CN112419983B - Novel AMOLED pixel driving circuit and driving method - Google Patents
Novel AMOLED pixel driving circuit and driving method Download PDFInfo
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- CN112419983B CN112419983B CN202011388773.3A CN202011388773A CN112419983B CN 112419983 B CN112419983 B CN 112419983B CN 202011388773 A CN202011388773 A CN 202011388773A CN 112419983 B CN112419983 B CN 112419983B
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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
- G09G3/3258—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 voltage across 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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- Control Of El Displays (AREA)
Abstract
The invention relates to a novel AMOLED pixel driving circuit and a driving method, and belongs to the technical field of display. The pixel driving circuit carries out threshold voltage compensation by directly capturing the threshold voltage of the compensation thin film transistor; applying the voltage of the organic light emitting diode to the node B through the parallel connection of the second capacitor and the third capacitor to perform mobility compensation; the influence of IR Drop is avoided by applying voltage externally to control the gate and source voltage of the driving thin film transistor, and the current flowing through the organic light-emitting diode is stable by compensating the threshold voltage, the mobility and the IR Drop of the driving thin film transistor, so that the light-emitting brightness and the display uniformity of the organic light-emitting diode are ensured, and the display quality of the OLED is improved; the invention improves the working efficiency, leads the organic light-emitting diode to have current to pass through only in the light-emitting stage through signal control, avoids unnecessary light emission of the organic light-emitting diode and reduces the power consumption.
Description
Technical Field
The invention belongs to the technical field of display, and relates to a novel AMOLED pixel driving circuit and a driving method.
Background
An Organic Light Emitting Diode (OLED) Display device has many advantages of self-luminescence, low driving voltage, high luminous efficiency, short response time, high definition and contrast, a viewing angle of approximately 180 °, a wide temperature range, flexible Display, large-area full color Display, and the like, and is considered as a Display device with the most potential for development.
The OLED display device may be classified into two major categories, i.e., direct addressing and thin film transistor Matrix addressing, of a Passive Matrix OLED (PMOLED) and an Active Matrix OLED (AMOLED) according to a driving method. The AMOLED has pixels arranged in an array, belongs to an active display type, has high luminous efficiency, and is generally used as a large-sized display device with high definition.
The AMOLED is a current-driven device, and when a current flows through an organic light emitting diode, the organic light emitting diode emits light, and the luminance is determined by the current flowing through the organic light emitting diode itself. Most of the existing Integrated circuits (Integrated Circuit ICs) only transmit voltage signals, so the pixel driving Circuit of the AMOLED needs to complete the task of converting the voltage signals into current signals. A conventional AMOLED pixel driving circuit is typically 2T1C, i.e. two thin film transistors plus a capacitor to convert a voltage into a current.
As shown in fig. 1, the conventional 2T1C pixel driving circuit for an AMOLED includes a first thin film transistor T10, a second thin film transistor T20, and a capacitor C, wherein the first thin film transistor T10 is a switching thin film transistor, the second thin film transistor T20 is a driving thin film transistor, and the capacitor C is a storage capacitor. Specifically, the gate of the first thin film transistor T10 is electrically connected to the Scan signal Scan, the source is electrically connected to the Data voltage Data, and the drain is electrically connected to the gate of the second thin film transistor T20 and one end of the capacitor C; the source electrode of the second thin film transistor T20 is electrically connected to the positive power voltage VDD0, and the drain electrode is electrically connected to the anode of the organic light emitting diode D0; the cathode of the organic light emitting diode D0 is electrically connected to the ground voltage GND 0; one end of the capacitor C is electrically connected to the drain of the first thin film transistor T10, and the other end is connected to the ground voltage GND 0. When the AMOLED displays, the Scan signal Scan controls the first thin film transistor T10 to be turned on, the Data voltage Data enters the gate of the second thin film transistor T20 and the capacitor C through the first thin film transistor T10, and then the first thin film transistor T10 is turned on, due to the storage effect of the capacitor C, the gate voltage of the second thin film transistor T20 can still keep the Data voltage, so that the second thin film transistor T20 is in a conducting state, and the driving current enters the organic light emitting diode D0 through the second thin film transistor T20 to drive the organic light emitting diode D0 to emit light.
