CN104485072B - Image element circuit and its driving method and active matrix/organic light emitting display - Google Patents
Image element circuit and its driving method and active matrix/organic light emitting display Download PDFInfo
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Abstract
In the image element circuit that the present invention provides and its driving method and active matrix/organic light emitting display, the data voltage that the electric current being exported as the 4th thin film transistor (TFT) of driving element in described image element circuit is provided by data wire and the initialization voltage of the 3rd power supply offer determine, and it is unrelated with the threshold voltage of outside supply voltage and described 4th thin film transistor (TFT), therefore, it is possible to avoid the brightness disproportionation caused by threshold voltage deviation and IR change in pressure drop, even if display picture is converted to, from low GTG, the compensation that high gray is also capable of IR pressure drop, thus, active square OLED using described image element circuit and its driving method can show the image with uniform luminance.
Description
Technical Field
The invention relates to the technical field of flat panel display, in particular to a pixel circuit, a driving method thereof and an active matrix organic light emitting display.
Background
The Organic light emitting display displays images by using Organic Light Emitting Diodes (OLEDs), is an active light emitting display, has a display mode different from that of a conventional Thin Film Transistor liquid crystal display (TFT-LCD), does not need a backlight, and has many advantages of high contrast, fast response speed, light weight, and the like. Therefore, the organic light emitting display is known as a new generation display that can replace the thin film transistor liquid crystal display.
Depending on the driving method, the Organic light Emitting Display is classified into a Passive Matrix Organic Light Emitting Display (PMOLED) and an Active Matrix Organic Light Emitting Display (AMOLED), which are also called Active Matrix Organic light Emitting displays.
The active matrix organic light emitting display comprises a scanning line, a data line and a pixel array defined by the scanning line and the data line, wherein each pixel of the pixel array comprises an organic light emitting diode and a pixel circuit for driving the organic light emitting diode. Please refer to fig. 1, which is a schematic structural diagram of a pixel circuit of an active matrix organic light emitting display in the prior art. As shown in fig. 1, the conventional pixel circuit 10 generally includes a switching thin film transistor T1, a driving thin film transistor T2, and a storage capacitor Cs, wherein a gate of the switching thin film transistor T1 is connected to a scan line Sn, a source of the switching thin film transistor T1 is connected to a data line Dm, a gate of the driving thin film transistor T2 is connected to a drain of the switching thin film transistor T1, a source of the driving thin film transistor T2 is connected to a first power ELVDD through a first power trace (not shown), a drain of the driving thin film transistor T2 is connected to an anode of the organic light emitting diode OLED, and a cathode of the organic light emitting diode OLED is connected to a second power ELVSS through a second power trace (not shown). When the switching transistor T1 is turned on by the scan line s (n), the data voltage Vdata provided by the data line is stored in the storage capacitor Cs via the switching transistor T1, thereby controlling the driving transistor T2 to generate current to drive the organic light emitting diode OLED to emit light.
The light emitting luminance of the organic light emitting diode OLED is determined by the current flowing through the organic light emitting diode OLED, and the current flowing through the organic light emitting diode OLED is affected by the threshold voltage of the driving transistor T2 and the power voltage VDD actually applied to the pixel circuit 10. When the threshold voltage of the driving transistor T2 and the power supply voltage VDD are changed, the current flowing through the organic light emitting diode OLED is greatly changed, so that the organic light emitting diode OLED still emits light of different brightness for the data signal of the same brightness.
At present, due to the limitation of the manufacturing process, the threshold voltages of the thin film transistors of the pixels in the active matrix organic light emitting display are different, which causes uneven brightness and affects the display effect. Moreover, a power trace connecting the first power ELVDD and the pixel circuits 10 has a certain impedance, and when a current flows through the power trace, the power trace may affect the positive power VDD actually reaching the pixel circuits 10, which may cause inconsistency of the positive power VDD received by each pixel circuit 10, thereby aggravating the uneven brightness.
Therefore, how to solve the problem of uneven brightness of the existing active matrix organic light emitting display becomes a technical problem to be solved urgently by the technical personnel in the field.
