CN109256088B - Pixel circuit, display panel, display device and pixel driving method - Google Patents
Pixel circuit, display panel, display device and pixel driving method Download PDFInfo
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- CN109256088B CN109256088B CN201811288354.5A CN201811288354A CN109256088B CN 109256088 B CN109256088 B CN 109256088B CN 201811288354 A CN201811288354 A CN 201811288354A CN 109256088 B CN109256088 B CN 109256088B
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- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—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
- G09G3/22—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
- G09G3/30—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
- 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]
- G09G3/3208—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] organic, e.g. using organic light-emitting diodes [OLED]
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Abstract
The invention discloses a pixel circuit, a display panel, a display device and a pixel driving method, wherein the pixel circuit comprises: the driving circuit comprises a driving transistor, a light emitting device, a reset sub-circuit, a threshold voltage compensation sub-circuit and a current density compensation sub-circuit, wherein the reset sub-circuit is used for writing a first working voltage provided by a first power supply end into a first node in a reset phase; the threshold voltage compensation subcircuit is used for conducting the first node and the third node in the threshold compensation stage, writing the data voltage provided by the data line into the second node, so that the voltage at the first node is charged to the first compensation voltage, and writing the second working voltage provided by the second power supply end into the second node in the display stage; the current density compensation sub-circuit is used for boosting the first compensation voltage at the first node to a second compensation voltage in the display phase. The technical scheme of the invention not only can compensate the threshold value of the driving transistor, but also can prolong the service life of the light-emitting device.
Description
Technical Field
The present invention relates to the field of display technologies, and in particular, to a pixel circuit, a display panel, a display device, and a pixel driving method.
Background
The organic light emitting diode panel can emit light and is driven by current generated when the driving transistor is in a saturated state, because different threshold voltages generate different driving currents when the same gray scale voltage is input, and current inconsistency is caused.
The traditional 2T1C pixel circuit has poor brightness uniformity, and to solve this problem, a better solution at present is to add a compensation circuit in the pixel, and eliminate the influence of the threshold voltage of the driving transistor on the driving current through the compensation circuit.
However, in practical applications, it is found that, for a pixel circuit in which the driving transistor is a P-type transistor, when a compensation circuit is used to eliminate the influence of the threshold voltage of the driving transistor on the driving current, the elimination of the threshold voltage increases the driving current output by the driving transistor, and the current density of the organic light emitting layer in the light emitting device inevitably increases, which easily causes the aging of the organic light emitting layer material, and the service life of the whole OLED panel is reduced.
Disclosure of Invention
The present invention is directed to at least one of the technical problems in the prior art, and provides a pixel circuit, a display panel, a display device and a pixel driving method.
To achieve the above object, the present invention provides a pixel circuit comprising: a driving transistor, a light emitting device, a reset sub-circuit, a threshold voltage compensation sub-circuit, and a current density compensation sub-circuit;
the control electrode of the driving transistor, the first electrode of the driving transistor and the second electrode of the driving transistor are respectively connected with the threshold voltage compensation sub-circuit to a first node, a second node and a third node;
the reset sub-circuit is connected with the first control signal line, the first power supply end and the first node and is used for responding to the control of the first control signal provided by the first control signal line in a reset phase and writing the first working voltage provided by the first power supply end into the first node;
the threshold voltage compensation sub-circuit is further connected with a gate line, a second control signal line, a data line and a second power supply end, and is used for conducting the first node and the third node in response to the control of a scanning signal provided by the gate line in a threshold compensation stage, and writing a data voltage provided by the data line into the second node so as to charge a voltage at the first node to a first compensation voltage; and in a display phase, in response to the control of a second control signal provided by the second control signal line, writing a second operating voltage provided by the second power supply terminal to the second node;
the current density compensation sub-circuit is connected to the second control signal line, the third control signal line, the first power supply terminal, and the first electrode of the light emitting device, and is configured to boost the first compensation voltage at the first node to a second compensation voltage in response to control of a second control signal provided by the second control signal line and a third control signal provided by the third control signal line during the display phase, where V2 is V1 +. DELTA.v, V1 represents the first compensation voltage, V2 represents the second compensation voltage, and Δ V represents a compensation voltage preset to reduce the current density at the light emitting device;
the first pole of the light-emitting device is connected with the third node, and the second pole of the light-emitting device is connected with a third power supply end;
the driving transistor is used for responding to the control of the second compensation voltage in the display stage and outputting driving current to the light-emitting device so as to drive the light-emitting device to display.
Optionally, the threshold voltage compensation sub-circuit comprises: the first switch tube, the second switch tube, the third switch tube and;
the control electrode of the first switch tube is connected with the grid line, the first electrode of the first switch tube is connected with the second node, and the second electrode of the first switch tube is connected with the data line;
a control electrode of the second switching tube is connected with the grid line, a first electrode of the second switching tube is connected with the first node, and a second electrode of the second switching tube is connected with the third node;
a control electrode of the third switching tube is connected with the second control signal line, a first electrode of the third switching tube is connected with the second power supply end, and a second electrode of the third switching tube is connected with the second node;
a first terminal of the first capacitor is connected to the second power terminal, and a second terminal of the first capacitor is connected to the first node.
