CN108428434B - Pixel circuit, organic light-emitting display panel and display device - Google Patents
Pixel circuit, organic light-emitting display panel and display device Download PDFInfo
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- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
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- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
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Abstract
The invention discloses a pixel circuit, an organic light-emitting display panel and a display device, wherein the pixel circuit is controlled by three scanning signal ends, and a first scanning signal end, a second scanning signal end and a third scanning signal end output scanning signals in sequence, so that the three scanning signal ends do not have a time period for outputting the scanning signals simultaneously, which means that in the pixel circuit provided by the embodiment of the invention, a fifth switching transistor, a seventh switching transistor, a fourth switching transistor, a first switching transistor and a sixth switching transistor are not turned on simultaneously, so that the current from Data to a Vref channel does not flow to a light-emitting device through the sixth switching transistor, and the problem that the dark state of the conventional pixel circuit is not dark is solved.
Description
Technical Field
The present invention relates to the field of display technologies, and in particular, to a pixel circuit, an organic light emitting display panel and a display device.
Background
Organic Light Emitting Diode (OLED) is one of the hot spots in the research field of flat panel displays, and compared with Liquid Crystal displays, OLED has the advantages of low energy consumption, low production cost, self-luminescence, wide viewing angle, fast response speed, etc. at present, in the flat panel Display field of mobile phones, PDAs, digital cameras, etc., OLED has begun to replace the traditional Liquid Crystal Display (LCD). The pixel circuit design is the core technical content of the OLED display, and has important research significance.
A conventional pixel circuit is shown in fig. 1, and includes 7 switching transistors: M1-M7, 1 driving transistor M0 and 1 capacitor C1. The corresponding input timing diagram is shown in fig. 2. Although the circuit improves the problem of display unevenness caused by the drift of the threshold voltage of the driving transistor M0 due to the process and the aging of the transistor through internal compensation, in actual operation, panel manufacturers find that a short T time period exists, the switching transistors M2, M3, M4, M5, M7 and M8 are all turned on, the signal of the data signal end Vdata sequentially flows to the reference signal end Vref through the turned-on switching transistors M2, M3, M5 and M7, so that current is generated at the reference signal end Vref, and the signal flows to the light-emitting device oled through the turned-on switching transistor M8, so that the light-emitting device oled emits light, and the problem of dark state is caused.
Disclosure of Invention
Embodiments of the present invention provide a pixel circuit, an organic light emitting display panel and a display device to solve the problem of dark state in the prior art.
The embodiment of the invention provides a pixel circuit, which comprises: the driving transistor, the first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, the fifth switching transistor, the sixth switching transistor, the seventh switching transistor and the first capacitor; wherein the content of the first and second substances,
the first switching transistor is used for providing a signal of a reference signal end to a first pole of the fourth switching transistor under the control of the first scanning signal end;
the second switch transistor is used for providing a signal of a power supply voltage end to the first pole of the driving transistor under the control of the light-emitting control end;
the third switching transistor is used for enabling a second pole of the driving transistor and a second pole of the third switching transistor to be conducted under the control of the light emitting control end;
a first pole of the fourth switching transistor and a second pole of the seventh switching transistor are electrically connected in series and used for enabling the grid electrode of the driving transistor to be conducted with the second pole of the driving transistor under the control of a second scanning signal end;
the fifth switching transistor is used for providing a signal of a data signal terminal to the first pole of the driving transistor under the control of the second scanning signal terminal, and the sixth switching transistor is used for providing a signal of the reference signal terminal to the anode of the light-emitting device under the control of the third scanning signal terminal; alternatively, the first and second electrodes may be,
the fifth switching transistor is used for supplying a signal of a data signal terminal to the first pole of the driving transistor under the control of a third scanning signal terminal, and the sixth switching transistor is used for supplying a signal of the reference signal terminal to the anode of the light-emitting device under the control of the first scanning signal terminal;
the first capacitor is used for keeping a voltage difference between the grid electrode of the driving transistor and the power supply voltage terminal stable;
the driving transistor is used for providing driving current for the light-emitting device under the control of the second switching transistor, the third switching transistor and the first capacitor.
Correspondingly, the embodiment of the invention also provides an organic light-emitting display panel, which comprises N rows of pixel units, N +2 scanning lines and N +2 stages of shift register units, wherein each stage of shift register unit is correspondingly connected with one scanning line, and N is an integer greater than 0;
the pixel unit comprises the pixel circuit and a light-emitting device connected with each pixel circuit;
the first scanning signal end of the pixel circuit in the nth row of pixel units is connected with the nth scanning line, the second scanning signal end of the pixel circuit in the nth row of pixel units is connected with the (n + 1) th scanning line, and the third scanning signal end of the pixel circuit in the nth row of pixel units is connected with the (n + 2) th scanning line.