Disclosure of Invention
The invention aims to provide a pixel circuit, a driving method thereof and an active matrix organic light emitting display, and aims to solve the problem of uneven brightness of the conventional active matrix organic light emitting display.
To solve the above problem, the present invention provides a pixel circuit, including:
a first thin film transistor connected between the data line and a first node, and having a gate connected to the first scan line;
a second thin film transistor connected between a third power source and a second node, a gate of which is connected to the first scan line;
a third thin film transistor connected between the first node and a third node, and having a gate connected to an emission control line;
a fourth thin film transistor connected between the first power source and a fourth node, a gate of which is connected to the third node;
a fifth thin film transistor connected between the third node and the fourth node, and having a gate connected to a second scan line;
a sixth thin film transistor connected between the fourth node and the second node, a gate of which is connected to the second scan line;
a seventh thin film transistor connected between the fourth node and an anode of the organic light emitting diode, a gate of which is connected to the emission control line;
a first capacitor connected between the first node and the second node; and
and an organic light emitting diode having an anode connected to the drain of the seventh thin film transistor and a cathode connected to a second power supply.
Optionally, the first power supply and the second power supply are used as driving power supplies of the organic light emitting diode, and the third power supply is used for providing a reference voltage, where the reference voltage is smaller than the data voltage provided by the data line.
Optionally, the first thin film transistor to the seventh thin film transistor are all P-type thin film transistors.
Optionally, the fourth thin film transistor is used as a driving transistor, and the current provided by the fourth thin film transistor to the organic light emitting diode is determined by the data voltage provided by the data line and the reference voltage provided by the third power supply, regardless of the power supply voltages provided by the first and second power supplies and the threshold voltage of the fourth thin film transistor.
Optionally, the power supply further comprises a second capacitor, and the second capacitor is connected between the second node and a second power supply.
Correspondingly, the invention also provides a driving method of the pixel circuit, the scanning period comprises a first time period, a second time period and a third time period, wherein,
in a first time period, a scanning signal provided by a first scanning line is changed from high level to low level, a scanning signal provided by a second scanning line and a control signal provided by an emission control line are both high level, a first thin film transistor and a second thin film transistor are turned on, a data voltage provided by a data line is provided to a first node through the first thin film transistor, and meanwhile, a reference voltage provided by a third power supply is provided to a second node through the second thin film transistor;
in a second time period, the scanning signal provided by the first scanning line is at a high level, the scanning signal provided by the second scanning line is changed from the high level to a low level, the control signal provided by the emission control line keeps at the high level, the fifth thin film transistor and the sixth thin film transistor are turned on, and the threshold voltage of the fourth thin film transistor is sampled;
in a third time period, the scanning signals provided by the first scanning line and the second scanning line are both high level, the control signal provided by the emission control line is changed from high level to low level, the third thin film transistor and the seventh thin film transistor are turned on, and the fourth thin film transistor outputs current and drives the organic light emitting diode to emit light.
Optionally, the scanning cycle further includes a fourth time period, and the fourth time period is set between the third time period and the first time period;
in a fourth time period, the scanning signals provided by the first scanning line and the second scanning line are both high level, the control signal provided by the emission control line is changed from low level to high level, the third thin film transistor and the seventh thin film transistor are both turned on and turned off, and the organic light emitting diode stops emitting light.
Optionally, the scanning cycle further includes a fifth time period, where the fifth time period is set between the first time period and the second time period;
in a fifth period, the scanning signal provided by the first scanning line changes from low level to high level, the scanning signal provided by the second scanning line and the control signal provided by the emission control line keep high level, the first thin film transistor and the second thin film transistor are both turned on and off, and the data voltage and the reference voltage stop being written.
Optionally, the scanning cycle further includes a sixth time period; the sixth time period is set between the second time period and the third time period;
in a sixth time period, the scanning signal provided by the first scanning line and the control signal provided by the emission control line are both kept at a high level, the scanning signal provided by the second scanning line is changed from a low level to a high level, the fifth thin film transistor and the sixth thin film transistor are both turned on and turned off, and the sampling of the threshold voltage of the fourth thin film transistor is stopped.
Correspondingly, the invention also provides an active matrix organic light-emitting display which comprises the pixel circuit.