The 2T1C pixel driving circuit for AMOLED of the conventional circuit described above is very sensitive to variations in threshold voltage and mobility of the thin film transistor. The threshold voltage and mobility of the second thin film transistor T20, i.e., the driving thin film transistor, may change with the operation time, thereby causing unstable light emission of the organic light emitting diode D0; further, the second thin film transistor T20 of each pixel, i.e., the driving thin film transistor, has a shift in threshold voltage and a change in mobility, which results in uneven light emission and brightness among the pixels. The non-uniformity of the AMOLED display brightness caused by using such a conventional 2T1C pixel drive circuit without compensation is about 50% or even higher.
Therefore, a new AMOLED pixel driving circuit is needed to solve the problem of non-uniform display brightness of the AMOLED.
Disclosure of Invention
In view of the above, the present invention provides a novel AMOLED pixel driving circuit and driving method, in which a compensation circuit is added to each pixel, that is, the threshold voltage and mobility of the driving thin film transistor in each pixel and the IR Drop phenomenon are compensated, so that the output current becomes independent of these factors, thereby solving the problem of non-uniform display brightness of the AMOLED.
In order to achieve the purpose, the invention provides the following technical scheme:
a novel AMOLED pixel drive circuit, comprising: a first thin film transistor T1, a second thin film transistor T2, a third thin film transistor T3, a fourth thin film transistor T4, a fifth thin film transistor T5, a first capacitor C1, a second capacitor C2, a third capacitor C3, and an organic light emitting diode OLED;
the gate of the first thin film transistor T1 is connected to a first scan control signal VSCAN1, the source is electrically connected to the first node a, and the drain is connected to a first data voltage VDATA 1;
the gate of the second thin film transistor T2 is connected to the drain of the second thin film transistor T2, the drain is connected to the second data voltage VDATA2, and the source is electrically connected to the source of the second node B;
the gate of the third thin film transistor T3 is electrically connected to the first node a, the drain is connected to the driving power supply VDD, and the source is electrically connected to the second node B;
the gate of the fourth thin film transistor T4 is connected to the third scan control signal VSCAN3, the drain is electrically connected to the anode of the organic light emitting diode OLED, and the source is electrically connected to one end of the third capacitor C3;
the grid electrode of the fifth thin film transistor T5 is connected to the second scanning control signal VSCAN2, the drain electrode of the fifth thin film transistor T5 is electrically connected to the anode of the organic light emitting diode OLED, and the source electrode of the fifth thin film transistor T5 is connected to the ground voltage GND;
one end of the first capacitor C1 is electrically connected to the first node a, and the other end is connected to a ground voltage GND;
one end of the second capacitor C2 is electrically connected to the second node B, and the other end is connected to a ground voltage GND;
one end of the third capacitor C3 is electrically connected to the second node B, and the other end is electrically connected to the source of the fourth tft T4;
the anode of the organic light emitting diode OLED is connected to the drain of the fourth thin film transistor T4, and the cathode of the organic light emitting diode OLED is connected to the low voltage GND.
Preferably, the first, second, third, fourth and fifth thin film transistors (T1, T2, T3, T4 and T5) are all low-temperature polysilicon thin film transistors, oxide semiconductor thin film transistors, amorphous silicon thin film transistors or organic thin film transistors.
Preferably, the third thin film transistor T3 is a driving thin film transistor, the second thin film transistor T2 is a compensation thin film transistor, and the threshold voltage magnitude and the variation trend thereof are approximately the same.
