning line, the second scanning line Sn corresponding to the pixel circuit in the nth row and the third scanning line Sn +1 corresponding to the pixel circuit in the (n-1) th row are the same scanning line, and n is an integer greater than or equal to 3.
In other embodiments, the control terminal of the seventh transistor T7 may also be selectively connected to the adjacent second scan line Sn according to the overall circuit layout.
Accordingly, the present invention also provides an organic light emitting display device including the pixel circuit 20 as described above. Please refer to the above, which is not described herein.
[ EXAMPLE III ]
Please refer to fig. 5, which is a schematic structural diagram of a pixel circuit according to a third embodiment of the present invention. As shown in fig. 5, the pixel circuit 30 includes: an organic light emitting diode OLED connected between the first power ELVDD and the second power ELVSS; a first transistor T1 having a first terminal connected to the data line DTAT, a second terminal connected to the first node N1, and a control terminal connected to the second scan line Sn; a second transistor T2 having a first terminal connected to the first node N1, a second terminal connected to a third node N3, and a control terminal connected to the second node N2; a third transistor T3 having a first terminal connected to the second node N2, a second terminal connected to the third node N3, and a control terminal connected to a second scan line Sn; a fourth transistor T4 having a first terminal connected to the first power source ELVDD, a second terminal connected to the first node N1, and a control terminal connected to an emission control line EM; a fifth transistor T5 having a first terminal connected to the third node N3, a second terminal connected to the anode of the organic light emitting diode OLED, and a control terminal connected to the emission control line EM; a sixth transistor T6 having a first terminal connected to the first initialization signal line VINT, a second terminal connected to the second node N2, and a control terminal connected to the first scan line Sn-1; a seventh transistor T7 having a first terminal connected to the second initialization signal line, a second terminal connected to the anode of the organic light emitting diode OLED, and a control terminal connected to the third scan line Sn + 1; and a storage capacitor Cs connected between the first power source ELVDD and the second node N2.
Specifically, the pixel circuit 30 is also a 7T1C type circuit structure, and includes 7 transistors, 1 storage capacitor Cs, and 1 organic light emitting diode OLED. The source of the sixth transistor T6 and the source of the seventh transistor T7 are not connected to each other, but are connected to different initialization signal lines. That is, the pixel circuit 30 is also designed with a dual initialization signal.
The difference between the first embodiment and the second embodiment is that the third transistor T3 and the sixth transistor T6 are dual-gate transistors, and the dual-gate transistors have low leakage characteristics, so that the potential variation of the second node N2 can be suppressed when the driving transistor T2 drives the organic light emitting diode OLED to emit light, and the potential variation of the second node N2 caused by the leakage of the initialization transistor T6 and the compensation transistor T3 can be avoided.
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, the low-state voltage thereof is a low-level signal, the high-state voltage thereof 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.
In this embodiment, the pixel circuit 20 is also compatible with a driving chip supporting only one Vint power supply. The external driving chip connected to the pixel circuit 20 has a first initialization signal end, the first initialization signal line VINT is connected to the first initialization signal end, the first initialization signal end is configured 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 a third scan 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 (i.e., the third scan signal) is used to initialize the anode electrode of the organic light emitting diode OLED.
In this embodiment, the control terminal 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). The first scanning line Sn-1 corresponding to the pixel circuit in the nth row and the second scanning line Sn +1 corresponding to the pixel circuit in the (n-1) th row are the same scanning line, the second scanning line Sn corresponding to the pixel circuit in the nth row and the third scanning line Sn +1 corresponding to the pixel circuit in the (n-1) th row are the same scanning line, and n is an integer greater than or equal to 3.
In other embodiments, the control terminal of the seventh transistor T7 may also be selectively connected to the adjacent second scan line Sn according to the overall circuit layout.
Accordingly, the present invention also provides an organic light emitting display device including the pixel circuit 30 as described above. Please refer to the above, which is not described herein.
