CN109308878B - Pixel circuit, driving method thereof and display device - Google Patents
Pixel circuit, driving method thereof and display device Download PDFInfo
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- CN109308878B CN109308878B CN201811158627.4A CN201811158627A CN109308878B CN 109308878 B CN109308878 B CN 109308878B CN 201811158627 A CN201811158627 A CN 201811158627A CN 109308878 B CN109308878 B CN 109308878B
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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]
- G09G3/3266—Details of drivers for scan electrodes
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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]
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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
Abstract
The present disclosure relates to a pixel circuit, a driving method thereof and a display device, wherein the pixel circuit comprises a light emitting unit, a driving transistor, a first switch unit, a first energy storage unit and a voltage division unit; the first end of the driving transistor is connected with a first power supply signal, the second end of the driving transistor is connected with the first end of the light-emitting unit, and the second end of the light-emitting unit is connected with a second power supply signal; the first switch unit is turned on in response to a scanning signal to transmit a data signal to the control terminal of the driving transistor; the first end of the first energy storage unit is connected to the control end of the driving transistor, and the second end of the first energy storage unit is connected to a first power supply signal; the voltage division unit is turned on in response to the scan signal to change the voltage of the driving terminal of the driving transistor by the first power signal. The driving dynamic range of the pixel circuit is enlarged, and the control precision of the control chip on the OLED screen brightness is improved.
Description
Technical Field
The disclosure relates to the technical field of display, and in particular relates to a pixel circuit, a driving method thereof and a display device.
Background
In an OLED (Organic Light Emitting Diode) pixel circuit, the Light Emitting unit is usually controlled to emit Light by a current driving transistor, and the Light Emitting brightness of the Light Emitting unit is determined by the driving current. The scan transistor charges the data voltage Vdata at the control end of the driving transistor in a preset time sequence, and the driving current can be controlled by controlling the size of the Vdata. The driving dynamic range may be defined as the difference between the Vdata maximum voltage value and the Vdata minimum voltage value.
The driving dynamic range determines the adjustable range of the maximum gray scale and the adjustable precision of the minimum gray scale of the OLED screen, and the smaller the driving dynamic range is, the more unfavorable the control chip is for accurately controlling the brightness of the OLED screen. At present, the pixel density of an OLED screen is continuously increased, the voltage range which can be loaded by a transistor control end is reduced due to the increase of the pixel density, and in order to ensure the normal work of a driving transistor, the dynamic range of the driving needs to be adjusted and reduced.
It is to be noted that the information disclosed in the above background section is only for enhancement of understanding of the background of the present disclosure, and thus may include information that does not constitute prior art known to those of ordinary skill in the art.
Disclosure of Invention
The disclosure aims to provide a pixel circuit, a driving method thereof and a display device, and solves the problem that a driving dynamic range of the pixel circuit is small due to the limitation of a range of voltage which can be loaded by a driving transistor in the related art.
According to a first aspect of the present disclosure, there is provided a pixel circuit comprising:
a light emitting unit;
a driving transistor, a first end of which is connected with a first power signal, a second end of which is connected with a first end of the light-emitting unit, and a second end of the light-emitting unit is connected with a second power signal;
a first switching unit turned on in response to a scan signal to transmit a data signal to a control terminal of the driving transistor;
a first end of the first energy storage unit is connected to the control end of the driving transistor, and a second end of the first energy storage unit is connected to a first power supply signal;
and the voltage division unit is turned on in response to the scanning signal so as to change the voltage of the driving end of the driving transistor through the first power supply signal.
According to an embodiment of the present disclosure, the first switching unit includes:
a first transistor, a first end of which is connected with a data signal, a second end of which is connected with a control end of the driving transistor, and a control end of which receives the scanning signal;
the voltage dividing unit includes:
a first end of the second transistor is connected to the second end of the first transistor, a second end of the second transistor is connected to the first power signal, and a control end of the second transistor receives the scanning signal.