Preferably, the first, second and third scan control signals (VSCAN1, VSCAN2 and VSCAN3), the first data voltage VDATA1, the second data voltage VDATA2 and the driving power VDD are all provided by an external timing controller.
Further, the driving sequence of the AMOLED pixel driving circuit sequentially comprises:
(1) a data voltage input stage: the first scan control signal VSCAN1, the second scan control signal VSCAN2, the first data voltage VDATA1, and the second data voltage VDATA2 all provide a high potential, and the third scan control signal VSCAN3 and the driving voltage VDD all provide a low potential;
(2) a light emitting stage: the third scan control signal VSCAN3, the second data voltage VDATA2, and the driving voltage VDD all provide high voltages, and the first scan control signal VSCAN1, the second scan control signal VSCAN2, and the first data voltage VDATA1 all provide low voltages.
Further, the novel AMOLED pixel driving method of the pixel driving circuit specifically comprises the following steps:
step 1: entering a data voltage input stage;
the first scan control signal VSCAN1, the second scan control signal VSCAN2, the first data voltage VDATA1, and the second data voltage VDATA2 all provide high voltage, and the third scan control signal VSCAN3, and the driving voltage VDD all provide low voltage;
the first thin film transistor T1 and the fifth thin film transistor T5 are turned on, the second thin film transistor T2 is always turned on, the gate and drain short of the second thin film transistor T2 keep a diode connection mode, and the third thin film transistor T3 and the fourth thin film transistor T4 are both turned off; the voltage at the first node a, i.e., the gate voltage of the driving tft T3, is initialized to VDATA1_ H, and the voltage at the second node B, i.e., the source voltage of the driving tft T3, is initialized to VDATA2-Vth, where VDATA1_ H is a high level of the first data voltage VDATA1, VDATA2 is a level of the second data voltage VDATA2, and Vth is a threshold voltage of the driving tft, i.e., the third tft T3, and the compensating tft, i.e., the second tft T2;
step 2: entering a light emitting stage;
the third scan control signal VSCAN3, the second data voltage VDATA2, and the driving voltage VDD provide high voltages, and the first scan control signal VSCAN1, the second scan control signal VSCAN2, and the first data voltage VDATA1 provide low voltages;
the third thin film transistor T3 and the fourth thin film transistor T4 are turned on, the second thin film transistor T2 is always turned on, the gate and drain short of the second thin film transistor T2 maintains a diode connection mode, the first thin film transistor T1 and the fifth thin film transistor T5 are turned off, and the second capacitor C2 and the third capacitor C3 are connected in parallel; the voltage at the first node a, i.e., the gate voltage of the driving thin film transistor T3, is still VDATA1_ H, the voltage at the second node B, i.e., the source voltage of the driving thin film transistor T3, is VDATA2-Vth + (C3/C2+ C3) VOLED, where C2 is the capacitance of the second capacitor C2, C3 is the capacitance of the third capacitor C3, VDATA1_ H is the high level of the first data voltage VDATA1, VDATA2 is the level of the second data voltage VDATA2, Vth is the threshold voltage of the driving thin film transistor, i.e., the third thin film transistor T3, and the compensation thin film transistor, i.e., the second thin film transistor T2, and VOLED is the anode voltage of the organic light emitting diode OLED; thereby making the current flowing through the organic light emitting diode OLED independent of the threshold voltage of the third thin film transistor T3, avoiding the influence of IR Drop, while suppressing the influence of the mobility change of the third thin film transistor T3 on the current flowing through the light emitting diode OLED.
The invention has the beneficial effects that: the invention can effectively compensate the threshold voltage and the mobility of the driving film, effectively inhibit the IR Drop phenomenon, stabilize the current flowing through the organic light-emitting diode, ensure the uniform brightness of the organic light-emitting diode and improve the display effect of the picture.
Additional advantages, objects, and features of the invention will be set forth in part in the description which follows and in part will become apparent to those having ordinary skill in the art upon examination of the following or may be learned from practice of the invention. The objectives and other advantages of the invention may be realized and attained by the means of the instrumentalities and combinations particularly pointed out hereinafter.
