CN112669774A - AMOLED pixel driving circuit and method for compensating material abnormity - Google Patents
AMOLED pixel driving circuit and method for compensating material abnormity Download PDFInfo
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Abstract
The invention provides an AMOLED pixel driving circuit and method for compensating material abnormity. The drain of the first transistor is connected with the sources of the second transistor and the fourth transistor, the grid is connected with the drain of the fourth transistor and the A end of the storage capacitor, the source is connected with the source of the third transistor and is connected with the ground through a light-emitting diode, the drain of the second transistor is connected with a power line, the grid is connected with a second scanning control line, the source is connected with the drain of the first transistor and the source of the fourth transistor, the drain of the third transistor is connected with the source of the fifth transistor and the B end of the storage capacitor, the grid is connected with the second scanning control line, the source is connected with the source of the first transistor and is connected with the ground through a light-emitting diode, the drain of the fourth transistor is connected with the grid of the first transistor and the A end of the storage capacitor, the grid is connected with the first scanning control line, the source is connected with the drain of the first transistor and the source of the second transistor, the drain of the fifth transistor is connected with a data line, the circuit can effectively compensate the uneven threshold voltage of the transistor and the degradation of the OLED opening voltage, so that the brightness of the OLED display picture is uniform, and high contrast is realized.
Description
Technical Field
An AMOLED pixel driving circuit and method for compensating material abnormality.
Background
Among the many types of flat panel displays, organic light emitting diode display technology is a promising emerging flat panel display technology, and OLEDs were published in 1987 by Kodak (Eastman Kodak Co.) corporation. It has the features of thin thickness, light weight, self-luminescence, low driving voltage, high efficiency, high contrast, high color saturation, fast reaction speed, flexibility, etc. And thus is considered a rather well-looked at display technology following the TFT-LCD. In recent years, the demand for high-quality full-color flat panel displays in mobile communication, digital products and digital televisions has increased rapidly. The OLED display not only has the advantages of lightness and thinness, power saving and full-color display of the LCD, but also has the characteristics of wider visual angle, active light emitting and high reaction speed compared with the LCD.
The OLED driving method can be divided into a Passive Matrix OLED (PMOLED) and an Active Matrix OLED (AMOLED). The PMOLED does not emit light when data is not written, and emits light only during data writing. The driving method has simple structure, low cost and easy design, and the early manufacturers all develop the technology. However, due to the driving method, the problems of large power consumption and short lifetime when developing a large-sized display are serious. Mainly applied to medium and small size displays. The biggest difference between the AMOLED and the PMOLED is that each pixel has a capacitor to store data, so that each pixel is kept in a light-emitting state. Therefore, the power consumption of the AMOLED is significantly less than that of the PMOLED, and the driving method thereof is suitable for developing a large-size and high-resolution display, so that the AMOLED is a major development direction in the future.
Although the AMOLED can store the pixel voltage in the capacitor to make it emit light continuously, if the P-type transistor is used as the driving component, the serious I-R Drop phenomenon occurs; on the other hand, if the N-type transistor is used as the driving device, the driving device is affected by the turn-on voltage of the OLED. In addition, the threshold voltage of the transistor varies between pixels due to the manufacturing process, which causes different currents to be generated when the same pixel voltage is input, resulting in non-uniform brightness.
In order to solve the problems of the variation of the threshold voltage of the pixel driving transistor and the non-uniform display brightness of the OLED picture, the invention provides the AMOLED pixel driving circuit and the AMOLED pixel driving method for compensating the material abnormality.
Disclosure of Invention
An AMOLED pixel driving circuit and method for compensating material abnormity is realized by the following technical scheme:
an AMOLED pixel drive circuit and method of compensating for material anomalies, the drive circuit comprising:
the OLED driving circuit comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a storage capacitor and an OLED.
The drain electrode of the first transistor is connected with the source electrodes of the second transistor and the fourth transistor, the grid electrode of the first transistor is connected with the drain electrode of the fourth transistor and the A end of the storage capacitor, the source electrode of the first transistor is connected with the source electrode of the third transistor and is connected with the ground through the light-emitting diode, and the first transistor is used for driving the OLED to emit light.
The drain electrode of the second transistor is connected with the power line, the grid electrode of the second transistor is connected with the second scanning control line, the source electrode of the second transistor is connected with the drain electrode of the first transistor and the source electrode of the fourth transistor, the second transistor plays a role of a switch and is used for cutting off the connection between the power line and the pixel data in the compensation stage, and the compensation operation can be correctly carried out.