According to an embodiment of the present disclosure, the pixel circuit further includes:
the third transistor is connected between the driving transistor and a first power supply signal, a first end of the third transistor is connected with the first power supply signal, a second end of the third transistor is connected with a first end of the driving transistor, and a control end of the third transistor is used for receiving a light-emitting control signal.
According to an embodiment of the present disclosure, the first switching unit includes:
a first transistor, a first end of which is connected with a data signal, a second end of which is connected with a control end of the driving transistor, and a control end of which receives the scanning signal;
the voltage dividing unit includes:
a first end of the fourth transistor is connected to the control end of the driving transistor, and the control end of the fourth transistor is used for receiving a first scanning signal;
a fifth transistor, a first terminal of which is connected to the second terminal of the fourth transistor, a second terminal of which is connected to the first power signal, and a control terminal of which is used for receiving the second scan signal;
and a first end of the second energy storage unit is connected to the first end of the first energy storage unit, and a second end of the second energy storage unit is connected to the second end of the fourth transistor.
According to an embodiment of the present disclosure, the pixel circuit further includes:
the first end of the sixth transistor is connected with the first power supply signal, the second end of the sixth transistor is connected with the first end of the driving transistor, and the control end of the sixth transistor is used for receiving the light-emitting control signal.
According to an embodiment of the present disclosure, all of the transistors are N-type thin film transistors or all of the transistors are P-type thin film transistors;
when all the transistors are N-type thin film transistors, the first power signal is a high level signal, the second power signal is a low level signal, the first end of the light emitting unit is an anode of the organic light emitting diode, and the second end of the light emitting unit is a cathode of the organic light emitting diode.
When all the transistors are P-type thin film transistors, the first power supply signal is a low level signal, the second power supply signal is a high level signal, the first end of the light emitting unit is a cathode of the organic light emitting diode, and the second end of the light emitting unit is an anode of the organic light emitting diode.
According to a second aspect of the present disclosure, there is provided a pixel driving method for driving the pixel circuit described above; the pixel driving method includes:
the method comprises the steps that a first switch unit and a voltage division unit are conducted through scanning signals to control the voltage of a control end of a driving transistor, the voltage of the control end of the driving transistor is written into a first end of a first energy storage unit, and a first power supply signal is written into a second end of the first energy storage unit;
and the first switch unit and the voltage division unit are turned off by using the scanning signal, and the driving transistor is turned on by using a voltage signal in the energy storage unit, so that a first power supply signal drives the light-emitting unit to emit light.
According to an embodiment of the present disclosure, the first switching unit includes a first transistor, the voltage dividing unit includes a second transistor, and the pixel driving method includes:
the method comprises the steps that a first transistor and a second transistor are conducted through a scanning signal to control the voltage of a control end of a driving transistor, the voltage of the control end of the driving transistor is written into a first end of a first energy storage unit, and a first power supply signal is written into a second end of the first energy storage unit;
and the first transistor and the second transistor are turned off by the scanning signal, and the driving transistor is turned on by a voltage signal in the energy storage unit, so that a first power supply signal drives the light emitting unit to emit light.
According to an embodiment of the present disclosure, the first switching unit includes a first transistor, the voltage dividing unit includes a fourth transistor, a fifth transistor, and a second energy storage unit, and the pixel driving method includes:
turning on the first transistor and the fourth transistor and turning off the fifth transistor by using a first scanning signal and a second scanning signal to write the data signal voltage into a first end of a first energy storage unit and write the first power supply signal into a second end of the first energy storage unit;
turning on a fifth transistor and turning off the first transistor and the fourth transistor by using the first scanning signal and the second scanning signal to write the first power supply signal into the second end of the second energy storage unit;
and turning off the first transistor, the fourth transistor and the fifth transistor by using the first scanning signal and the second scanning signal, and turning on the driving transistor through a voltage signal in the first energy storage unit, the second energy storage unit and the first energy storage unit so that a first power supply signal drives the light-emitting unit to emit light.
