CN108053792A - A kind of pixel circuit and its driving method, display device - Google Patents
A kind of pixel circuit and its driving method, display device Download PDFInfo
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- CN108053792A CN108053792A CN201810054566.0A CN201810054566A CN108053792A CN 108053792 A CN108053792 A CN 108053792A CN 201810054566 A CN201810054566 A CN 201810054566A CN 108053792 A CN108053792 A CN 108053792A
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- G—PHYSICS
- 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]
- G09G3/3225—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] using an active matrix
- G09G3/3233—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] using an active matrix with pixel circuitry controlling the current through the light-emitting element
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Abstract
This application discloses a kind of pixel circuit and its driving method, display device, including light emitting diode, storage capacitance, driving transistor, first switch transistor, second switch transistor, the 3rd switching transistor, the 4th switching transistor, the 5th switching transistor, the 6th switching transistor.In the compensated stage of pixel circuit, the grid of driving transistor is connected with source electrode, it is formed from the second end of storage capacitance and flows through driving transistor, 3rd switching transistor, 4th switching transistor is to initial voltage signal line, the grid for making driving transistor is identical with the voltage of drain electrode, the source voltage of driving transistor is consistent with the voltage of the second end of storage capacitance, and the second terminal voltage of storage capacitance includes drive transistor threshold voltage, so that threshold voltage is included in the gate source voltage of driving transistor, and then in the glow phase of pixel circuit, the electric current for flowing through light emitting diode is unrelated with drive transistor threshold voltage, so as to fulfill the compensation to drive transistor threshold voltage.
Description
Technical Field
The present disclosure relates to the field of display technologies, and in particular, to a pixel circuit, a driving method thereof, and a display device.
Background
An active matrix organic light emitting display device (AMOLED) drives organic light emitting diodes. The active matrix organic display device includes a plurality of pixels arranged at intersections between scan lines and data lines. In addition, each pixel includes an organic light emitting diode and a pixel circuit for driving the organic light emitting diode. The pixel circuit is generally composed of a plurality of switching transistors, a driving transistor, and a storage capacitor.
Due to the problems of uniformity of transistor process, and the like, the threshold voltage of the transistor is not uniform, thereby affecting the display effect of the panel. Moreover, as the size of the AMOLED panel becomes larger, the problem of power line voltage drop becomes more serious, and the display effect of the display panel is further affected.
Disclosure of Invention
The embodiment of the application provides a pixel circuit, a driving method thereof and a display device, which are used for solving the problem of uneven threshold voltage of a transistor caused by the uniformity of the transistor process in the prior art.
The embodiment of the application adopts the following technical scheme:
in a first aspect, the present application provides a pixel circuit comprising:
a light emitting diode, a storage capacitor, a driving transistor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a fifth switching transistor, a sixth switching transistor, wherein,
the source electrode of the driving transistor is respectively connected with the drain electrode of the first switch transistor and the second end of the storage capacitor, and the source electrode of the first switch transistor is connected with a first power supply;
the grid electrode of the driving transistor is respectively connected with the drain electrode of the second switching transistor and the source electrode of the third switching transistor, the source electrode of the second switching transistor is respectively connected with the first end of the storage capacitor and the source electrode of the fifth switching transistor, and the drain electrode of the fifth switching transistor is connected with the data line;
the drain electrode of the driving transistor is respectively connected with the drain electrode of the third switching transistor, the source electrode of the fourth switching transistor and the source electrode of the sixth switching transistor, and the drain electrode of the fourth switching transistor is connected with an initial voltage signal line; and the drain electrode of the sixth switching transistor is connected with the light-emitting diode, and the light-emitting diode is connected with a second power supply.
Further, the voltage of the initial voltage signal is lower than the voltage of the second power supply.
Further, the first power supply is used for providing a power supply voltage for the driving transistor;
when the light emitting diode emits light, current flows into the second power supply.
Further, the initial voltage signal line provides an initial voltage signal, and the initial voltage signal is a negative voltage and is used for initializing the gate and the drain of the driving transistor and the anode of the light emitting diode.