In other embodiments, in order to further improve the flicker phenomenon, the second transistor T2 and the sixth transistor T6 in the pixel circuit may be covered by an opaque metal material to reduce the influence of the external light on the thin film transistors, improve the stability of the thin film transistors, and further improve the display flicker problem.
Accordingly, the present invention also provides an organic light emitting display device including: a substrate (not shown), a plurality of signal lines (not shown), and a plurality of pixel circuits as described above; the signal lines and the pixel circuits are formed on the substrate, the pixel circuits are distributed in an array, and the signal lines are electrically connected with the pixel circuits; in each pixel circuit, an orthographic projection of an anode of the organic light emitting diode OLED on the substrate covers an orthographic projection of the second transistor T2 and the sixth transistor T6 on the substrate; or the orthographic projection of the signal line on the substrate covers the orthographic projection of the second transistor T2 and the sixth transistor T6 on the substrate.
Preferably, the signal line is a data line DTAT or a second scan line Sn.
In this embodiment, each transistor in the pixel circuit is a Low Temperature Polysilicon (LTPS) thin film transistor, and a metal layer for shielding external light is disposed above the second transistor T2 and the sixth transistor T6, so that the pixel structure is optimized to reduce the photo-induced hysteresis effect of the second transistor T2 and the leakage current of the sixth transistor T6, thereby improving the flicker phenomenon.
In the prior art, a low-temperature poly-silicon oxide (LTPO) display technology combines two thin film transistors, namely low-temperature poly-silicon (LTPS) and Indium Gallium Zinc Oxide (IGZO), so that a display panel has the characteristics of strong driving capability and low power consumption, and is suitable for high-frequency display and low-frequency display. However, the LTPO technology has high process complexity, and the number of MASKs (MASKs) is larger than that of the LTPS technology, and 5 MASKs are usually required, which not only increases the manufacturing cost, but also affects the product yield.
In this embodiment, the organic light emitting display device is manufactured by using LTPS technology, and high frequency display and low frequency display can be achieved without increasing MASK as in LTPO technology. Experiments prove that the organic light-emitting display device provided by the embodiment does not flicker when the refresh rate is 5 HZ.
It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other.
The figures described above are only schematic representations of the pixel circuits provided by the present invention. For clarity, the shapes and the numbers of the elements in the above figures are simplified and some elements are omitted, and those skilled in the art can make changes according to actual needs, and these changes are all within the protection scope of the present invention and are not described herein again.
In summary, the pixel circuit and the organic light emitting display device provided by the invention adopt the pixel circuit with the double initialization signal line design, and initialize the gate of the driving transistor and the anode of the organic light emitting diode respectively through the two initialization signal lines, thereby reducing the source-drain voltage difference of the sixth transistor, further reducing the leakage current of the sixth transistor, and improving the problem that the display image of the organic light emitting display device flickers under the low-frequency driving. In addition, the positions of the anode metal layer or other metal layers are adjusted to cover the second transistor and the sixth transistor, so that the influence of outside 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.
The foregoing is a more detailed description of the present application in connection with specific preferred embodiments and it is not intended that the present application be limited to these specific details. For those skilled in the art to which the present application pertains, several simple deductions or substitutions can be made without departing from the concept of the present application, and all should be considered as belonging to the protection scope of the present application.
Claims (13)
1. A pixel circuit, comprising:
an organic light emitting diode connected between a first power source and a second power source;
a first transistor having a first terminal connected to the data line, a second terminal connected to the first node, and a control terminal connected to the second scan line;
a second transistor having a first terminal connected to the first node, a second terminal connected to a third node, and a control terminal connected to a second node;
a third transistor having a first terminal connected to the second node, a second terminal connected to the third node, and a control terminal connected to a second scan line;
a fourth transistor having a first terminal connected to the first power supply, a second terminal connected to the first node, and a control terminal connected to an emission control line;
a fifth transistor having a first terminal connected to the third node, a second terminal connected to an anode of the organic light emitting diode, and a control terminal connected to an emission control line;
a sixth transistor having a first terminal connected to the first initialization signal line, a second terminal connected to the second node, and a control terminal connected to the first scan line;
a seventh transistor having a first terminal connected to the second initialization signal line, a second terminal connected to the anode of the organic light emitting diode, and a control terminal connected to the third scan line;
a storage capacitor connected between the first power supply and the second node.