The drain electrode of the third transistor is connected with the source electrode of the fifth transistor and the end B of the storage capacitor, the grid electrode of the third transistor is connected with the second scanning control line, the source electrode of the third transistor is connected with the source electrode of the first transistor and is connected with the ground through the light-emitting diode, and the third transistor plays a role of a switch and is used for detecting the starting voltage of the OLED and then carries out compensation operation.
The drain of the fourth transistor is connected with the grid of the first transistor and the A end of the storage capacitor, the grid is connected with the first scanning control line, the source is connected with the drain of the first transistor and the source of the second transistor, and the fourth transistor enables the first transistor to form a diode connection method under the condition of being turned on, so that the circuit can generate the threshold voltage of the first transistor in the compensation stage and record the threshold voltage.
The drain electrode of the fifth transistor is connected with the data line, the grid electrode of the fifth transistor is connected with the first scanning control line, the source electrode of the fifth transistor is connected with the drain electrode of the third transistor and the end B of the storage capacitor, and the fifth transistor is used for switching and controlling the time of data input.
The AMOLED pixel driving method for compensating for material anomalies includes the following steps:
(1) a reset phase: the first scanning control line, the second scanning control line are in high level, the second transistor, the third transistor, the fourth transistor and the fifth transistor which are used as switches are all conducted, the voltage at the point B is the data line preprogramming voltage, and the point A is charged to the power line.
(2) And (3) compensation stage: the first scanning control line is at high level, the second scanning control line is at low level, the second transistor and the third transistor are closed, the fourth transistor and the fifth transistor are turned on, at the moment, the first transistor forms diode connection due to the fact that the fourth transistor is turned on, and the point A is discharged through the fourth transistor until the first transistor is turned off.
(3) A buffering stage: the first scanning control line and the second scanning control line are in low level, the second transistor, the third transistor, the fourth transistor and the fifth transistor which are used as switches are all closed, and the stage is to prevent the circuit from generating unnecessary noise due to switch switching.
(4) A light emitting stage: the first scanning control line is at a low level, the second scanning control line is at a high level, the second transistor and the third transistor are conducted, the fourth transistor and the fifth transistor are closed, the first transistor drives the OLED to emit light, and the grid-source voltage of the first transistor is kept unchanged in the light emitting stage.
In the step (2), the threshold voltage of the first transistor is stored by discharging the OLED until the first transistor is turned off, and the voltage at the point a of the storage capacitor is the sum of the threshold voltage of the OLED and the threshold voltage of the first transistor.
Drawings
The subject matter regarded as the invention is particularly pointed out and distinctly claimed in the claims at the conclusion of the patent application. The invention, however, both as to organization and method of operation, together with objects, features, and advantages thereof, may best be understood by reference to the following detailed description when read with the accompanying drawings.
Fig. 1 is an AMOLED pixel drive circuit that compensates for material anomalies.
Fig. 2 is a signal timing diagram of fig. 1.
Detailed Description
In the following detailed description, specific details are set forth in order to provide a thorough understanding of the invention. However, one skilled in the art will recognize that the invention may be practiced with other similar details.
Examples
As shown in fig. 1, the AMOLED pixel driving circuit for compensating for material anomaly according to the present invention includes a first transistor T1, a second transistor T2, a third transistor T3, a fourth transistor T4, a fifth transistor T5, a storage capacitor C0, a light emitting diode OLED, a first scan control line S1, a second scan control line S2, a power line VDD, a ground line VSS, a data line V, and a control line VDATA。
The drain of the first transistor T1 is connected to the sources of the second transistor T2 and the fourth transistor T4, the gate is connected to the drain of the fourth transistor T4 and the a terminal of the storage capacitor C0, the source is connected to the source of the third transistor T33, and the first transistor is connected to the ground VSS through the light emitting diode OLED, and the first transistor is used for driving the OLED to emit light.
The drain of the second transistor T2 is connected to the power line, the gate is connected to the second scan control line S2, the source is connected to the drain of the first transistor T1 and the source of the fourth transistor T4, the second transistor T2 is used for switching off the power line VDD and the pixel data V in the compensation stageDATAThe compensation operation of the connection between the two elements can be correctly carried out.
The drain of the third transistor T3 is connected to the source of the fifth transistor T4 and the B terminal of the storage capacitor C0, the gate is connected to the second scanning control line S2, the source is connected to the source of the first transistor T1, and is connected to the ground VSS through the light emitting diode OLED, and the third transistor T3 functions as a switch for detecting the OLED turn-on voltage and then performs a compensation operation.
The drain of the fourth transistor T4 is connected to the gate of the first transistor T1 and the a terminal of the storage capacitor C0, the gate is connected to the first scan control line S1, the source is connected to the drain of the first transistor T1 and the source of the second transistor T2, and when the fourth transistor T4 is turned on, the first transistor T1 is connected to a diode, so that the circuit can generate the threshold voltage of the first transistor T1 itself in the compensation stage, and the threshold voltage is recorded.