Optionally, the current density compensation sub-circuit comprises: the fourth switching tube, the fifth switching tube and the second capacitor;
a control electrode of the fourth switching tube is connected with the second control signal line, a first electrode of the fourth switching tube is connected with the second power supply end, and a second electrode of the fourth switching tube is connected with the second end of the second capacitor;
a control electrode of the fifth switching tube is connected with the third control signal line, a first electrode of the fifth switching tube is connected with the second end of the second capacitor, and a second electrode of the fifth switching tube is connected with the first electrode of the light-emitting device;
the first end of the second capacitor is connected with the first node.
Optionally, one of the fourth switching tube and the fifth switching tube is an N-type switching tube, and the other is a P-type switching tube;
the second control signal line and the third control signal line are the same control signal line.
Optionally, the reset sub-circuit comprises: a sixth switching tube;
a control electrode of the sixth switching tube is connected to the first control signal line, a first electrode of the sixth switching tube is connected to the first power supply terminal, and a second electrode of the sixth switching tube is connected to the first node.
Optionally, the method further comprises: a light emission control sub-circuit through which a first pole of the light emitting device is connected to the third node;
the light-emitting control sub-circuit is connected to the third control signal line, and is configured to turn on the first electrode of the light-emitting device and the third node in response to control of the third control signal during the display phase.
Optionally, the light emission control sub-circuit comprises: a seventh switching tube;
a control electrode of the seventh switching tube is connected to the second control signal line, a first electrode of the seventh switching tube is connected to the third node, and a second electrode of the seventh switching tube is connected to the first electrode of the light emitting device.
To achieve the above object, the present invention also provides a display panel including: such as the pixel circuit described above.
Optionally, the display panel further comprises: the pixel circuit comprises a plurality of grid lines and a plurality of data lines, wherein all the grid lines and all the data lines define a plurality of pixel units, and each row of the pixel circuit corresponds to one grid line;
in addition to the pixel circuits in the first row, in the pixel circuits in other rows, the first control signal line connected to the pixel circuit is a gate line corresponding to the pixel circuit in the row before the first control signal line.
In order to achieve the above object, the present invention also provides a display device including: such as the display panel described above.
In order to achieve the above object, the present invention further provides a pixel driving method, based on the above pixel circuit, including:
in the reset phase, the reset sub-circuit responds to the control of the first control signal and writes the first working voltage into the first node;
in a threshold compensation phase, the threshold voltage compensation sub-circuit writes the first compensation voltage to the first node in response to control of the scan signal;
in the display stage, the current density compensation sub-circuit responds to the control of the second control signal and the third control signal to boost the first compensation voltage at the first node to a second compensation voltage, the threshold voltage compensation sub-circuit responds to the control of the second control signal to write the second working voltage into a second node, and the driving transistor responds to the control of the second compensation voltage to output a driving current to the light emitting device so as to drive the light emitting device to display.
Drawings
Fig. 1 is a circuit diagram of a pixel circuit according to the prior art;
fig. 2 is a circuit diagram of a pixel circuit according to an embodiment of the invention;
fig. 3 is a circuit diagram of a pixel circuit according to a second embodiment of the present invention;
FIG. 4 is a timing diagram illustrating the operation of the pixel circuit shown in FIG. 3;
fig. 5 is a circuit diagram of a pixel circuit according to a third embodiment of the present invention;
fig. 6 is a flowchart of a pixel driving method according to a fourth embodiment of the present invention;
fig. 7 is a circuit diagram of a pixel unit in an nth row and an mth column in a display panel according to a fifth embodiment of the present invention.
Detailed Description
In order to make those skilled in the art better understand the technical solution of the present invention, a pixel circuit, a display panel, a display device and a pixel driving method provided by the present invention are described in detail below with reference to the accompanying drawings.
In order to make those skilled in the art better understand the technical solution of the present invention, a pixel circuit, a display device and a pixel driving method provided by the present invention are described in detail below with reference to the accompanying drawings.
The Light Emitting device in the present invention may be a current-driven Light Emitting device including an LED (Light Emitting Diode) or an OLED (Organic Light Emitting Diode) in the prior art, and in the present embodiment, the Light Emitting device is exemplified as an OLED.
Fig. 1 is a circuit diagram of a pixel circuit according to the prior art, and as shown in fig. 1, a conventional pixel driving circuit adopts a 2T1C circuit, and the 2T1C circuit includes two thin film transistors (a switching transistor T0 and a driving transistor DTFT) and 1 storage capacitor C.
However, since the uniformity of the threshold voltage Vth between the driving transistors DTFT on the display substrate is poor in the conventional low temperature polysilicon process, and the threshold voltage Vth may drift during the use process, when the Scan line Scan (also called as gate line) controls the switching transistor T0 to be turned on to input the same data voltage Vdata to the driving transistors DTFT, different driving currents are generated due to different threshold voltages of the driving transistors DTFT, so that the uniformity of the luminance of the light emitting device OLED is poor.
With continued reference to fig. 1, during the display phase, the voltage of the control electrode of the driving transistor DTFT is Vdata, which is obtained according to the formula of the saturation driving current of the driving transistor DTFT:
I1＝K*(Vgs-Vth)2
＝K*(Vdata-Vdd-Vth)2
＝K*(Vdd+Vth-Vdata)2
wherein I1 is the driving current output by the driving transistor DTFT, K is a constant, and Vgs is the gate-source voltage of the driving transistor DTFT; the data voltage Vdata is less than Vdd; when the driving transistor DTFT is a P-type transistor, the threshold voltage Vth is negative, and Vdd + Vth-Vdata is greater than 0.