Drawings
For the purposes of promoting a better understanding of the objects, aspects and advantages of the invention, reference will now be made to the following detailed description taken in conjunction with the accompanying drawings in which:
fig. 1 is a circuit diagram of a conventional 2T1C pixel driving circuit for an AMOLED;
FIG. 2 is a circuit diagram of a 5T3C pixel driving circuit for an AMOLED according to the present invention;
FIG. 3 is a timing diagram of the 5T3C pixel driving circuit for AMOLED according to the present invention;
FIG. 4 is a schematic diagram of a data voltage input stage in the AMOLED pixel driving method according to the present invention;
FIG. 5 is a schematic diagram of a light-emitting stage in the AMOLED pixel driving method according to the present invention;
Detailed Description
The embodiments of the present invention are described below with reference to specific embodiments, and other advantages and effects of the present invention will be easily understood by those skilled in the art from the disclosure of the present specification. The invention is capable of other and different embodiments and of being practiced or of being carried out in various ways, and its several details are capable of modification in various respects, all without departing from the spirit and scope of the present invention. It should be noted that the drawings provided in the following embodiments are only for illustrating the basic idea of the present invention in a schematic way, and the features in the following embodiments and examples may be combined with each other without conflict.
Referring to fig. 2 to 5, the present invention provides a novel AMOLED pixel driving circuit, including: the organic light emitting diode includes a first thin film transistor T1, a second thin film transistor T2, a third thin film transistor T3, a fourth thin film transistor T4, a fifth thin film transistor T5, a first capacitor C1, a second capacitor C2, a third capacitor C3, and an organic light emitting diode OLED.
The concrete connection mode is as follows: the gate of the first thin film transistor T1 is connected to a first scan control signal VSCAN1, the source is electrically connected to the first node a, and the drain is connected to a first data voltage VDATA 1; the gate of the second thin film transistor T2 is connected to the drain of the second thin film transistor T2, the drain is connected to the second data voltage VDATA2, and the source is electrically connected to the source of the second node B; the gate of the third thin film transistor T3 is electrically connected to the first node a, the drain is connected to the driving power supply VDD, and the source is electrically connected to the second node B; a gate of the fourth thin film transistor T4 is connected to the third scan control signal VSCAN3, a drain thereof is electrically connected to the anode of the organic light emitting diode OLED, and a source thereof is electrically connected to one end of the third capacitor C3; a gate of the fifth thin film transistor T5 is connected to the second scan control signal VSCAN2, a drain thereof is electrically connected to an anode of the organic light emitting diode OLED, and a source thereof is connected to the ground voltage GND; one end of the first capacitor C1 is electrically connected to the first node a, and the other end is connected to a ground voltage GND; one end of the second capacitor C2 is electrically connected to the second node B, and the other end is connected to the ground voltage GND; one end of the third capacitor C3 is electrically connected to the second node B, and the other end is electrically connected to the source of the fourth tft T4. The anode of the organic light emitting diode OLED is connected to the drain of the fourth thin film transistor T4, and the cathode is connected to the low voltage GND.
Note that the threshold voltage of the third thin film transistor T3, i.e., the driving thin film transistor, and the threshold voltage of the second thin film transistor T2, i.e., the compensation thin film transistor, are approximately the same in magnitude and change tendency.
Preferably, the first, second, third, fourth, and fifth thin film transistors (T1, T2, T3, T4, and T5) are all low-temperature polysilicon thin film transistors, oxide semiconductor thin film transistors, amorphous silicon thin film transistors, or organic thin film transistors.
Preferably, the scan control signals (VSCAN1, VSCAN2, VSCAN3), the first data voltage VDATA1, the second data voltage VDATA2, and the driving power VDD are all provided by an external timing controller.