Correspondingly, the embodiment of the invention also provides a display device which comprises the organic light-emitting display panel provided by the embodiment of the invention.
The invention has the following beneficial effects:
in the pixel circuit, the organic light emitting display panel and the display device provided by the embodiment of the invention, the pixel circuit is controlled by three scanning signal ends, and the first scanning signal end, the second scanning signal end and the third scanning signal end sequentially output scanning signals, so that the three scanning signal ends do not have a time period for simultaneously outputting scanning signals, which means that in the pixel circuit provided by the embodiment of the invention, the situation that the fifth switching transistor, the seventh switching transistor, the fourth switching transistor, the first switching transistor and the sixth switching transistor are simultaneously turned on does not exist, and therefore, the current from Data to a Vref channel does not flow to a light emitting device through the sixth switching transistor, so that the problem that the dark state of the conventional pixel circuit is not dark is solved.
Drawings
Fig. 1 is a schematic structural diagram of a pixel circuit provided in the related art;
FIG. 2 is an input timing diagram corresponding to the pixel circuit shown in FIG. 1;
fig. 3 is a schematic structural diagram of a pixel circuit according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of another pixel circuit according to an embodiment of the present invention;
FIG. 5 is a timing diagram of an input process corresponding to the pixel circuit according to the embodiment of the invention;
fig. 6 is a schematic structural diagram of an organic light emitting display panel according to an embodiment of the present invention;
fig. 7 is a schematic structural diagram of a display device according to an embodiment of the present invention.
Detailed Description
Specifically, in the pixel circuit shown in fig. 1, when Scan1 and Scan2 are low-level signals at the same time, simulation shows that Data current flows to Vref, the current on one pixel circuit is about 1.14uA, the total current on one row of pixel circuits is estimated to be 3.28mA, in the dark state, the current on one pixel circuit is about 2.18uA, and the total current on one row of pixel circuits is estimated to be 6.28mA, so that the light-emitting device has a problem that the dark state is not dark.
Embodiments of the present invention provide a pixel circuit, an organic light emitting display panel and a display device to solve the problem of dark state.
In order to make the objects, technical solutions and advantages of the present invention clearer, the present invention will be described in further detail with reference to the accompanying drawings, and it is apparent that the described embodiments are only a part of the embodiments of the present invention, not all of the embodiments. All other embodiments, which can be derived by a person skilled in the art from the embodiments given herein without making any creative effort, shall fall within the protection scope of the present invention.
The shapes and sizes of the various elements in the drawings are not to scale and are merely intended to illustrate the invention.
Specifically, an embodiment of the present invention provides a pixel circuit, as shown in fig. 3 and 4, including: a driving transistor M0, a first switching transistor M1, a second switching transistor M2, a third switching transistor M3, a fourth switching transistor M4, a fifth switching transistor M5, a sixth switching transistor M6, a seventh switching transistor M7, and a first capacitor C1; wherein the content of the first and second substances,
the first switching transistor M1 is used for providing a signal of a reference signal terminal Vref to a first pole of the fourth switching transistor M4 under the control of the first Scan signal terminal Scan 1;
the second switching transistor M2 is used to provide the signal of the first power voltage terminal VDD to the first pole of the driving transistor M0 under the control of the emission control terminal Emit;
the third switching transistor M3 is used for making the second pole of the driving transistor M0 and the second pole of the third switching transistor M3 conductive under the control of the light emitting control terminal Emit;
a first pole of the fourth switching transistor M4 and a second pole of the seventh switching transistor M7 are electrically connected in series for making the gate of the driving transistor M0 and the second pole of the driving transistor M0 conductive under the control of the second Scan signal terminal Scan 2;
as shown in fig. 3, the fifth switching transistor M5 is for supplying a signal of the Data signal terminal Data to the first pole of the driving transistor M0 under the control of the second Scan signal terminal Scan2, and the sixth switching transistor M6 is for supplying a signal of the reference signal terminal Vref to the anode of the light emitting device oled under the control of the third Scan signal terminal Scan 3; alternatively, as shown in fig. 4, the fifth switching transistor M5 is for supplying the signal of the Data signal terminal Data to the first pole of the driving transistor M0 under the control of the third Scan signal terminal Scan3, and the sixth switching transistor M6 is for supplying the signal of the reference signal terminal Vref to the anode of the light emitting device oled under the control of the first Scan signal terminal Scan 1;
the first capacitor C1 is used to keep the voltage difference between the gate of the driving transistor M0 and the power supply voltage terminal stable;
the driving transistor M0 is used to provide a driving current to the light emitting device under the control of the second switching transistor M2, the third switching transistor M3 and the first capacitor C1.