In the prior art, the principle of eliminating the influence of the threshold voltage of the driving transistor DTFT on the driving current by adding the compensation circuit is as follows, the threshold voltage of the driving transistor DTFT is obtained in the compensation stage, and then the voltage at the control electrode of the driving transistor DTFT is controlled to be Vdata + Vth in the display stage, and at this time, the threshold voltage can be obtained according to the saturated driving current formula of the driving transistor DTFT:
I2＝K*(Vgs-Vth)2
＝K*(Vdata+Vth-Vdd-Vth)2
＝K*(Vdd-Vdata)2
i2 is the driving current output by the driving transistor DTFT after threshold compensation. Since Vdata is less than Vdd and Vth is negative, K (Vdd-Vdata)2Greater than K (Vdd + Vth-Vdata)2I.e., I2 is greater than I1. Therefore, when threshold compensation is performed on the P-type driving transistor DTFT in the prior art, the driving current output by the driving transistor DTFT corresponding to the same data voltage is increased, and the current density of the organic light emitting layer in the light emitting device OLED is inevitably increased, which affects the service life of the light emitting device OLED.
To solve the above problems, the present invention provides a new pixel circuit, a display panel, a display device, and a pixel driving method.
It should be noted that the switching tube in the present invention may be a thin film transistor or a field effect transistor or other switching devices with the same characteristics. Transistors generally include three poles: the gate, source and drain, the source and drain in a transistor are symmetrical in structure, and the two may be interchanged as desired. In the present invention, the control electrode refers to a gate electrode of the transistor, and one of the first electrode and the second electrode is a source electrode and the other is a drain electrode.
Further, the transistors may be classified into N-type transistors and P-type transistors according to transistor characteristics; when the transistor is an N-type transistor, the on voltage of the transistor is high level voltage, and the off voltage of the transistor is low level voltage; when the transistor is a P-type transistor, the on voltage is a low level voltage and the off voltage is a high level voltage. In the invention, the 'active level state' refers to a voltage state that a signal can control the corresponding transistor to be turned on, and the 'inactive level state' refers to a voltage state that a signal can control the corresponding transistor to be turned off; therefore, when the transistor is an N-type transistor, the active level state refers to a high level state, and the inactive level state refers to a low level state; when the transistor is a P-type transistor, the active level state refers to a low level state, and the inactive level state refers to a high level state. In the present invention, the driving transistor is only limited to be a P-type transistor, and the switching transistors are not limited to be N-type or P-type.
Example one
Fig. 2 is a circuit schematic diagram of a pixel circuit according to an embodiment of the present invention, and as shown in fig. 2, the pixel circuit includes: a driving transistor DTFT, a light emitting device OLED, a reset sub-circuit 1, a threshold voltage compensation sub-circuit 2, and a current density compensation sub-circuit 3; the control electrode of the driving transistor DTFT, the first electrode of the driving transistor DTFT, and the second electrode of the driving transistor DTFT are connected to the first node N1, the second node N2, and the third node N3, respectively, with the threshold voltage compensation sub-circuit 2.
The reset sub-circuit 1 is connected to the first control signal line E1, the first power source terminal, and the first node N1, and is configured to write the first operating voltage provided by the first power source terminal into the first node N1 in response to the control of the first control signal provided by the first control signal line E1 during a reset phase.
The threshold voltage compensation sub-circuit 2 is further connected to the Gate line Gate, the second control signal line E2, the Data line Data, and the second power source terminal, and is configured to turn on the first node N1 and the third node N3 in response to the control of the scan signal provided by the Gate line Gate during the threshold compensation phase, and write the Data voltage provided by the Data line Data into the second node N2, so that the voltage at the first node N1 is charged to the first compensation voltage; and writing the second operating voltage supplied from the second power supply terminal to the second node N2 in response to control of the second control signal supplied from the second control signal line E2 during the display phase.
In the threshold compensation phase, the voltage at the second node N2 is Vdata, the signal at the second node N2 charges the first node N1 through the driving transistor DTFT and the third node N3, and the driving transistor DTFT is turned off and the charging is ended until the voltage at the first node N1 is charged to Vdata + Vth. Therefore, the first compensation voltage V1 is Vdata + Vth.
The current density compensation sub-circuit 3 is connected to the second control signal line E2, the third control signal line E3, the first power supply terminal, and the first pole of the light emitting device OLED, and is configured to boost the first compensation voltage at the first node N1 to a second compensation voltage in response to the control of the second control signal provided by the second control signal line E2 and the third control signal provided by the third control signal line E3 during the display phase, where V2 is V1 +. DELTA.v is Vdata + Vth +. DELTA.v, V2 represents the second compensation voltage, DELTA.v represents a compensation voltage preset to reduce the current density at the light emitting device OLED, and DELTA.v is a positive value.
The first pole of the light emitting device OLED is connected to the third node N3, and the second pole of the light emitting device OLED is connected to the third power source terminal.
The driving transistor DTFT is configured to output a driving current to the light emitting device OLED in response to the control of the second compensation voltage during the display phase to drive the light emitting device OLED to display.
In this embodiment, a description is given by taking, as an example, a first operating voltage provided by the first power supply terminal as a reset voltage Vint, a second operating voltage provided by the second power supply terminal as a high-level operating voltage Vdd, and a third operating voltage provided by the third power supply terminal as a low-level operating voltage Vss (Vss is used as a reference voltage, generally OV). In addition, the predetermined compensation voltage Δ V is smaller than Vdd-Vdata _ max, where Vdata _ max is the maximum value of the Data voltage that the Data line Data can supply.