The drain electrode of the fifth transistor T5 is connected with the data line VDATAThe gate is connected to the first scan control line S1, the source is connected to the drain of the third transistor T3 and the B terminal of the storage capacitor, and the fifth transistor T5 is used for switching the time of controlling the data input.
When the pixel driving circuit operates, the first transistor T1 performs a driving function and operates in a saturation region, and the second transistor T2, the third transistor T3, the fourth transistor T4, and the fifth transistor T5 all operate in a linear region. The input timing sequence of each signal line is shown in fig. 2, the two groups of control lines have the same signal format, but are opposite in phase and have a phase difference between the two groups of signals, so that the circuit can have a short period of time before compensation as the circuit reset time, and each compensation operation can be correctly performed. The pixel driving circuit is realized by the following method steps:
(1) in the reset stage, the first scan control line S1, the second scan control line S2 are at high level, the second transistor T2, the third transistor T3, the fourth transistor T4 and the fifth transistor T5 are all turned on, and the voltage at point B is the data line pre-programming voltage VDATAThe point a charges the power line VDD, which is to reset the voltage value of the previous frame stored in the capacitor, so that the accuracy of the next compensation operation is not affected.
(2) In the compensation stage, the first scan control line S1 is at high level, the second scan control line S2 is at low level, the second transistor T2 and the third transistor T3 are turned off, the fourth transistor T4 and the fifth transistor T5 are turned on, the first transistor T1 is diode-connected due to the turn-on of the fourth transistor T4, the point a is charged to a high voltage in the previous stage, and the second transistor T2 is turned off, the point a is discharged through the fourth transistor T4, when discharging to no current, the voltage at point a is locked at V by the factor of the voltage at point a known in the circuitTH_OLED+VTH_TFTAnd the voltage position of point B is at VDATAIn which V isTH_OLEDAnd VTH_TFTThe threshold voltages of the OLED and the first transistor, respectively.
(3) In the buffering stage, the first scan control line S1 and the second scan control line S2 are at low level, the second transistor T2, the third transistor T3, the fourth transistor T4 and the fifth transistor T5 are all turned off, so that the circuit will not generate unnecessary noise due to the switching, and in this stage, the circuit does not operate, and the voltage stored in the storage capacitor C0 is maintained, and V is maintainedAB =VTH_OLED+VTH_TFT-VDATA。
(4) In the light emitting stage, the first scan control line S1 is at a low level, the second scan control line S2 is at a high level, the second transistor T2 and the third transistor T3 are turned on, the fourth transistor T4 and the fifth transistor T5 are turned off, and the voltage at the point B becomes VOLED_INSince the point A is in floating state, the capacitor stores voltage VTH_OLED+VTH_TFT-VDATASo that the voltage at point A will become VTH_OLED+VTH_TFT-VDATA+VOLED_INIn which V isOLED_INIs the turn-on voltage when the OLED emits light. It can thus be seen that the gate-source voltage V of the first transistor T1 at this timeGS=VTH_OLED+VTH_TFT-VDATAAnd the current formula of the first transistor T1 is Id=K(VGS- VTH)2Where K is a fixed process parameter, in which case V isGSBy substituting the formula of current, I can be obtainedd=K(VTH_OLED-VDATA)2From the current formula, the current flowing through the light emitting diode OLED and the threshold voltage V of the first transistor T1TH_TFTIs irrelevant, and V appears in the current formulaTH_OLEDIn this case, when the OLED emits light for a long time and the material is attenuated, the compensation circuit generates an extra current to compensate the reduced light emitting efficiency.
While the description herein describes certain features of the invention and one implementation, many modifications, substitutions, changes, and equivalents will now occur to those skilled in the art. Therefore, the protection scope of the present invention is subject to the scope of the appended claims.