2. The pixel circuit according to claim 1, wherein a cathode of the organic light emitting diode is connected to the second power supply, the first power supply and the second power supply serve as a driving power supply for the organic light emitting diode, the first power supply is configured to supply a first power supply voltage, and the second power supply is configured to supply a second power supply voltage;
the first initialization signal line is used for transmitting a first initialization signal, and the first initialization signal is used for initializing the grid voltage of the second transistor;
the second initialization signal line is used for transmitting a second initialization signal, and the second initialization signal is used for initializing the anode voltage of the organic light emitting diode.
3. The pixel circuit according to claim 2, wherein a voltage of the first initialization signal ranges between-2V to 0V; or alternatively
The voltage of the first initialization signal is dynamically adjusted according to the display brightness, so that the leakage current of the sixth transistor is minimized.
4. The pixel circuit according to claim 2, wherein a voltage of the second initialization signal is less than or equal to a second power supply voltage supplied 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 each connected to an external driver chip, the driver 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 configured to output the first initialization signal, the second initialization signal line is connected to the second initialization signal terminal, and the second initialization signal terminal is configured to output the second initialization signal.
6. The pixel circuit according to claim 5, wherein the second initialization signal has a voltage ranging between-4.5V and-3V.
7. The pixel circuit according to claim 2, wherein the first initialization signal line and the second initialization signal line are connected to an external driver chip, the driver 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 configured 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 configured to output a low-level signal, and a second initialization signal transmitted by the second initialization signal line is the low-level signal.
8. The pixel circuit according to claim 7, wherein the voltage of the low level signal ranges between-6.5V and-5.5V.
9. The pixel circuit according to claim 2, wherein the first initialization signal line is connected to an external driver chip, the driver 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 configured to output the first initialization signal, the second initialization signal line is connected to the third scan line, and a second initialization signal transmitted by the second initialization signal line is a third scan line signal.
10. The pixel circuit according to claim 9, wherein the third scan line signal is an ac signal having a low-state voltage of between-6.5V and-5.5V and a high-state voltage of between 4V and 6V.
11. An organic light emitting display device, comprising: a pixel circuit as claimed in any one of claims 1 to 10.
12. The organic light emitting display device according to claim 11, further comprising: a substrate base plate and a signal line;
the pixel circuit and the signal line are both formed on the substrate, and the signal line is electrically connected with the pixel circuit;
in the pixel circuit, an orthographic projection of an anode of an organic light emitting diode on the substrate covers an orthographic projection of the second transistor and the sixth transistor on the substrate; or
The orthographic projection of the signal line on the substrate covers the orthographic projection of the second transistor and the orthographic projection of 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.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111030900.7A CN115762406A (en) | 2021-09-03 | 2021-09-03 | Pixel circuit and organic light emitting display device |
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202111030900.7A CN115762406A (en) | 2021-09-03 | 2021-09-03 | Pixel circuit and organic light emitting display device |
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| Publication Number | Publication Date |
|---|---|
| CN115762406A true CN115762406A (en) | 2023-03-07 |
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| CN202111030900.7A Pending CN115762406A (en) | 2021-09-03 | 2021-09-03 | Pixel circuit and organic light emitting display device |
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| Country | Link |
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| CN (1) | CN115762406A (en) |
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- 2021-09-03 CN CN202111030900.7A patent/CN115762406A/en active Pending
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