In the display phase, the current density compensation sub-circuit 3 pulls up the voltage Vdata + Vth at the first node N1 to Vdata + Vth +/Δ V, and the threshold voltage compensation sub-circuit 2 writes a high-level operating voltage into the second node N2, which is obtained according to the saturated driving current formula of the driving transistor DTFT:
I3＝K*(Vgs-Vth)2
＝K*(Vdata+Vth+△V-Vdd-Vth)2
＝K*(Vdata-Vdd+△V)2
＝K*(Vdd-Vdata-△V)2
here, I3 is a driving current output from the driving transistor DTFT after threshold compensation and voltage compensation. Since Vdd-Vdata > Vdd-Vdata- Δ V > 0, K (Vdd-Vdata)2＞K*(Vdd-Vdata-△V)2I.e., I2 > I3.
Therefore, the technical scheme of the invention can compensate the threshold voltage of the driving transistor DTFT, and simultaneously can reduce the driving current output by the driving transistor DTFT when the same data voltage is corresponded, the current density of the organic light-emitting layer in the light-emitting device OLED is inevitably reduced, and the service life of the light-emitting device OLED can be effectively prolonged.
In practical applications, the magnitude of Δ V can be designed and adjusted according to actual needs to control the reduction amount of the driving current output by the driving transistor.
Example two
Fig. 3 is a circuit schematic diagram of a pixel circuit according to a second embodiment of the present invention, and as shown in fig. 3, the pixel circuit shown in fig. 3 is a specific scheme based on the pixel circuit shown in fig. 2.
Optionally, the threshold voltage compensation sub-circuit 2 comprises: the circuit comprises a first switch tube T1, a second switch tube T2, a third switch tube T3 and a first capacitor C1.
A control electrode of the first switch transistor T1 is connected to the Gate line Gate, a first electrode of the first switch transistor T1 is connected to the second node N2, and a second electrode of the first switch transistor T1 is connected to the Data line Data.
A control electrode of the second switching transistor T2 is connected to the Gate line Gate, a first electrode of the second switching transistor T2 is connected to the first node N1, and a second electrode of the second switching transistor T2 is connected to the third node N3.
A control electrode of the third switching transistor T3 is connected to the second control signal line E2, a first electrode of the third switching transistor T3 is connected to the second power source terminal, and a second electrode of the third switching transistor T3 is connected to the second node N2.
A first terminal of the first capacitor C1 is connected to the second power supply terminal, and a second terminal of the first capacitor C1 is connected to the first node N1.
Optionally, the current density compensation sub-circuit 3 comprises: a fourth switching tube T4, a fifth switching tube T5 and a second capacitor C2.
A control electrode of the fourth switch transistor T4 is connected to the second control signal line E2, a first electrode of the fourth switch transistor T4 is connected to the second power source terminal, and a second electrode of the fourth switch transistor T4 is connected to the second terminal of the second capacitor C2.
A control electrode of the fifth switching tube T5 is connected to the third control signal line E3, a first electrode of the fifth switching tube T5 is connected to the second end of the second capacitor C2, and a second electrode of the fifth switching tube T5 is connected to the first electrode of the light emitting device OLED. A first terminal of the second capacitor C2 is connected to the first node N1.
Optionally, the reset sub-circuit 1 comprises: a sixth switching tube T6; a control electrode of the sixth switch transistor T6 is connected to the first control signal line E1, a first electrode of the sixth switch transistor T6 is connected to the first power source terminal, and a second electrode of the sixth switch transistor T6 is connected to the first node N1.
Optionally, the pixel circuit further comprises: the light emission control sub-circuit 4, the first pole of the light emitting device OLED is connected to the third node N3 through the light emission control sub-circuit 4.
The light emission control sub-circuit 4 is connected to the third control signal line E3, and is configured to conduct the first electrode of the light emitting device OLED with the third node N3 in response to the control of the third control signal during the display phase.
In the present invention, by providing the light emission control sub-circuit 4, the problem that the light emitting device OLED emits light by mistake due to the current generated at the driving transistor DTFT flowing through the light emitting device OLED can be avoided during the non-display period.
Further optionally, the light emission control sub-circuit 4 comprises: a seventh switching tube T7; a control electrode of the seventh switching transistor T7 is connected to the second control signal line E2, a first electrode of the seventh switching transistor T7 is connected to the third node N3, and a second electrode of the seventh switching transistor T7 is connected to the first electrode of the light emitting device OLED.
The operation of the pixel circuit shown in fig. 3 will be described in detail with reference to the accompanying drawings. In this embodiment, a first working voltage provided by a first power supply terminal is a reset voltage Vint, a second working voltage provided by a second power supply terminal is a high-level working voltage Vdd, a third working voltage provided by a third power supply terminal is a low-level working voltage Vss, and each switching tube is a P-type transistor for example; at this time, the first electrode of the light emitting device OLED is an anode, and the second electrode is a cathode. Further, assuming that the threshold voltage of the light emitting device OLED is Voled, Voled is greater than 0.
For convenience of description, a connection point of the second terminal of the second capacitor C2, the second pole of the fourth switch T4, and the first pole of the fifth switch T5 is referred to as a fourth node N4.
Fig. 4 is a timing diagram illustrating the operation of the pixel circuit shown in fig. 3, and as shown in fig. 4, the operation of the pixel circuit includes the following three stages:
a reset phase t 1; the first control signal in the first control signal line E1 is in a low state, the second control signal in the second control signal line E2 is in a high state, the third control signal in the third control signal line E3 is in a low state, and the scan signal in the Gate line Gate is in a high state. At this time, the fifth switching tube T5 and the sixth switching tube T6 are turned on, and the first switching tube T1, the second switching tube T2, the third switching tube T3, the fourth switching tube T4 and the seventh switching tube T7 are turned off.