Further, the gate of the first switch transistor, the gate of the second switch transistor, and the gate of the sixth switch transistor are connected to a first scan line, and when a first scan signal provided by the first scan line controls the first switch transistor, the second switch transistor, and the sixth switch transistor to be in a conducting state, the light emitting diode emits light;
the grid electrode of the third switching transistor is connected with a second scanning line, and a second scanning signal provided by the second scanning line controls the third switching transistor to be in a conducting state, so that the threshold voltage of the driving transistor is compensated;
and when a third scanning signal provided by the third scanning line controls the fourth switching transistor and the fifth switching transistor to be in a conducting state, the grid and the drain of the driving transistor and the anode of the light emitting diode are initialized.
Further, the driving transistor, the first switch transistor, the second switch transistor, the third switch transistor, the fourth switch transistor, the fifth switch transistor, and the sixth switch transistor are PMOS transistors.
Further, the data line provides a data voltage signal, the data voltage signal applies a voltage to the first end of the storage capacitor through the fifth switching transistor, the same voltage between the gate and the drain of the driving transistor is Vinit, and the second end of the storage capacitor discharges to a voltage Vinit + | Vth |, so as to compensate for the threshold voltage of the driving transistor, where Vinit is the initial voltage and Vth is the threshold voltage of the driving transistor.
Further, a power supply voltage is applied to the source of the driving transistor by the first power supply, the same voltage of the drain and the gate of the driving transistor is Vinit, and the voltage of the source of the driving transistor is decreased to Vinit + | Vth |, so as to compensate the threshold voltage of the driving transistor, wherein Vinit is the initial voltage, and Vth is the threshold voltage of the driving transistor.
In a second aspect, the present application provides a driving method of the pixel circuit, including:
in the first stage, a first scanning signal controls the first switch transistor, the second switch transistor and the sixth switch transistor to be in a conducting state, a second scanning signal controls the third switch transistor to be in a stopping state, a third scanning signal controls the fourth switch transistor and the fifth switch transistor to be in a conducting state, and an initial voltage signal initializes the grid electrode and the drain electrode of the first thin film transistor and the anode electrode of the light emitting diode;
in the second stage, the first scanning signal controls the first switching transistor, the second switching transistor and the sixth switching transistor to be in a cut-off state, the second scanning signal controls the third switching transistor to be in a conducting state, and the third scanning signal controls the fourth switching transistor and the fifth switching transistor to be in a conducting state, so that the threshold voltage of the driving film transistor is compensated;
in a third stage, the first scan signal controls the first switch transistor, the second switch transistor and the sixth switch transistor to be in a conducting state, the second scan signal controls the third switch transistor to be in a blocking state, the third scan signal controls the fourth switch transistor and the fifth switch transistor to be in a blocking state, current flows into the light emitting diode, and the light emitting diode emits light.
Further, in the second stage, the source voltage of the driving transistor is Vinit + | Vth |, and the gate voltage of the driving transistor is Vinit, so as to implement compensation of the threshold voltage of the driving transistor, where Vinit is the initial voltage, and Vth is the threshold voltage of the driving transistor.
Further, in the third stage, the voltage at the second terminal of the storage capacitor is Vdd, the voltage at the first terminal of the storage capacitor is Va ═ Vdata + Vdd- | Vth | -Vinit, and the current Ids flowing through the driving transistor is β/2(Vgs-Vth)2＝β/2(Vdd-Vdata-Vdd-|Vth|+Vinit+|Vth|)2＝β/2(Vinit-Vdata)2The compensation of the threshold voltage of the driving transistor and the compensation of the voltage drop of the first power supply are realized;
wherein Vdata is the data voltage, Vdd is a voltage of the first power supply, Vinit is the initial voltage, Vth is a threshold voltage of the driving transistor, Vgs is a voltage difference between the second terminal of the storage capacitor and the gate of the driving transistor, and β is a constant.
In a third aspect, the present application provides a display device comprising: the pixel circuit described above.
