Patent Application
20240161689
The present disclosure relates to a display technology field, and more particularly to a pixel circuit, a driving method thereof, and a display panel.
Currently, a pixel driving circuit of an AMOLED display panel may use a 2T1C or 3T1C driving architecture. The 2T1C driving architecture includes one driving transistor, one switching transistor, and one storage capacitor. In the 2T1C driving architecture, since an initial state of a source of the driving transistor is a floating state, an initial potential of the source of the driving transistor is unstable, and a threshold voltage of the driving transistor cannot be detected in real time. This may cause a gate-source potential difference Vgs of the driving transistor to be unstable, so that light emitting brightness of the organic light emitting diode is unstable, and flicker occurs on the AMOLED display panel. The 3T1C driving architecture refers to a driving architecture obtained by adding one sensing transistor to the 2T1C driving architecture. The sensing transistor is connected to a source of the driving transistor, so that the initial potential of the source of the driving transistor can be stabilized. The threshold voltage and a mobility can be detected, through which the threshold voltage and the mobility can be compensated. However, compared with the 2T1C driving architecture, the 3T1C driving architecture needs to add a scanning line to control the sensing transistor. Therefore, a series of negative effects such as a decreased aperture ratio of the display panel, an increased frame of the display panel, and a need of adding a control timing related to the scanning line may occur.
In view of this, a new pixel driving circuit needs to be provided, so as to solve problems in the prior art that may occur when the switching transistor and the sensing transistor are respectively controlled with two scanning lines in the 3T1C pixel driving circuit, such as a decreased aperture ratio of the display panel, an increased frame of the display panel, and a need of adding a control timing related to the scanning line.
To resolve the foregoing problem, embodiments of the present disclosure provide a pixel driving circuit, a driving method thereof, and a display panel, so that the gate-source potential difference of the driving transistor can be kept stable in a detection stage, and a source-drain current flowing through the driving transistor can also be kept stable. Therefore, the mobility of the driving transistor is accurately detected, thereby accurately compensating for the mobility.
In a first aspect, an embodiment of the present disclosure provides a pixel driving circuit, including a scanning line, a data line, a sensing line, a reset line, a driving transistor, a switching transistor, a sensing transistor, a storage capacitor, and a reset switch, wherein a gate of the driving transistor is respectively connected to a drain of the switching transistor and a first terminal of the storage capacitor, a drain of the driving transistor is connected to an input terminal of a power supply, a source of the driving transistor is respectively connected to a drain of the sensing transistor and a second terminal of the storage capacitor, both a gate of the switching transistor and a gate of the sensing transistor are connected to the scanning line, a source of the switching transistor is connected to the data line, a source of the sensing transistor is connected to the sensing line, a first terminal of the reset switch is connected to the source of the sensing transistor, and a second terminal of the reset switch is connected to the reset line;
In some embodiments, the pixel driving circuit further includes a sampling switch and a processing unit, wherein a first terminal of the sampling switch is connected to the sensing line, and a second terminal of the sampling switch is connected to the processing unit.
In some embodiments, in the detection stage, the driving transistor is turned on and the sampling switch is turned off.
In some embodiments, in the sampling stage following the detection stage, the sampling switch is closed, the reset switch is opened, the switching transistor remains to be turned off, and both the driving transistor and the sensing transistor remains to be turned on.
In some embodiments, in the pre-charging stage, a low level is provided at the input terminal of the power supply; in the detection stage and the sampling stage, a high level is provided at the input terminal of the power supply.
In some embodiments, in the case that the switching transistor is an N-type thin film transistor, the second scanning voltage is less than the first scanning voltage.
In some embodiments, in the case that the switching transistor is a P-type thin film transistor, the second scanning voltage is greater than the first scanning voltage.