Since the fifth switch tube T5 is turned on, the voltage Voled at the anode of the light emitting device OLED can be written into the fourth node N4 through the fifth switch tube T5 (it can also be regarded as the fourth node N4 discharging through the third power source terminal), and at this time, the voltage at the fourth node N4 is Voled; meanwhile, since the sixth switch transistor T6 is turned on, the reset voltage Vint can be written into the first node N1 through the sixth switch transistor T6, and the voltage at the first node N1 is Vint.
A threshold compensation phase t 2; the first control signal in the first control signal line E1 is in a high state, the second control signal in the second control signal line E2 is in a high state, the third control signal in the third control signal line E3 is in a low state, and the scan signal in the Gate line Gate is in a low state. At this time, the first switching tube T1, the second switching tube T2 and the fifth switching tube T5 are turned on, and the third switching tube T3, the fourth switching tube T4, the sixth switching tube T6 and the seventh switching tube T7 are turned off.
Since the first and second switching transistors T1 and T2 are turned on, the signal at the second node N2 charges the first node N1 through the driving transistor DTFT and the third node N3 until the voltage at the first node N1 is charged to Vdata + Vth, the driving transistor DTFT is turned off, and the charging is finished, that is, the first compensation voltage V1 is Vdata + Vth. Meanwhile, since the fifth switching tube T5 is kept on, the voltage of the third node N3 is kept Voled; at this time, the voltage difference between the two ends of the second capacitor C2 is Vdata + Vth-Voled.
Displaying the stage t 3; the first control signal in the first control signal line E1 is in a high state, the second control signal in the second control signal line E2 is in a low state, the third control signal in the third control signal line E3 is in a high state, and the scan signal in the Gate line Gate is in a high state. At this time, the third switching tube T3, the fourth switching tube T4 and the seventh switching tube T7 are turned on, and the first switching tube T1, the second switching tube T2, the fifth switching tube T5 and the sixth switching tube T6 are turned off.
Since the second switch transistor T2 and the sixth switch transistor T6 are turned off, the first node N1 is in a Floating state (Floating). Since the third switch transistor T3 is turned on, the high level operating voltage Vdd is written into the second node N2 through the third switch transistor T3, and the voltage at the second node N2 is Vdd.
Since the fourth switch transistor T4 is turned on, the high level operating voltage Vdd is written into the fourth node N4 through the fourth switch transistor T4The voltage at the node N4 is raised from Voled to Vdd. Due to the capacitor bootstrap, the voltage at the first node N1 will rise accordingly, and the magnitude of the rise is
Where C1 and C2 are the capacitance magnitudes of the first capacitor C1 and the second capacitor C2, respectively. In this embodiment, the following
The preset compensation voltage Δ V is used to reduce the driving current outputted by the driving transistor DTFT during the display period. At this time, the voltage of the first node N1 jumps to Vdata + Vth +. DELTA.V, where
Therefore, in practical applications, the compensation voltage Δ V can be set by controlling the high-level operating voltage Vdd, the threshold voltage Voled of the light emitting device OLED, the capacitance C1 of the first capacitor C1, and the capacitance C2 of the second capacitor C2.
At this time, the formula of the saturation driving current of the driving transistor DTFT can be obtained:
as can be seen from the above formula, the driving current generated by the driving transistor DTFT is independent of the threshold voltage of the driving transistor DTFT, so that the influence of the threshold voltage of the driving transistor DTFT on the driving current of the light emitting device OLED is eliminated, and the luminance uniformity of the light emitting device OLED in the display device is improved. In addition, due to the existence of the compensation voltage Δ V, the driving current output by the driving transistor DTFT corresponding to the same data voltage can be reduced, the current density of the organic light emitting layer in the light emitting device OLED is inevitably reduced, and the service life of the light emitting device OLED can be effectively prolonged.
It should be noted that, in this embodiment, the first to seventh switching tubes and the driving transistor are all P-type transistors, which is a preferred embodiment of the present invention, and at this time, the same transistor manufacturing process can be adopted to simultaneously manufacture the switching tubes and the driving transistor, so that the manufacturing process can be saved and the manufacturing period can be shortened.
EXAMPLE III
Fig. 5 is a circuit schematic diagram of a pixel circuit according to a third embodiment of the present invention, and as shown in fig. 5, unlike the second embodiment in which the fourth switching transistor T4 and the fifth switching transistor T5 are both P-type transistors, one of the fourth switching transistor T4 and the fifth switching transistor T5 in the present embodiment is an N-type transistor, the other is a P-type transistor, and the second control signal line E2 and the third control signal line E3 are the same control signal line.
It should be noted that, in the figure, the case that the fourth switching transistor T4 is a P-type transistor and the fifth switching transistor T5 is an N-type transistor is only exemplified, at this time, the control electrode of the fourth switching transistor T4 and the control electrode of the fifth switching transistor T5 are both connected to the second control signal line E2 (refer to the timing sequence of the second control signal shown in fig. 4). In this case, the pixel circuit does not need to be additionally provided with the third control signal line E3, so that the complexity of the pixel circuit can be effectively simplified.
