CN110890055A - Self-luminous display device and in-pixel compensation circuit - Google Patents
Self-luminous display device and in-pixel compensation circuit Download PDFInfo
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- CN110890055A CN110890055A CN201911163302.XA CN201911163302A CN110890055A CN 110890055 A CN110890055 A CN 110890055A CN 201911163302 A CN201911163302 A CN 201911163302A CN 110890055 A CN110890055 A CN 110890055A
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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]
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- G—PHYSICS
- G09—EDUCATION; CRYPTOGRAPHY; DISPLAY; ADVERTISING; SEALS
- G09G—ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION
- G09G3/00—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes
- G09G3/20—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters
- G09G3/22—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources
- G09G3/30—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels
- G09G3/32—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED]
- G09G3/3208—Control arrangements or circuits, of interest only in connection with visual indicators other than cathode-ray tubes for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix no fixed position being assigned to or needed to be assigned to the individual characters or partial characters using controlled light sources using electroluminescent panels semiconductive, e.g. using light-emitting diodes [LED] organic, e.g. using organic light-emitting diodes [OLED]
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Abstract
The invention provides a self-luminous display device and a pixel internal compensation circuit, wherein the pixel internal compensation circuit comprises a first driving TFT connected with a luminous element, a first switch TFT and a storage capacitor positioned between the first driving TFT and the first switch TFT; wherein the access point is located between the first switching TFT and the storage capacitor; the first driving TFT is charged, the input data voltage and the threshold voltage of the first driving TFT are extracted, the threshold voltage of the first driving TFT is compensated, and the light-emitting element enters a light-emitting stage in sequence in a first time period, a second time period, a third time period and a fourth time period which are continuous. According to the invention, the threshold voltage Vth of the first switching TFT is extracted by the first driving TFT in a diode connection mode, and the driving voltage of the first driving TFT is compensated through a capacitive coupling effect, so that the adverse effects of Vth unevenness and Vth drift on the display effect are counteracted.
Description
Technical Field
The invention relates to the technical field of display panels, in particular to a self-luminous display device and an in-pixel compensation circuit.
Background
In recent years, display devices are increasingly developed toward thinning, lightening and flexibility, and self-luminous displays include organic electroluminescent OLEDs, quantum dot electroluminescent QLEDs, and Micro electroluminescent Micro-LEDs, which have natural advantages in these respects.
In a light-emitting element for a self-luminous display, the luminance of light emitted is in a positive correlation with both applied voltage and current. The relationship between the light emission luminance and the voltage changes under the influence of factors such as the ambient temperature and the operating time. Therefore, it is difficult to control the uniformity and stability of the luminance of the self-luminous display by using the voltage-driven light emitting element. In contrast, the brightness of a light-emitting device is substantially proportional to the applied current, and is not susceptible to interference from other factors. Therefore, the self-light emitting display generally adopts a current driving type design.
The current for driving the light emitting element is provided by the TFT backplane, including LTPS TFT and oxide semiconductor TFT. However, the characteristics of the TFT (including threshold voltage Vth and mobility) are likely to be deviated or shifted, which causes deviation or shift of the driving current and affects display uniformity and lifetime. Therefore, a compensation TFT characteristic deviation or drift circuit is usually provided in a pixel circuit for self-luminous display to improve display uniformity and lifetime.
The pixel compensation circuit is typically composed of a current control mode and a voltage control mode. The current control mode can simultaneously compensate the threshold voltage and the mobility of the TFT; the voltage control mode can generally only compensate for the threshold voltage of the TFT. However, the current control mode has the following two problems: (1) the control current is weak current, and the design requirement on a drive IC is high; (2) due to the influence of parasitic capacitance, the pixel compensation circuit in the current control mode needs a longer setting time to achieve the compensation effect. Therefore, the current pixel compensation circuit mostly adopts a voltage control mode.