According to a third aspect of the present disclosure, there is provided a display device including the pixel circuit described above.
The pixel circuit, the driving method thereof and the display device provided by the exemplary embodiments of the present disclosure can be used for increasing the driving dynamic range. The pixel circuit comprises a light-emitting unit, a driving transistor, a first switch unit, a voltage division unit and an energy storage unit; in the pixel circuit working engineering, the first power supply signal is transmitted to the control end of the driving transistor through the voltage division unit so as to change the voltage of the control end of the driving transistor, the voltage range of the control end of the driving transistor can be adjusted and reduced by adjusting the parameters of the voltage division unit, and then the voltage range of the control end of the driving transistor can be ensured to meet the working requirement under the condition of increasing the driving dynamic range, the driving dynamic range of the pixel circuit is increased, and the control precision of the control chip on the brightness of an OLED screen is improved.
It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure.
Drawings
The above and other features and advantages of the present disclosure will become more apparent by describing in detail exemplary embodiments thereof with reference to the attached drawings.
Fig. 1 is a circuit diagram of a pixel circuit provided in the related art;
fig. 2 is a circuit diagram of a first pixel circuit provided in an exemplary embodiment of the present disclosure;
fig. 3 is a circuit diagram of a second pixel circuit provided in an exemplary embodiment of the present disclosure;
FIG. 4 is a comparison graph of a charge simulation of the pixel circuit of FIG. 1 and the pixel circuit of FIG. 2;
fig. 5 is a circuit diagram of a third pixel circuit provided in an exemplary embodiment of the present disclosure;
fig. 6 is a circuit diagram of a fourth pixel circuit provided in an exemplary embodiment of the present disclosure;
FIG. 7 is a driving timing diagram of the pixel circuit shown in FIG. 5;
FIG. 8 is a comparison graph of a charge simulation of the pixel circuit of FIG. 1 and the pixel circuit of FIG. 5;
fig. 9 is a flowchart of a pixel circuit driving method according to an exemplary embodiment of the present disclosure.
In the figure:
t1, a first transistor; t2, a second transistor; t3, a third transistor; t4, a fourth transistor; t5, a fifth transistor; t6, a sixth transistor; DT, drive transistor; OLED, organic light emitting diode; VDD, a first power supply signal; VSS, a second power supply signal; gn, scanning signal; EM, emission control signal; vdata, and a data signal.
Detailed Description
Example embodiments will now be described more fully with reference to the accompanying drawings. Example embodiments may, however, be embodied in many different forms and should not be construed as limited to the examples set forth herein; rather, these embodiments are provided so that this disclosure will be thorough and complete, and will fully convey the concept of example embodiments to those skilled in the art. The described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are provided to give a thorough understanding of embodiments of the disclosure. One skilled in the relevant art will recognize, however, that the subject matter of the present disclosure can be practiced without one or more of the specific details, or with other methods, components, devices, steps, and the like. In other instances, well-known technical solutions have not been shown or described in detail to avoid obscuring aspects of the present disclosure.
Furthermore, the drawings are merely schematic illustrations of the present disclosure and are not necessarily drawn to scale. The same reference numerals in the drawings denote the same or similar parts, and thus their repetitive description will be omitted. Some of the block diagrams shown in the figures are functional entities and do not necessarily correspond to physically or logically separate entities. These functional entities may be implemented in the form of software, or in one or more hardware modules or integrated circuits, or in different networks and/or processor devices and/or microcontroller devices.
In the 2T1C pixel circuit of the related art, as shown in fig. 1, the voltage range of the control terminal of the driving transistor DT is determined by the driving dynamic range, and the driving dynamic range in practical application is limited because the voltage range that the driving terminal of the driving transistor DT can carry is limited. In the case of an OLED display with high pixel density such as VR/MR, the driving dynamic range needs to be increased to improve the control accuracy of the OLED brightness.