Claims (4)
1. An AMOLED pixel driving circuit and method for compensating for material anomalies, the driving circuit comprising:
the OLED driving circuit comprises a first transistor, a second transistor, a third transistor, a fourth transistor, a fifth transistor, a storage capacitor and an OLED;
the drain electrode of the first transistor is connected with the source electrodes of the second transistor and the fourth transistor, the grid electrode of the first transistor is connected with the drain electrode of the fourth transistor and the end A of the storage capacitor, the source electrode of the first transistor is connected with the source electrode of the third transistor and is connected with the ground through the light-emitting diode, and the first transistor is used for driving the OLED to emit light;
the drain electrode of the second transistor is connected with the power line, the grid electrode of the second transistor is connected with the second scanning control line, the source electrode of the second transistor is connected with the drain electrode of the first transistor and the source electrode of the fourth transistor, the second transistor plays a role of a switch and is used for cutting off the connection between the power line and the pixel data in the compensation stage, and the compensation operation can be correctly carried out;
the drain electrode of the third transistor is connected with the source electrode of the fifth transistor and the end B of the storage capacitor, the grid electrode of the third transistor is connected with the second scanning control line, the source electrode of the third transistor is connected with the source electrode of the first transistor and is connected with the ground through the light-emitting diode, the third transistor plays a role of a switch and is used for detecting the starting voltage of the OLED and then performing compensation operation;
the drain of the fourth transistor is connected with the grid of the first transistor and the A end of the storage capacitor, the grid is connected with the first scanning control line, the source is connected with the drain of the first transistor and the source of the second transistor, and the fourth transistor enables the first transistor to form a diode connection method under the condition of being turned on, so that the circuit can generate and record the threshold voltage of the first transistor in the compensation stage;
the drain electrode of the fifth transistor is connected with the data line, the grid electrode of the fifth transistor is connected with the first scanning control line, the source electrode of the fifth transistor is connected with the drain electrode of the third transistor and the end B of the storage capacitor, and the fifth transistor is used for switching and controlling the time of data input.
2. An AMOLED pixel driving circuit for compensating for material anomalies as set forth in claim 1, wherein the transistor is one of a low temperature polysilicon thin film transistor and an amorphous silicon thin film transistor.
3. An AMOLED pixel driving method to compensate for material anomalies as claimed in claim 1, comprising the steps of:
(1) a reset phase: the first scanning control line, the second scanning control line is in high level, the second transistor, the third transistor, the fourth transistor and the fifth transistor which are used as switches are all conducted, at the moment, the voltage at the point B is the pre-programmed voltage of the data line, and the point A is charged to the power line;
(2) and (3) compensation stage: the first scanning control line is at a high level, the second scanning control line is at a low level, the second transistor and the third transistor are closed, the fourth transistor and the fifth transistor are turned on, at the moment, the first transistor forms diode connection due to the fact that the fourth transistor is turned on, and the point A is discharged through the fourth transistor until the first transistor is turned off;
(3) a buffering stage: the first scanning control line and the second scanning control line are in low level, the second transistor, the third transistor, the fourth transistor and the fifth transistor which are used as switches are all closed, and the stage is to prevent the circuit from generating unnecessary noise due to switch switching;
(4) a light emitting stage: the first scanning control line is at a low level, the second scanning control line is at a high level, the second transistor and the third transistor are conducted, the fourth transistor and the fifth transistor are closed, the first transistor drives the OLED to emit light, and the grid-source voltage of the first transistor is kept unchanged in the light emitting stage.
4. The method of claim 3, wherein the step (2) of storing the threshold voltage of the first transistor is performed by discharging the OLED until the first transistor is turned off, and the voltage at the A point of the storage capacitor is the sum of the threshold voltage of the OLED and the threshold voltage of the first transistor.
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| CN101305409A (en) * | 2005-09-13 | 2008-11-12 | 伊格尼斯创新有限公司 | Compensation technique for luminance degradation in electro-luminance devices |
| CN103700342A (en) * | 2013-12-12 | 2014-04-02 | 京东方科技集团股份有限公司 | OLED (Organic Light-Emitting Diode) pixel circuit, driving method and display device |
| CN104167168A (en) * | 2014-06-23 | 2014-11-26 | 京东方科技集团股份有限公司 | Pixel circuit and driving method thereof and display device |
| CN104575378A (en) * | 2014-12-23 | 2015-04-29 | 北京大学深圳研究生院 | Pixel circuit, display device and display driving method |
| CN104882095A (en) * | 2014-12-03 | 2015-09-02 | 四川虹视显示技术有限公司 | Pixel drive circuit |
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- 2019-10-16 CN CN201910985375.0A patent/CN112669774A/en active Pending
Patent Citations (5)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101305409A (en) * | 2005-09-13 | 2008-11-12 | 伊格尼斯创新有限公司 | Compensation technique for luminance degradation in electro-luminance devices |
| CN103700342A (en) * | 2013-12-12 | 2014-04-02 | 京东方科技集团股份有限公司 | OLED (Organic Light-Emitting Diode) pixel circuit, driving method and display device |
| CN104167168A (en) * | 2014-06-23 | 2014-11-26 | 京东方科技集团股份有限公司 | Pixel circuit and driving method thereof and display device |
| CN104882095A (en) * | 2014-12-03 | 2015-09-02 | 四川虹视显示技术有限公司 | Pixel drive circuit |
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Application publication date: 20210416 |