In a second aspect, an embodiment of the present disclosure further provides a driving method of a pixel driving circuit applied to the pixel driving circuit as described above, wherein the driving method includes:
In some embodiments, the driving method further include: in the sampling stage following the detection stage, closing the sampling switch, maintaining the reset switch to be opened, maintaining the switching transistor to be turned off, maintaining both the driving transistor and the sensing transistor to be turned on, obtaining a threshold voltage of the driving transistor by a sensing line, and obtaining a mobility of the driving transistor according to a current flowing through the driving transistor.
In some embodiments, the driving method further includes: in the pre-charging stage, superimposing the threshold voltage of the driving transistor obtained in the sampling stage onto a data voltage provided to the data line, and then inputting the superimposed voltage into the gate of the driving transistor.
In some embodiments, in the case that the switching transistor is an N-type thin film transistor, the first scanning voltage provided to the scanning line is decreased to the second scanning voltage at the detection stage.
In some embodiments, in the case that the switching transistor is a P-type thin film transistor, the first scanning voltage provided to the scanning line is increased to the second scanning voltage at the detection stage.
In a third aspect, an embodiment of the present disclosure further provides a display panel, wherein the display panel includes an organic light emitting diode and the pixel driving circuit as described above, wherein an anode of the organic light emitting diode is connected to a source of a driving transistor, and a cathode of the organic light emitting diode is connected to a negative terminal of a power supply; and
In some embodiments, the pixel driving circuit further includes a sampling switch and a processing unit, wherein a first terminal of the sampling switch is connected to the sensing line, and a second terminal of the sampling switch is connected to the processing unit.
In some embodiments, in the detection stage, the driving transistor is turned on and the sampling switch is turned off.
In some embodiments, in the sampling stage following the detection stage, the sampling switch is closed, the reset switch is opened, the switching transistor remains to be turned off, and both the driving transistor and the sensing transistor remains to be turned on.
In some embodiments, in the pre-charging stage, a low level is provided at the input terminal of the power supply; in the detection stage and the sampling stage, a high level is provided at the input terminal of the power supply.
In some embodiments, in the case that the switching transistor is an N-type thin film transistor, the second scanning voltage is less than the first scanning voltage.
In some embodiments, in the case that the switching transistor is a P-type thin film transistor, the second scanning voltage is greater than the first scanning voltage.
According to the pixel driving circuit, the driving method thereof, and the display panel provided in the embodiments of the present disclosure, the switching transistor and the sensing transistor are controlled by the same scanning line. In the pre-charging stage, the reset switch is closed, and the first scanning voltage provided to the scanning line, the data voltage provided to the data line, and the reset voltage provided to the reset line enable both the switching transistor and the sensing transistor to be turned on, so that the driving transistor is turned on. In the detection stage, the reset switch is opened to change the first scanning voltage provided to the scanning signal line to the second scanning voltage, so as to enable the sensing transistor to be turned on and the switching transistor to be turned off, so that both the gate and the source of the driving transistor are in the floating state. As a result, when the source potential of the driving transistor rises at the input terminal of the power supply, the gate potential of the driving transistor rises due to a coupling effect of the storage capacitor, and the gate-source potential difference of the driving transistor remains to be stable, so that the source-drain current flowing through the driving transistor can also remain to be stable. In this way, the mobility of the driving transistor can be accurately detected, and therefore the mobility of the driving transistor can be compensated accurately.
That is, other than controlling the switching transistor and the sensing transistor with the same scanning line in the embodiments of the present disclosure, a scanning voltage provided to the scanning line can be further adjusted in the detection stage, thereby realizing the timing effect that, in the prior art, the switching transistor and the sensing transistor are controlled by the two scanning lines respectively in the prior art and an accurate measure of the mobility of the driving transistor.
To make the objectives, technical solutions, and effects of the present disclosure more clear and definite, the present disclosure is illustrated in detail below by referring to the accompanying drawings and illustrating the embodiments. It should be understood that the specific implementations described here are only used to explain the present disclosure, and are not used to limit the present disclosure.
