Patent Application
20240135883
This application claims the benefit of priority of Chinese Patent Application No. 202211327113.3 filed on Oct. 25, 2022, the contents of which are incorporated herein by reference in their entirety.
The present disclosure relates to the field of display, in particular to a pixel driving circuit, a display panel, and a driving method of the pixel driving circuit.
Most of transistors in existing pixel driving circuits are low temperature polysilicon thin film transistors or oxide thin film transistors. Compared with conventional amorphous silicon thin film transistors, the low temperature polysilicon thin film transistors and the oxide thin film transistors have higher mobility and more stable characteristics, and are more suitable for active matrix organic light emitting diode displays.
However, due to limitation of crystallization process, the low temperature polysilicon thin film transistors made on large area glass substrates often have non-uniformity in electrical parameters such as threshold voltage and mobility, and so on. The non-uniformity will be transformed into driving current differences and brightness differences of organic light emitting diode devices, which will be perceived by human eyes, that is, it is a phenomenon of color non-uniformity. Although a process uniformity of the oxide thin film transistor is good, it is similar to the amorphous silicon thin film transistors. Under a long-term biasing and a high temperature, a threshold voltage of the oxide thin film transistor will drift, which will lead to different display quality. Because of different threshold drift of thin film transistors in different parts of a display panel, it will cause different brightness and uneven display of light-emitting devices.
The present disclosure provides a pixel driving circuit, a display panel, and a driving method of the pixel driving circuit to compensate a threshold voltage drift of a driving transistor, to improve a luminous uniformity of a light emitting device, and further to improve an image quality.
In a first aspect, the disclosure provides a pixel driving circuit. The pixel driving circuit includes a driving transistor, a reset module, a writing module, a first control module, and a light emitting device. A gate electrode of the driving transistor is electrically connected to a first node, a first electrode of the driving transistor is electrically connected to a second node, and a second electrode of the driving transistor is electrically connected to a third node. The reset module is electrically connected to a first scanning signal terminal, a second scanning signal terminal, a first reset signal terminal, and a second reset signal terminal respectively. The reset module is further electrically connected to the first node and the third node and is configured to reset the first node and the third node. The writing module is respectively connected to a data signal terminal and a third scanning signal terminal. The writing module is further electrically connected to the third node and is configured to output a data signal to the third node. The first control module is connected to a first control signal terminal, is electrically connected to the third node and the fourth node, and is configured to control a conduction or a disconnection between the third node and the fourth node. A first terminal of the light emitting device is electrically connected to a fourth node, and a second terminal of the light emitting device is electrically connected to a first power supply terminal.
Optionally, in an embodiment of the present disclosure, the reset module includes a first transistor, a second transistor, and a first capacitor. A gate electrode of the first transistor is electrically connected to the first scanning signal terminal, a first electrode of the first transistor is electrically connected to the first reset signal terminal, and a second electrode of the first transistor is electrically connected to the first node. A gate electrode of the second transistor is electrically connected to the second scanning signal terminal, a first electrode of the second transistor is electrically connected to the second reset signal terminal, and a second electrode of the second transistor is electrically connected to the third node. A first terminal of the first capacitor is electrically connected to the first node, and a second terminal of the first capacitor is electrically connected to the third node.
Optionally, in an embodiment of the present disclosure, the writing module includes a third transistor and a second capacitor. A gate electrode of the third transistor is electrically connected to the third scanning signal terminal, a first electrode of the third transistor is electrically connected to the data signal terminal, and a second electrode of the third transistor is electrically connected to a first terminal of the second capacitor. A second terminal of the second capacitor is electrically connected to the third node.
Optionally, in an embodiment of the present disclosure, the pixel driving circuit further includes a second control module. The second control module is electrically connected to a fourth scanning signal end and a reference signal terminal, is electrically connected to the first terminal of the second capacitor, and is configured to prolong time for compensating a threshold voltage of the driving transistor.
Optionally, in an embodiment of the present disclosure, the second control module includes a fourth transistor. A gate of the fourth transistor is electrically connected to the fourth scanning signal terminal, a first electrode of the fourth transistor is electrically connected to the reference signal terminal, and a second electrode of the fourth transistor is electrically connected to the first terminal of the second capacitor.
