CN111312173A - Pixel circuit and pixel driving method - Google Patents
Pixel circuit and pixel driving method Download PDFInfo
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- CN111312173A CN111312173A CN201811511317.6A CN201811511317A CN111312173A CN 111312173 A CN111312173 A CN 111312173A CN 201811511317 A CN201811511317 A CN 201811511317A CN 111312173 A CN111312173 A CN 111312173A
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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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- 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]
- G09G3/3275—Details of drivers for data electrodes
- G09G3/3291—Details of drivers for data electrodes in which the data driver supplies a variable data voltage for setting the current through, or the voltage across, the light-emitting elements
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- General Physics & Mathematics (AREA)
- Theoretical Computer Science (AREA)
- Control Of El Displays (AREA)
- Control Of Indicators Other Than Cathode Ray Tubes (AREA)
Abstract
The embodiment of the invention relates to the technical field of display, and discloses a pixel circuit and a pixel driving method. The pixel circuit of the present invention includes: the device comprises a current sampling module, a current control module, a pixel driving module and a display module; the output end of the pixel driving module is electrically connected with the input end of the current control module, and the output end of the current control module is electrically connected with the input end of the display module; the output end of the current sampling module is electrically connected with the control end of the current control module, and the sampling end of the current sampling module is electrically connected with the output end of the display module; the current sampling module samples the current output by the display module, obtains compensation voltage according to the sampled current and transmits the compensation voltage to the current control module; the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage. According to the embodiment of the invention, the display module can continuously and stably display, and the display performance of the pixel circuit is improved.
Description
Technical Field
The embodiment of the invention relates to the technical field of display, in particular to a pixel circuit and a pixel driving method.
Background
An Organic Light-Emitting Diode (OLED) is called an Organic Light-Emitting Diode (OLED), and has many advantages, such as no need of a backlight source for active Light emission, a wide viewing angle, a fast response speed, high definition and contrast, and a wide temperature range for use, and can realize flexible display and large-area full color display, and is applied to televisions, displays, and the like.
A conventional OLED pixel driving circuit is a 2T1C (2-Transistor-1-Capacitor) pixel driving circuit. The 2T1C pixel driving circuit is composed of two Metal-Oxide-Semiconductor Field Effect transistors (MOSFETs) and a storage capacitor, wherein one MOSFET is used as a driving Transistor, and the other MOSFET is used as a switching Transistor. However, the driving transistor threshold voltage (V) between the pixel circuitsth) The drift problem can cause the brightness of different pixel points to have deviation, resulting in the uneven brightness of the OLED display. Therefore, a compensation circuit for eliminating the influence of the threshold voltage is generally provided in the OLED pixel driving circuit.
The inventor finds that at least the following problems exist in the prior art: in the pixel circuit of the OLED, no matter whether the pixel circuit with the compensation function is provided, after a long time of operation, the problem of unstable light emission of the OLED occurs, which affects the display performance of the OLED.
Disclosure of Invention
An objective of the embodiments of the present invention is to provide a pixel circuit and a pixel driving method, so that a display module can continuously and stably display, and the display performance of the pixel circuit is improved.
To solve the above technical problem, an embodiment of the present invention provides a pixel circuit including: the device comprises a current sampling module, a current control module, a pixel driving module and a display module; the output end of the pixel driving module is electrically connected with the input end of the current control module, the output end of the current control module is electrically connected with the input end of the display module, and the output end of the display module is electrically connected with the negative voltage; the output end of the current sampling module is electrically connected with the control end of the current control module, and the sampling end of the current sampling module is electrically connected with the output end of the display module; the pixel driving module is used for driving the display module according to the signal output by the data line; the current sampling module samples the current output by the display module, obtains compensation voltage according to the sampled current and transmits the compensation voltage to the current control module; the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage. The embodiment of the present invention further provides a pixel driving method, which is applied to the pixel circuit described above, and the pixel driving method specifically includes: in the initial time period, the pixel driving module eliminates the data signal in the previous period through the initial voltage signal under the condition that the reset signal is effective; in the light-emitting time period, the current sampling module samples the current output by the display module, converts the sampled current into compensation voltage and transmits the compensation voltage to the current control module; the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage.