The embodiment of the application adopts at least one technical scheme which can achieve the following beneficial effects:
in the pixel circuit provided by the embodiment of the application, in the compensation stage of the pixel circuit, the gate electrode of the driving transistor is connected with the source electrode, and the voltage flowing from the second end of the storage capacitor to the initial voltage signal line through the driving transistor, the third switching transistor and the fourth switching transistor is formed, so that the voltage of the gate electrode and the voltage of the drain electrode of the driving transistor are the same, the voltage of the source electrode of the driving transistor is consistent with the voltage of the second end of the storage capacitor, and the voltage of the second end of the storage capacitor contains the threshold voltage of the driving transistor, so that the threshold voltage of the driving transistor is contained in the gate-source voltage of the driving transistor, and further, in the light emitting stage of the pixel circuit, the current flowing through the light emitting diode is unrelated to the threshold voltage of the driving transistor, so.
In addition, in the light emitting stage of the pixel circuit, the current flowing through the light emitting diode is independent of the voltage of the first power supply applied to the source of the driving transistor, thereby achieving compensation of the voltage drop of the first power supply.
Drawings
The accompanying drawings, which are included to provide a further understanding of the application and are incorporated in and constitute a part of this application, illustrate embodiment(s) of the application and together with the description serve to explain the application and not to limit the application. In the drawings:
fig. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present disclosure;
fig. 2 is a timing diagram of a driving method of a pixel circuit according to an embodiment of the present disclosure.
Detailed Description
In order to make the objects, technical solutions and advantages of the present application more apparent, the technical solutions of the present application will be described in detail and completely with reference to the following specific embodiments of the present application and the accompanying drawings. It should be apparent that the described embodiments are only some of the embodiments of the present application, and 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 application.
Fig. 1 is a schematic structural diagram of a pixel circuit according to an embodiment of the present disclosure. As shown in fig. 1, a pixel circuit provided in an embodiment of the present application may include: the light emitting diode D1, the storage capacitor C, the driving transistor T, the first switching transistor T1, the second switching transistor T2, the third switching transistor T3, the fourth switching transistor T4, the fifth switching transistor T5, and the sixth switching transistor T6.
In the pixel circuit shown in fig. 1, the driving transistor T, the first switching transistor T1, the second switching transistor T2, the third switching transistor T3, the fourth switching transistor T4, the fifth switching transistor T5 and the sixth switching transistor T6 are all PMOS transistors.
The circuit connection structure of the pixel circuit shown in fig. 1 is as follows:
the source of the driving transistor T is connected to the drain of the first switching transistor T1 and the second terminal of the storage capacitor C, respectively, and the source of the first switching transistor T1 is connected to the first power supply Vdd.
The gate of the driving transistor T is connected to the drain of the second switching transistor T2 and the source of the third switching transistor T3, respectively, the source of the second switching transistor T2 is connected to the first end of the storage capacitor C and the source of the fifth switching transistor T5, respectively, and the drain of the fifth switching transistor T5 is connected to the data line.
A drain of the driving transistor T is connected to a drain of the third switching transistor T3, a source of the fourth switching transistor T4, and a source of the sixth switching transistor T6, respectively, and a drain of the fourth switching transistor T4 is connected to an initial voltage signal line; the sixth switching transistor T6 has a drain connected to the light emitting diode D1, and the light emitting diode D1 connected to the second power source Vss.
In the embodiment of the present application, the first power supply Vdd may be a high level voltage and may be used to provide a power supply voltage for the driving transistor T, the driving transistor T may output a current under the action of the first power supply Vdd, the current flows into the light emitting diode D1, so that the light emitting diode D1 emits light, the current flows into the second power supply Vss when the light emitting diode D1 emits light, and the second power supply Vss may be a low level voltage.
The data line is used for providing a data voltage Vdata, and the initial voltage signal line is used for providing an initial voltage signal Vinit. In the embodiment of the present application, the initial voltage signal Vinit may be a negative voltage and used to initialize the gate and the drain of the driving transistor T and the anode of the light emitting diode D1.