Fig. 1 shows a conventional uncompensated pixel driving circuit, which includes a switching TFT1, a driving TFT2 and a storage capacitor 3, wherein the switching TFT1 is controlled by a Scan signal Scan to input a data signal Vdata to a gate-path terminal of the driving TFT2, and the driving TFT2 is controlled by a voltage of the gate-path terminal to output a driving current under the action of a power supply ELVDD, and the current flows through a light emitting element 5 to emit light. The storage capacitor 3 is connected to the gate path terminal of the driving TFT2 and the power source ELVDD, and is used to maintain the voltage at the gate path terminal of the driving TFT2 and prevent it from varying due to leakage in one refresh cycle.
The uncompensated pixel compensation circuit does not compensate for the characteristics of the TFTs, and the current flowing through the light emitting element may vary due to variations and drifts in the characteristics of the driving TFTs, resulting in display uniformity and lifetime problems.
Fig. 2 shows a conventional voltage-controlled pixel compensation circuit, which includes 5 TFTs and 2 capacitors. The 110TFT is a driving TFT and supplies current to the light-emitting element, and the magnitude of the current is controlled by the grid voltage of the light-emitting element; 111TFT is a switching TFT for data voltage input, and is used for switching control of data voltage input; 112TFT is another switching TFT for switching control of input of a reference voltage; the 113TFT is another switch TFT for controlling the gate and drain of the driving TFT to be shorted so that the 110TFT forms a diode connection mode for extracting the threshold voltage Vth of the 110 TFT; the 114TFT is another switching TFT for switching light emission of the light emitting element while performing Vth extraction operation in cooperation with the 113 TFT.
The pixel compensation circuit can charge the gate of the 110TFT at t 0-t 1 through the cooperation of the 113TFT and the 114TFT, and extract the threshold voltage Vth of the 110TFT through the discharge of the 110TFT at t 1-t 2. At time t 3-t 4, the data voltage is input to point A and coupled to the gate of the 110TFT by capacitive coupling of 121. Thereby implementing the Vth compensation process of the 110 TFT.
However, the pixel compensation circuit needs 2 capacitors, wherein 121 capacitor is used for coupling the data voltage, and 122 capacitor is used for storing the pixel voltage to prevent the leakage. In order to achieve better coupling and voltage holding effects, the sizes of 2 capacitors need to be designed to be enough, and under the design of higher pixel density, the capacitors occupy larger layout space, so that the improvement of the pixel density is limited.
Disclosure of Invention
The invention provides a self-luminous display device and an in-pixel compensation circuit, which can reduce the number of components of the in-pixel compensation circuit and prolong the service life.
The invention provides an in-pixel compensation circuit, which is connected with a light-emitting element; the light emitting element is positioned between the first power supply and the second power supply and is controlled by the first light emitting control signal and the second light emitting control signal; the method is characterized in that: the light-emitting diode comprises a first driving TFT connected with the light-emitting element, a first switching TFT positioned at the intersection of a scanning line and a data line, a storage capacitor positioned between the first driving TFT and the first switching TFT, a second switching TFT, a third switching TFT, a fourth switching TFT and an access point; wherein the access point is located between the first switching TFT and the storage capacitor; the second switching TFT is connected among the first power supply, the second light-emitting control signal and the first driving TFT; the third switch TFT is connected with a scanning control signal provided by the scanning line; the fourth switch TFT is connected with the reference voltage and the first light-emitting control signal; the first driving TFT is charged, the input data voltage and the threshold voltage of the first driving TFT are extracted, the threshold voltage of the first driving TFT is compensated, and the light-emitting element enters a light-emitting stage in sequence in a first time period, a second time period, a third time period and a fourth time period which are continuous.
Preferably, the storage capacitor is a capacitor having both a coupling capacitor and a storage capacitor.