Compared with the prior art, the embodiment of the invention can sample the current flowing through the display module in real time through the current sampling module to obtain the magnitude of the current flowing through the display module, and the current sampling module can obtain the compensation voltage according to the magnitude of the current; therefore, the display module is compensated through the compensation voltage, so that the problem of unstable display of the display module caused by electric leakage or voltage drop fluctuation in a pixel circuit can be avoided, and the display performance of the display module is improved; meanwhile, the current flowing through the display module can be effectively controlled, abnormal distortion of signals is prevented, the display module can be effectively protected, damage to the display module due to the abnormal distortion of the signals is avoided, and therefore the service life of the display module is further prolonged.
In addition, optionally, the current sampling module specifically includes: a resistor and an error operational amplifier; the input end of the resistor is electrically connected with the output end of the display module, and the output end of the resistor is electrically connected with the negative voltage; the negative input end of the error operational amplifier is electrically connected with the output end of the display module, the positive input end of the error operational amplifier inputs reference voltage, and the output end of the error operational amplifier is electrically connected with the control end of the current control module; the negative input end of the error operational amplifier converts the current into negative input voltage according to the resistance value of the resistor and the collected current; and comparing the negative input voltage with the reference voltage to obtain the compensation voltage. The negative input end of the error operational amplifier converts the sampled current into a negative input voltage through a resistor, and the negative input voltage is compared with a reference voltage by the error operational amplifier, so that the compensation voltage suitable for the current display module can be accurately determined, and the current flowing through the display module can be accurately controlled within a preset current range.
In addition, optionally, the pixel circuit further comprises a pixel compensation module; the pixel compensation module at least comprises a first switch transistor, the grid electrode of the first switch transistor is electrically connected with the scanning line, the input end of the first switch transistor is electrically connected with the drain electrode of the driving transistor in the pixel driving module, and the output end of the first switch transistor is electrically connected with the grid electrode of the driving transistor; the first switching transistor performs threshold compensation on the driving transistor under the control of the scan line. Under the condition that the grid electrode of the first switch transistor is selected by the scanning line, the first switch transistor is conducted, so that the grid electrode and the drain electrode of the driving transistor are electrically connected to form a diode, threshold compensation is carried out on the driving transistor, the influence of the threshold voltage of the driving transistor on the current flowing through the display module is eliminated, and the display module is further enabled to stably display.
Further optionally, the current control module is a second switching transistor. Since the second switching transistor is a switching device and the switching device can convert a voltage into a current, the current flowing through the display module can be rapidly and simply controlled.
In addition, optionally, the reference voltage is a voltage of the display module in an ideal operating state. Because the display module has the voltage under the ideal state and the loss to the display module is the minimum, the reference voltage is set to the voltage of the display module under the ideal working state, the current flowing through the display module can be accurately controlled, the difference between the working voltage of the display module and the voltage under the ideal state is reduced, and the loss to the display module is reduced.
In addition, optionally, the pixel circuit further comprises a reset switch module; the input end of the reset switch module is electrically connected with an initial voltage, the output end of the reset switch module is electrically connected with the input end of a driving transistor in the pixel driving module, and the control end of the reset switch module is electrically connected with a reset wire; the reset switch module is used for initializing the input end of the driving transistor under the control of the reset wire. The input end of the driving transistor is initialized under the condition that the reset line outputs an effective reset signal, so that the data signal existing in the last frame at the input end of the driving transistor can be eliminated, the interference on the subsequently input data signal is avoided, and the display performance of the display module is improved.
In addition, optionally, the reset switch module is a third switching transistor; the control end of the third switching transistor is electrically connected with the reset wire, the input end of the third switching transistor is electrically connected with the initial voltage, and the output end of the third switching transistor is electrically connected with the input end of the driving transistor; when the reset line outputs a reset signal, the third switching transistor is turned on to initialize the input terminal of the driving transistor. The third switching transistor is used as a switching module, so that the realization is simple, and meanwhile, the control end of the third switching transistor is electrically connected with the reset wire, so that an additional signal is not needed to be used as an initial signal, and the circuit connection is simplified.