In the pixel circuit, the driving method thereof, and the active matrix organic light emitting display according to the present invention, since the current output from the fourth thin film transistor as the driving element in the pixel circuit is determined by the data voltage supplied from the data line and the initialization voltage supplied from the third power source, regardless of the external power source voltage and the threshold voltage of the fourth thin film transistor, it is possible to prevent brightness unevenness caused by threshold voltage deviation and IR drop variation, and to compensate for the IR drop even when the display screen is switched from a low gray level to a high gray level, and thus, the active matrix organic light emitting display using the pixel circuit and the driving method thereof can display an image having uniform brightness.
Drawings
FIG. 1 is a schematic diagram of a prior art pixel circuit of an active matrix organic light emitting display;
fig. 2 is a schematic structural diagram of a pixel circuit according to a first embodiment of the invention;
fig. 3 is a timing diagram of a driving method of a pixel circuit according to an embodiment of the present invention;
fig. 4 is a schematic structural diagram of a pixel circuit according to a second embodiment of the invention.
Detailed Description
A pixel circuit, a driving method thereof, and an active matrix organic light emitting display according to the present invention will be described in detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
[ EXAMPLES one ]
Fig. 2 is a schematic structural diagram of a pixel circuit according to a first embodiment of the invention. As shown in fig. 2, the pixel circuit 20 includes: a first thin film transistor T1 connected between the Data line Data and the first node N1, and having a gate connected to the first scan line Sn-1; a second thin film transistor T2 connected between the third power supply and a second node N2, and having a gate connected to the first scan line Sn-1; a third thin film transistor T3 connected between the first node N1 and the third node N3, and having a gate connected to the emission control line Em; a fourth thin film transistor T4 connected between the first power source and the fourth node N4, and having a gate connected to the third node N3; a fifth thin film transistor T5 connected between the third node N3 and the fourth node N4, and having a gate connected to the second scan line Sn; a sixth thin film transistor T6 connected between the fourth node N4 and the second node N2, and having a gate connected to the second scan line Sn; a seventh thin film transistor T7 connected between the fourth node N4 and the anode of the organic light emitting diode OLED, and having a gate connected to the emission control line Em; a first capacitor C1 connected between the first node N1 and the second node N2; the organic light emitting diode OLED has an anode connected to the drain of the seventh thin film transistor T7 and a cathode connected to the second power source.
Specifically, the pixel circuit 20 receives a first power supply, a second power supply, and a third power supply supplied from the outside (for example, from a power supply). The first power supply and the second power supply are used as driving power supplies of the organic light emitting diode OLED, the first power supply is used for providing a first power supply voltage Vdd, the second power supply is used for providing a second power supply voltage Vss, and the third power supply is used for providing a reference voltage Vinit. The first power supply is typically a high level voltage source and the second and third power supplies are typically low level voltage sources. The reference voltage Vinit is typically a dc voltage having a fixed value. In this embodiment, the reference voltage Vinit is smaller than the Data voltage Vdata provided by the Data line Data.
As shown in fig. 2, the pixel circuit 20 is a 7T1C type circuit structure, and includes 7 thin film transistors and 1 capacitor, where the 7 thin film transistors are P-type thin film transistors, the pixel circuit 20 controls the first thin film transistor T1 and the second thin film transistor T2 through the first scan line Sn-1, controls the fifth thin film transistor T5 and the sixth thin film transistor T6 through the second scan line Sn, and controls the third thin film transistor T3 and the seventh thin film transistor T7 through the emission control line Em.
When the scan signal supplied from the first scan line Sn-1 transitions to a low level, the first thin film transistor T1 and the second thin film transistor T2 are both turned on, the Data voltage Vdata supplied from the Data line Data is supplied to the first node N1 through the first thin film transistor T1, and the reference voltage Vinit supplied from the third power source is applied to the second node N2 through the second thin film transistor T2.
When the scan signal supplied from the second scan line Sn transitions to a low level, both the fifth thin film transistor T5 and the sixth thin film transistor T6 are turned on, and the gate and the drain of the fourth thin film transistor T4 are shorted.