It should be noted that in the embodiment of the present application, the initial voltage signal Vinit may be a negative voltage lower than the second power supply Vss, so that when the initial voltage signal Vinit initializes the anode of the light emitting diode D1, it can be ensured that the light emitting diode D1 does not emit light. Wherein, as an alternative, the initial voltage signal Vinit may be-3V. In addition, since the embodiment of the present application can initialize the anode of the led D1, the hysteresis effect caused by the led D1 can be effectively avoided during the light emitting stage of the led D1.
In fig. 1, Em is a first scan signal provided by a first scan line, Sn is a second scan signal provided by a second scan line, and Sn-1 is a third scan signal provided by a third scan line. Wherein,
the gate of the first switching transistor T1, the gate of the second switching transistor T2, and the gate of the sixth switching transistor T6 are connected to a first scan line, and a first scan signal Em provided by the first scan line is used to control the first switching transistor T1, the second switching transistor T2, and the sixth switching transistor T6 to be in an on state or an off state. In the embodiment of the present application, when the first scan signal Em controls the first switching transistor T1, the second switching transistor T2 and the sixth switching transistor T6 to be in the on state, the light emitting diode D1 emits light.
The gate of the third switching transistor T3 is connected to the second scan line, and the second scan signal Sn provided by the second scan line is used to control the third switching transistor T3 to be in an on state or an off state. In the embodiment of the present application, when the third switching transistor T3 is controlled to be in a conducting state by the second scan signal Sn, the threshold voltage of the driving transistor T is compensated.
The gate of the fourth switching transistor T4 and the gate of the fifth switching transistor T5 are connected to the third scan line, and the third scan line provides the third scan signal Sn-1 for controlling the fourth switching transistor T4 and the fifth switching transistor T5 to be in an on state or an off state. In the embodiment of the present application, when the fourth switching transistor T4 and the fifth switching transistor T5 are controlled to be in the on state by the third scan signal Sn-1, the gate and the source of the driving transistor T and the anode of the light emitting diode D1 are initialized.
Compared with the prior art, the pixel circuit provided by the embodiment of the application can realize the compensation of the threshold voltage of the driving transistor, and specifically comprises the following steps:
applying a power supply voltage to the source electrode of the driving transistor by the first power supply, wherein the voltages of the drain electrode and the gate electrode of the driving transistor are same as Vinit, and the voltage of the source electrode of the driving transistor is reduced to Vinit + | Vth |, so that the gate-source voltage Vgs of the driving transistor contains the threshold voltage Vth of the driving transistor, and the current Ids flowing through the light-emitting diode in the light-emitting stage of the pixel circuit is β/2(Vgs-Vth)2And further realizing the compensation of the threshold voltage of the driving transistor, wherein Vinit is the initial voltage, and Vth is the threshold voltage of the driving transistor.
In addition, during the light emitting stage of the pixel circuit, the current Ids flowing through the light emitting diode may be expressed as:
Ids＝β/2(Vgs-Vth)2＝β/2(Vdd-Vdata-Vdd-|Vth|+Vinit+|Vth|)2＝β/2(Vinit-Vdata)2
where Vdata is a data voltage, Vdd is a voltage of the first power supply Vdd, Vinit is an initial voltage, Vth is a threshold voltage of the driving transistor T, Vgs is a gate-source voltage of the driving transistor T, and β is a constant.
As can be seen from the above equation, the current flowing through the light emitting diode is independent of the voltage of the first power source applied to the source of the driving transistor, thereby achieving compensation of the voltage drop of the first power source.
Fig. 2 is a timing diagram of a driving method of a pixel circuit according to an embodiment of the present disclosure, where the driving method of the pixel circuit corresponding to the timing diagram can be used to drive the pixel circuit shown in fig. 1.