In addition, optionally, the display module is an organic light emitting diode or a light emitting diode.
Drawings
One or more embodiments are illustrated by way of example in the accompanying drawings, which correspond to the figures in which like reference numerals refer to similar elements and which are not to scale unless otherwise specified.
Fig. 1 is a schematic diagram illustrating connection relationships among parts of a pixel circuit according to a first embodiment of the present invention;
fig. 2 is a schematic circuit diagram of a pixel driving module in a pixel circuit according to a first embodiment of the invention;
fig. 3 is a schematic circuit structure diagram of a current sampling module in a pixel circuit according to a first embodiment of the present invention;
fig. 4 is a schematic circuit structure diagram of a pixel circuit according to a first embodiment of the present invention;
FIG. 5 is a timing diagram illustrating the operation of a pixel circuit according to a first embodiment of the present invention;
fig. 6 is a schematic diagram of a pixel circuit structure according to a second embodiment of the present invention;
FIG. 7 is a flowchart illustrating a pixel driving method according to a third embodiment of the present invention;
fig. 8 is a flowchart illustrating a pixel driving method according to a fourth embodiment of the invention.
Detailed Description
In order to make the objects, technical solutions and advantages of the embodiments of the present invention more apparent, embodiments of the present invention will be described in detail below with reference to the accompanying drawings. However, it will be appreciated by those of ordinary skill in the art that numerous technical details are set forth in order to provide a better understanding of the present application in various embodiments of the present invention. However, the technical solution claimed in the present application can be implemented without these technical details and various changes and modifications based on the following embodiments.
A first embodiment of the present invention relates to a pixel circuit. The pixel circuit is applied to a display device, and the display device can be a product or a component with a display function, such as a mobile phone, a tablet computer, a television, a display, a notebook computer, a digital photo frame or a navigator. The pixel circuit includes: a current sampling module 101, a current control module 102, a pixel driving module 103, and a display module 104, and the connection structure between the parts of the pixel circuit is shown in fig. 1.
The output end of the pixel driving module 103 is electrically connected to the input end of the current control module 102, the output end of the current control module 102 is electrically connected to the input end of the display module 104, and the output end of the display module 104 is electrically connected to the negative voltage (not shown in fig. 1); the output end of the current sampling module 101 is electrically connected with the control end of the current control module 102, and the sampling end of the current sampling module 101 is electrically connected with the output end of the display module 104. The current sampling module 101 samples the current output by the display module 104, obtains a compensation voltage according to the sampled current, and transmits the compensation voltage to the current control module 102; the current control module 102 controls the current flowing through the display module 104 within a preset current range according to the compensation voltage, wherein the current control module 102 may be a second switching transistor.
Specifically, the display module 104 may be an organic light emitting diode or a light emitting diode, and since the OLED or the LED is a current driving device, the voltage signal transmitted by the data line is converted into a current signal by the pixel driving module 103 to drive the display module 104. The pixel driving module 103 may adopt a common driving circuit with a 2T1C structure, the driving circuit with a 2T1C structure is shown in fig. 2, when the switching transistor M1 is turned on, the voltage signal inputted on the data line is transferred to the Gate of the driving transistor M2, when the switching transistor M1 is not selected, the voltage signal inputted on the data line is maintained at the Gate of M2 due to the existence of the storage capacitor C1, so that the driving transistor M2 is continuously turned on, thereby continuously and stably driving the OLED/LED to emit light, wherein Gate _ n in fig. 2 represents a scan line, V _ n represents a scan line, and V _ 1 _ C represents a scan linedataRepresents a voltage signal output from the data line, and Vss represents a negative voltage. The driving Transistor M2 and the switching Transistor M1 may be N-type Thin Film Transistors (TFTs) or P-type TFTs according to actual applications.