The pixel driving circuit of the AMOLED display panel may use a 2T1C driving structure. As shown in
Therefore, there is another driving structure, a 3T1C driving structure. As shown in
In view of this, an embodiment of the present disclosure provides a new pixel driving circuit based on the 3T1C driving structure. As shown in
However, it should be noted that, when the switching transistor T2 and the sensing transistor T3 are controlled by the same scanning line Scan, if the control voltage of the scanning line Scan is not changed all the time (that is, as shown in
Therefore, according to the pixel driving circuit provided in the embodiment of the present disclosure, as shown in
Specifically, in the pre-charging stage t1, the gate-source voltage difference Vgs of the switching transistor T2 is Vscan1−Vdata′, and the gate-source voltage difference Vgs of the sensing transistor T3 is Vscan1−Vref, which enable the switching transistor T2 and the sensing transistor T3 to be turned on, so that the potential of the gate of the driving transistor T1 is Vdata′, the potential of the source thereof is Vref, and the gate-source potential difference Vgs of the driving transistor T1 is Vdata′−Vref, which enables the driving transistor T1 to be turned on. In the detection stage t2, when the threshold voltage of the driving transistor T1 is detected, the voltage of the scanning line Scan is adjusted, so that the first scanning voltage Vscan1 provided to the scan signal line Scan is changed to the second scan voltage Vscan2. As a result, the gate-source voltage difference Vgs of the switching transistor T2 is Vscan2−Vdata′, which enables the switching transistor T2 to be turned off, so that the gate g of the driving transistor T1 is in the floating state. Meanwhile, the gate-source potential difference of the sensing transistor T3 is Vscan2−Vref, which enables the sensing transistor T3 to be turned on. In this case, the reset switch S1 is turned off, and the source s of the driving transistor T1 is also in the floating state. That is, in this case, both the gate g and the source of the driving transistor T1 remain in the floating state. Therefore, when the potential of the source s of the driving transistor T1 and the potential of the sensing line Sense are pulled up by the input terminal VDD of the power supply, the potential of the gate g of the driving transistor T1 is also increased under the coupling effect of the storage capacitor Cst, that is, the gate-source potential difference Vgs of the driving transistor T1 can remain unchanged.
According to the pixel driving circuit provided in the embodiment of the present disclosure, the switching transistor T2 and the sensing transistor T3 are controlled by the same scanning line Scan. In the pre-charging stage t1, the reset switch S1 is closed, and the first scanning voltage Vscan 1 provided to the scanning line Scan, the data voltage Vdata′ provided to the data line Data, and the reset voltage Vref provided to the reset line Ref enable both the switching transistor T2 and the sensing transistor T3 to be turned on, so that the driving transistor T1 is turned on. In the detection stage t2, the reset switch S1 is opened to change the first scanning voltage Vscan1 provided to the scanning signal line Scan to the second scanning voltage Vscan2, so as to enable the sensing transistor T3 to be turned on and the switching transistor T2 to be turned off, so that both the gate g and the source s of the driving transistor are in the floating state. As a result, when the potential of the source s of the driving transistor T1 rises at the input terminal VDD of the power supply, the potential of the gate g of the driving transistor T1 rises due to a coupling effect of the storage capacitor Cst, and the gate-source potential difference Vgs of the driving transistor T1 remains to be stable, so that the source-drain current Ids flowing through the driving transistor T1 can also remain to be stable. In this way, the mobility of the driving transistor T1 can be accurately detected, thereby accurately compensating for the mobility of the driving transistor T1.
Further, please continue to refer to
Based on the foregoing embodiments, an embodiment of the present disclosure further provides a display panel, where the display panel includes an organic light emitting diode OLED and the pixel driving circuit as described above, an anode of the organic light emitting diode OLED is connected to a source of the driving transistor T1, and a cathode of the organic light emitting diode OLED is connected to a negative terminal VSS of the power supply. Since the display panel has the same structure and beneficial effects as the pixel driving circuit, and the pixel driving circuit has been described in detail in the foregoing embodiments, details thereof are not described repeatedly herein.