As shown in fig. 3, the first scan control signal VSCAN1, the second scan control signal VSCAN2, the third scan control signal VSCAN3, the first data voltage VDATA1 and the second data voltage VDATA2 are combined, and the driving voltage VDD is combined to correspond to the data voltage input (1) and the light emitting stage (2) in sequence;
in the data voltage input stage (1), the first scan control signal VSCAN1, the second scan control signal VSCAN2, the first data voltage VDATA1, and the second data voltage VDATA2 all provide high voltage, and the third scan control signal VSCAN3, and the driving voltage VDD all provide low voltage; the first thin film transistor T1 and the fifth thin film transistor T5 are turned on, the second thin film transistor T2 is always turned on, the short circuit of the gate and the drain of the second thin film transistor T2 keeps a diode connection mode, and the third thin film transistor T3 and the fourth thin film transistor T4 are both turned off; the voltage at the first node a, i.e., the gate voltage of the driving thin film transistor T3, is initialized to VDATA1_ H, and the voltage at the second node B, i.e., the source voltage of the driving thin film transistor T3, is initialized to VDATA2-Vth, where VDATA1_ H is a high level of the first data voltage VDATA1, VDATA2 is a level of the second data voltage VDATA2, and Vth is a threshold voltage of the driving thin film transistor, i.e., the third thin film transistor T3, and the compensation thin film transistor, i.e., the second thin film transistor T2.
In the light-emitting period (2), the third scan control signal VSCAN3, the second data voltage VDATA2, and the driving voltage VDD provide a high voltage, and the first scan control signal VSCAN1, the second scan control signal VSCAN2, and the first data voltage VDATA1 provide a low voltage.
The third thin film transistor T3 and the fourth thin film transistor T4 are turned on, the second thin film transistor T2 is always turned on, the gate and drain short of the second thin film transistor T2 keeps a diode connection mode, the first thin film transistor T1 and the fifth thin film transistor T5 are turned off, and the second capacitor C2 and the third capacitor C3 are connected in parallel; the voltage at the first node a, i.e., the gate voltage of the driving thin film transistor T3, is still VDATA1_ H, the voltage at the second node B, i.e., the source voltage of the driving thin film transistor T3, is VDATA2-Vth + (C3/C2+ C3) VOLED, where C2 is the capacitance of the second capacitor C2, C3 is the capacitance of the third capacitor C3, VDATA1_ H is the high level of the first data voltage VDATA1, where VDATA2 is the level of the second data voltage VDATA2, Vth is the threshold voltage of the driving thin film transistor T3 and the compensation thin film transistor T2, and VOLED is the anode voltage of the organic light emitting diode OLED; thereby making the current flowing through the organic light emitting diode OLED independent of the threshold voltage of the third thin film transistor T3, avoiding the influence of the IR Drop, and simultaneously suppressing the influence of the mobility change of the third thin film transistor T3 on the current flowing through the light emitting diode OLED.
With reference to fig. 3 to 5, the method for implementing the driving of the oled pixel by the AMOLED pixel driving circuit with the 5T3C structure shown in fig. 2 specifically includes the following steps:
referring to fig. 3 and 4, the first scan control signal VSCAN1, the second scan control signal VSCAN2, the first data voltage VDATA1, and the second data voltage VDATA2 all provide high voltage, and the third scan control signal VSCAN3, and the driving voltage VDD all provide low voltage; the first thin film transistor T1 and the fifth thin film transistor T5 are turned on, the second thin film transistor T2 is always turned on, the gate and drain short of the second thin film transistor T2 maintains a diode connection mode, and the third thin film transistor T3 and the fourth thin film transistor T4 are both turned off; the voltage at the first node a, i.e., the gate voltage of the driving thin film transistor T3, is initialized to VDATA1_ H, the voltage at the second node B, i.e., the source voltage of the driving thin film transistor T3, is initialized to VDATA2-Vth, where VDATA1_ H is a high level of the first data voltage VDATA1, where VDATA2 is a level of the second data voltage VDATA2, and Vth is a threshold voltage of the driving thin film transistor, i.e., the third thin film transistor T3, and the compensation thin film transistor, i.e., the second thin film transistor T2, at which stage the gate and source voltages of the driving thin film transistor, i.e., the third thin film transistor T3, are directly determined by the first data voltage VDATA1 and the second data voltage VDATA2, the influence of the IR Drop phenomenon on the pixel current is suppressed, and the organic light emitting diode OLED does not emit light.