In a specific embodiment, a specific circuit structure of the current sampling module 101 is shown in fig. 3, where the current sampling module 101 specifically includes: a resistor 1011 and an error operational amplifier 1012; the input end of the resistor 1011 is electrically connected to the output end (e.g., end B in fig. 3) of the display module 104, and the output end of the resistor 1011 is electrically connected to a negative voltage (e.g., Vss in fig. 3); the negative input end of the error operational amplifier 1012 is electrically connected to the output end of the display module 104, the positive input end of the error operational amplifier 1012 inputs a reference voltage (such as Vref in fig. 3), and the output end of the error operational amplifier 1012 is electrically connected to the control end of the current control module 102; the negative input end of the error operational amplifier 1012 converts the current into a negative input voltage according to the resistance value of the resistor 1011 and the sampled current; the error op-amp 1012 compares the negative input voltage with a reference voltage to obtain a compensation voltage. The reference voltage may be a voltage of the display module 104 in an ideal operating state.
Specifically, the negative input terminal of the error operational amplifier 1012 is electrically connected to the output terminal of the display module 104, as shown in fig. 3, point B, and the input terminal of the resistor 1011 is electrically connected to the output terminal of the display module 104, thereby sampling the current flowing through the display module 104, inputting a reference voltage to the positive input terminal of the error operational amplifier 1012, due to the resistor 1011, the inverting input terminal of the error operational amplifier 1012 converts the sampled current into a negative input voltage, the error operational amplifier 1012 outputs a compensation voltage for the display module 104 by comparing the reference voltage with the negative input voltage, since the gate of the second switching transistor 102 is electrically connected to the output compensation voltage, the compensation voltage controls the current flowing between the source and drain of the second switching transistor 102 through the gate of the second switching transistor 102, thereby controlling the current flowing through the display module 104. In addition, the reference voltage can be preset according to the voltage of the display module 104 in an ideal working state, and is kept as a constant input in the pixel circuit, so that the generated compensation voltage can be ensured to be within a preset voltage range, and further, the current flowing through the display module 104 is ensured to be within a preset current range, and the problem that the current flowing through the OLED exceeds the preset current range due to the leakage current of the driving transistor in the pixel driving module, and the OLED emits light unevenly is avoided. In fig. 3, the connection relationship between the pixel driving module and the data line, the scan line and the input voltage is not shown, and the specific connection relationship refers to fig. 4.
It should be noted that the pixel driving module 103 may drive the OLED/LED to emit light by using the circuit structure of 2T1C, but the circuit structure of 2T1C has no compensation structure for compensating the threshold voltage of the driving transistor, so that the pixel driving module 103 is sensitive to the threshold voltage of the driving transistor. The pixel circuit may further include a pixel compensation module for performing threshold compensation on the driving transistor 1031 in the pixel driving module 103, so as to eliminate the display influence of the threshold voltage in the driving transistor 1031 on the display module 104.
The pixel compensation module at least comprises a first switching transistor 1051, wherein the grid electrode of the first switching transistor 1051 is electrically connected with the scanning line, the input end of the first switching transistor 1051 is electrically connected with the drain electrode of a driving transistor 1031 in the pixel driving module 103, and the output end of the first switching transistor 1051 is electrically connected with the grid electrode of the driving transistor 1031; the first switching transistor 1051 performs threshold compensation on the driving transistor 1031 under the control of the scan line.
Specifically, since the pixel compensation module is used for threshold compensation of the driving transistor 1031 in the pixel driving module 103, and therefore the pixel compensation module should be used in conjunction with the pixel driving module 103, a pixel circuit with a pixel compensation module, whose circuit structure is shown in fig. 4, and whose transistors are P-type TFTs, will be described in detail below. A Gate of the first switching transistor 1051 is electrically connected to a scan line (e.g., Gate _ n in fig. 4), a source of the first switching transistor 1051 is electrically connected to a drain of the driving transistor 1031, and a drain of the first switching transistor 1051 is electrically connected to a Gate of the driving transistor 1031. Meanwhile, other switching transistors (such as the switching transistors M1, M2, M4, M6, and M8 in fig. 4) are also included in the pixel circuit, so that the driving performance of the pixel driving module 103 can be further optimized. The operation principle of the pixel circuit in one frame period is described below with reference to the timing chart 5 and the pixel circuit in fig. 4.