Optionally, in an embodiment of the present disclosure, the first control module includes a fifth transistor. A gate of the fifth transistor is electrically connected to the first control signal terminal, a first electrode of the fifth transistor is electrically connected to the third node, and a second electrode of the fifth transistor is electrically connected to the fourth node.
Optionally, in an embodiment of the present disclosure, the pixel driving circuit further includes a third control module. The third control module is electrically connected to the second control signal terminal, is electrically connected to a second power supply terminal and the second node, and is configured to control a conduction or a disconnection between the second power supply terminal and the second node.
Optionally, in an embodiment of the present disclosure, the third control module includes a sixth transistor. A gate of the sixth transistor is electrically connected to the second control signal terminal, a first electrode of the sixth transistor is electrically connected to the second power supply terminal, and a second electrode of the sixth transistor is electrically connected to the second node.
A driving method of the pixel drive circuit, which is configured to drive the pixel drive circuit as described above, is further provided. The driving method includes: in a reset phase, resetting the first node according to a first reset signal under a control of a first scanning signal and resetting the third node according to a second reset signal under a control of a second scanning signal by the reset module; in a compensation phase, continuously outputting the first reset signal to the first node by means of the reset module under the control of the first scanning signal to make a voltage difference between the first node and the third node to be larger than the threshold voltage of the driving transistor, so as to turn on the driving transistor and to charge the third node by the second power supply terminal until the voltage difference between the first node and the third node is equal to the threshold voltage of the driving transistor; in a data writing phase, outputting the data signal to the third node by means of the writing module under the control of the third scanning signal; and in a light emitting phase, emitting light by means of the light emitting device.
Optionally, in an embodiment of the present disclosure, the first scanning signal and the third scanning signal are the same signal.
Optionally, in an embodiment of the present disclosure, the data signal comprises a first potential and a second potential, the data signal is switched from the first potential to the second potential in the reset phase, and the data signal is switched from the second potential to the first potential in the data writing phase.
On another hand, a display panel is further provided by the present disclosure. The display panel includes a plurality of pixels arranged in an array, and each of the pixels includes the pixel driving circuit described above.
The disclosure provides a pixel driving circuit, a display panel, and a driving method of the pixel driving circuit, and the pixel driving circuit includes a driving transistor, a reset module, a writing module, a first control module, and a light emitting device. A gate electrode of the driving transistor is electrically connected to a first node, a first electrode of the driving transistor is electrically connected to a second node, and a second electrode of the driving transistor is electrically connected to a third node. The reset module is electrically connected to a first scanning signal terminal, a second scanning signal terminal, a first reset signal terminal, and a second reset signal terminal respectively. The reset module is further electrically connected to the first node and the third node and is configured to reset the first node and the third node. The writing module is respectively connected to a data signal terminal and a third scanning signal terminal. The writing module is further electrically connected to the third node and is configured to output a data signal to the third node. The first control module is connected to a first control signal terminal, is electrically connected to the third node and the fourth node, and is configured to control a conduction or a disconnection between the third node and the fourth node. A first terminal of the light emitting device is electrically connected to a fourth node, and a second terminal of the light emitting device is electrically connected to a first power supply terminal. The pixel driving circuit may compensate the threshold voltage drift of the driving transistor, improve the luminescence uniformity of the light emitting device, and further improve the image quality.
In order to more clearly explain the technical proposal in the embodiment of the present disclosure, drawings required to be used in the description of embodiments will be briefly described below, and it will be apparent that the drawings described below correspond only to some embodiments of the present disclosure, from which other drawings may be obtained without creative effort by those skilled in the art.
Technical proposals in the embodiment of the present disclosure will be clearly and completely described in the following with reference to the drawings in embodiments of the present disclosure. It will be apparent that the described embodiments are only parts of and not all of the embodiments of the present disclosure. Based on the embodiments in the present disclosure, all other embodiments obtained by those skilled in the art without making creative efforts fall within the scope of protection of the present application.