Based on the foregoing embodiment, an embodiment of the present disclosure further provides a method for driving a pixel driving circuit. As shown in
in a pre-charging stage t1, closing the reset switch S1 so that a first scanning voltage Vscan1 provided to a scanning line, a data voltage Vdata′ provided to a data line, and a reset voltage provided to a reset line enable both a switching transistor T2 and a sensing transistor T3 to be turned on; and
in a detection stage following the pre-charging stage, opening the reset switch S1 so that a second scanning voltage Vscan2 provided to the scanning line Scan enables the switching transistor T2 to be turned off and the sensing transistor T3 to be turned on, and both the gate and the source of the driving transistor T1 being in a floating state.
In some embodiments, the driving method of the pixel driving circuit further include: in a sampling stage t3 following the detection stage t2, closing the sampling switch S2, maintaining the reset switch S1 to be opened, maintaining the switching transistor T2 to be turned off, maintaining both the driving transistor T1 and the sensing transistor T3 to be turned on, obtaining a threshold voltage Vth1 of the driving transistor T1 by a sensing line Sense, and obtaining a mobility of the driving transistor T1 according to a current flowing through the driving transistor T1.
In some embodiments, the driving method of the pixel driving method further includes: in the pre-charging stage t1, superimposing the threshold voltage Vth1 of the driving transistor T1 obtained in the sampling stage t3 onto a data voltage Vdata provided to the data line Data to obtain a new data voltage Vdata′, and then inputting the new data voltage Vdata′ into the gate g of the driving transistor.
Specifically, after the threshold voltage Vth1 of the driving transistor T1 obtained in the sampling stage t3 is superimposed onto the data voltage Vdata provided to the data line Data, the resulting new data voltage Vdata′ is input to the gate of the driving transistor T1, that is, Vdata′=Vdata+Vth, to compensate for the threshold voltage of the driving transistor T1, so that the current flowing through the driving transistor T1 is independent of the threshold voltage of the driving transistor T1 but only related to the mobility. Therefore, a mobility difference may be determined, so as to compensate for the mobility difference. Meanwhile, the reset switch S1 is closed, so as to input the reset voltage Vref provided to the reset line Ref to the source s of the driving transistor T1, so that the potential of the first terminal g of the storage capacitor Cst is the data voltage Vdata′, and the potential of the second terminal s thereof is the reset voltage Vref, thereby completing charging of the storage capacitor Cst.
It should be noted that, in the pre-charging stage t1, the input terminal VDD of the power supply is at a low level, so as to prevent the organic light emitting diode OLED from emitting light. In detection stage t2 and sampling stage t3, the input terminal VDD of the power supply is at a high level, so as to cause the driving transistor T1 to drive the organic light emitting diode OLED to emit light.
It should be further noted that, after the pre-charging stage t1, the detection stage t2, and the sampling stage t3, the second scanning voltage Vscan2 provided to the scanning line Scan is changed to the third scanning voltage Vscan3, so that both the switching transistor T2 and the sensing transistor T3 are turned off.
In some embodiments, as shown in
That is, when the switching transistor T2 is an N-type thin film transistor, and the sensing transistor T3 is an N-type thin film transistor or a P-type thin film transistor, a high potential VGH of the first scanning voltage Vscan1 provided in the pre-charging stage t1 by the scanning line Scan is decreased to an intermediate potential VGM of the second scanning voltage Vscan2 provided in the detection stage t2, so that the gate-source potential difference Vgs of the switching transistor T2 is less than a threshold voltage Vth2 of the switching transistor T2, which enables the switching transistor T2 to be turned off. However, when the sensing transistor T3 is an N-type thin film transistor, it needs to be ensured that the gate-source potential difference Vgs of the sensing transistor T3 is greater than the threshold voltage Vth3 of the sensing transistor T3, so that the sensing transistor T3 is turned on. When the sensing transistor T3 is a P-type thin film transistor, the gate-source potential difference Vgs of the sensing transistor T3 may be decreased as the scanning voltage Vscan provided to the scanning line Scan is decreased, so that the sensing transistor T3 may be turned on more thoroughly.