The driving method of the pixel circuit corresponding to the timing diagram shown in fig. 2 may include three stages: a first stage t1, a second stage t2, and a third stage t3, wherein,
em is a first scan signal supplied to the first scan line, and may be used to control the first, second, and sixth switching transistors T1, T2, and T6 shown in fig. 1 to be in an on state or an off state, Sn is a second scan signal supplied to the second scan line, and may be used to control the third switching transistor T3 shown in fig. 1 to be in an on state or an off state, Sn-1 is a third scan signal supplied to the third scan line, and may be used to control the fourth and fifth switching transistors T4 and T5 shown in fig. 1 to be in an on state or an off state, Vdata is a data voltage supplied to the data line, and Vinit is an initial voltage supplied to the initial voltage signal line.
The driving method of the pixel circuit corresponding to the timing diagram shown in fig. 2 specifically includes:
in the first stage T1, the first scan signal Em controls the first switch transistor T1, the second switch transistor T2 and the sixth switch transistor T6 to be in an on state, the second scan signal Sn controls the third switch transistor T3 to be in an off state, the third scan signal Sn-1 controls the fourth switch transistor T4 and the fifth switch transistor T5 to be in an on state, and the initial voltage signal pulls down the gate voltage and the drain voltage of the driving transistor and pulls down the anode voltage of the light emitting diode D1, so as to initialize the gate and the drain of the driving transistor and the anode of the light emitting diode D1.
In the second stage T2, the first scan signal Em controls the first switch transistor T1, the second switch transistor T2 and the sixth switch transistor T6 to be in an off state, the second scan signal Sn controls the third switch transistor T3 to be in an on state, and the third scan signal Sn-1 controls the fourth switch transistor T4 and the fifth switch transistor T5 to be in an on state, so as to compensate the threshold voltage of the driving transistor.
In the third stage T3, the first scan signal Em controls the first, second and sixth switching transistors T1, T2 and T6 to be in an on state, the second scan signal Sn controls the third switching transistor T3 to be in an off state, the third scan signal Sn-1 controls the fourth and fifth switching transistors T4 and T5 to be in an off state, current flows into the light emitting diode D1, and the light emitting diode D1 emits light.
The following detailed analysis was performed for each of the three stages:
for the first stage t 1:
since the first scan signal Em is at a low level, the second scan signal Sn is at a high level, and the third scan signal Sn-1 is at a low level, the first switching transistor T1 is in a turned-on state, the second switching transistor T2 and the fifth switching transistor T5 are in a turned-on state, the fourth switching transistor T4 and the sixth switching transistor T6 are in a turned-on state, and the third switching transistor T3 is in a turned-off state.
At this time, the first power supply Vdd applies a voltage to the source of the driving transistor T, the first power supply Vdd simultaneously applies a voltage to Vdd to the second terminal of the storage capacitor C, the initial voltage signal Vinit respectively pulls down the anode voltage of the light emitting diode D1 and the gate voltage and the drain voltage of the driving transistor T to Vinit, thereby implementing initialization of the anode of the light emitting diode D1 and the gate and drain of the driving transistor T, and simultaneously, the data signal line applies a voltage to the first terminal of the storage capacitor C through the fifth switching transistor T5, respectively pulls down the gate voltage and the drain voltage of the driving transistor T and the anode voltage of the light emitting diode D1, thereby implementing initialization of the gate and drain of the driving transistor T and the anode of the light emitting diode D1.
It should be noted that, since the led D1 has a capacitance effect and has a certain voltage, the anode of the led D1 is initialized at the first stage t1, so that the voltage of the led D1 is reduced, and further, the led D1 can emit light rapidly at the light emitting stage of the led D1, thereby effectively avoiding the hysteresis effect caused by the led D1.
For the transition phase t12 from the first phase t1 to the second phase t 2:
the first scan signal Em changes from low level to high level, the second scan signal Sn and the third scan signal Sn-1 remain unchanged, at this time, the voltage at the first end of the storage capacitor C remains Vdata, and the voltage at the second end of the storage capacitor C remains Vdd.
For the second stage t 2:
since the first scan signal Em is at a high level, the second scan signal Sn is at a low level from a high level, and the third scan signal Sn-1 is at a low level, the first switching transistor T1, the second switching transistor T2, and the sixth switching transistor T6 are turned off from an on state, the third switching transistor T3 is turned on from an off state, and the fourth switching transistor T4 and the fifth switching transistor T5 are still in an on state.