referring to fig. 3 and 5, the third scan control signal VSCAN3, the second data voltage VDATA2, and the driving voltage VDD provide high voltage, and the first scan control signal VSCAN1, the second scan control signal VSCAN2, and the first data voltage VDATA1 provide low voltage.
The third thin film transistor T3 and the fourth thin film transistor T4 are turned on, the second thin film transistor T2 is always turned on, the gate and drain short of the second thin film transistor T2 keeps a diode connection mode, the first thin film transistor T1 and the fifth thin film transistor T5 are turned off, and the second capacitor C2 and the third capacitor C3 are connected in parallel; the voltage at the first node a, i.e., the gate voltage of the driving thin film transistor T3, is still VDATA1_ H, the voltage at the second node B, i.e., the source voltage of the driving thin film transistor T3, is VDATA2-Vth + (C3/C2+ C3) VOLED, where C2 is the capacitance of the second capacitor C2, C3 is the capacitance of the third capacitor C3, VDATA1_ H is the high level of the first data voltage VDATA1, where VDATA2 is the level of the second data voltage VDATA2, Vth is the threshold voltage of the driving thin film transistor T3 and the compensation thin film transistor T2, and VOLED is the anode voltage of the organic light emitting diode OLED; thereby making the current flowing through the organic light emitting diode OLED independent of the threshold voltage of the third thin film transistor T3, avoiding the influence of the IR Drop, and simultaneously suppressing the influence of the mobility change of the third thin film transistor T3 on the current flowing through the light emitting diode OLED.
The threshold voltage magnitude and the variation tendency of the third thin film transistor T3, i.e., the driving thin film transistor, and the second thin film transistor T2, i.e., the compensating thin film transistor, are approximately the same.
It should be noted that, when the N-type thin film transistor is adopted as the driving thin film transistor according to the prior art, the current formula flowing through the organic light emitting diode is as follows:
IOLED＝K(VGS_T3-Vth) 2
the IOLED is a current flowing through the organic light emitting diode OLED, K is a structural parameter of the driving thin film transistor T3, VGS _ T3 is a voltage difference between a gate and a source of the driving thin film transistor T3, Vth is a threshold voltage of the third thin film transistor T3 and the second thin film transistor T2, and at this time, a voltage difference between the gate and the source of the third thin film transistor T3 is VDATA1_ H-VDATA2+ Vth- (C3/C2+ C3) VOLED.
Thus, IOLED ═ K (VGS _ T3-Vth) 2 ＝K(VDATA1_H-VDATA2-(C3/C2+C3)VOLED) 2 Wherein C2 is the capacitance of the second capacitor, C3 is the capacitance of the third capacitor, VDATA1_ H is the high voltage level of the first data voltage VDATA1, VDATA2 is the voltage level of the second data voltage VDATA2, VOLED is the voltage across the organic light emitting diode OLED, for the thin film transistor with the same structure, the K value is relatively stable, the value of (C3/C2+ C3) VOLED is also relatively stable, so that the current flowing through the organic light emitting diode OLED is independent of the threshold voltage of the third thin film transistor T3, the (C3/C2+ C3) VOLED can suppress the influence of the mobility change of the third thin film transistor on the current flowing through the organic light emitting diode, therefore, the threshold voltage and the mobility of the driving thin film transistor T3 can be effectively compensated, the stability of the current flowing through the organic light emitting diode OLED is ensured, the brightness uniformity of the organic light emitting diode is ensured, and the display quality of the organic light emitting diode is improved.