The pixel circuit provided by the embodiment of the invention is controlled by three scanning signal ends, and the first scanning signal end, the second scanning signal end and the third scanning signal end output scanning signals in sequence, so that the three scanning signal ends do not have a time period for outputting the scanning signals at the same time, which means that the pixel circuit provided by the embodiment of the invention does not have the condition that the fifth switching transistor, the seventh switching transistor, the fourth switching transistor, the first switching transistor and the sixth switching transistor are simultaneously conducted, so that the current from Data to a Vref channel does not flow to a light-emitting device through the sixth switching transistor, and the problem that the dark state of the conventional pixel circuit is not dark is solved.
Specifically, in the pixel circuit provided by the embodiment of the invention, as shown in fig. 3 and 4, the cathode of the light emitting device oled is connected to the second power voltage terminal VEE, and the voltage of the second power voltage terminal VEE is generally a negative voltage or ground.
Specifically, in the pixel circuit provided in the embodiment of the present invention, the light emitting device oled is generally an organic light emitting diode, and is not limited herein.
Specifically, in the pixel circuit provided by the embodiment of the present invention, as shown in fig. 3 and 4, the gate of the second switching transistor M2 is connected to the emission control terminal Emit, the first pole of the second switching transistor M2 is connected to the power supply voltage terminal, and the second pole of the second switching transistor M2 is connected to the first pole of the driving transistor M0. When the second switching transistor M2 is turned on under the control of the emission control terminal Emit, the signal of the first power voltage terminal VDD is transmitted to the second node N2.
Specifically, in the pixel circuit provided by the embodiment of the present invention, as shown in fig. 3 and 4, the gate of the third switching transistor M3 is connected to the emission control terminal Emit, the first pole of the third switching transistor M3 is connected to the second pole of the driving transistor M0, and the second pole of the third switching transistor M3 is connected to the anode of the light emitting device. When the third switching transistor M3 is turned on under the control of the light emission control terminal Emit, the driving transistor M0 supplies a driving current to the light emitting device oled.
Specifically, in the pixel circuit provided by the embodiment of the present invention, as shown in fig. 3 and 4, the gate of the fourth switching transistor M4 is connected to the second Scan signal terminal Scan2, the first pole of the fourth switching transistor M4 is connected to the gate of the driving transistor M0, the second pole of the fourth switching transistor M4 is connected to the first pole of the seventh switching transistor M7, the second pole of the seventh switching transistor M7 is connected to the second pole of the driving transistor M0, and the gate of the seventh switching transistor M7 is connected to the second Scan signal terminal Scan 2. When the fourth and seventh switching transistors M4 and M7 are turned on under the control of the second Scan signal terminal Scan2, the driving transistor M0 is connected in a diode structure, thereby compensating for the threshold voltage of the driving transistor M0. In addition, since the fourth switching transistor M4 is turned off during the light emitting period, even if a leakage current flows to the second pole of the fourth switching transistor M4, the leakage current does not further flow to the gate of the driving transistor M0, that is, the gate potential of the driving transistor M0 during the light emitting period is not affected by the leakage current of the other transistors, so that the light emitting uniformity during the light emitting period is fully ensured.
Optionally, in the pixel circuit provided by the embodiment of the present invention, the width-to-length ratio of the driving transistor is the transistor with the smallest width-to-length ratio in the entire pixel driving circuit, that is, the width-to-length ratio of the driving transistor is smaller than that of any one of the switching transistors, so that it is ensured that the magnitude of the driving current flowing through the driving transistor can satisfy the requirement of higher light-emitting brightness of the light-emitting device. Meanwhile, in the embodiment of the present invention, in order to sufficiently ensure the stability of the gate potential of the driving transistor, the width-to-length ratio of the fourth switching transistor is smaller than the width-to-length ratio of any one of the first switching transistor, the second switching transistor, the third switching transistor, the fifth switching transistor, the sixth switching transistor, and the seventh switching transistor.
Specifically, in the pixel circuit provided by the embodiment of the invention, as shown in fig. 3 and 4, the gate of the first switching transistor M1 is connected to the first Scan signal terminal Scan1, the first pole of the first switching transistor M1 is connected to the reference signal terminal Vref, and the second pole of the first switching transistor M1 is connected between the second pole of the fourth switching transistor M4 and the first pole of the seventh switching transistor M7.
Specifically, in the pixel circuit provided by the embodiment of the invention, as shown in fig. 3, the gate of the fifth switching transistor M5 is connected to the second Scan signal terminal Scan2, the first pole of the fifth switching transistor M5 is connected to the Data signal terminal Data, and the second pole of the fifth switching transistor M5 is connected to the first pole of the driving transistor M0. When the fifth switching transistor M5 is turned on under the control of the second Scan signal terminal Scan2, the Data signal terminal Data supplies a Data signal to the second node N2 through the fifth switching transistor M5.