At this time, the data voltage Vdata applies a voltage to Vdata to the first end of the storage capacitor C through the fifth switching transistor T5, the source and the gate of the driving transistor T are connected, the gate and the drain of the driving transistor T have the same voltage and rapidly change to Vinit, the second end of the storage capacitor C is discharged and is reduced from the voltage Vdd to a voltage Vinit + | Vth |, and thus, compensation of the threshold voltage of the driving transistor T can be achieved, where Vth is the threshold voltage of the driving transistor T.
For the transition phase t23 from the first phase t2 to the second phase t 3:
the third scan signal Sn-1 changes from low level to high level, and the first scan signal Em and the second scan signal Sn remain unchanged, at this time, the left substrate (e.g., node a in fig. 1) of the storage capacitor C is kept away from the outside, and the voltage between the node a and the node b at the two ends of the storage capacitor C remains unchanged, that is, Va-Vb ═ Vdata-Vinit-Vth |.
For the third stage t 3:
since the first scan signal Em changes from a high level to a low level and the second scan signal Sn and the third scan signal Sn-1 remain unchanged, the first switching transistor T1, the second switching transistor T2, and the sixth switching transistor T6 change from an off state to an on state, the third switching transistor T3 changes from an on state to an off state, and the fourth switching transistor T4 and the fifth switching transistor T5 change from an on state to an off state.
At this time, the first power supply Vdd charges the second terminal of the storage capacitor C, so that the voltage of the second terminal of the storage capacitor C is changed from Vdata-Vth to Vdd, and the voltage of the first terminal of the storage capacitor C is changed from Vdata to Vdata + Vdd-Vth-Vinit according to the charge conservation principle. At this time, the current through the light emitting diode D1, that is, the current Ids through the driving transistor T, can be expressed as:
Ids＝β/2(Vgs-Vth)2＝β/2(Vdd-Vdata-Vdd-|Vth|+Vinit+|Vth|)2＝β/2(Vinit-Vdata)2
where Vdata is a data voltage, Vdd is a voltage of the first power supply Vdd, Vinit is an initial voltage, Vth is a threshold voltage of the driving transistor T, Vgs is a gate-source voltage of the driving transistor T, and β is a constant.
In specific implementation, the reference voltages of the signals may be: vdd is 4.6V, Vss is-3V, VGH (high) is 7V, VGL (low) is-7V, VREF (reference voltage) is-2V, and Vdata is-6.6V to-0.6V.
In specific implementation, the pixel circuit provided by the embodiment of the application is adopted. If Ids is 675nA, the threshold voltage of the driving transistor T is-1V; if Ids is 658nA, the threshold voltage of the driving transistor T is-1.5V; if Ids is 640nA, the threshold voltage of the driving transistor T is-2V. It is understood that when the threshold voltage of the driving transistor T varies ± 0.5V, the current varies by less than 5%.
In specific implementation, the pixel circuit provided by the embodiment of the application is adopted. If Ids is 680nA, the voltage Vdd of the first power supply is 4.8V; if Ids is 659nA, the voltage Vdd of the first power supply is 4.6V; if Ids is 638nA, the voltage Vdd of the first power supply is 4.4V. It can be seen that when the voltage Vdd of the first power supply varies by ± 0.2V, the current varies by less than 5%.
As can be seen from the above formula, the current flowing through the light emitting diode D1 is independent of the threshold voltage of the driving transistor T, and compensation of the threshold voltage of the driving transistor T is achieved. In addition, the current flowing through the light emitting diode D1 is independent of the voltage of the first power supply, and compensation of the voltage drop of the first power supply is achieved.
Embodiments of the present application further provide a display device, which may include a pixel circuit. The pixel circuit may include: the light-emitting diode, the storage capacitor, the driving transistor, the first switching transistor, the second switching transistor, the third switching transistor, the fourth switching transistor, the fifth switching transistor and the sixth switching transistor.