Preferably, the path end of the first driving TFT is connected to the first end of the storage capacitor, the first path end of the first driving TFT is connected to the first path end of the second switching TFT, and the second path end of the first switching TFT is connected to the anode of the light emitting element; the path end of the first switch TFT is connected with the scanning line, the first path end of the first switch TFT is connected with the data line, and the second path end of the first switch TFT is connected with the second end of the storage capacitor; the path end of the second switch TFT is connected with a second light-emitting control signal, and the second path end of the second switch TFT is connected with a first power supply; the channel end of the third switching TFT is connected with a scanning control signal provided by a scanning line, the first channel end of the third switching TFT is connected with the first channel end of the second switching TFT, and the second channel end of the third switching TFT is connected with the first channel end of the first driving TFT; and a path end of the fourth switch TFT is connected with the first light-emitting control signal, a first path end of the fourth switch TFT is connected with the reference voltage, and a second path end of the fourth switch TFT is connected with the second end of the storage capacitor.
Preferably, the second path end of the first switch TFT, the second end of the storage capacitor, and the second path end of the fourth switch TFT also meet the access point; the pixel unit is precharged in a first time period, and the input voltage of the access point is maintained as the reference voltage in a third time period.
Preferably, the scan signal of the scan line is inputted with a high level, the first lighting control signal is inputted with a low level, the first switching TFT is turned on, the fifth switching transistor is turned off, and the data voltage is inputted to the access point during the first period; the third switch TFT and the second switch TFT are also in an open state, the first power supply is input to the channel end of the first drive TFT, and the access point is precharged.
Preferably, the second switching TFT is turned off when the second light emission control signal is input at a low level for a second period of time; the first driving TFT is in an open state, the path end of the first driving TFT is connected with the first path end, and the first driving TFT forms a diode connection mode; the electric charges at the passage end of the first driving TFT are discharged to the light-emitting element through the first driving TFT until the first driving TFT is closed when the voltage between the grid electrode and the source electrode of the first driving TFT is reduced to the threshold voltage, and the discharging is stopped.
Preferably, the scan signal and the scan control signal of the scan line are input with a low level, the first light emitting control signal is input with a high level, the third switch TFT is turned off, the charge at the pass terminal of the first driving TFT is locked, and the voltage difference across the storage capacitor is also locked at the same time; the voltage of the access point is changed from the data voltage to the joining voltage, and the voltage change of the access point is coupled to the pass terminal of the first driving TFT.
Preferably, the second light emission control signal is inputted with a high level during the fourth period, the second switching TFT is turned on, a conductive path is formed between the first power source and the second power source, and a current flows through the light emitting element to emit light.
The invention also provides a self-luminous display device which comprises an N-level grid drive circuit, a luminous control circuit for outputting N levels and an in-pixel compensation circuit which is connected with the grid drive circuit and the luminous control circuit, wherein a scanning signal of a scanning line is connected to the output end of the nth-level grid drive circuit, a first luminous control signal is connected to the nth-level output end of the luminous control circuit, a second luminous control signal is connected to the (N + 1) th-level output end of the luminous control circuit, and N is less than or equal to N.
According to the invention, the threshold voltage Vth of the first switching TFT is extracted by the first driving TFT in a diode connection mode, and the driving voltage of the first driving TFT is compensated through a capacitive coupling effect, so that the adverse effects of Vth unevenness and Vth drift on the display effect are counteracted; the invention reduces the number of components of the compensation circuit in the pixel; the working life of the self-luminous display device is prolonged.
Drawings
FIG. 1 shows a conventional uncompensated pixel driving circuit;
FIG. 2 shows a conventional voltage-controlled pixel compensation circuit;
FIG. 3 is a schematic diagram of an in-pixel compensation circuit according to the present invention;
FIG. 4 is a waveform diagram of a driving signal of the in-pixel compensation circuit according to the present invention;
FIG. 5 is a schematic diagram of the driving signal waveform of FIG. 4 during a first time period;
FIG. 6 is a schematic diagram of the driving signal waveform of FIG. 4 in a second time period;
FIG. 7 is a schematic diagram of the driving signal waveform of FIG. 4 in a third time period;
FIG. 8 is a schematic diagram of the driving signal waveform of FIG. 4 during a fourth period;
FIG. 9 is a schematic structural diagram of a self-luminous display device according to the present invention;
fig. 10 is a waveform diagram of driving signals of the self-light emitting display device shown in fig. 9;
FIG. 11 is a schematic diagram of a circuit simulation performed at different data voltages according to the present invention;
fig. 12 is a schematic diagram of a circuit simulation performed when Vth developed by the first TFT changes according to the present invention.