In the present exemplary embodiment, there is provided a pixel circuit, as shown in fig. 2, including: the LED driving circuit comprises a light emitting unit, a driving transistor DT, a first switch unit, a first energy storage unit and a voltage division unit;
a first end of the driving transistor DT is connected with a first power supply signal VDD, a second end of the driving transistor DT is connected with a first end of the light emitting unit, and a second end of the light emitting unit is connected with a second power supply signal VSS;
the first switching unit is turned on in response to a scan signal to transmit a data signal Vdata to the control terminal of the driving transistor DT;
the first end of the first energy storage unit is connected to the control end of the driving transistor DT, and the second end of the first energy storage unit is connected to a first power supply signal VDD;
the voltage dividing unit is turned on in response to the scan signal to change the voltage of the driving terminal of the driving transistor DT by the first power signal VDD.
The pixel circuit provided by the exemplary embodiment of the disclosure can be used for increasing the driving dynamic range. The pixel circuit comprises a light emitting unit, a driving transistor DT, a first switch unit, a voltage division unit and an energy storage unit; in the working engineering of the pixel circuit, the first power supply signal VDD is transmitted to the control end of the driving transistor DT through the voltage division unit so as to change the voltage of the control end of the driving transistor DT, the voltage range of the control end of the driving transistor DT can be adjusted and reduced by adjusting the parameters of the voltage division unit, and then the voltage range of the control end of the driving transistor DT can be ensured to meet the working requirement under the condition of the increased driving dynamic range, the driving dynamic range of the pixel circuit is increased, and the control precision of the control chip on the brightness of an OLED screen is improved.
In a possible embodiment of the present disclosure, the first switch unit includes, as shown in fig. 2: a first transistor T1 having a first terminal connected to the data signal Vdata, a second terminal connected to the control terminal of the driving transistor DT, and a control terminal receiving the scan signal;
the voltage dividing unit includes: a second transistor T2, having a first terminal connected to the second terminal of the first transistor T1, a second terminal connected to the first power signal VDD, and a control terminal receiving the scan signal.
On this basis, as shown in fig. 3, the pixel circuit provided by the embodiment of the present disclosure further includes: a third transistor T3 coupled between the driving transistor DT and the first power signal VDD, wherein a first terminal of the third transistor T3 is coupled to the first power signal VDD, a second terminal of the third transistor T3 is coupled to the first terminal of the driving transistor DT, and a control terminal of the third transistor T3 is configured to receive the emission control signal EM.
The operation of the pixel circuit shown in fig. 2 will be described in detail below. Taking all the transistors as P-type thin film transistors as an example for explanation, the driving voltage of each transistor is a low level voltage; in this case, the first power signal VDD may be a low level signal, the second power signal VSS may be a high level signal, the first terminal of the light emitting unit is a cathode of the OLED, and the second terminal of the light emitting unit is an anode of the OLED.
When the scan signal Gn is at a low level, the first transistor T1 and the second transistor T2 are turned on, the turn-on resistance of the first transistor T1 is RT1, the turn-on resistance of the second transistor T2 is RT2, and RT1 and RT2 are connected in series between Vdata and VDD, and the voltage Vg at the control terminal of the control transistor is calculated by equation (1):
as shown in equation (1), the RT1 and RT2 may be controlled by adjusting the W/L and the number of the first transistor T1 and the second transistor T2, thereby controlling the voltage of the driving terminal of the driving transistor DT to increase the driving dynamic range of the driving terminal of the driving transistor DT.
For example, it can be assumed that W/L of the first transistor T1 and the second transistor T2 are equal and channel distribution is uniform, and RT1 and RT2 are the same, when formula (1) is transformed into formula (2):
taking VDD as 5V and Vdata as 3V to 5V as an example, the driving dynamic range is 2V, Vg as 4V to 5V, and the voltage range of the control terminal of the driving transistor DT is 1V. Therefore, when the voltage range of the driving terminal of the driving transistor DT is Vg equal to 4V to 5V, the corresponding Vdata in the related art is 4V to 5V, the driving dynamic range is 1V, and the corresponding Vdata in the embodiment of the present disclosure is 3V to 5V. In practical use, the scaling ratio can be controlled by adjusting the W/L and the number of the first transistor T1 and the second transistor T2, and the like.