The circuit connection structure of the pixel circuit is as follows:
the source electrode of the driving transistor is respectively connected with the drain electrode of the first switch transistor and the second end of the storage capacitor, and the source electrode of the first switch transistor is connected with the first power supply.
The grid electrode of the driving transistor is respectively connected with the drain electrode of the second switching transistor and the source electrode of the third switching transistor, the source electrode of the second switching transistor is respectively connected with the first end of the storage capacitor and the source electrode of the fifth switching transistor, and the drain electrode of the fifth switching transistor is connected with the data line.
The drain electrode of the driving transistor is respectively connected with the drain electrode of the third switching transistor, the source electrode of the fourth switching transistor and the source electrode of the sixth switching transistor, and the drain electrode of the fourth switching transistor is connected with the initial voltage signal line; the drain of the sixth switching transistor is connected with the light emitting diode, and the light emitting diode is connected with the second power supply.
The grid electrode of the first switch transistor, the grid electrode of the second switch transistor and the grid electrode of the sixth switch transistor are connected with a first scanning line, and when a first scanning signal provided by the first scanning line controls the first switch transistor, the second switch transistor and the sixth switch transistor to be in a conducting state, the light-emitting diode emits light;
the grid electrode of the third switching transistor is connected with the second scanning line, and the second scanning signal provided by the second scanning line controls the third switching transistor to be in a conducting state, so that the threshold voltage of the driving transistor is compensated;
and when a third scanning signal provided by the third scanning line controls the fourth switching transistor and the fifth switching transistor to be in a conducting state, the grid electrode and the drain electrode of the driving transistor and the anode of the light emitting diode are initialized.
It is to be added here that the display device may further include a scan driver which sequentially supplies the first scan signal, the second scan signal, and the third scan signal to the first scan line, the second scan line, and the third scan line. A data driver supplying a data signal to the data lines.
In the embodiments of the present application, specific implementations of the pixel circuit and technical effects achieved by the pixel circuit are referred to in the related contents of the above embodiments, and details of the embodiments of the present application are not repeated.
It should be apparent to those skilled in the art that while the preferred embodiments of the present application have been described, additional variations and modifications to these embodiments may occur to those skilled in the art once they learn of the basic inventive concepts. Therefore, it is intended that the appended claims be interpreted as including preferred embodiments and all alterations and modifications as fall within the scope of the application.
It will be apparent to those skilled in the art that various changes and modifications may be made in the present application without departing from the scope of the application. Thus, if such modifications and variations of the present application fall within the scope of the claims of the present application and their equivalents, the present application is intended to include such modifications and variations as well.
Claims (10)
1. A pixel circuit, comprising: a light emitting diode, a storage capacitor, a driving transistor, a first switching transistor, a second switching transistor, a third switching transistor, a fourth switching transistor, a fifth switching transistor, a sixth switching transistor, wherein,
the source electrode of the driving transistor is respectively connected with the drain electrode of the first switch transistor and the second end of the storage capacitor, and the source electrode of the first switch transistor is connected with a first power supply;
the grid electrode of the driving transistor is respectively connected with the drain electrode of the second switching transistor and the source electrode of the third switching transistor, the source electrode of the second switching transistor is respectively connected with the first end of the storage capacitor and the source electrode of the fifth switching transistor, and the drain electrode of the fifth switching transistor is connected with the data line;
the drain electrode of the driving transistor is respectively connected with the drain electrode of the third switching transistor, the source electrode of the fourth switching transistor and the source electrode of the sixth switching transistor, and the drain electrode of the fourth switching transistor is connected with an initial voltage signal line; and the drain electrode of the sixth switching transistor is connected with the light-emitting diode, and the light-emitting diode is connected with a second power supply.
2. The pixel circuit according to claim 1,
the initial voltage signal line provides an initial voltage signal, and the initial voltage signal is a negative voltage and is used for initializing the grid and the drain of the driving transistor and the anode of the light emitting diode.
3. The pixel circuit according to claim 2, wherein a voltage of the initial voltage signal is lower than a voltage of the second power supply.