Detailed Description
The present invention is further illustrated by the following figures and specific examples, which are to be understood as illustrative only and not as limiting the scope of the invention, which is to be given the full breadth of the appended claims and any and all equivalent modifications thereof which may occur to those skilled in the art upon reading the present specification.
For the sake of simplicity, the drawings only schematically show the parts relevant to the present invention, and they do not represent the actual structure as a product. In addition, in order to make the drawings concise and understandable, components having the same structure or function in some of the drawings are only schematically illustrated or only labeled. In this document, "one" means not only "only one" but also a case of "more than one".
Fig. 3 is a schematic diagram of an in-pixel compensation circuit for compensating a self-luminous display device according to the present invention, the in-pixel compensation circuit is connected to a light emitting element 30, wherein the light emitting element 30 is located between a first power ELVDD and a second power ELVSS, and the light emitting element 30 is controlled by a first light emission control signal EM1 and a second light emission control signal EM 2.
The first power ELVDD is a positive power terminal, and the second power ELVSS is a negative power terminal.
The self-luminous display device comprises scanning lines and data lines which are crisscrossed, pixel units defined by the intersection of the scanning lines and the data lines and pixel units positioned in the pixel units; the Scan lines provide Scan signals Scan and Scan control signals Scan, and the data lines provide data voltages Vdata.
The in-pixel compensation circuit includes a first driving TFT11 connected to the light emitting element 30, a first switching TFT12, a second switching TFT13, a third switching TFT14, a fourth switching TFT15, one storage capacitor 20, and an access point (abbreviated as PIX point) at the intersection of the scan line and the data line, wherein the first driving TFT11 is a driving TFT switch; the access point (abbreviated as PIX point) is located at the intersection of the first switch TFT12, the fourth switch TFT15 and the storage capacitor 20; the storage capacitor 20 has both the function of a coupling capacitor and the function of a storage capacitor, thereby reducing the number of elements of the compensation circuit in the pixel and providing the possibility of a self-luminous display device with higher PPI.
It should be noted that each TFT switch according to the following embodiments includes a pass terminal, a first pass terminal, and a second pass terminal, where the pass terminal is a gate, one of the pass terminals is a source, and the other pass terminal is a drain. When the voltages received by the path end, the first path end and the second path end meet the opening condition of the TFT switch, the source electrode and the drain electrode are connected through the semiconductor layer, and the TFT switch is in an opening state at the moment, otherwise, the TFT switch is in a closing state.
The first driving TFT11 is located between the light emitting element 30 and the first power source ELVDD, and is connected in series with the light emitting element 30. Specifically, the on terminal of the first driving TFT11 is connected to the first terminal of the storage capacitor 20, the first on terminal of the first driving TFT11 is connected to the first on terminal of the second switching TFT13, and the second on terminal of the first switching TFT11 is connected to the anode of the light emitting element 30.
An on terminal of the first switching TFT12 is connected to the scan line, a first on terminal of the first switching TFT12 is connected to the data line, and a second on terminal of the first switching TFT12 is connected to the second terminal of the storage capacitor 20.
The second switching TFT13 is disposed between the first driving TFT11 and the first power source ELVDD, and in particular, a path terminal of the second switching TFT13 is connected to the second emission control signal EM2, a second path terminal of the second switching TFT13 is connected to the first power source ELVDD, a first path terminal of the second switching TFT13 is connected to a first path terminal of the first driving TFT11, and in practice, the second switching TFT13, the first driving TFT11, and the light emitting device 30 are connected in series between the first power source ELVDD and the second power source ELVSS.