Fig. 4 shows a comparison graph of analog charging of a pixel circuit provided in the related art and a pixel circuit provided in the embodiment of the present disclosure, where Vdata is 3V to 4V, VDD is 5V, Vg' is 3.1V to 4.1V in the related art, and Vg is 4.2V to 4.6V in the pixel circuit provided in the present disclosure.
When the pixel circuit further includes the third transistor T3, when the driving transistor DT is turned on, the third transistor T3 is controlled to be turned on by the emission control signal EM, and current flows through the light emitting cell, driving the light emitting cell to emit light.
In another possible embodiment of the present disclosure, as shown in fig. 5, the first switching unit includes: a first transistor T1 having a first terminal connected to the data signal Vdata, a second terminal connected to the control terminal of the driving transistor DT, and a control terminal receiving the scan signal;
the voltage dividing unit includes: a fourth transistor T4, a first end of which is connected to the control end of the driving transistor DT, and a control end of which is used for receiving the first scanning signal; a fifth transistor T5, having a first terminal connected to the second terminal of the fourth transistor T4, a second terminal connected to the first power signal VDD, and a control terminal for receiving the second scan signal; a first terminal of the second energy storage unit is connected to the first terminal of the first energy storage unit, and a second terminal of the second energy storage unit is connected to the second terminal of the fourth transistor T4.
On this basis, as shown in fig. 6, the pixel circuit provided by the embodiment of the present disclosure further includes: a sixth transistor T6 connected between the driving transistor DT and the first power signal VDD, wherein a first terminal of the sixth transistor T6 is connected to the first power signal VDD, a second terminal of the sixth transistor T6 is connected to the first terminal of the driving transistor DT, and a control terminal of the sixth transistor T6 is configured to receive the emission control signal EM.
The operation of the pixel circuit shown in fig. 5 will be described in detail below with reference to the timing chart shown in fig. 7. The timing chart shows the level states of the first scan signal Gn and the second scan signal Gn +1 for three periods. Taking all transistors as P-type thin film transistors as an example, the driving voltage of each transistor is low level voltage; in this case, the first power signal VDD may be a low level signal, the second power signal VSS may be a high level signal, the first terminal of the light emitting element is a cathode of the OLED, and the second terminal of the light emitting element is an anode of the OLED.
First period t 1: the first scan signal Gn is at a low level, the second scan signal Gn +1 is at a high level, the first transistor T1 and the fourth transistor T4 are turned on, and the fifth transistor T5 is turned off, charging Vdata to the control terminal G of the driving transistor DT and the second terminal Q of the second energy storage element.
Second period t 2: the first scanning signal Gn is at a high level, the second scanning signal Gn +1 is at a low level, the first transistor T1 and the fourth transistor T4 are turned off, and the fifth transistor T5 is turned on, so as to pull the voltage at the second end of the second energy storage element to VDD, and in the process, the driving end of the driving transistor DT is coupled through the first energy storage element and the second energy storage element, so that the potential of the driving end G of the driving transistor DT changes. The first energy storage element and the second energy storage element may be capacitors, the capacitor of the first energy storage element is Cst1, and the capacitor of the second energy storage element is Cst 2. In the process of changing the second terminal voltage of the second energy storage element, the change amount of the control terminal voltage of the driving transistor DT is as shown in formula (3):
finally, the voltage at the control terminal of the driving transistor DT is as shown in equation (4):
for example, when Cst1 equals Cst2, equation (4) is transformed into equation (5):
taking VDD as 5V and Vdata as 3V to 5V as an example, the driving dynamic range is 2V, Vg as 4V to 5V, and the voltage range of the control terminal of the driving transistor DT is 1V. Therefore, when the voltage range of the driving terminal of the driving transistor DT is Vg equal to 4V to 5V, the corresponding Vdata in the related art is 4V to 5V, the driving dynamic range is 1V, and the corresponding Vdata in the embodiment of the present disclosure is 3V to 5V. In practical use, the scaling ratio can be controlled by adjusting the capacitance, the number and the like of the first energy storage element and the second energy storage element.