4. The pixel circuit according to claim 2,
the grid electrode of the first switch transistor, the grid electrode of the second switch transistor and the grid electrode of the sixth switch transistor are connected with a first scanning line, and when a first scanning signal provided by the first scanning line controls the first switch transistor, the second switch transistor and the sixth switch transistor to be in a conducting state, the light-emitting diode emits light;
the grid electrode of the third switching transistor is connected with a second scanning line, and a second scanning signal provided by the second scanning line controls the third switching transistor to be in a conducting state, so that the threshold voltage of the driving transistor is compensated;
and when a third scanning signal provided by the third scanning line controls the fourth switching transistor and the fifth switching transistor to be in a conducting state, the grid and the drain of the driving transistor and the anode of the light emitting diode are initialized.
5. The pixel circuit according to any one of claims 1 to 4,
the data line provides a data voltage signal, the data voltage signal applies a voltage to the first end of the storage capacitor through the fifth switching transistor, the same voltage between the gate and the drain of the driving transistor is Vinit, and the second end of the storage capacitor discharges to a voltage Vinit + | Vth |, so as to compensate the threshold voltage of the driving transistor, wherein Vinit is the initial voltage, and Vth is the threshold voltage of the driving transistor.
6. The pixel circuit according to any one of claims 1 to 4,
applying a power supply voltage to the source electrode of the driving transistor by the first power supply, wherein the voltages of the drain electrode and the grid electrode of the driving transistor are identical to Vinit, and the voltage of the source electrode of the driving transistor is reduced to Vinit + | Vth |, so that the compensation of the threshold voltage of the driving transistor is realized, wherein Vinit is the initial voltage, and Vth is the threshold voltage of the driving transistor.
7. A method of driving a pixel circuit according to any one of claims 1 to 6, comprising:
in the first stage, a first scanning signal controls the first switch transistor, the second switch transistor and the sixth switch transistor to be in a conducting state, a second scanning signal controls the third switch transistor to be in a stopping state, a third scanning signal controls the fourth switch transistor and the fifth switch transistor to be in a conducting state, and an initial voltage signal initializes the grid electrode and the drain electrode of the first thin film transistor and the anode electrode of the light emitting diode;
in the second stage, the first scanning signal controls the first switching transistor, the second switching transistor and the sixth switching transistor to be in a cut-off state, the second scanning signal controls the third switching transistor to be in a conducting state, and the third scanning signal controls the fourth switching transistor and the fifth switching transistor to be in a conducting state, so that the threshold voltage of the driving film transistor is compensated;
in a third stage, the first scan signal controls the first switch transistor, the second switch transistor and the sixth switch transistor to be in a conducting state, the second scan signal controls the third switch transistor to be in a blocking state, the third scan signal controls the fourth switch transistor and the fifth switch transistor to be in a blocking state, current flows into the light emitting diode, and the light emitting diode emits light.
8. The pixel circuit driving method according to claim 7,
in the second stage, the source voltage of the driving transistor is Vinit + | Vth |, and the gate voltage of the driving transistor is Vinit, so as to compensate the threshold voltage of the driving transistor, where Vinit is the initial voltage and Vth is the threshold voltage of the driving transistor.
9. The pixel circuit driving method according to claim 7,
in the third stage, the voltage at the second end of the storage capacitor is Vdd, the voltage at the first end of the storage capacitor is Va ═ Vdata + Vdd- | Vth | -Vinit, and the current Ids flowing through the driving transistor is β/2(Vgs-Vth)2＝β/2(Vdd-Vdata-Vdd-|Vth|+Vinit+|Vth|)2＝β/2(Vinit-Vdata)2The compensation of the threshold voltage of the driving transistor and the compensation of the voltage drop of the first power supply are realized;
wherein Vdata is the data voltage, Vdd is a voltage of the first power supply, Vinit is the initial voltage, Vth is a threshold voltage of the driving transistor, Vgs is a voltage difference between the second terminal of the storage capacitor and the gate of the driving transistor, and β is a constant.
10. A display device, comprising: a pixel circuit according to any one of claims 1 to 6.
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