In some embodiments, as shown in
That is, when the switching transistor T2 is a P-type thin film transistor, and the sensing transistor T3 is an N-type thin film transistor or a P-type thin film transistor, a low potential VGL of the first scanning voltage Vscan1 provided in the pre-charging stage t1 by the scanning line Scan is increased to an intermediate potential VGM of the second scanning voltage Vscan2 provided in the detection stage t2, so that the gate-source potential difference Vgs of the switching transistor T2 is greater than a threshold voltage Vth2 of the switching transistor T2, which enables the switching transistor T2 to be turned off. Further, when the sensing transistor T3 is an N-type thin film transistor, the gate-source potential difference Vgs of the sensing transistor T3 may be increased as the scanning voltage Vscan provided to the scanning line Scan is increased, so that the sensing transistor T3 may be turned on more thoroughly. When the sensing transistor T3 is a P-type thin film transistor, it needs to be ensured that the gate-source potential difference Vgs of the sensing transistor T3 is less than the threshold voltage Vth3 of the sensing transistor T3, so that the sensing transistor T3 is turned on.
It should be noted that the potentials of the first scan voltage Vscan1 and the second scan voltage Vscan2 provided to the scanning line Scan in the foregoing embodiment refer to actual potentials. For example, the potential is adjusted from −8V to −12 V so as to decrease the potential, and the potential is adjusted from −15 V to −7V so as to increase the potential. VGH in
Based on the foregoing embodiment, an example that the driving transistor T1, the switching transistor T2, and the sensing transistor T3 in the pixel driving circuit are all N-type thin film transistors is taken. With reference to
In the pre-charging t1, the first scanning voltage Vscan1 of the high potential VGH (for example, 28V) provided to the scanning line Scan enables the switching transistor T2 and the sensing transistor T3 to be turned on, so that the threshold voltage Vth1 of the driving transistor T1 detected in real time is superposed onto the data voltage Vdata provided to the data line Data to obtain the compensated data voltage Vdata′=Vdata+Vth and input Vdata′ to the gate of the driving transistor T1. As a result, the potential of the gate of the driving transistor T1 is Vdata+Vth. According to following current formula of a current flowing through the driving transistor T1, I=K(vgs−vth)2, where K represents an intrinsic conduction factor of the driving transistor T1, and Vgs represents a gate-source voltage difference of the driving transistor T1, the current flowing through the driving transistor T1 is I=K(Vgs−Vth)2=(Vdata+Vth−VDD−Vth)2=(Vdata˜VDD)2. That is, fthe current I flowing through the driving transistor T1 is independent of a threshold voltage Vth1 of the driving transistor T1, thereby compensating for a threshold voltage of the driving transistor T1 before the detection. That is, the compensation of the threshold voltage of the driving transistor T1 is completed before detecting the realtime threshold voltage of the driving transistor T1. In addition, the reset switch S1 is closed, so as to input the reset voltage Vref provided to the reset line Ref to the source s of the driving transistor T1, so that the potential of the first terminal g of the storage capacitor Cst is the data voltage Vdata′, and the potential of the second terminal s thereof is the reset voltage Vref, thereby completing charging of the storage capacitor Cst.
It should be noted that in this case, the data voltage Vdata′ provided to the data line Data should be relatively large (for example, 10V), and the reset voltage Vref provided to the reset line Ref should be relatively small (for example, 1V). In this way, it is better that the switching transistor T2 is turned off and the sensing transistor is turned on under the control of the second scan voltage Vscan2 provided to the voltage modulated scanning line Scan in the detection stage t2.