Third period t 3: the first transistor T1, the fourth transistor T4 and the fifth transistor T5 are turned off by the first scan signal Gn and the second scan signal Gn +1, and the driving transistor DT is turned on by a voltage signal in the first energy storage cell and the second energy storage cell, so that the light emitting cell is driven to emit light by the first power supply signal VDD.
Fig. 8 shows a comparison graph of analog charging of a pixel circuit provided in the related art and a pixel circuit provided in the embodiment of the present disclosure, where Vdata is 3V to 4V, VDD is 5V, Vg' is 3.1V to 4.1V in the related art, and Vg is 4.2V to 4.6V in the pixel circuit provided in the present disclosure.
When the pixel circuit further includes the sixth transistor T6, in the above-described third period, the emission control signal EM is at a low level, the sixth transistor T6 is turned on, a current flows through the light emitting cell, and the light emitting cell is driven to emit light.
In the present exemplary embodiment, each transistor has a control terminal, a first terminal, and a second terminal. Specifically, the control terminal of each transistor may be a gate, the first terminal may be a source, and the second terminal may be a drain; alternatively, the control terminal of each transistor may be a gate, the first terminal may be a drain, and the second terminal may be a source. Further, each transistor may be an enhancement transistor or a depletion transistor, which is not particularly limited in this exemplary embodiment.
On the basis, all the transistors can be N-type thin film transistors, and the driving voltage of each transistor is high-level voltage; in this case, the first power signal VDD may be a high level signal, the second power signal VSS may be a low level signal, the first terminal of the light emitting element is an anode of the OLED, and the second terminal of the light emitting element is a cathode of the OLED.
Or, all the transistors may be P-type thin film transistors, and the driving voltage of each transistor is a low level voltage; in this case, the first power signal VDD may be a low level signal, the second power signal VSS may be a high level signal, the first terminal of the light emitting element is a cathode of the OLED, and the second terminal of the light emitting element is an anode of the OLED.
It should be noted that, in the above specific embodiment, all the transistors are P-type transistors, in which case the first power signal VDD is a low level signal, the cathode of the OLED is connected to the driving transistor DT, and the anode of the OLED is connected to a high level signal. The adoption of the all-P type thin film transistor has the following advantages: for example, strong noise suppression; for example, low level is easy to realize in charge management because of low level conduction; for example, the P-type thin film transistor has simple manufacturing process and relatively low price; such as better stability of the P-type thin film transistor, etc. Those skilled in the art will readily appreciate that pixel drive circuits in which all transistors are N-type transistors are available in accordance with the pixel circuits provided by the present disclosure. Of course, the pixel driving circuit provided in the present disclosure may also be replaced by a CMOS (Complementary Metal Oxide Semiconductor) circuit, etc., and is not limited to the pixel circuit provided in this embodiment, and will not be described herein again.
The present exemplary embodiment also provides a pixel driving method for driving the pixel circuit described above; as shown in fig. 9, the pixel driving method includes:
step S100, conducting a first switch unit and a voltage division unit by using a scanning signal to control the voltage of a control end of a driving transistor, writing the voltage of the control end of the driving transistor into a first end of a first energy storage unit, and writing a first power supply signal into a second end of the first energy storage unit;
and step S200, the first switch unit and the voltage division unit are turned off by using the scanning signal, and the driving transistor is turned on by using the voltage signal in the energy storage unit, so that the light-emitting unit is driven by a first power supply signal to emit light.