Of course, in this embodiment, the third switch tube T3, the fourth switch tube T4, and the seventh switch tube T7 may also be N-type transistors, and the fifth switch tube T5 is P-type transistors, where the control electrode of the third switch tube T3, the control electrode of the fourth switch tube T4, the control electrode of the seventh switch tube T7, and the control electrode of the fifth switch tube T5 are all connected to the third control signal line E3 (see the timing of the third control signal shown in fig. 4); at this time, the pixel circuit does not need to be additionally provided with a second control signal line E2, so that the complexity of the pixel circuit can be effectively simplified; no corresponding figures are given in this case.
For a description of the working process of the pixel circuit in this embodiment, reference may be made to the contents of the foregoing second embodiment, and details are not repeated here.
Example four
Fig. 6 is a flowchart of a pixel driving method according to a fourth embodiment of the present invention, as shown in fig. 6, the pixel driving method is based on the pixel circuit provided in any one of the first to third embodiments, and for the structural description of the pixel circuit, reference may be made to the contents in the foregoing embodiments, which are not repeated here, and the pixel driving method includes:
in step S1, in the reset phase, the reset circuit writes the first operating voltage into the first node in response to the control of the first control signal.
In step S2, in the threshold compensation phase, the threshold voltage compensation sub-circuit writes the first compensation voltage to the first node in response to the control of the scan signal.
Specifically, the threshold voltage compensation sub-circuit turns on the first node and the third node, writes the data voltage provided by the data line into the second node, charges the first node with a signal at the second node through the driving transistor and the third node until the voltage at the first node is charged to Vdata + Vth, turns off the driving transistor DTFT, and the charging is finished. At this time, the first compensation voltage V1 is Vdata + Vth.
Step S3, in the display phase, the current density compensation sub-circuit responds to the control of the second control signal and the third control signal to boost the first compensation voltage at the first node to the second compensation voltage, the threshold voltage compensation sub-circuit responds to the control of the second control signal to write the second working voltage into the second node, and the driving transistor responds to the control of the second compensation voltage to output the driving current to the light emitting device to drive the light emitting device to display.
Here, the second compensation voltage V2 is V1 +. Δ V, and Δ V represents a compensation voltage preset to reduce the current density at the light emitting device OLED.
For the detailed description of the above steps, reference may be made to the corresponding matters in the foregoing embodiments, and detailed description is omitted here.
The technical scheme of the invention can not only compensate the threshold value of the driving transistor, but also reduce the driving current output by the driving transistor when corresponding to the same data voltage, and reduce the current density of the organic light-emitting layer in the light-emitting device, thereby prolonging the service life of the light-emitting device.
EXAMPLE five
An embodiment of the present invention provides a display panel, which includes a pixel circuit, where the pixel circuit is the pixel circuit described in any one of the first to third embodiments.
In this embodiment, the display panel further includes: the pixel circuit comprises N grid lines and M data lines, wherein all the grid lines and all the data lines define M x N pixel units, and each pixel unit comprises a pixel circuit. The pixel circuit in the nth row corresponds to the nth grid line, the pixel unit in the mth column corresponds to the mth data line, N is larger than or equal to 1 and smaller than or equal to N, M is larger than or equal to 1 and smaller than or equal to M, and both N and M are integers.
Preferably, in addition to the pixel circuit in the first row, in the pixel circuits in other rows, the first control signal line connected to the pixel circuit is a gate line corresponding to the pixel circuit in the row before the first control signal line. The following description will be made in conjunction with the accompanying drawings.
Fig. 7 is a schematic circuit diagram of a pixel unit in the nth row and the mth column in the display panel according to the fifth embodiment of the present invention, as shown in fig. 7, the Gate line corresponding to the pixel unit is the nth Gate line Gate _ n (the control electrodes of the first switch tube T1 and the second switch tube T2 are both connected to the Gate line Gate _ n), and the Data line Data corresponding to the pixel unit is the mth Data line Data _ m (the second electrode of the first switch tube T1 is connected to the Data line Data _ m).
In the pixel cell, the first control signal line E1 connected to the control electrode of the sixth switching tube T6 is the (n-1) th Gate line Gate _ n-1 corresponding to the pixel cell located in the (n-1) th row (the control electrode of the sixth switching tube T6 is connected to the Gate line Gate _ n-1).
In this embodiment, the Gate lines Gate are multiplexed into the first control signal line E1 connected to the pixel units in the next row, so that the first control signal line E1 is not required to be additionally disposed, and the number of signal lines in the display panel can be effectively reduced, which is beneficial to increasing the pixel aperture ratio.
In addition, when one of the fourth switch tube T4 and the fifth switch tube T5 is an N-type transistor, the other is a P-type transistor, and the second control signal line E2 and the third control signal line E3 are the same control signal line, only one control signal line (one second control signal line E2 or one third control signal line E3, which is only exemplarily shown in the figure where the pixel unit is connected with only the second control signal line E2) needs to be provided for each row of pixel units at this time.
EXAMPLE six
An embodiment of the present invention provides a display device, including: for a specific description, reference may be made to the contents of the fifth embodiment, and details are not described herein.
The display device of the present invention may specifically include: the display device comprises any product or component with a display function, such as electronic paper, an OLED panel, a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame, a navigator and the like.
It will be understood that the above embodiments are merely exemplary embodiments taken to illustrate the principles of the present invention, which is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and substance of the invention, and these modifications and improvements are also considered to be within the scope of the invention.