A gate of the sixth switching transistor M6 is connected to the third Scan signal terminal Scan3, a first pole of the sixth switching transistor M6 is connected to the reference signal terminal Vref, and a second pole of the sixth switching transistor M6 is connected to the second pole of the third switching transistor M3. When the sixth switching transistor M6 is turned on under the control of the third Scan signal terminal Scan3, the reference signal terminal Vref resets the anode of the light emitting device oled through the sixth switching transistor M6.
Or, specifically, in the pixel circuit provided by the embodiment of the invention, as shown in fig. 4, the gate of the fifth switching transistor M5 is connected to the third Scan signal terminal Scan3, the first pole of the fifth switching transistor M5 is connected to the Data signal terminal Data, and the second pole of the fifth switching transistor M5 is connected to the first pole of the driving transistor M0. When the fifth switching transistor M5 is turned on under the control of the third Scan signal terminal Scan3, the Data signal terminal Data supplies the Data signal to the second node N2 through the fifth switching transistor M5.
A gate of the sixth switching transistor M6 is connected to the first Scan signal terminal Scan1, a first pole of the sixth switching transistor M6 is connected to the reference signal terminal Vref, and a second pole of the sixth switching transistor M6 is connected to the second pole of the third switching transistor M3. When the sixth switching transistor M6 is turned on under the control of the first Scan signal terminal Scan1, the reference signal terminal Vref resets the anode of the light emitting device oled through the sixth switching transistor M6.
Compared with a single-gate structure, the double-gate structure has the advantages of stronger breakdown resistance, reduced leakage current and the like, so that any switching transistor can be set to be the double-gate structure in specific implementation, and is not limited herein.
In a specific implementation, in the pixel circuit provided in the embodiment of the present invention, one of the first pole and the second pole of the transistor is a source, and the other is a drain.
In specific implementation, in the display panel provided in the embodiment of the present invention, the driving transistor is a P-type transistor, and for the case that the driving transistor is an N-type transistor, the design principle is the same as that of the present invention, and also falls within the protection scope of the present invention.
In specific implementation, in the display panel provided in the embodiment of the present invention, all the transistors may be designed as P-type transistors, so that the manufacturing process flow of the pixel circuit can be simplified.
In one embodiment, the Scan signals are outputted from the first Scan signal terminal Scan1, the second Scan signal terminal Scan2 and the third Scan signal terminal Scan3 in terms of timing. As shown in fig. 5, the Scan signal at the first Scan signal terminal Scan1 and the Scan signal at the second Scan signal terminal Scan2 partially overlap in timing, the Scan signal at the second Scan signal terminal Scan2 and the Scan signal at the third Scan signal terminal Scan3 also partially overlap in timing, and the Scan signal at the first Scan signal terminal Scan1 and the Scan signal at the third Scan signal terminal Scan3 do not overlap in timing. In the pixel circuit shown in fig. 1, there is a path from the data signal terminal Vdata to the reference signal terminal Vref, and a current on the path flows to the light emitting device oled, so that the light emitting device oled emits light, thereby generating a problem that a dark state is not dark. In the pixel circuit provided by the embodiment of the invention, the connection relationship is redesigned for the pixel circuit shown in fig. 1, so that a passage from Vdata to Vref is avoided or a current from Vdata to the Vref passage is prevented from flowing to the light emitting device, and therefore, the problem that the dark state of the pixel circuit shown in fig. 1 is not dark can be solved.
The operation of the pixel circuit provided by the embodiment of the present invention is described below with reference to a circuit timing diagram.
Example one
Taking the pixel circuit shown in fig. 3 as an example, all the switch transistors are P-type transistors, and the corresponding input timing is shown in fig. 5. Specifically, five stages of T1, T2, T3, T4, and T5 in the input timing chart shown in fig. 5 are selected.
At the stage T1, only the first Scan signal terminal Scan1 is a low level signal. The first switching transistor M1 is turned on. In the pixel circuit of fig. 4 only, the first switching transistor M1 resets the first node N1.
At the stage T2, the second Scan signal terminal Scan2 becomes a low level signal. The first Scan signal terminal Scan1 changes from a low level signal to a high level signal after a certain time. The fifth switching transistor M5 is turned on, the signal of the Data signal terminal Data is transmitted to the second node N2, and the potential of the second node N2 is Vdata. The fourth switching transistor M4 and the seventh switching transistor M7 are turned on, and the driving transistor M0 forms a diode structure. When the first Scan signal terminal Scan1 is a low level signal, the signal of the reference signal terminal Vref is transmitted to the first node N1, and the potential of the first node N1 is Vref. The driving transistor M0 of the diode structure is turned on. When the first Scan signal terminal Scan1 becomes a high level signal, the first node N1 starts to be charged until the potential of the first node N1 becomes Vdata- | Vth |, and the driving transistor M0 is turned off. Vth is the threshold voltage of the drive transistor. At this stage, although there is a path of Data to Vref, since the sixth switching transistor M6 is turned off, no current can flow to the light emitting device oled, and the light emitting device oled does not emit light.