At time T1, when the Reset signal (Reset signal in fig. 5) is at low level, the switching transistors M8 and M4 are turned on respectively, so that the initial voltage (e.g., Vinit in fig. 4) initializes the capacitor C1, facilitating the charging of the capacitor C1 at the subsequent time; meanwhile, since the reference voltage Vref is constantly input, the resistor 1011 is electrically connected to a negative voltage (Vss in fig. 4), so that the second switching transistor 102 is turned on, thereby enabling the initialization of the anode of the OLED at time T1. At time T2, the scan signal (Gate _ n signal in fig. 5) is at low level, the switching transistor M1 and the first switching transistor 1051 are turned on, and the Gate voltage of the driving transistor 1031 is Vg＝Vdata–|VthL, wherein VdataVoltage of data line, VthIndicating the threshold voltage of the driving transistor 1031. At time T3, the emission control signal (e.g., EM signal in fig. 5) is at low level, M2 and M6 are turned on, and the source V of the driving transistor 1031 is drivensVDD, due to the gate voltage V of the driving transistor 1031g＝Vdata–|VthI, then Vsg-|Vth|＝Vs–Vg-|Vth|＝VDD–(Vdata–|Vth|)-|VthI so that a source-drain current I flowing through the driving transistor 1031dsIs not affected by the threshold voltage of the driving transistor 1031.
The time T3 is a light emitting time period of the pixel circuit, that is, the display module 104 is in a light emitting state, and the current control module 102 is in a conducting state at this time, the current sampling module 101 samples the current at the point B, converts the sampled current into a reverse input voltage through the resistor 1011, and outputs a compensation voltage for the OLED together with the reference voltage through the error operational amplifier 1012, so as to control the magnitude of the current flowing through the current control module 102, and further control the current flowing through the OLED to be within a preset current range.
It should be noted that the pixel circuit in this embodiment may include a pixel driving module (such as the pixel driving module in fig. 2), and does not have a compensation function for the whole pixel circuit, and of course, other circuits with compensation for the pixel driving module may also be adopted, such as a circuit structure of 3T1C, or a circuit structure of 4T2C, etc., and only the output terminal of the pixel driving module needs to be electrically connected to the input terminal of the current control module, and the present invention is not limited to the pixel circuit structure of 7T1C listed in this embodiment.
Compared with the prior art, the embodiment of the invention can sample the current flowing through the display module in real time through the current sampling module to obtain the magnitude of the current flowing through the display module, and the current sampling module can obtain the compensation voltage according to the magnitude of the current; therefore, the display module is compensated through the compensation voltage, so that the problem of unstable display of the display module caused by electric leakage or voltage drop fluctuation in a pixel circuit can be avoided, and the display performance of the display module is improved; meanwhile, the current flowing through the display module can be effectively controlled, abnormal distortion of signals is prevented, the display module can be effectively protected, damage to the display module due to the abnormal distortion of the signals is avoided, and therefore the service life of the display module is further prolonged.
A second embodiment of the present invention relates to a pixel circuit. The second embodiment is a further improvement of the first embodiment, and the main improvements are as follows: the pixel circuit further includes a reset switch module 106, an input terminal of the reset switch module 106 is electrically connected to the initial voltage, an output terminal of the reset switch module 106 is electrically connected to an input terminal of the driving transistor 1031 in the pixel driving module 103, and a control terminal of the reset switch module 106 is electrically connected to the reset line; the reset switch module 106 is used to initialize the input terminal of the driving transistor 1031 under the control of the reset line. A specific pixel circuit is shown in fig. 6.
Specifically, the reset switch module 106 may be a third switching transistor; a control terminal of the third switching transistor 106 is electrically connected to the reset line, an input terminal of the third switching transistor 106 is electrically connected to the initial voltage, and an output terminal of the third switching transistor 106 is electrically connected to an input terminal of the driving transistor 1031; when the reset line outputs a reset signal, the third switching transistor 106 is turned on to initialize the input terminal of the driving transistor 1031.