When the control signal provided by the emission control line Em transitions to a low level, the third thin film transistor T3 and the seventh thin film transistor T7 are both turned on, so that the fourth thin film transistor T4 is turned on and provides a driving current to the organic light emitting diode OLED, and the organic light emitting diode OLED emits light with a corresponding brightness according to the driving current to normally display an image.
In this embodiment, the fourth thin film transistor T4 functions as a driving transistor, and the current supplied to the organic light emitting diode OLED is determined by the Data voltage Vdata supplied from the Data line Data and the reference voltage Vinit supplied from the third power source, regardless of the first power voltage Vdd and Vss supplied from the first power source and the second power voltage Vss supplied from the second power source and the threshold voltage of the fourth thin film transistor T4. Therefore, the pixel circuit 20 can avoid the uneven brightness caused by the threshold voltage deviation of the thin film transistor and the power supply voltage variation, thereby improving the display quality of the display.
Correspondingly, the invention also provides a driving method of the pixel circuit. Referring to fig. 2 and fig. 3 in combination, the driving method of the pixel circuit includes:
the scan cycle includes a first period t1, a second period t2, and a third period t 3; wherein,
in the first period T1, the scan signal supplied from the first scan line Sn-1 changes from high level to low level, the scan signal supplied from the second scan line Sn and the control signal supplied from the emission control line Em are both high level, the first thin film transistor T1 and the second thin film transistor T2 are turned on, the Data voltage Vdata supplied from the Data line Data is supplied to the first node N1 via the first thin film transistor T1, and simultaneously, the reference voltage Vinit supplied from the third power supply is supplied to the second node N2 via the second thin film transistor T2;
in the second period T2, the scan signal supplied from the first scan line Sn-1 is at a high level, the scan signal supplied from the second scan line Sn is changed from the high level to a low level, the control signal supplied from the emission control line Em maintains the high level, the fifth thin film transistor T5 and the sixth thin film transistor T6 are turned on, and the threshold voltage of the fourth thin film transistor T4 is sampled;
in the third period T3, the scan signals provided by the first scan line Sn-1 and the second scan line Sn are both at a high level, the control signal provided by the emission control line Em changes from the high level to a low level, the third thin film transistor T3 and the seventh thin film transistor T7 are turned on, and the fourth thin film transistor T4 outputs current and drives the organic light emitting diode to emit light.
Specifically, in the first period T1, since the first thin film transistor T1 is turned on, the Data voltage Vdata provided by the Data line Data is written into the first node N1 through the first thin film transistor T1, and the voltage of the first node N1 (i.e., the first substrate of the first capacitor C1) is equal to Vdata. Meanwhile, since the fourth tft T4 is turned on, the third power source is connected to the second node N2 through the second tft T2, and the voltage of the second node N2 (i.e., the second substrate of the first capacitor C1) is equal to Vinit.
In the second period T2, since the first thin film transistor T1 has been turned off, the Data voltage Vdata supplied from the Data line Data stops being written into the first node N1, and the fifth and sixth thin film transistors T5 and T6 are both turned on, the gate and drain of the fourth thin film transistor T4 are shorted, and at this time, the voltage of the second node N2 becomes Vdd-Vth. Where Vth is the threshold voltage of the fourth thin film transistor T4. Due to the coupling effect of the first capacitor C1, the voltage at the first node N1 jumps from Vinit to Vdata + Vdd-Vth-Vinit. Thereby, the threshold voltage Vth of the fourth thin film transistor T4 is stored in the first capacitor C1, thereby enabling sampling of the threshold voltage of the fourth thin film transistor T4.
In the third time period T3, since the third thin film transistor T3 is turned on, the gate voltage of the fourth thin film transistor T4 is equal to the voltage of the first node N1 (i.e., Vg4 ═ Vdata + Vdd-Vth-Vinit), and the fourth thin film transistor T4 is turned on at this time. Meanwhile, since the seventh thin film transistor T7 is turned on, the driving current outputted from the fourth thin film transistor T4 flows to the second power source along the path of the first power source through the fourth thin film transistor T4, the seventh thin film transistor T7 and the organic light emitting diode OLED, so that the organic light emitting diode OLED lights up to emit light.