Alternatively, when the first switching unit includes the first transistor T1 and the voltage dividing unit includes the second transistor T2, the pixel driving method includes:
step S110, turning on a first transistor T1 and a second transistor T2 by using a scanning signal to control the voltage of the control end of a driving transistor DT, writing the voltage of the control end of the driving transistor DT into the first end of a first energy storage unit, and writing a first power supply signal VDD into the second end of the first energy storage unit;
in step S210, the first transistor T1 and the second transistor T2 are turned off by the scan signal, the driving transistor DT is turned on by the voltage signal in the energy storage unit, and the light emitting unit is driven to emit light by the first power signal VDD.
Optionally, when the first switching unit includes the first transistor T1, and the voltage dividing unit includes the fourth transistor T4, the fifth transistor T5, and the second energy storing unit, the pixel driving method includes:
step S120, turning on the first transistor T1 and the fourth transistor T4 and turning off the fifth transistor T5 by using a first scan signal and a second scan signal to write the data signal Vdata voltage into the first end of the first energy storage unit and write the first power signal VDD into the second end of the first energy storage unit;
a step S130 of turning on a fifth transistor T5 and turning off the first transistor T1 and the fourth transistor T4 by using the first scan signal and the second scan signal to write the first power signal VDD into the second terminal of the second energy storage unit;
in step S220, the first transistor T1, the fourth transistor T4 and the fifth transistor T5 are turned off by the first scan signal and the second scan signal, and the driving transistor DT is turned on by the voltage signal in the first energy storage cell and the second energy storage cell, so that the light emitting unit is driven to emit light by the first power signal VDD.
It should be noted that although the various steps of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that these steps must be performed in this particular order, or that all of the depicted steps must be performed, to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions, etc.
The present exemplary embodiment also provides a display device including the pixel circuit described above. The display device includes: a plurality of scan lines for providing scan signals; a plurality of data lines for supplying data signals Vdata; a plurality of pixel circuits electrically connected to the scan lines and the data lines; at least one of the pixel circuits includes any of the pixel driving circuits described above in this exemplary embodiment. The display device may include any product or component with a display function, such as a mobile phone, a tablet computer, a television, a notebook computer, a digital photo frame, and a navigator.
It should be noted that: the specific details of each module unit in the display device have been described in detail in the corresponding pixel driving circuit, and therefore are not described herein again.
It should be noted that although in the above detailed description several modules or units of the device for action execution are mentioned, such a division is not mandatory. Indeed, the features and functionality of two or more modules or units described above may be embodied in one module or unit, according to embodiments of the present disclosure. Conversely, the features and functions of one module or unit described above may be further divided into embodiments by a plurality of modules or units.
Moreover, although the steps of the methods of the present disclosure are depicted in the drawings in a particular order, this does not require or imply that the steps must be performed in this particular order, or that all of the depicted steps must be performed, to achieve desirable results. Additionally or alternatively, certain steps may be omitted, multiple steps combined into one step execution, and/or one step broken down into multiple step executions, etc.
Through the above description of the embodiments, those skilled in the art will readily understand that the exemplary embodiments described herein may be implemented by software, or by software in combination with necessary hardware. Therefore, the technical solution according to the embodiments of the present disclosure may be embodied in the form of a software product, which may be stored in a non-volatile storage medium (which may be a CD-ROM, a usb disk, a removable hard disk, etc.) or on a network, and includes several instructions to enable a computing device (which may be a personal computer, a server, a mobile terminal, or a network device, etc.) to execute the method according to the embodiments of the present disclosure.
Other embodiments of the disclosure will be apparent to those skilled in the art from consideration of the specification and practice of the disclosure disclosed herein. This application is intended to cover any variations, uses, or adaptations of the disclosure following, in general, the principles of the disclosure and including such departures from the present disclosure as come within known or customary practice within the art to which the disclosure pertains. It is intended that the specification and examples be considered as exemplary only, with a true scope and spirit of the disclosure being indicated by the following claims.