At the stage T3, the third Scan signal terminal Scan3 becomes a low level signal. The second Scan signal terminal Scan2 changes from a low level signal to a high level signal after a certain time. The sixth switching transistor M6 is turned on, a signal of the reference signal terminal Vref is transmitted to the fourth node N4, the potential of the fourth node N4 is Vref, the anode of the light emitting device oled is reset, and the light emitting device oled does not emit light. When the second Scan signal terminal Scan1 is a low-level signal, the potential of the second node N2 still maintains Vdata, and the potential of the first node N1 still maintains Vdata- | Vth |. When the second Scan signal terminal Scan2 becomes a high level signal, the potential of the first node N1 is still maintained at Vdata- | Vth |, under the action of the capacitor C1. At this stage, although the signal of the reference signal terminal Vref is transmitted to the fourth node N4, since the first switching transistor M1 is turned off, there is no path for Data to the Vref, and thus Data does not affect the Vref, and the light emitting device oled is still not emitting light.
At the stage T4, the third Scan signal terminal Scan3 changes from a low level signal to a high level signal after a certain time. When the third Scan signal terminal Scan3 is a low signal, the potential of the fourth node N4 is still Vref. When the third Scan signal terminal Scan3 becomes a high level signal, the potential of the first node N1 remains Vdata- | Vth |, and the light emitting device oled remains unlit.
In the stage T5, only the emission control terminal Emit is a low level signal, and the second switching transistor and the third switching transistor are turned on. The signal of the first power voltage terminal VEE is transmitted to the second node N2, the potential of the second node N2 is VDD, the potential of the first node N1 is Vdata- | Vth | due to the effect of the capacitor C1, the gate-source voltage Vsg of the driving transistor M0 is VDD-Vdata + | Vth |, and the driving current I of the driving transistor M0 is K (Vsg- | Vth |)2＝K(VDD-Vdata)2＝K(VDD-Vdata+|Vth|-|Vth|)2(ii) a The driving light emitting device oled of the driving transistor M0 operates to emit light.
Since K is a structural parameter, this value is relatively stable in the same structure and can be calculated as a constant. It can be seen that the current flowing to the light emitting device oled is not affected by the threshold voltage of the driving transistor, and the influence of the driving transistor due to the threshold voltage drift is solved, thereby improving the display non-uniformity of the panel. In addition, since the fifth switching transistor, the seventh switching transistor, the fourth switching transistor, the first switching transistor and the sixth switching transistor are not turned on at the same time, although a Data-to-Vref path exists, when the Data-to-Vref path exists, the reference signal terminal Vref and the light emitting device are turned off, so that no current flows through the light emitting device in the current row, and although the signal of the reference signal terminal Vref in the current row is influenced by Data in the previous row, the voltage drop of the Vref in the current row is small. Through testing, the dark state circuit can be reduced from 0.8nit to 0.2 nit. Therefore, compared with the pixel circuit of fig. 1, the problem of dark state can be greatly improved.
Example two
Taking the pixel circuit shown in fig. 4 as an example, all the switch transistors are P-type transistors, and the corresponding input timing is shown in fig. 5. Specifically, five stages of T1, T2, T3, T4, and T5 in the input timing chart shown in fig. 5 are selected.
At the stage T1, only the first Scan signal terminal Scan1 is a low level signal. The first switching transistor M1 and the sixth switching transistor M6 are turned on. In the pixel circuit of fig. 7 only, the first switching transistor M1 resets the first node N1. The signal of the reference signal terminal Vref is transmitted to the fourth node N4 through the sixth switching transistor M6, the potential of the fourth node N4 is Vref, the anode of the light emitting device oled is reset, and the light emitting device oled does not emit light.
At the stage T2, the second Scan signal terminal Scan2 becomes a low level signal. The first Scan signal terminal Scan1 changes from a low level signal to a high level signal after a certain time. The fourth switching transistor M4 and the seventh switching transistor M7 are turned on, and the driving transistor M0 forms a diode structure. When the first Scan signal terminal Scan1 is a low level signal, the signal of the reference signal terminal Vref is transmitted to the first node N1, and the potential of the first node N1 is Vref. The driving transistor M0 of the diode structure is turned on. Although the sixth switching transistor M6 is turned on and the reference signal terminal Vref is turned on with the fourth node N4, since the fifth switching transistor M5 is turned off, there is no path from Data to Vref, and therefore the signal at the reference signal terminal Vref is not affected by the Data at the Data signal terminal Data, the potential at the fourth node N4 remains Vref, and the light emitting device oled still does not emit light. When the first Scan signal terminal Scan1 becomes a high level signal, the potential of the first node N1 is still Vref at this stage due to the action of the capacitor C1. The sixth switching transistor M6 is turned off, and thus the light emitting device oled still does not emit light.