A path terminal of the third switching TFT14 is connected to a Scan control signal Scan supplied from a Scan line, a first path terminal of the third switching TFT14 is connected to a first path terminal of the second switching TFT13, and a second path terminal of the third switching TFT14 is connected to a first path terminal of the first driving TFT11, that is, the first path terminal of the first driving TFT11, the second path terminal of the third switching TFT14, and the first path terminal of the second switching TFT13 meet at one point.
A path end of the fourth switch TFT15 is connected to the first light emission control signal EM1, a first path end of the fourth switch TFT15 is connected to the reference voltage Vref, and a second path end of the fourth switch TFT15 is connected to the second end of the storage capacitor 20, that is, the second path end of the first switch TFT12, the second end of the storage capacitor 20, and the second path end of the fourth switch TFT15 also meet at the PIX point.
The path end of the first driving TFT11 is a point G, and the second path end of the first switching TFT12, the second end of the storage capacitor 20 and the second path end of the fourth switching TFT15 also meet at the point G; the first path end of the first driving TFT11 is a point a, and the first path end of the first driving TFT11, the second path end of the third switching TFT14 and the first path end of the second switching TFT13 meet at the point a; the second path terminal of the first driving TFT11 is a point B, and the second path terminal of the first switching TFT11 and the anode of the light emitting element 30 meet at the point B.
Fig. 4 shows a waveform diagram of a driving signal of the in-pixel compensation circuit of the present invention, in which a PIX point is precharged and a gate terminal G point of the first driving TFT11 is charged, a data voltage Vdata is input and a threshold voltage Vth of the gate terminal G point of the first driving TFT11 is extracted, the PIX point is input and maintained as a reference voltage Vref and the threshold voltage Vth of the gate terminal G point of the first driving TFT11 is compensated, and the light emitting element 30 enters a light emitting phase in sequence in a first period (specifically, a period T1), a second period (specifically, a period T2), a third period (specifically, a period T3) and a fourth period (specifically, a period T4) which are consecutive.
Specifically, the PIX point (i.e., the access point) is precharged for a first period of time (specifically, during T1), and the path terminal G point of the first driving TFT11 is charged; a data voltage Vdata is input through the data line for a second period (specifically, during T2), and the Vth is extracted at the path terminal G point of the first driving TFT 11; a sustain reference voltage Vref is input to a PIX point (i.e., an access point) in a third period (specifically, during T3), and Vth of a G point of a path terminal of the first driving TFT11 is compensated; the fourth period (specifically, during T4) is when the light emitting element 30 enters the light emitting phase; the time lengths of T1, T2 and T3 are the same, and T4 is not less than the sum of the times of T1, T2 and T3.
When the Scan signal Scan and the Scan control signal Scan of the Scan line are at a high level during the period T1 and the period T2, they are at a low level during the period T3 and the period T4; the first light emission control signal EM1 is at a low level during the period T1 and the period T2, and is at a high level during the period T3 and the period T4; the second light emission control signal EM1 is at a high level during the period T1 and the period T4, and is at a low level during both the period T2 and the period T3; the data voltage Vdata is at a high level during T2, and at a low level during T1, T3, and T4.
As shown in fig. 5, during a period T1, the Scan signal Scan of the Scan line is inputted with a high level, the first emission control signal EM1 is inputted with a low level, at this time, the first switching TFT12 is turned on, the fifth switching transistor 15 is turned off, and the data voltage Vdata is inputted to the PIX point; meanwhile, the third switching TFT14 and the second switching TFT13 are also in an on state, the path terminal G point of the first driving TFT11 corresponds to the direct input of the first power ELVDD, and the PIX point is precharged.
As shown in fig. 6, during T2, the second emission control signal EM2 inputs a low level, at which time the second switching TFT13 is turned off; the first driving TFT11 is in an on state, the first driving TFT11 and the first path end are connected, the first driving TFT11 forms a diode connection mode, the charge at the point G of the path end of the first driving TFT11 is discharged to the light emitting element 30 through the first driving TFT11 until the first driving TFT11 is turned off when the Vgs (between the gate and the source) voltage of the first driving TFT11 drops to Vth, and the discharge stops, at this time, the voltage at the point G of the path end of the first driving TFT11 is (ELVSS + Voled + Vth), Voled is the voltage of the light emitting element 30; thus, the Vth of the path terminal G of the first driving TFT11 is successfully extracted to the path terminal G of the first driving TFT11 and stored by the capacitor Cst of the storage capacitor 20.