In the third time period T3, since the source voltage of the fourth thin film transistor T4 is equal to the first power voltage Vdd supplied by the first power source, the gate-source voltage Vgs4 of the fourth thin film transistor T4 (i.e., the voltage difference between the gate and the source of the fourth thin film transistor T4) is calculated as:
vgs4 ═ Vdd- (Vdata + Vdd-Vth-Vinit) formula 1;
and the calculation formula of the current Ion flowing through the organic light emitting diode OLED is:
Ion＝K×(Vgs4-Vth)2formula 2;
wherein K is the product of the electron mobility, the width-to-length ratio and the unit area capacitance of the thin film transistor.
From equation 1 and equation 2, we can obtain:
Ion＝K×(Vinit-Vdata)2formula 3;
as can be seen from the expression of formula 3, the current flowing through the organic light emitting diode OLED has no relation with the first power voltage Vdd, the second power voltage Vss, and the threshold voltage of the fourth thin film transistor T4, and is related only with the data voltage Vdata, the reference voltage Vinit, and the constant K. Even if the power supply voltage varies due to the power supply line impedance or the threshold voltage of the fourth thin film transistor T4 varies, the current Ion flowing through the organic light emitting diode OLED is not affected. Therefore, the pixel circuit 20 and the driving method thereof can compensate for the threshold voltage and the IR drop, and avoid the uneven brightness caused by the deviation of the threshold voltage and the power trace impedance.
The pixel circuit 20 mainly performs the compensation function of the threshold voltage Vth and the IR drop through the operations in the above three periods.
With continued reference to fig. 3, the scan cycle further includes a fourth time period t4, a fifth time period t5, and a sixth time period t 6. The fourth time period t4 is set between the third time period t3 and the first time period t1, the fifth time period t5 is set between the first time period t1 and the second time period t2, and the sixth time period t6 is set between the second time period t2 and the third time period t 3.
In the fourth period T4, the scan signals provided by the first scan line Sn-1 and the second scan line Sn are all at a high level, the control signal provided by the emission control line Em changes from a low level to a high level, both the third thin film transistor T3 and the seventh thin film transistor T7 controlled by the emission control line Em change from on to off, and the organic light emitting diode OLED stops emitting light.
In the fifth period T5, the scan signal supplied from the first scan line Sn-1 is changed from a low level to a high level, the scan signal supplied from the second scan line Sn and the control signal supplied from the emission control line Em are maintained at a high level, both the first thin film transistor T1 and the second thin film transistor T2 controlled by the first scan line Sn-1 are turned on to be turned off, the data voltage Vdata stops writing since the first thin film transistor T1 is turned off, and the reference voltage Vinit stops inputting since the second thin film transistor T2 is turned off.
In the sixth period T6, the scan signal supplied from the first scan line Sn-1 and the control signal supplied from the emission control line Em are both maintained at the high level, the scan signal supplied from the second scan line Sn is changed from the low level to the high level, both the fifth thin film transistor T5 and the sixth thin film transistor T6 controlled by the second scan line Sn are changed from on to off, and sampling of the threshold voltage of the fourth thin film transistor T4 is stopped.
The working processes of the fourth period t4, the first period t1, the fifth period t5, the second period t2, the sixth period t6 and the third period t3 are repeated, and the image display function is completed. Moreover, in the image display process, the compensation function of the IR drop is not affected by switching the gray-scale pictures.
If the current frame is a low gray level frame (e.g., the darkest frame, the gray level is 0), since the current passing through the power trace is small, the IR drop is small, the corresponding power voltage on the pixel is high, assuming Vdd1, the next frame is converted into a high gray level frame (e.g., the brightest frame, the gray level is 255), since the current passing through the power trace is large, the IR drop is large, the corresponding power voltage on the pixel is low, assuming Vdd2, Vdd1> Vdd 2; in the next frame threshold compensation phase (i.e., the second time period T2), the voltage difference Vgs between the gate and the source of the fourth thin film transistor T4 is equal to Vdd2- (Vdata + Vdd1-Vth-Vinit), and since Vdd1> Vdd2 and Vdata > Vinit, Vgs is less than Vth, and at this time, the fourth thin film transistor T4 is in a conducting state, so Vdd2 can write into the third node N3, thereby realizing the compensation of the IR drop.