In summary, the novel AMOLED pixel driving circuit designed by the present invention is a pixel driving circuit with a 5T3C structure and is matched with a specific driving timing sequence, and the influence of IR Drop is suppressed by directly controlling the gate and source voltages of the driving thin film transistor, i.e., the third thin film transistor, through the external data voltage; threshold voltage compensation is carried out by directly grabbing the threshold voltage of a compensation thin film transistor, namely a second thin film transistor; applying a part of the voltage of the organic light emitting diode OLED to the node B through the parallel connection of the third capacitor and the second capacitor for mobility compensation; by compensating the threshold voltage, the mobility and the IR Drop of the driving thin film transistor, the current flowing through the organic light-emitting diode is stable, and the light-emitting brightness of the organic light-emitting diode is ensured; the organic light emitting diode is controlled by the signal to have current passing only in the light emitting stage, so that unnecessary light emission of the organic light emitting diode is avoided, the display quality of the organic light emitting diode is improved, and the power consumption is reduced.
Finally, the above embodiments are only intended to illustrate the technical solutions of the present invention and not to limit the present invention, and although the present invention has been described in detail with reference to the preferred embodiments, it will be understood by those skilled in the art that modifications or equivalent substitutions may be made on the technical solutions of the present invention without departing from the spirit and scope of the technical solutions, and all of them should be covered by the claims of the present invention.
Claims (6)
1. A novel AMOLED pixel driving circuit, comprising: a first thin film transistor (T1), a second thin film transistor (T2), a third thin film transistor (T3), a fourth thin film transistor (T4), a fifth thin film transistor (T5), a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), and an Organic Light Emitting Diode (OLED);
the grid electrode of the first thin film transistor (T1) is connected to a first scanning control signal (VSCAN1), the source electrode is electrically connected to a first node (A), and the drain electrode is connected to a first data voltage (VDATA 1);
the grid electrode of the second thin film transistor (T2) is connected to the drain electrode of the second thin film transistor (T2), the drain electrode is connected to a second data voltage (VDATA2), and the source electrode is electrically connected to the source electrode of the second node (B);
the grid electrode of the third thin film transistor (T3) is electrically connected to the first node (A), the drain electrode is connected to a driving power supply (VDD), and the source electrode is electrically connected to the second node (B);
the grid electrode of the fourth thin film transistor (T4) is connected to a third scanning control signal (VSCAN3), the drain electrode of the fourth thin film transistor is electrically connected to the anode of the Organic Light Emitting Diode (OLED), and the source electrode of the fourth thin film transistor is electrically connected to one end of a third capacitor (C3);
the grid electrode of the fifth thin film transistor (T5) is connected to a second scanning control signal (VSCAN2), the drain electrode of the fifth thin film transistor is electrically connected to the anode of the Organic Light Emitting Diode (OLED), and the source electrode of the fifth thin film transistor is connected to the ground voltage (GND);
one end of the first capacitor (C1) is electrically connected to the first node (A), and the other end is connected to a ground voltage (GND);
one end of the second capacitor (C2) is electrically connected to the second node (B), and the other end is connected to the ground voltage (GND);
one end of the third capacitor (C3) is electrically connected to the second node (B), and the other end is electrically connected to the source of the fourth thin film transistor (T4);
and the anode of the Organic Light Emitting Diode (OLED) is connected to the drain of the fourth thin film transistor (T4), and the cathode of the Organic Light Emitting Diode (OLED) is connected to the low voltage (GND).
2. A novel AMOLED pixel driving circuit as claimed in claim 1, wherein the first, second, third, fourth and fifth thin film transistors (T1, T2, T3, T4, T5) are all low temperature polysilicon thin film transistors, oxide semiconductor thin film transistors, amorphous silicon thin film transistors or organic thin film transistors.