As shown in fig. 7, at time T3, the Scan signal Scan and the Scan control signal Scan of the Scan line are inputted with a low level, the first emission control signal EM1 is inputted with a high level, the third switching TFT14 is turned off, the charge at the G point of the pass terminal of the first driving TFT11 is locked, and the voltage difference across the capacitor Cst of the storage capacitor 20 is also locked; meanwhile, the voltage at the PIX point is changed from Vdata to Vref, and since the voltage difference across the capacitor Cst of the storage capacitor 20 is locked, the voltage change at the PIX point is coupled to the path terminal G point of the first driving TFT11, and thus the voltage at the path terminal G point of the first driving TFT11 is changed to (ELVSS + Voled + Vth + Vref-Vdata).
As shown in fig. 8, in the period T4, the second emission control signal EM2 is inputted with a high level, the second switching TFT13 is turned on, a conductive path is formed between the first power source ELVDD and the second power source ELVSS, and a current flows through the light emitting element 30 to emit light, that is, to enter the emission period.
In the light-emitting period, a current flowing through the light-emitting element 30 is controlled by the first driving TFT 11. Since the first-path terminal voltage of the first driving TFT11 is ELVDD, the first driving TFT11 operates in a saturation region with an operating current of 1/2K (Vgs-Vth)2, that is, 1/2K (Vref-Vdata) 2. With this current formula, it can be found that the drive current flowing through the light emitting element 30 is related only to the Vdata voltage and the Vref voltage, Vref is a constant reference voltage, and the drive current is actually controlled only by the Vdata voltage. Since Vth of the first driving TFT11 is extracted during T2, the current in the light emission phase is not affected by Vth of the first driving TFT11, and a compensation effect of Vth is achieved.
After Vth compensation, the luminous brightness is not affected by Vth deviation caused by process uniformity, so that the luminous brightness of the display area is more uniform, and better image quality performance is realized. Meanwhile, as the Vth is compensated, even if the Vth of the first driving TFT11 drifts after a long time of operation, the brightness is not affected significantly, and the service life and reliability of the self-luminous display device are improved.
The invention also discloses a self-luminous display device which comprises an N-level grid driving circuit, a luminous control circuit outputting N levels and an in-pixel compensation circuit which is connected with the grid driving circuit and the luminous control circuit.
Fig. 9 is a schematic structural diagram of the self-light emitting display device of the present invention, in which a Scan signal of a Scan line Scan is connected to an output Gn of an nth-stage gate driving circuit, a first emission control signal EM1 is connected to an nth-stage output EMn of an emission control circuit, and a second emission control signal EM2 is connected to an N +1 th-stage output EMn +1 of the emission control circuit, where N is less than or equal to N.
Fig. 10 is a waveform diagram of driving signals of the self-light emitting display device shown in fig. 9, which is the same as the waveform diagram of the driving signals shown in fig. 4, that is, the timing of the output terminal Gn of the nth stage gate driving circuit is the same as the timing of the scanning signal of the scanning line Scan, the timing of the output terminal EMn of the nth stage of the light emission control circuit is the same as the timing of the first light emission control signal EM1, and the timing of the output terminal EMn +1 of the n +1 th stage of the light emission control circuit is the same as the timing of the second light emission control signal EM 2.
Fig. 11 and 12 are schematic diagrams showing circuit simulation results of a self-luminous display device, in which after the in-pixel compensation circuit of the present invention is used, fig. 11 shows the driving current variation under different Vdata voltages, and the simulation results show that the Vdata voltage can normally control the driving current of the pixel circuit. Fig. 12 shows the variation of the driving current at different Vth when the Vth of the first driving TFT is varied, and it can be seen that the driving current of each gray level maintains a good stability without significant current decay over a wide Vth voltage variation range.