Claims (6)
1. A pixel circuit, comprising:
a light emitting unit;
a driving transistor, a first end of which is connected with a first power signal, a second end of which is connected with a first end of the light-emitting unit, and a second end of the light-emitting unit is connected with a second power signal;
a first switching unit turned on in response to a scan signal to transmit a data signal to a control terminal of the driving transistor;
a first end of the first energy storage unit is connected to the control end of the driving transistor, and a second end of the first energy storage unit is connected to a first power supply signal;
a voltage division unit turned on in response to the scan signal to change a voltage of a driving terminal of the driving transistor by the first power signal;
wherein the first switching unit includes:
a first transistor, a first end of which is connected with a data signal, a second end of which is connected with a control end of the driving transistor, and a control end of which receives the scanning signal;
the voltage dividing unit includes:
a first end of the fourth transistor is connected to the control end of the driving transistor, and the control end of the fourth transistor is used for receiving a first scanning signal;
a fifth transistor, a first terminal of which is connected to the second terminal of the fourth transistor, a second terminal of which is connected to the first power signal, and a control terminal of which is used for receiving the second scan signal;
and a first end of the second energy storage unit is connected to the first end of the first energy storage unit, and a second end of the second energy storage unit is connected to the second end of the fourth transistor.
2. The pixel circuit of claim 1, wherein the pixel circuit further comprises:
the first end of the sixth transistor is connected with the first power supply signal, the second end of the sixth transistor is connected with the first end of the driving transistor, and the control end of the sixth transistor is used for receiving the light-emitting control signal.
3. A pixel circuit according to claim 1 or 2, wherein all of the transistors are N-type thin film transistors or all of the transistors are P-type thin film transistors;
when all the transistors are N-type thin film transistors, the first power supply signal is a high level signal, the second power supply signal is a low level signal, the first end of the light-emitting unit is the anode of the organic light-emitting diode, and the second end of the light-emitting unit is the cathode of the organic light-emitting diode;
when all the transistors are P-type thin film transistors, the first power supply signal is a low level signal, the second power supply signal is a high level signal, the first end of the light emitting unit is a cathode of the organic light emitting diode, and the second end of the light emitting unit is an anode of the organic light emitting diode.
4. A pixel driving method for driving the pixel circuit according to any one of claims 1 to 3; the pixel driving method includes:
the method comprises the steps that a first switch unit and a voltage division unit are conducted through scanning signals to control the voltage of a control end of a driving transistor, the voltage of the control end of the driving transistor is written into a first end of a first energy storage unit, and a first power supply signal is written into a second end of the first energy storage unit;
and the first switch unit and the voltage division unit are turned off by using the scanning signal, and the driving transistor is turned on by using a voltage signal in the energy storage unit, so that a first power supply signal drives the light-emitting unit to emit light.
5. The pixel driving method according to claim 4, wherein the first switching unit includes a first transistor, the voltage dividing unit includes a fourth transistor, a fifth transistor, and a second energy storing unit, the pixel driving method comprising:
turning on the first transistor and the fourth transistor and turning off the fifth transistor by using a first scanning signal and a second scanning signal to write the data signal voltage into a first end of a first energy storage unit and write the first power supply signal into a second end of the first energy storage unit;
turning on a fifth transistor and turning off the first transistor and the fourth transistor by using the first scanning signal and the second scanning signal to write the first power supply signal into the second end of the second energy storage unit;
and turning off the first transistor, the fourth transistor and the fifth transistor by using the first scanning signal and the second scanning signal, and turning on the driving transistor through a voltage signal in the first energy storage unit, the second energy storage unit and the first energy storage unit so that a first power supply signal drives the light-emitting unit to emit light.
6. A display device comprising the pixel circuit according to any one of claims 1 to 3.
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| CN111179838A (en) * | 2020-02-21 | 2020-05-19 | 深圳市华星光电半导体显示技术有限公司 | Pixel circuit, display panel and method for improving low gray scale uniformity of display panel |
| CN113674701A (en) * | 2021-08-02 | 2021-11-19 | Tcl华星光电技术有限公司 | Pixel driving circuit and mobile terminal |
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