It can be seen that the pixel circuit 20 can compensate for the IR drop even when the low gray scale picture is changed to the high gray scale picture.
[ example two ]
Fig. 4 is a circuit diagram of a pixel circuit according to a second embodiment of the invention. As shown in fig. 4, the pixel circuit 30 includes: a first thin film transistor T1 connected between the Data line Data and the first node N1, and having a gate connected to the first scan line Sn-1; a second thin film transistor T2 connected between the third power supply and a second node N2, and having a gate connected to the first scan line Sn-1; a third thin film transistor T3 connected between the first node N1 and the third node N3, and having a gate connected to the emission control line Em; a fourth thin film transistor T4 connected between the first power source and the fourth node N4, and having a gate connected to the third node N3; a fifth thin film transistor T5 connected between the third node N3 and the fourth node N4, and having a gate connected to the second scan line Sn; a sixth thin film transistor T6 connected between the fourth node N4 and the second node N2, and having a gate connected to the second scan line Sn; a seventh thin film transistor T7 connected between the fourth node N4 and the anode of the organic light emitting diode OLED, and having a gate connected to the emission control line Em; a first capacitor C1 connected between the first node N1 and the second node N2; the organic light emitting diode OLED has an anode connected to the drain of the seventh thin film transistor T7 and a cathode connected to the second power source.
Specifically, the pixel circuit 30 includes all the features of the pixel circuit 20 in the first embodiment, and the present embodiment is different from the first embodiment in that a second capacitor C2 is disposed between the second node N2 and the second power supply, and the voltage across the first capacitor C1 can be prevented from drifting in the light-emitting phase (i.e., the third time period t3) by the second capacitor C2, so as to further improve the display quality.
The timing requirements of the scan signals provided by the first scan line Sn-1 and the second scan line Sn and the control signals provided by the emission control line Em in this embodiment are the same as the timing requirements of the scan signals provided by the first scan line Sn-1 and the second scan line Sn and the control signals provided by the emission control line Em in the first embodiment, and details are not repeated here, for details, please refer to the first time period t1 to the sixth time period t6 of the driving method of the pixel circuit in the first embodiment.
It should be noted that, in the present specification, the embodiments are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments may be referred to each other. For the pixel circuit disclosed in the embodiment, since the driving method corresponds to the driving method of the pixel circuit disclosed in the embodiment, the description is relatively simple, and the relevant points can be referred to the description of the method part.
Correspondingly, the invention also provides an active matrix organic light-emitting display which comprises the pixel circuit. Please refer to the above, which is not described herein.
In summary, in the pixel circuit, the driving method thereof, and the active matrix organic light emitting display according to the present invention, the current output from the fourth thin film transistor as the driving element in the pixel circuit is determined by the data voltage supplied from the data line and the initialization voltage supplied from the third power supply, regardless of the external power supply voltage and the threshold voltage of the fourth thin film transistor, so that it is possible to avoid the brightness unevenness caused by the threshold voltage deviation and the IR drop variation, and to compensate the IR drop even when the display screen is switched from the low gray scale to the high gray scale, and thus the active matrix organic light emitting display using the pixel circuit and the driving method thereof can display an image with uniform brightness.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (10)
1. A pixel circuit, comprising:
a first thin film transistor connected between the data line and a first node, and having a gate connected to the first scan line;
a second thin film transistor connected between a third power source and a second node, a gate of which is connected to the first scan line;
a third thin film transistor connected between the first node and a third node, and having a gate connected to an emission control line;
a fourth thin film transistor connected between the first power source and a fourth node, a gate of which is connected to the third node;
a fifth thin film transistor connected between the third node and the fourth node, and having a gate connected to a second scan line;
a sixth thin film transistor connected between the fourth node and the second node, a gate of which is connected to the second scan line;
a seventh thin film transistor connected between the fourth node and an anode of the organic light emitting diode, a gate of which is connected to the emission control line;
a first capacitor connected between the first node and the second node; and
and an organic light emitting diode having an anode connected to the drain of the seventh thin film transistor and a cathode connected to a second power supply.