3. A novel AMOLED pixel driver circuit as claimed in claim 1, wherein the third tft (T3) is a driving tft and the second tft (T2) is a compensating tft, and their threshold voltage magnitudes and trends are approximately the same.
4. A novel AMOLED pixel driving circuit as claimed in claim 1, wherein the first, second and third scan control signals (VSCAN1, VSCAN2, VSCAN3), the first data voltage (VDATA1), the second data voltage (VDATA2), and the driving power (VDD) are all provided through an external timing controller.
5. The novel AMOLED pixel driving circuit as claimed in claim 1, wherein the driving sequence of the AMOLED pixel driving circuit sequentially comprises:
(1) a data voltage input stage: the first scan control signal (VSCAN1), the second scan control signal (VSCAN2), the first data voltage (VDATA1), and the second data voltage (VDATA2) all provide a high potential, and the third scan control signal (VSCAN3) and the driving Voltage (VDD) all provide a low potential;
(2) a light emitting stage: the second scan control signal (VSCAN2), the third scan control signal (VSCAN3), the second data voltage (VDATA2), and the driving Voltage (VDD) all provide a high potential, and the first scan control signal (VSCAN1) and the first data voltage (VDATA1) all provide a low potential.
6. A novel AMOLED pixel driving method suitable for use in the pixel driving circuit of claim 1, the method comprising in particular the steps of:
step 1: entering a data voltage input stage;
the first scan control signal (VSCAN1), the second scan control signal (VSCAN2), the first data voltage (VDATA1), and the second data voltage (VDATA2) all provide high potentials, and the third scan control signal (VSCAN3) and the driving Voltage (VDD) all provide low potentials;
the first thin film transistor (T1) and the fifth thin film transistor (T5) are turned on, the second thin film transistor (T2) is always turned on, the grid electrode and the drain electrode of the second thin film transistor (T2) are shorted, a diode connection mode is kept, and the third thin film transistor (T3) and the fourth thin film transistor (T4) are turned off; the voltage at the first node (a), i.e., the gate voltage of the driving thin film transistor (T3), is initialized to VDATA1_ H, the voltage at the second node (B), i.e., the source voltage of the driving thin film transistor (T3), is initialized to VDATA2-Vth, where VDATA1_ H is a high level of the first data voltage (VDATA1), where VDATA2 is a level of the second data voltage (VDATA2), and Vth is a threshold voltage of the driving thin film transistor, i.e., the third thin film transistor (T3), and the compensation thin film transistor, i.e., the second thin film transistor (T2);
step 2: entering a light emitting stage;
the third scan control signal (VSCAN3), the driving Voltage (VDD), and the second data voltage (VDATA2) provide a high potential, and the first scan control signal (VSCAN1), the second scan control signal (VSCAN2), and the first data voltage (VDATA1) provide a low potential;
a third thin film transistor (T3) and a fourth thin film transistor (T4) are turned on, the second thin film transistor (T2) is always turned on, the grid and drain short of the second thin film transistor (T2) keeps a diode connection mode, the first thin film transistor (T1) and the fifth thin film transistor (T5) are turned off, and the second capacitor (C2) and the third capacitor (C3) are connected in parallel; the voltage at the first node (a), i.e., the gate voltage of the driving thin film transistor (T3), is still VDATA1_ H, the voltage at the second node (B), i.e., the source voltage of the driving thin film transistor (T3), is VDATA2-Vth + (C3/C2+ C3) VOLED, where C2 is the capacitance value of the second capacitor (C2), C3 is the capacitance value of the third capacitor (C3), VDATA1_ H is the high level of the first data voltage (VDATA1), VDATA2 is the level of the second data voltage (VDATA2), Vth is the threshold voltage of the driving thin film transistor, i.e., the third thin film transistor (T3), and the compensation thin film transistor, i.e., the second thin film transistor (T2), and VOLED is the anode voltage of the Organic Light Emitting Diode (OLED).
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