Note that, in this embodiment, only the circuit configuration of 7T1C (the transistor is a P-type TFT in fig. 6) is described, and in practical applications, a pixel driving circuit configuration of 2T1C, a pixel driving circuit configuration of 3T1C, and the like can be adopted, and this embodiment is not limited thereto.
When the reset line outputs a low-level reset signal, the switching transistor M4, the switching transistor M8, and the third switching transistor 106 in fig. 6 are all turned on, so as to initialize the point a and the capacitor C1, and in this embodiment, the third switching transistor 106 and the switching transistor M8 can also initialize the anode of the OLED, thereby reducing the interference of the subsequently input data signal.
The operation of the pixel circuit in a frame period is described with reference to a timing diagram of the pixel circuit shown in fig. 6, wherein the timing diagram of the present embodiment is similar to the timing diagram of fig. 5 of the first embodiment, please refer to the timing diagram of fig. 5.
At time T1, when the Reset signal (Reset signal in fig. 5) is at low level, the third switching transistor 106, the switching transistor M8, and the transistor M4 are turned on respectively, so that the initial voltage (e.g., Vinit in fig. 4) initializes a point a and the capacitor C1, and initializes the point a, the data signal existing at the input terminal of the driving transistor 1031 in the previous frame can be completely eliminated, and the capacitor C1 is initialized to facilitate charging the C1 at the subsequent time; meanwhile, since the reference voltage Vref is constantly input, the resistor 1011 is electrically connected to a negative voltage (Vss in fig. 4), so that the second switching transistor 102 is turned on, thereby enabling the initialization of the anode of the OLED at time T1. At time T2, the scan signal (Gate _ n signal in fig. 5) is at low level, the switching transistor M1 and the first switching transistor 1051 are turned on, and the Gate voltage of the driving transistor 1031 is Vg＝Vdata–|VthL, wherein VdataVoltage of data line, VthIndicating the threshold voltage of the driving transistor 1031. At time T3, the emission control signal (e.g., EM signal in fig. 5) is at low level, M2 and M6 are turned on, and the source V of the driving transistor 1031 is drivensVDD, due to the gate voltage V of the driving transistor 1031g＝Vdata–|VthI, then Vsg-|Vth|＝Vs–Vg-|Vth|＝VDD–(Vdata–|Vth|)-|VthI so that a source-drain current I flowing through the driving transistor 1031dsIs not affected by the threshold voltage of the driving transistor 1031.
The time T3 is a light emitting time period of the pixel circuit, that is, the display module 104 is in a light emitting state, and the current control module 102 is in a conducting state at this time, the current sampling module 101 samples the current at the point B, converts the sampled current into a reverse input voltage through the resistor 1011, and outputs a compensation voltage for the OLED together with the reference voltage through the error operational amplifier 1012, so as to control the magnitude of the current flowing through the current control module 102, and further control the current flowing through the OLED to be within a preset current range.
In the pixel circuit provided by the embodiment, the input end of the driving transistor is initialized under the condition that the reset line outputs the effective reset signal, so that the data signal existing in the last frame at the input end of the driving transistor can be eliminated, interference on the subsequently input data signal is avoided, and the display performance of the display module is improved.
A third embodiment of the present invention relates to a method of pixel driving applied to a pixel circuit as in the first embodiment. In this embodiment, the method of driving the pixel will be described with reference to the pixel circuit of fig. 4 in the first embodiment, and a specific flow of the pixel driving is shown in fig. 7.
Step 301: in the initial period, the pixel driving module eliminates the data signal in the previous period through the initial voltage signal under the condition that the reset signal is effective.
Specifically, in the initial period, the reset line outputs the reset signal, the switching transistor M8 is turned on at a low level, and when the reset signal is at a low level, the reset signal is active, at which time, M4 and M8 are turned on, M4 is turned on, the gate of the driving transistor 1031 is initialized, and the transition period of the previous cycle display of the pixel circuit is ended.