2. The pixel circuit according to claim 1, wherein the first power supply and the second power supply serve as a driving power supply of the organic light emitting diode, and the third power supply is configured to supply a reference voltage that is smaller than a data voltage supplied from the data line.
3. The pixel circuit according to claim 1, wherein the first to seventh thin film transistors are all P-type thin film transistors.
4. The pixel circuit according to claim 1, wherein the fourth thin film transistor functions as a driving transistor, and a current supplied to the organic light emitting diode by the fourth thin film transistor is determined by a data voltage supplied from the data line and a reference voltage supplied from the third power source, regardless of a power source voltage supplied from the first and second power sources and a threshold voltage of the fourth thin film transistor.
5. The pixel circuit according to claim 1, further comprising a second capacitor connected between the second node and a second power supply.
6. A driving method of a pixel circuit according to any one of claims 1 to 5, wherein the scanning period includes a first period, a second period, and a third period, wherein,
in a first time period, a scanning signal provided by a first scanning line is changed from high level to low level, a scanning signal provided by a second scanning line and a control signal provided by an emission control line are both high level, a first thin film transistor and a second thin film transistor are turned on, a data voltage provided by a data line is provided to a first node through the first thin film transistor, and meanwhile, a reference voltage provided by a third power supply is provided to a second node through the second thin film transistor;
in a second time period, the scanning signal provided by the first scanning line is at a high level, the scanning signal provided by the second scanning line is changed from the high level to a low level, the control signal provided by the emission control line keeps at the high level, the fifth thin film transistor and the sixth thin film transistor are turned on, and the threshold voltage of the fourth thin film transistor is sampled;
in a third time period, the scanning signals provided by the first scanning line and the second scanning line are both high level, the control signal provided by the emission control line is changed from high level to low level, the third thin film transistor and the seventh thin film transistor are turned on, and the fourth thin film transistor outputs current and drives the organic light emitting diode to emit light.
7. The method for driving the pixel circuit according to claim 6, wherein the scan cycle further includes a fourth period of time, the fourth period of time being set between the third period of time and the first period of time;
in a fourth time period, the scanning signals provided by the first scanning line and the second scanning line are both high level, the control signal provided by the emission control line is changed from low level to high level, the third thin film transistor and the seventh thin film transistor are both turned on and turned off, and the organic light emitting diode stops emitting light.
8. The method for driving the pixel circuit according to claim 6, wherein the scan cycle further includes a fifth period of time, the fifth period of time being provided between the first period of time and the second period of time;
in a fifth period, the scanning signal provided by the first scanning line changes from low level to high level, the scanning signal provided by the second scanning line and the control signal provided by the emission control line keep high level, the first thin film transistor and the second thin film transistor are both turned on and off, and the data voltage and the reference voltage stop being written.
9. The method for driving the pixel circuit according to claim 6, wherein the scan cycle further includes a sixth period; the sixth time period is set between the second time period and the third time period;
in a sixth time period, the scanning signal provided by the first scanning line and the control signal provided by the emission control line are both kept at a high level, the scanning signal provided by the second scanning line is changed from a low level to a high level, the fifth thin film transistor and the sixth thin film transistor are both turned on and turned off, and the sampling of the threshold voltage of the fourth thin film transistor is stopped.
10. An active matrix organic light emitting display, comprising: a pixel circuit as claimed in any one of claims 1 to 5.
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| CN111164669A (en) * | 2019-12-19 | 2020-05-15 | 重庆康佳光电技术研究院有限公司 | Electroluminescent display, pixel compensation circuit and voltage compensation method thereof |
| CN111179850A (en) * | 2020-01-13 | 2020-05-19 | 深圳市华星光电半导体显示技术有限公司 | Pixel compensation circuit, array substrate and display panel |
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| CN103035197B (en) * | 2011-10-07 | 2015-07-29 | 元太科技工业股份有限公司 | Active organic light emitting diode pixel circuit and operation method thereof |
| US9576535B2 (en) * | 2013-01-17 | 2017-02-21 | Samsung Display Co., Ltd. | Pixel and organic light emitting display using the same |
| CN103117041A (en) * | 2013-01-31 | 2013-05-22 | 华南理工大学 | Pixel circuit of active organic electroluminescent display and programming method of pixel circuit |
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