Transistors employed in all embodiments of the present disclosure may be thin film transistors or field effect transistors or other devices of the same characteristics. Since a first electrode and a second electrode of the transistor used here are symmetrical, the first electrode and the second electrode are interchangeable. In the embodiment of the present disclosure, in order to distinguish two poles of the transistor except the gate electrode, one of the poles is referred as the first electrode and the other is referred as the second electrode.
In addition, the transistors used in the embodiment of the present disclosure may include two types of P-type transistors and/or N-type transistors, wherein, the P-type transistors are turned on when the gate of the transistor is at a low level and are turned off when the gate of the transistor is at a high level, and the N-type transistors are turned on when the gate of the transistor is at a high level and are turned off when the gate of the transistor is at a low level.
Referring to
It should be noted that the light emitting device D may be micro light emitting diode (Micro-LED), mini light emitting diode (Mini-LED) or organic light emitting diode (OLED). In some embodiments, the light emitting device D may include a Micro-LED, a Mini-LED, or an OLED. In other embodiments, the light emitting device D may include a plurality of Micro-LEDs, a plurality of Mini-LEDs, or a plurality of OLEDs. The plurality of Micro-LEDs may be arranged in series or in parallel, and the plurality of Mini-LEDs and the plurality of OLEDs may be arranged in series or in parallel.
Specifically, a gate electrode of the driving transistor T0 is electrically connected to a first node Q, a first electrode of the driving transistor T0 is electrically connected to a second node N, the second node N is electrically connected to a second power supply terminal VDD, and a second electrode of the driving transistor T0 is electrically connected to the third node A. The reset module 101 is electrically connected to a first scanning signal terminal SCAN1, a second scanning signal terminal SCAN2, a first reset signal terminal INT1, and a second reset signal terminal INT2 respectively. The reset module 101 is further electrically connected to the first node Q and the third node A. The writing module 102 is electrically connected to a data signal terminal DATA and a third scanning signal terminal SCAN3, and is electrically connected to the third node A. The first control module 103 is electrically connected to a first control signal terminal EM1, and is electrically connected to the third node A and a fourth node B. A first terminal of the light emitting device D is electrically connected to the fourth node B, and a second terminal of the light emitting device D is electrically connected to a first power supply terminal VSS, wherein the second power supply terminal VDD and the first power supply terminal VSS are both DC voltage sources.
It should be noted that the first scanning signal terminal SCAN1 is configured to output a first scanning signal SCAN1, the second scanning signal terminal SCAN2 is configured to output a second scanning signal SCAN2, the first reset signal terminal INT1 is configured to output a first reset signal INT1, the second reset signal terminal INT2 is configured to output a second reset signal INT2, the data signal terminal DATA is configured to output a data signal DATA, the third scanning signal terminal SCAN3 is configured to output a third scanning signal SCAN3, and the first control signal terminal EM1 is configured to output a first control signal EM1.
In some embodiments, the data signal DATA includes a first potential and a second potential. The data signal DATA is switched from the first potential to the second potential during a period when the second scanning signal SCAN2 is at a high potential, and is switched from the second potential to the first potential before the first scanning signal SCAN1 is switched from a high potential to a low potential. The first potential is a low potential and a data signal is output under the low potential. The second potential is a high potential at which a first terminal of a second capacitor C2 is charged to stabilize a voltage of the second capacitor C2.
In some embodiments, the third scanning signal SCAN3 is the same signal as the first scanning signal SCAN1.
Specifically, the driving transistor T0 is configured to control a current flowing through the pixel driving circuit. The reset module 101 is configured to reset the first node Q under a control of the first scanning signal SCAN1, and the reset module 101 is further configured to reset the third node A under a control of the second scanning signal SCAN2. The writing module 102 is configured to output the data signal DATA to the first terminal of the second capacitor C2 under a control of the third scanning signal SCAN3, and to transmit the data signal DATA to the third node A through a coupling action of the second capacitor C2. The first control module 103 is configured to control a conduction or a disconnection between the third node A and the fourth node B under a control of the first control signal EM1.