Claims (10)
1. A pixel circuit, comprising: a driving transistor, a light emitting device, a reset sub-circuit, a threshold voltage compensation sub-circuit, and a current density compensation sub-circuit;
the control electrode of the driving transistor, the first electrode of the driving transistor and the second electrode of the driving transistor are respectively connected with the threshold voltage compensation sub-circuit to a first node, a second node and a third node;
the reset sub-circuit is connected with the first control signal line, the first power supply end and the first node and is used for responding to the control of the first control signal provided by the first control signal line in a reset phase and writing the first working voltage provided by the first power supply end into the first node;
the threshold voltage compensation sub-circuit is further connected with a gate line, a second control signal line, a data line and a second power supply end, and is used for conducting the first node and the third node in response to the control of a scanning signal provided by the gate line in a threshold compensation stage, and writing a data voltage provided by the data line into the second node so as to charge a voltage at the first node to a first compensation voltage; and in a display phase, in response to the control of a second control signal provided by the second control signal line, writing a second operating voltage provided by the second power supply terminal to the second node;
the current density compensation sub-circuit is connected with the second control signal line, a third control signal line, the second power supply terminal and the first pole of the light emitting device, and is used for raising the first compensation voltage at the first node to a second compensation voltage in response to the control of a second control signal provided by the second control signal line and a third control signal provided by the third control signal line in the display phase, wherein V2 is V1+ Δ V, V1 represents the first compensation voltage, V2 represents the second compensation voltage, and Δ V represents a preset compensation voltage for reducing the current density at the light emitting device;
the first pole of the light-emitting device is connected with the third node, and the second pole of the light-emitting device is connected with a third power supply end;
the driving transistor is used for responding to the control of the second compensation voltage in the display stage and outputting a driving current to the light-emitting device so as to drive the light-emitting device to display;
the current density compensation sub-circuit comprises: the fourth switching tube, the fifth switching tube and the second capacitor;
a control electrode of the fourth switching tube is connected with the second control signal line, a first electrode of the fourth switching tube is connected with the second power supply end, and a second electrode of the fourth switching tube is connected with the second end of the second capacitor;
a control electrode of the fifth switching tube is connected with the third control signal line, a first electrode of the fifth switching tube is connected with the second end of the second capacitor, and a second electrode of the fifth switching tube is connected with the first electrode of the light-emitting device;
the first end of the second capacitor is connected with the first node.
2. The pixel circuit of claim 1, wherein the threshold voltage compensation sub-circuit comprises: the circuit comprises a first switching tube, a second switching tube, a third switching tube and a first capacitor;
the control electrode of the first switch tube is connected with the grid line, the first electrode of the first switch tube is connected with the second node, and the second electrode of the first switch tube is connected with the data line;
a control electrode of the second switching tube is connected with the grid line, a first electrode of the second switching tube is connected with the first node, and a second electrode of the second switching tube is connected with the third node;
a control electrode of the third switching tube is connected with the second control signal line, a first electrode of the third switching tube is connected with the second power supply end, and a second electrode of the third switching tube is connected with the second node;
a first terminal of the first capacitor is connected to the second power terminal, and a second terminal of the first capacitor is connected to the first node.
3. The pixel circuit according to claim 1, wherein one of the fourth switching tube and the fifth switching tube is an N-type switching tube, and the other is a P-type switching tube;
the second control signal line and the third control signal line are the same control signal line.
4. The pixel circuit of claim 1, wherein the reset sub-circuit comprises: a sixth switching tube;
a control electrode of the sixth switching tube is connected to the first control signal line, a first electrode of the sixth switching tube is connected to the first power supply terminal, and a second electrode of the sixth switching tube is connected to the first node.
5. The pixel circuit according to claim 1, further comprising: a light emission control sub-circuit through which a first pole of the light emitting device is connected to the third node;
the light emitting control sub-circuit is connected to the second control signal line, and is configured to turn on the first electrode of the light emitting device and the third node in response to control of the second control signal during the display phase.
6. The pixel circuit of claim 5, wherein the light emission control sub-circuit comprises: a seventh switching tube;
a control electrode of the seventh switching tube is connected to the second control signal line, a first electrode of the seventh switching tube is connected to the third node, and a second electrode of the seventh switching tube is connected to the first electrode of the light emitting device.
7. A display panel, comprising: a pixel circuit as claimed in any one of claims 1-6.
8. The display panel according to claim 7, characterized by further comprising: the pixel circuit comprises a plurality of grid lines and a plurality of data lines, wherein all the grid lines and all the data lines define a plurality of pixel units, and each row of the pixel circuit corresponds to one grid line;
in addition to the pixel circuits in the first row, in the pixel circuits in other rows, the first control signal line connected to the pixel circuit is a gate line corresponding to the pixel circuit in the row before the first control signal line.
9. A display device, comprising: a display panel as claimed in claim 7 or 8.
10. A pixel driving method, wherein the pixel driving method is based on a pixel circuit using the pixel circuit of any one of claims 1 to 6, and the pixel driving method comprises:
in the reset phase, the reset sub-circuit responds to the control of the first control signal and writes the first working voltage into the first node;
in a threshold compensation phase, the threshold voltage compensation sub-circuit writes the first compensation voltage to the first node in response to control of the scan signal;
in the display stage, the current density compensation sub-circuit responds to the control of the second control signal and the third control signal to boost the first compensation voltage at the first node to a second compensation voltage, the threshold voltage compensation sub-circuit responds to the control of the second control signal to write the second working voltage into a second node, and the driving transistor responds to the control of the second compensation voltage to output a driving current to the light emitting device so as to drive the light emitting device to display.