In the detection stage t2, the high potential VGH (for example, 28V) of the first scanning voltage Vscan1 provided to the scanning line Scan is decreased to the intermediate potential VGM (for example, 6V) of the second scanning voltage Vscan2. In this case, if both the source potential and the drain potential of the switching transistor T2 are Vdata′, for example, 10V, the gate-source potential difference Vgs of the switching transistor T2 is −4V. Meanwhile, if both the source potential and the drain potential of the sensing transistor T3 are Vref, for example, 1V, the gate-source potential difference Vgs of the sensing transistor T3 is 5V. Therefore, the switching transistor T2 is turned off and the sensing transistor T3 is turned on, so that the gate of the driving transistor T1 is in the floating state. In addition, the reset switch S1 is opened, so that the source of the driving transistor T1 is also in the floating state. In this case, the source potential Vs of the driving transistor T1 is increased together with the increase of the gate potential Vg due to a coupling effect of the storage capacitor Cst, and the gate-source potential difference Vgs of the driving transistor T1 remains to be stable, which results in better turn-off of the driving transistor T1.
It should be noted that, in the pre-charging stage t1 and the detection stage t2, the source potential Vs of the driving transistor T1 needs to be kept less than Voled, which is a lighting voltage of the organic light emitting diode OLED, so as to prevent the organic light emitting diode OLED from emitting light in a non-light emitting stage.
In the sampling stage t3, the scanning line Scan remains at an intermediate potential VGM (for example, 6V) of the second scanning voltage Vscan2. The sampling switch S3 is turned off, a threshold voltage of the driving transistor T1 is obtained by using the sensing line Sense, and according to the current flowing through the driving transistor T1, the processing unit 100 (including an analog-to-digital converter ADC) is connected to the source of the sampling switch S3 for data processing and voltage acquisition to obtain the voltage data, so as to obtain the mobility of the driving transistor T1, and further determine the mobility compensation coefficient of the driving transistor T1 to accurately compensate for the mobility error of the driving transistor T1.
After the pre-charging stage t1, the detection stage t2, and the sampling stage t3, the intermediate potential VGM (for example, 6V) of the second scanning voltage Vscan2 provided to the scanning line Scan is changed to the low potential VGL (for example, −6V) of the third scanning voltage Vscan3, so that both the switching transistor T2 and the sensing transistor T3 are turned off.
According to the driving method of the pixel driving circuit provided in the embodiment of the present disclosure, the switching transistor T2 and the sensing transistor T3 are controlled by the same scanning line Scan. In the pre-charging stage t1, the reset switch S1 is closed, and the first scanning voltage Vscan 1 provided to the scanning line Scan, the data voltage Vdata′ provided to the data line Data, and the reset voltage Vref provided to the reset line Ref enable both the switching transistor T2 and the sensing transistor T3 to be turned on, so that the driving transistor T1 is turned on. In the detection stage t2, the reset switch S1 is opened to change the first scanning voltage Vscan1 provided to the scanning signal line Scan to the second scanning voltage Vscan2, so as to enable the sensing transistor T3 to be turned on and the switching transistor T2 to be turned off, so that both the gate g and the source s of the driving transistor are in the floating state. As a result, when the potential of the source s of the driving transistor T1 rises at the input terminal VDD of the power supply, the potential of the gate g of the driving transistor T1 rises due to a coupling effect of the storage capacitor, and the gate-source potential difference Vgs of the driving transistor T1 remains to be stable, so that the source-drain current Ids flowing through the driving transistor T1 can also remain to be stable. In this way, the mobility of the driving transistor T1 can be accurately detected, and therefore the mobility of the driving transistor T1 can be compensated accurately.
It can be understood that, for those ordinary skilled in the art, equivalent replacements or changes can be made according to the technical solutions and inventive concepts of the present disclosure, and all such changes or replacements should fall within the protection scope of the claims appended to the present disclosure.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202210371789.6 | Apr 2022 | CN | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/CN2022/088415 | 4/22/2022 | WO |