It should be noted that since the third scanning signal SCAN3 and the first scanning signal SCAN1 are the same signal, a number of signals can be simplified and a crosstalk between the signals can be reduced. Of course, the third scanning signal SCAN3 and the first scanning signal SCAN1 may be different signals, so that loading on a first scanning signal line SCAN1 and a third scanning signal line SCAN3 can be reduced, and the output driving power of the first scanning signal SCAN1 and the third scanning signal SCAN3 can be improved. In addition, the first node Q, the third node A, and the fourth node B are all denoted as nodes electrically connected to corresponding devices, and here are only denoted as electrical connection relationships, wherein the first node Q, the third node A, and the fourth node B are not denoted as terminals.
In some embodiments, please refer to
In some embodiments, the first reset signal INT1 is the same signal as a first power supply signal VSS provided by the first power supply terminal VSS.
In some embodiments, please refer to
In some embodiments, please refer to
In some embodiments, please refer to
In some embodiments, please refer to
In some embodiments, please refer to
In some embodiments, please refer to
It should be noted that the driving transistor T0, the first transistor T1, the second transistor T2, the third transistor T3, the fourth transistor T4, the fifth transistor T5, and the sixth transistor T6 may be one or more types of a low-temperature polysilicon thin film transistor, an oxide semiconductor thin film transistors, and an amorphous silicon thin film transistor. Furthermore, the driving transistor T0, the first transistor T1, the second transistor T2, the third transistor T3, the fourth transistor T4, the fifth transistor T5, and the sixth transistor T6 are all transistors of the same type, and preferably are all N-type transistors or P-type transistors.
Furthermore, embodiments of the present disclosure will describe a complete circuit of the pixel driving circuit. Referring to
The transistors in the pixel driving circuit provided by the embodiment of the disclosure are the same type of transistors, which are beneficial to avoid an influence of differences between transistors of different types onto the pixel driving circuit.
The gate of the driving transistor T0 is electrically connected to the first node Q, the first electrode of the driving transistor T0 is electrically connected to the second node N, i.e., the second power supply terminal VDD, and the second electrode of the driving transistor T0 is electrically connected to the third node A. The first terminal of the light emitting device D is electrically connected to the fourth node B, and the second end of the light emitting device D is electrically connected to the first power supply terminal VSS. The gate electrode of the first transistor T1 is electrically connected to the first scanning signal SCAN1, the first electrode of the first transistor T1 is electrically connected to the first reset signal terminal INT1, and the second electrode of the first transistor T1 is electrically connected to the first node Q. The gate electrode of the second transistor T2 is electrically connected to the second scanning signal terminal SCAN2, the first electrode of the second transistor T2 is electrically connected to the second reset signal terminal INT2, and the second electrode of the second transistor T2 is electrically connected to the third node A. The first terminal of the first capacitor C1 is electrically connected to the first node Q, and the second terminal of the first capacitor C1 is electrically connected to the third node A. The gate of the third transistor T3 is electrically connected to the third scanning signal SCAN3, the first electrode of the third transistor T3 is electrically connected to the DATA signal terminal DATA, and the second electrode of the third transistor T3 is electrically connected to the first terminal of the second capacitor. The second terminal of the second capacitor is electrically connected to the third node A. The gate of the fifth transistor T5 is electrically connected to the first control signal terminal EM1, the first electrode of the fifth transistor T5 is electrically connected to the third node A, and the second electrode of the fifth transistor T5 is electrically connected to the fourth node B.
It should be noted that since the third scanning signal SCAN3 and the first scanning signal SCAN1 are the same signal, this design may simplify the number of signals and reduce the crosstalk between the signals. Of course, the third scanning signal SCAN3 and the first scanning signal SCAN1 may be different signals, so that loadings respectively on the first scanning signal line SCAN1 and the third scanning signal line SCAN3 can be reduced, and the output driving power of the first scanning signal SCAN1 and the third scanning signal SCAN3 can be improved.
Please refer to
In a reset phase t1, both the first scanning signal SCAN1 and the second scanning signal SCAN2 are at a high potential, and the first transistor T1 is turned on under the control of the first scanning signal SCAN1 to reset the first node Q, so that a gate voltage of the driving transistor T0 is reset to the first reset voltage VINT1 provided by the first reset signal INT1. The second transistor T2 is turned on under the control of the second scanning signal SCAN2 to reset the third node A, so that a second electrode voltage of the driving transistor T0 is reset to the second reset voltage VINT2 provided by the second reset signal INT2, and the second reset voltage VINT2 is smaller than the voltage difference between the first reset voltage VINT1 and the threshold voltage Vth of the driving transistor T0.