It should be noted that the pixel circuit in fig. 4 includes a threshold compensation circuit for the driving transistor in the pixel driving module, and therefore, the operating period of the pixel circuit further includes a compensation time period, after the initial time period, the compensation time period is entered, in the compensation time period, the reset line outputs an invalid reset signal, the scan line selects the switching transistor 1051, compensates the threshold voltage of the gate of the driving transistor 1031, and then the light emitting phase is entered.
If the light-emitting device only comprises the pixel driving module and does not comprise the pixel compensation module, the light-emitting time period is directly started after the initial time period.
Step 302: in the light-emitting time period, the current sampling module samples the current output by the display module, converts the sampled current into compensation voltage and transmits the compensation voltage to the current control module.
Specifically, in the light emitting period, the light emitting control line outputs an active signal (i.e., low level), the scan signal is set to high level, the transistors M2 and M6 are turned on, and the driving transistor 1031 is kept turned on due to the presence of the storage capacitor C1, thereby driving the OLED to emit light. And meanwhile, the current sampling module samples the current of the point B, converts the sampled current into negative input voltage through the resistance value of the resistor, and feeds the negative input voltage back to the negative input end of the error operational amplifier. The error operational amplifier compares the inverted input voltage with a reference voltage, outputs a compensation voltage to the OLED, and transmits the compensation voltage to the current control module.
Step 303: the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage.
Specifically, the current control module may be a second switching transistor, and the output end of the error operational amplifier is electrically connected to the gate of the second switching transistor, so that the compensation voltage controls the current flowing through the OLED through the gate of the second switching transistor, and the current flowing through the OLED is within a preset current range.
It should be understood that this embodiment is a method example corresponding to the first embodiment, and may be implemented in cooperation with the first embodiment. The related technical details mentioned in the first embodiment are still valid in this embodiment, and are not described herein again in order to reduce repetition. Accordingly, the related-art details mentioned in the present embodiment can also be applied to the first embodiment.
The steps of the above methods are divided for clarity, and the implementation may be combined into one step or split some steps, and the steps are divided into multiple steps, so long as the same logical relationship is included, which are all within the protection scope of the present patent; it is within the scope of the patent to add insignificant modifications to the algorithms or processes or to introduce insignificant design changes to the core design without changing the algorithms or processes.
A fourth embodiment of the present invention relates to a method of pixel driving. The fourth embodiment is a further improvement of the third embodiment, and the main improvements are as follows: in the initial period, the method for driving the pixel further comprises initializing an input terminal of a driving transistor in the pixel driving module under the condition that the reset signal is effective. A specific flow of the pixel driving method is shown in fig. 8.
Note that the pixel driving method in this embodiment mode is applied to a pixel circuit as in the second embodiment mode, and this pixel driving method will be described in this embodiment mode with reference to the pixel circuit diagram of fig. 6 in the second embodiment mode.
Step 401: in the initial period, the pixel driving module eliminates the data signal in the previous period through the initial voltage signal under the condition that the reset signal is effective.
Step 402: in the initial period, the method for driving the pixel further comprises initializing an input terminal of a driving transistor in the pixel driving module under the condition that the reset signal is effective.
Specifically, the reset switch module may be a third switching transistor; the control end of the third switching transistor is electrically connected with the reset wire, the input end of the third switching transistor is electrically connected with the initial voltage, and the output end of the third switching transistor is electrically connected with the input end of the driving transistor; under the condition that the reset signal output by the reset line is effective, the third switching transistor 106 and the switching transistor M8 are turned on, and the drain of the third switching transistor 106 is electrically connected with the drain of the switching transistor M1, so that the initialization of the point a is realized, and the influence of the previous frame of digital signal on the current period is eliminated.
Step 403: in the light-emitting time period, the current sampling module samples the current output by the display module, converts the sampled current into compensation voltage and transmits the compensation voltage to the current control module.
Step 404: the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage.
It should be noted that step 401, step 403, and step 404 in this embodiment are substantially the same as step 301 to step 303 in the third embodiment, and will not be described again here.