At the stage T3, the third Scan signal terminal Scan3 becomes a low level signal. The second Scan signal terminal Scan2 changes from a low level signal to a high level signal after a certain time. The fifth switching transistor M5 is turned on, the signal of the Data signal terminal Data is transmitted to the second node N2, and the potential of the second node N2 is Vdata. When the second Scan signal terminal Scan1 is a low level signal, the first node N1 starts to charge until the potential of the first node N1 becomes Vdata- | Vth |, and the driving transistor M0 is turned off. Vth is the threshold voltage of the drive transistor. When the second Scan signal terminal Scan2 becomes a high level signal, the fourth switching transistor M4 and the seventh switching transistor M7 are turned off, and the potential of the first node N1 still maintains Vdata- | Vth |, under the action of the capacitor C1. At this stage, since the first switching transistor M1 is turned off, there is no path for Data to Vref, and thus Data does not affect Vref, and the sixth switching transistor M6 is turned off, and thus the light emitting device oled is still not emitting light.
At the stage T4, the third Scan signal terminal Scan3 changes from a low level signal to a high level signal after a certain time. When the third Scan signal terminal Scan3 is a low-level signal, the potential of the second node N2 is still Vdata, the potential of the first node N1 is still Vdata- | Vth |, and the light emitting device oled is still non-emitting. When the third Scan signal terminal Scan3 becomes a high level signal, the potential of the first node N1 remains Vdata- | Vth |. At this stage, since the first switching transistor M1 is turned off, there is no path for Data to Vref, and thus Data does not affect Vref, and the sixth switching transistor M6 is turned off, and thus the light emitting device oled is still not emitting light.
In the stage T5, only the emission control terminal Emit is a low level signal, and the second switching transistor and the third switching transistor are turned on. The signal of the first power voltage terminal VEE is transmitted to the second node N2, the potential of the second node N2 is VDD, the potential of the first node N1 is Vdata- | Vth | due to the effect of the capacitor C1, the gate-source voltage Vsg of the driving transistor M0 is VDD-Vdata + | Vth |, and the driving current I of the driving transistor M0 is K (Vsg- | Vth |)2＝K(VDD-Vdata)2＝K(VDD-Vdata+|Vth|-|Vth|)2(ii) a The driving light emitting device oled of the driving transistor M0 operates to emit light.
Since K is a structural parameter, this value is relatively stable in the same structure and can be calculated as a constant. It can be seen that the current flowing to the light emitting device oled is not affected by the threshold voltage of the driving transistor, and the influence of the driving transistor due to the threshold voltage drift is solved, thereby improving the display non-uniformity of the panel. In addition, the fifth switching transistor, the seventh switching transistor, the fourth switching transistor, the first switching transistor and the sixth switching transistor are not turned on at the same time, so that a path from Data to Vref does not exist, that is, Data does not affect Vref, and therefore the problem that a dark state is not dark does not exist.
Based on the same inventive concept, an embodiment of the present invention further provides an organic light emitting display panel, as shown in fig. 6, including N rows of pixel units PX, N +2 scan lines Gaten, and N +2 stages of shift register units VSRn, where each stage of shift register unit VSRn is correspondingly connected to one scan line Gaten, and N is an integer greater than 0; fig. 6 illustrates an example where n is 1, 2, 3, 4, 5, and 6.
Each pixel unit PX includes the pixel circuit provided in the embodiment of the present invention and a light emitting device connected to each pixel circuit (the specific structure of the pixel unit is not shown in fig. 6);
the first scanning signal end of the pixel circuit in the nth row of pixel units PX is connected to the nth scanning line Gaten, the second scanning signal end of the pixel circuit in the nth row of pixel units PX is connected to the (n + 1) th scanning line Gaten +1, and the third scanning signal end of the pixel circuit in the nth row of pixel units PX is connected to the (n + 2) th scanning line Gaten + 2.
Optionally, in the organic light emitting display panel provided in the embodiment of the present invention, as shown in fig. 6, two rows of dummy pixel units DPX are further included;
the DPX virtual pixel unit comprises a pixel circuit, and the pixel circuit in the DPX virtual pixel unit has the same structure as the pixel circuit in the PX pixel unit;
the third scanning signal end of the pixel circuit of the 1 st row of virtual pixel units is connected with the 1 st scanning line;
and the third scanning signal end of the pixel circuit in the 2 nd row of virtual pixel units is connected with the 2 nd scanning line, and the second scanning signal end of the pixel circuit in the 2 nd row of virtual pixel units is connected with the 2 nd scanning line connected with the 1 st scanning line.