In a compensation phase t2, the second scanning signal SCAN2 is at a low potential, the first scanning signal SCAN1 maintains a high potential, the first transistor T1 remains on, the first reset signal INT1 is continuously output to the first node Q, a voltage difference between the first node Q and the third node A is larger than the threshold voltage Vth of the driving transistor T0, the driving transistor T0 is turned on, the second power supply terminal VDD charges the third node A until the voltage difference between the first node Q and the third node A is equal to the threshold voltage Vth of the driving transistor T0, and the threshold voltage Vth is stored in the first capacitor C1.
In a data writing phase t3, the second scanning signal SCAN2 is maintained at a low potential and the first scanning signal SCAN1 is maintained at a high potential, at which the data signal DATA is switched from the second potential to the first potential to output the data signal DATA. Due to a coupling effect of the second capacitor C2, the data signal DATA is transmitted to the third node A, so that a potential VA of the third node A satisfies: VA=VVSS−Vth+(VREF−VDATA) (C2/(C2+C1)).
Moreover, in some embodiments, the first reset signal INT1 and the first power supply signal VSS are the same signal, that is, a potential of the first node Q is the first power supply voltage VVSS, so the first capacitor C1 stores the voltage value. That is, the voltage difference Vgs between the gate electrode of the driving transistor TO and the second electrode of the driving transistor T0 is Vth+(VDATA−VREF) (C2/(C1+C2)), and the first capacitor C1 may play a role in stabilizing the voltage.
In the light emitting phase t4, the first control signal EM1 is at a high potential, and the light emitting device D emits light. Since Vgs is stored in the first capacitor, so that, in the light emitting phase t4, Vgs−Vth=(VDATA−VREF) (C2/(C1+C2)). That is, a driving current Ioled is independent of the drift of the threshold voltage Vth, and the threshold voltage Vth compensation function of the driving transistor T0 is realized in the light emitting phase.
The pixel driving circuit provided by the present disclosure includes the light emitting device D, the driving transistor T0, the reset module 101, the writing module 102, and the first control module 103. The pixel driving circuit may compensate the drift of the threshold voltage Vth of the driving transistor T0, improve the luminous uniformity of the light emitting device, and further improve the image quality.
Please refer to
In the reset phase t1 and the compensation phase t2, the second control signal terminal EM2 maintains a high potential, and the fourth transistor T4 is turned on under the control of the second control signal EM2.
In a compensation phase t2, the second scanning signal SCAN2 is at a low potential, the first scanning signal SCAN1 maintains a high potential, the first transistor T1 remains on, the first reset signal INT1 is continuously output to the first node Q and make the voltage difference between the first node Q and the third node A to be larger than the threshold voltage Vth of the driving transistor T0, the driving transistor T0 is turned on, the second power supply terminal VDD charges the third node A until the voltage difference between the first node Q and the third node A is equal to the threshold voltage Vth of the driving transistor T0, and the threshold voltage Vth is stored in the first capacitor C1.
In a data writing phase t3, the second scanning signal SCAN2 is maintained at a low potential, and the first scanning signal SCAN1 and the third scanning signal SCAN3 are both maintained at a high potential. At this timing, the data signal DATA is switched from the second potential to the first potential to output the data signal DATA. Due to a coupling effect of the second capacitor C2, the data signal DATA is transmitted to the third node A. The second control signal EM2 is switched to a low potential, and the sixth transistor T6 is turned off under the control of the second control signal EM2, so as to ensure that the second power supply terminal VDD and the second reset signal INT2 do not continue to charge the third node A after the data signal DATA is written, which is beneficial to improving the stability of the voltage difference Vgs between the gate electrode of the driving transistor T0 and the second electrode of the driving transistor T0.
It should be noted that the third scanning signal SCAN3 and the first scanning signal SCAN1 are the same signal, so that a number of signals may be simplified and a crosstalk between signals can be reduced. Of course, the third scanning signal SCAN3 and the first scanning signal SCAN1 may be different signals, so that the loadings respectively on the first scanning signal line SCAN1 and the third scanning signal line SCAN3 can be reduced, and the output driving power of the first scanning signal SCAN1 and the third scanning signal SCAN3 can be improved.