The in-pixel compensation circuit can also compensate the fluctuation influence of the first power supply ELVDD. Since the self light emitting display device is driven by a current, the first power source ELVDD and the second power source ELVSS are required to supply a large current. When the current flows through the conductive path, a voltage drop IR-drop is generated, which causes a difference between the first power ELVDD and the second power ELVSS actually obtained for each pixel of the display area, resulting in an uneven display effect.
The driving current of the compensation circuit in the pixel is only related to the Vdata voltage, the first power supply ELVDD and the second power supply ELVSS are compensated, the picture unevenness caused by IR-drop is avoided, and the better picture display effect is favorably realized.
The in-pixel compensation circuit of the invention can also compensate the threshold voltage of the light-emitting element. The threshold voltage of the light emitting element can drift after long-time operation, so that the display brightness is reduced; the in-pixel compensation circuit compensates the threshold voltage Voled of the light-emitting element, the driving current of the in-pixel compensation circuit is only related to Vdata, and the brightness reduction caused by the aging of a light-emitting device is avoided. The lifetime of the display device is improved.
The in-pixel compensation circuit of the invention has the application range including but not limited to self-luminous flat panel displays such as organic light emitting diodes, Micro-LEDs, quantum dot LEDs and the like, and the used semiconductor technology includes but not limited to a-Si: H, oxide and LTPS.
According to the invention, the threshold voltage Vth of the first switching TFT is extracted by the first driving TFT in a diode connection mode, and the driving voltage of the first driving TFT is compensated through a capacitive coupling effect, so that the adverse effects of Vth unevenness and Vth drift on the display effect are counteracted; the invention reduces the number of components of the compensation circuit in the pixel; the working life of the self-luminous display device is prolonged.
Although the preferred embodiments of the present invention have been described in detail, the present invention is not limited to the details of the foregoing embodiments, and various equivalent changes (such as number, shape, position, etc.) may be made to the technical solution of the present invention within the technical spirit of the present invention, and these equivalent changes are all within the protection scope of the present invention.
Claims (9)
1. An in-pixel compensation circuit connected to a light emitting element; the light emitting element is positioned between the first power supply and the second power supply and is controlled by the first light emitting control signal and the second light emitting control signal; the method is characterized in that: the light-emitting diode comprises a first driving TFT connected with the light-emitting element, a first switching TFT positioned at the intersection of a scanning line and a data line, a storage capacitor positioned between the first driving TFT and the first switching TFT, a second switching TFT, a third switching TFT, a fourth switching TFT and an access point; wherein the access point is located between the first switching TFT and the storage capacitor; the second switching TFT is connected among the first power supply, the second light-emitting control signal and the first driving TFT; the third switch TFT is connected with a scanning control signal provided by the scanning line; the fourth switch TFT is connected with the reference voltage and the first light-emitting control signal; the first driving TFT is charged, the input data voltage and the threshold voltage of the first driving TFT are extracted, the threshold voltage of the first driving TFT is compensated, and the light-emitting element enters a light-emitting stage in sequence in a first time period, a second time period, a third time period and a fourth time period which are continuous.
2. The in-pixel compensation circuit of claim 1, wherein the storage capacitor is a capacitor having both a coupling capacitor and a storage capacitor.
3. The in-pixel compensation circuit according to claim 2, wherein an on terminal of the first driving TFT is connected to a first terminal of the storage capacitor, a first on terminal of the first driving TFT is connected to a first on terminal of the second switching TFT, and a second on terminal of the first switching TFT is connected to an anode of the light emitting element; the path end of the first switch TFT is connected with the scanning line, the first path end of the first switch TFT is connected with the data line, and the second path end of the first switch TFT is connected with the second end of the storage capacitor; the path end of the second switch TFT is connected with a second light-emitting control signal, and the second path end of the second switch TFT is connected with a first power supply; the channel end of the third switching TFT is connected with a scanning control signal provided by a scanning line, the first channel end of the third switching TFT is connected with the first channel end of the second switching TFT, and the second channel end of the third switching TFT is connected with the first channel end of the first driving TFT; and a path end of the fourth switch TFT is connected with the first light-emitting control signal, a first path end of the fourth switch TFT is connected with the reference voltage, and a second path end of the fourth switch TFT is connected with the second end of the storage capacitor.