In the implementation, the dummy pixel unit is provided in order to keep the load on the scan line connected to the pixel unit uniform. Since the dummy pixel unit does not emit light, a light emitting device is not generally provided at the time of design, or a light emitting device is provided, but the light emitting device is not connected to the pixel circuit.
Based on the same inventive concept, embodiments of the present invention further provide a display device, as shown in fig. 7, including any one of the organic light emitting display panels provided by embodiments of the present invention. The display device may be: any product or component with a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator and the like. Since the principle of the display device to solve the problem is similar to that of the organic light emitting display panel, the implementation of the display device can be referred to the implementation of the organic light emitting display panel, and repeated details are omitted.
In the pixel circuit, the organic light emitting display panel and the display device provided by the embodiment of the invention, the pixel circuit is controlled by three scanning signal ends, and the first scanning signal end, the second scanning signal end and the third scanning signal end sequentially output scanning signals, so that the three scanning signal ends do not have a time period for simultaneously outputting the scanning signals, which means that in the pixel circuit provided by the embodiment of the invention, the situation that a fifth switching transistor, a seventh switching transistor, a fourth switching transistor, a first switching transistor and a sixth switching transistor are simultaneously conducted does not exist, and therefore, the current from Data to a Vref channel does not flow to a light emitting device through the sixth switching transistor, so that the problem that the dark state of the conventional pixel circuit is not dark is solved.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present invention without departing from the spirit and scope of the invention. Thus, if such modifications and variations of the present invention fall within the scope of the claims of the present invention and their equivalents, the present invention is also intended to include such modifications and variations.
Claims (12)
1. A pixel circuit, comprising: the driving transistor, the first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, the fifth switching transistor, the sixth switching transistor, the seventh switching transistor and the first capacitor; wherein the content of the first and second substances,
the first switch transistor is used for providing a signal of a reference signal end to a first pole of the fourth switch transistor under the control of a first scanning signal end;
the second switch transistor is used for providing a signal of a power supply voltage end to the first pole of the driving transistor under the control of the light-emitting control end;
the third switching transistor is used for enabling a second pole of the driving transistor and a second pole of the third switching transistor to be conducted under the control of the light emitting control end;
a first pole of the fourth switching transistor and a second pole of the seventh switching transistor are electrically connected in series and used for enabling the grid electrode of the driving transistor to be conducted with the second pole of the driving transistor under the control of a second scanning signal end;
the fifth switching transistor is used for providing a signal of a data signal terminal to the first pole of the driving transistor under the control of the second scanning signal terminal, and the sixth switching transistor is used for providing a signal of the reference signal terminal to the anode of the light-emitting device under the control of the third scanning signal terminal; alternatively, the first and second electrodes may be,
the fifth switching transistor is used for supplying a signal of a data signal terminal to the first pole of the driving transistor under the control of a third scanning signal terminal, and the sixth switching transistor is used for supplying a signal of the reference signal terminal to the anode of the light-emitting device under the control of the first scanning signal terminal;
the first capacitor is used for keeping a voltage difference between the grid electrode of the driving transistor and the power supply voltage terminal stable;
the driving transistor is used for providing driving current for the light-emitting device under the control of the second switching transistor, the third switching transistor and the first capacitor;
the first scanning signal end, the second scanning signal end and the third scanning signal end output scanning signals in sequence, no time period for outputting scanning signals simultaneously exists in the first scanning signal end, the second scanning signal end and the third scanning signal end, the time for outputting scanning signals by the first scanning signal end is partially overlapped with the time for outputting scanning signals by the second scanning signal end, and the time for outputting scanning signals by the second scanning signal end is partially overlapped with the time for outputting scanning signals by the third scanning signal end.
2. The pixel circuit according to claim 1,
the grid electrode of the second switch transistor is connected with the light-emitting control end, the first pole of the second switch transistor is connected with the power supply voltage end, and the second pole of the second switch transistor is connected with the first pole of the driving transistor.
3. The pixel circuit according to claim 1,
the grid electrode of the third switching transistor is connected with the light-emitting control end, the first pole of the third switching transistor is connected with the second pole of the driving transistor, and the second pole of the third switching transistor is connected with the anode of the light-emitting device.
4. The pixel circuit according to claim 1,
the grid electrode of the fourth switching transistor is connected with the second scanning signal end, the first electrode of the fourth switching transistor is connected with the grid electrode of the driving transistor, the second electrode of the seventh switching transistor is connected with the second electrode of the driving transistor, and the grid electrode of the seventh switching transistor is connected with the second scanning signal end.
5. The pixel circuit according to claim 4,
the width-to-length ratio of the fourth switching transistor is smaller than the width-to-length ratio of any one of the first switching transistor, the second switching transistor, the third switching transistor, the fifth switching transistor, the sixth switching transistor and the seventh switching transistor.