In the light emitting phase t4, the first control signal EM1 and the second control signal EM2 are both at a high potential, the fifth transistor T5 is turned on under the control of the first control signal EM1, the fourth transistor T4 is turned on under the control of the second control signal EM2, and the light emitting device D emits light.
The pixel driving circuit provided by the present disclosure includes the light emitting device D, the driving transistor T0, the reset module 101, the writing module 102, and the first control module 103. The pixel driving circuit may compensate the drift of the threshold voltage Vth of the driving transistor T0, improve the luminous uniformity of the light emitting device, and further improve the image quality.
Please refer to
In the reset phase t1, the first scanning signal SCAN1, the second scanning signal SCAN2, the fourth scanning signal SCAN4, and the second control signal EM2 are all at a high potential.
In a compensation phase t2, the second scanning signal SCAN2, the fourth scanning signal SCAN4, and the second control signal EM2 maintain a high potential.
In a data writing phase t3, the second scanning signal SCAN2 and the third control signal EM3 are both at a high potential.
In the light emitting phase t4, the first scanning signal SCAN1 and the second control signal EM2 are both at a high potential, and the light emitting device D emits light.
In particular, in some embodiments, the reference signal REF is the same as the first power supply signal VSS, and therefore, in the reset phase t1 and the compensation phase t2, the fifth transistor T5 is turned on under the control of the fourth scanning signal SCAN4, so that the first power supply voltage VVSS output from the first power supply terminal VSS is transmitted to the first terminal of the second capacitor C2, and the first power supply voltage VVSS is transmitted to the third node A through the coupling action of the second capacitor C2.
In the data writing phase T3, the third transistor T3 is turned on under the control of the third scanning signal SCAN3, and the fifth transistor T5 is turned off under the control of the fourth scanning signal SCAN4, so that the data signal VDATA is transmitted to the first terminal of the second capacitor C2, and the data signal VDATA is transmitted to the third node A through the coupling action of the second capacitor C2.
By dividing the data signal DATA and the second power supply terminal VSS into two branches and performing a writing in different phases, the first terminal of the second capacitor may be charged through the fourth transistor T4 before the data signal DATA is written, so as to stabilize the voltage of the second capacitor C2. Furthermore, the time of threshold compensation is no longer limited by the time of outputting the data signal terminal, which is beneficial to prolong the compensation time for the threshold voltage Vth of the driving transistor T0, so as to improve the threshold compensation effect.
The present disclosure also provides a driving method. Please refer to
S10: a reset phase, resetting the first node Q according to a first reset signal INT1 under a control of a first scanning signal SCAN1 and resetting the third node A according to a second reset signal INT2 under a control of a second scanning signal SCAN2 by the reset module 101.
S20: a compensation phase, continuously outputting the first reset signal INT1 to the first node Q by means of the reset module 101 under the control of the first scanning signal SCAN1 to make a voltage difference between the first node Q and the third node A to be larger than the threshold voltage of the driving transistor T0, so as to turn on the driving transistor T0 and to charge the third node A by the second power supply terminal VDD until the voltage difference between the first node Q and the third node A is equal to the threshold voltage of the driving transistor T0.
S30: a data writing phase, outputting the data signal DATA to the third node A by means of the writing module 102 under the control of the third scanning signal SCAN3.
S40: a light emitting phase, emitting light by means of the light emitting device D.
Please refer to
The pixel driving circuit provided by the present disclosure includes a light emitting device D, a driving transistor T0, a reset module 101, a writing module 102 and a first control module 103. The pixel driving circuit may compensate the drift of the threshold voltage Vth of the driving transistor T0, improve the luminous uniformity of the light emitting device, and further improve the image quality.
The foregoing is a preferred embodiment of the present disclosure, and it should be noted that, to those of ordinary skill in the art, several modifications and embellishments may be made without departing from the principles set forth in the present disclosure, and such modifications and embellishments are also to be considered within the scope of the present.
| Number | Date | Country | Kind |
|---|---|---|---|
| 202211327113.3 | Oct 2022 | CN | national |