4. The in-pixel compensation circuit of claim 3, wherein the second path terminal of the first switching TFT, the second terminal of the storage capacitor, and the second path terminal of the fourth switching TFT also meet at the access point; the access point is precharged in the first time period, and the input voltage of the access point is maintained as the reference voltage in the third time period.
5. The in-pixel compensation circuit according to claim 3, wherein the scan signal of the scan line is input to a high level, the first light emission control signal is input to a low level, the first switching TFT is turned on, the fifth switching transistor is turned off, and the data voltage is input to the access point during the first period; the third switch TFT and the second switch TFT are also in an open state, the first power supply is input to the channel end of the first drive TFT, and the access point is precharged.
6. The in-pixel compensation circuit according to claim 5, wherein the second light emission control signal is input to a low level during the second period, and the second switching TFT is turned off; the first driving TFT is in an open state, the path end of the first driving TFT is connected with the first path end, and the first driving TFT forms a diode connection mode; the electric charges at the passage end of the first driving TFT are discharged to the light-emitting element through the first driving TFT until the first driving TFT is closed when the voltage between the grid electrode and the source electrode of the first driving TFT is reduced to the threshold voltage, and the discharging is stopped.
7. The in-pixel compensation circuit according to claim 6, wherein the scan signal of the scan line and the scan control signal are inputted with a low level, the first light emission control signal is inputted with a high level, the third switching TFT is turned off, the charge of the pass terminal of the first driving TFT is locked, and the voltage difference across the storage capacitor is also locked at the same time; the voltage of the access point is changed from the data voltage to the joining voltage, and the voltage change of the access point is coupled to the pass terminal of the first driving TFT.
8. The in-pixel compensation circuit of claim 7, wherein during the fourth period when the second emission control signal is inputted with a high level, the second switching TFT is turned on, a conductive path is formed between the first power source and the second power source, and a current flows through the light emitting element to emit light.
9. A self-luminous display device comprising an N-stage gate drive circuit, a light emission control circuit outputting N stages, and an in-pixel compensation circuit connected to both the gate drive circuit and the light emission control circuit, the in-pixel compensation circuit being the in-pixel compensation circuit according to any one of claims 1 to 8; the scanning signal of the scanning line is connected to the output end of the nth level gate drive circuit, the first light-emitting control signal is connected to the nth level output end of the light-emitting control circuit, the second light-emitting control signal is connected to the (N + 1) th level output end of the light-emitting control circuit, and N is less than or equal to N.
Priority Applications (2)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201911163302.XA CN110890055A (en) | 2019-11-25 | 2019-11-25 | Self-luminous display device and in-pixel compensation circuit |
| PCT/CN2020/086364 WO2021103406A1 (en) | 2019-11-25 | 2020-04-23 | Self-luminous display device, and in-pixel compensation circuit |
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| Application Number | Priority Date | Filing Date | Title |
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| CN201911163302.XA CN110890055A (en) | 2019-11-25 | 2019-11-25 | Self-luminous display device and in-pixel compensation circuit |
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| CN110890055A true CN110890055A (en) | 2020-03-17 |
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| CN201911163302.XA Pending CN110890055A (en) | 2019-11-25 | 2019-11-25 | Self-luminous display device and in-pixel compensation circuit |
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| WO (1) | WO2021103406A1 (en) |
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| CN115440161A (en) * | 2022-11-09 | 2022-12-06 | 惠科股份有限公司 | Pixel driving circuit and display panel |
| CN117316112A (en) * | 2023-08-31 | 2023-12-29 | 长沙惠科光电有限公司 | Display panel and display terminal |
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