Since the second embodiment corresponds to the present embodiment, the present embodiment can be implemented in cooperation with the second embodiment. The related technical details mentioned in the second embodiment are still valid in this embodiment, and the technical effects that can be achieved in the second embodiment can also be achieved in this embodiment, and are not described herein again in order to reduce the repetition. Accordingly, the related-art details mentioned in the present embodiment can also be applied to the second embodiment.
It will be understood by those of ordinary skill in the art that the foregoing embodiments are specific examples for carrying out the invention, and that various changes in form and details may be made therein without departing from the spirit and scope of the invention in practice.
Claims (10)
1. A pixel circuit, comprising: the device comprises a current sampling module, a current control module, a pixel driving module and a display module;
the output end of the pixel driving module is electrically connected with the input end of the current control module, the output end of the current control module is electrically connected with the input end of the display module, and the output end of the display module is electrically connected with the negative voltage;
the output end of the current sampling module is electrically connected with the control end of the current control module, and the sampling end of the current sampling module is electrically connected with the output end of the display module;
the pixel driving module is used for driving the display module according to the signal output by the data line;
the current sampling module is used for sampling the current output by the display module, obtaining a compensation voltage according to the sampled current and transmitting the compensation voltage to the current control module;
and the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage.
2. The pixel circuit according to claim 1, wherein the current sampling module specifically comprises: a resistor and an error operational amplifier;
the input end of the resistor is electrically connected with the output end of the display module, and the output end of the resistor is electrically connected with the negative voltage;
the negative input end of the error operational amplifier is electrically connected with the output end of the display module, the positive input end of the error operational amplifier inputs a reference voltage, and the output end of the error operational amplifier is electrically connected with the control end of the current control module;
the negative input end of the error operational amplifier converts the current into a negative input voltage according to the resistance value of the resistor and the collected current;
and comparing the negative input voltage with the reference voltage to obtain the compensation voltage.
3. The pixel circuit of claim 1, further comprising a pixel compensation module;
the pixel compensation module at least comprises a first switch transistor, the grid electrode of the first switch transistor is electrically connected with the scanning line, the input end of the first switch transistor is electrically connected with the drain electrode of the driving transistor in the pixel driving module, and the output end of the first switch transistor is electrically connected with the grid electrode of the driving transistor;
the first switching transistor performs threshold compensation on the driving transistor under the control of a scan line.
4. The pixel circuit of claim 1, wherein the current control module is a second switching transistor.
5. The pixel circuit according to claim 2, wherein the reference voltage is a voltage of the display module under an ideal operating condition.
6. The pixel circuit according to any one of claims 1 to 5, further comprising a reset switch module;
the input end of the reset switch module is electrically connected with an initial voltage, the output end of the reset switch module is electrically connected with the input end of a driving transistor in the pixel driving module, and the control end of the reset switch module is electrically connected with a reset wire;
the reset switch module is used for initializing the input end of the driving transistor under the control of the reset wire.
7. The pixel circuit according to claim 6, wherein the reset switch module is a third switching transistor;
the control end of the third switching transistor is electrically connected with the reset wire, the input end of the third switching transistor is electrically connected with the initial voltage, and the output end of the third switching transistor is electrically connected with the input end of the driving transistor;
and under the condition that the reset line outputs a reset signal to be effective, the third switching transistor is conducted to initialize the input end of the driving transistor.
8. The pixel circuit according to claim 7, wherein the display module is an organic light emitting diode or a light emitting diode.
9. A pixel driving method applied to the pixel circuit according to any one of claims 1 to 8, wherein the pixel driving method specifically includes:
in the initial time period, the pixel driving module eliminates the data signal in the previous period through the initial voltage signal under the condition that the reset signal is effective;
in a light-emitting time period, the current sampling module samples the current output by the display module, converts the sampled current into compensation voltage and transmits the compensation voltage to the current control module;
the current control module controls the current flowing through the display module within a preset current range according to the compensation voltage.
10. The method of pixel driving according to claim 9, further comprising, during the initial period of time:
and initializing the input end of the driving transistor in the pixel driving module under the condition that the reset signal is effective.
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