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| CN109767724A (en) * | 2019-03-11 | 2019-05-17 | 合肥京东方显示技术有限公司 | Pixel circuit, display panel, display device and image element driving method |
| CN113966528B (en) * | 2020-03-12 | 2024-03-19 | 京东方科技集团股份有限公司 | Pixel circuit, driving method thereof and display device |
Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US20100164847A1 (en) * | 2008-12-29 | 2010-07-01 | Lee Baek-Woon | Display device and driving method thereof |
| US7825469B2 (en) * | 2007-09-05 | 2010-11-02 | International Business Machines Corporation | Threshold voltage compensation for pixel design of CMOS image sensors |
| CN102842283A (en) * | 2012-08-14 | 2012-12-26 | 北京大学深圳研究生院 | Pixel circuit, display device and driving method |
| CN103226931A (en) * | 2013-04-27 | 2013-07-31 | 京东方科技集团股份有限公司 | Pixel circuit and organic light emitting display |
| CN103329190A (en) * | 2011-01-31 | 2013-09-25 | 全球Oled科技有限责任公司 | Electroluminescent device multilevel-drive chromaticity-shift compensation |
| CN104036726A (en) * | 2014-05-30 | 2014-09-10 | 京东方科技集团股份有限公司 | Pixel circuit and driving method, organic light-emitting diode (OLED) display panel and device thereof |
| CN106683619A (en) * | 2017-03-28 | 2017-05-17 | 京东方科技集团股份有限公司 | Pixel driving circuit, pixel driving method and display device |
| CN106898304A (en) * | 2017-04-10 | 2017-06-27 | 深圳市华星光电技术有限公司 | A kind of OLED pixel drive circuit and OLED display |
| CN107393476A (en) * | 2017-08-23 | 2017-11-24 | 深圳市华星光电半导体显示技术有限公司 | Pixel-driving circuit and its driving method |
| CN107919093A (en) * | 2018-01-05 | 2018-04-17 | 京东方科技集团股份有限公司 | A kind of pixel compensation circuit and its driving method, display device |
| CN207425322U (en) * | 2017-08-30 | 2018-05-29 | 京东方科技集团股份有限公司 | Pixel circuit, display base plate and display device |
| US10068529B2 (en) * | 2016-11-07 | 2018-09-04 | International Business Machines Corporation | Active matrix OLED display with normally-on thin-film transistors |
Family Cites Families (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US8217928B2 (en) * | 2009-03-03 | 2012-07-10 | Global Oled Technology Llc | Electroluminescent subpixel compensated drive signal |
| KR101850994B1 (en) * | 2011-11-18 | 2018-04-23 | 삼성디스플레이 주식회사 | Method for controlling brightness in a display device and the display device using the same |
| CN103971637B (en) * | 2014-04-29 | 2017-02-08 | 四川虹视显示技术有限公司 | Pixel driving circuit of AMOLED panel |
| CN104157238B (en) * | 2014-07-21 | 2016-08-17 | 京东方科技集团股份有限公司 | Image element circuit, the driving method of image element circuit and display device |
| CN104715723B (en) * | 2015-03-19 | 2017-08-29 | 北京大学深圳研究生院 | Display device and its image element circuit and driving method |
| CN106652906B (en) * | 2017-01-05 | 2019-02-05 | 上海天马有机发光显示技术有限公司 | Display panel, driving method and display device |
-
2018
- 2018-10-31 CN CN201811288354.5A patent/CN109256088B/en active Active
Patent Citations (12)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7825469B2 (en) * | 2007-09-05 | 2010-11-02 | International Business Machines Corporation | Threshold voltage compensation for pixel design of CMOS image sensors |
| US20100164847A1 (en) * | 2008-12-29 | 2010-07-01 | Lee Baek-Woon | Display device and driving method thereof |
| CN103329190A (en) * | 2011-01-31 | 2013-09-25 | 全球Oled科技有限责任公司 | Electroluminescent device multilevel-drive chromaticity-shift compensation |
| CN102842283A (en) * | 2012-08-14 | 2012-12-26 | 北京大学深圳研究生院 | Pixel circuit, display device and driving method |
| CN103226931A (en) * | 2013-04-27 | 2013-07-31 | 京东方科技集团股份有限公司 | Pixel circuit and organic light emitting display |
| CN104036726A (en) * | 2014-05-30 | 2014-09-10 | 京东方科技集团股份有限公司 | Pixel circuit and driving method, organic light-emitting diode (OLED) display panel and device thereof |
| US10068529B2 (en) * | 2016-11-07 | 2018-09-04 | International Business Machines Corporation | Active matrix OLED display with normally-on thin-film transistors |
| CN106683619A (en) * | 2017-03-28 | 2017-05-17 | 京东方科技集团股份有限公司 | Pixel driving circuit, pixel driving method and display device |
| CN106898304A (en) * | 2017-04-10 | 2017-06-27 | 深圳市华星光电技术有限公司 | A kind of OLED pixel drive circuit and OLED display |
| CN107393476A (en) * | 2017-08-23 | 2017-11-24 | 深圳市华星光电半导体显示技术有限公司 | Pixel-driving circuit and its driving method |
| CN207425322U (en) * | 2017-08-30 | 2018-05-29 | 京东方科技集团股份有限公司 | Pixel circuit, display base plate and display device |
| CN107919093A (en) * | 2018-01-05 | 2018-04-17 | 京东方科技集团股份有限公司 | A kind of pixel compensation circuit and its driving method, display device |
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