6. The pixel circuit according to claim 4,
the grid electrode of the first switch transistor is connected with the first scanning signal end, the first pole of the first switch transistor is connected with the reference signal end, and the second pole of the first switch transistor is connected between the second pole of the fourth switch transistor and the first pole of the seventh switch transistor.
7. The pixel circuit according to claim 1,
a grid electrode of the fifth switching transistor is connected with the second scanning signal end, a first pole of the fifth switching transistor is connected with the data signal end, and a second pole of the fifth switching transistor is connected with a first pole of the driving transistor;
the gate of the sixth switching transistor is connected to the third scanning signal terminal, the first pole of the sixth switching transistor is connected to the reference signal terminal, and the second pole of the sixth switching transistor is connected to the second pole of the third switching transistor.
8. The pixel circuit according to claim 1,
a grid electrode of the fifth switching transistor is connected with the third scanning signal end, a first pole of the fifth switching transistor is connected with the data signal end, and a second pole of the fifth switching transistor is connected with a first pole of the driving transistor;
the grid electrode of the sixth switching transistor is connected with the first scanning signal end, the first pole of the sixth switching transistor is connected with the reference signal end, and the second pole of the sixth switching transistor is connected with the second pole of the third switching transistor.
9. A pixel circuit according to any one of claims 1-8, wherein all of the transistors are P-type transistors.
10. An organic light-emitting display panel is characterized by comprising N rows of pixel units, N +2 scanning lines and N +2 stages of shift register units, wherein each stage of shift register unit is correspondingly connected with one scanning line, and N is an integer greater than 0;
the pixel unit includes the pixel circuit according to any one of claims 1 to 9 and a light emitting device connected to each of the pixel circuits;
the first scanning signal end of the pixel circuit in the nth row of pixel units is connected with the nth scanning line, the second scanning signal end of the pixel circuit in the nth row of pixel units is connected with the (n + 1) th scanning line, and the third scanning signal end of the pixel circuit in the nth row of pixel units is connected with the (n + 2) th scanning line.
11. The organic light emitting display panel of claim 10, further comprising two rows of dummy pixel cells;
the virtual pixel unit comprises a pixel circuit, and the pixel circuit in the virtual pixel unit has the same structure as the pixel circuit in the pixel unit;
the third scanning signal end of the pixel circuit of the virtual pixel unit in the 1 st row is connected with the 1 st scanning line;
and the third scanning signal end of the pixel circuit in the virtual pixel unit in the 2 nd row is connected with the 2 nd scanning line, and the second scanning signal end of the pixel circuit in the virtual pixel unit in the 2 nd row is connected with the 2 nd scanning line connected with the 1 st scanning line.
12. A display device characterized by comprising the organic light-emitting display panel according to claim 10 or 11.
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| CN109215582A (en) * | 2018-09-28 | 2019-01-15 | 昆山国显光电有限公司 | Display panel, the driving method of pixel circuit and display device |
| CN109243369A (en) * | 2018-09-28 | 2019-01-18 | 昆山国显光电有限公司 | Display panel, the driving method of pixel circuit and display device |
| CN109712565B (en) * | 2019-03-20 | 2021-08-03 | 京东方科技集团股份有限公司 | Pixel circuit, driving method thereof and electroluminescent display panel |
| EP4131233A4 (en) * | 2020-03-25 | 2023-05-24 | BOE Technology Group Co., Ltd. | Display panel and display device |
| CN111816119B (en) * | 2020-08-31 | 2022-02-25 | 武汉天马微电子有限公司 | Display panel and display device |
| CN112259050B (en) * | 2020-10-30 | 2023-01-06 | 武汉天马微电子有限公司 | Display panel, driving method thereof and display device |
| CN112562591A (en) * | 2020-12-29 | 2021-03-26 | 湖北长江新型显示产业创新中心有限公司 | Pixel circuit, driving method, light-emitting control circuit, display panel and device |
| CN113096604B (en) * | 2021-04-01 | 2023-06-02 | 京东方科技集团股份有限公司 | Pixel circuit, display panel and display device |
| CN112992071A (en) * | 2021-04-22 | 2021-06-18 | 京东方科技集团股份有限公司 | Pixel circuit, driving method thereof and display device |
| CN114783382B (en) * | 2022-03-24 | 2023-12-26 | 京东方科技集团股份有限公司 | Pixel circuit, driving method thereof, display panel and display device |
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| CN103761935B (en) * | 2014-01-21 | 2016-01-06 | 深圳市华星光电技术有限公司 | Display panel |
| KR102472783B1 (en) * | 2016-02-29 | 2022-12-02 | 삼성디스플레이 주식회사 | Display device and method of compensating degradation |
| CN106710529B (en) * | 2016-12-19 | 2019-02-05 | 上海天马有机发光显示技术有限公司 | A kind of pixel-driving circuit, driving method and organic light emitting display panel |
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