Pixel circuit, method for driving the same, display panel and display device

This application claims the priority to Chinese Patent Application No. CN201710717874.2, filed on Aug. 21, 2017, the content of which is hereby incorporated by reference in its entirety.

The present disclosure relates to the technical field of displaying, in particular to a pixel circuit, a method for driving the same, a display panel and a display device.

Organic Light-Emitting Diode (OLED) displays have become a hot field for flat panel display research. Compared with a Liquid Crystal Display (LCD), an OLED display has advantages in lower power consumption, a lower production cost, a wider viewing angle, a faster response speed and is self-luminous. Among presently existing technologies, OLED displays have come to take the place of traditional LCDs in flat panel displays such as mobile phones, Personal Digital Assistants (PDAs) and digital cameras. Pixel circuit design is a core content of OLED display technology and has great research significance.

Embodiment of the present disclosure provides a pixel circuit, a method for driving the same, a display panel and a display device, in order to solve an existing problem that the brightness of a first frame is low after images displayed by a pixel circuit have switched from low-grayscale images to high-grayscale images.

A pixel circuit according to the disclosure, the pixel circuit including a driving transistor, a light emission control module, a first initialization module, a second initialization module, a threshold compensation module, a data writing module, a storage module and a light emitting device.

The light emission control module is configured to provide a signal of a first voltage terminal to a first terminal of the driving transistor under the control of a first light emission control terminal and to make a connection between a second terminal of the driving transistor and an anode of the light emitting device conductive under the control of a second light emission control terminal.

The first initialization module is configured to reset a gate of the driving transistor.

The second initialization module is configured to enable the signal of the first voltage terminal to flow through the driving transistor before the light emitting device emits light.

The threshold compensation module is configured to compensate a threshold voltage of the driving transistor. The data writing module is configured to write a data signal of a data signal terminal into the gate of the driving transistor.

The storage module is configured to keep a gate voltage of the driving transistor stable.

The driving transistor is configured to generate a driving current according to the data signal to drive the light emitting device to emit light.

In addition, the embodiment of the present disclosure further provides a display panel including a pixel circuit. The pixel circuit includes a driving transistor, a light emission control module, a first initialization module, a second initialization module, a threshold compensation module, a data writing module, a storage module and a light emitting device. The light emission control module is configured to provide a signal of a first voltage terminal to a first terminal of the driving transistor under the control of a first light emission control terminal and to make a connection between a second terminal of the driving transistor and an anode of the light emitting device conductive under the control of a second light emission control terminal. The first initialization module is configured to reset a gate of the driving transistor. The second initialization module is configured to enable the signal of the first voltage terminal to flow through the driving transistor before the light emitting device emits light. The threshold compensation module is configured to compensate a threshold voltage of the driving transistor. The data writing module is configured to write a data signal of a data signal terminal into the gate of the driving transistor. The storage module is configured to keep a gate voltage of the driving transistor stable. The driving transistor is configured to generate a driving current according to the data signal to drive the light emitting device to emit light.

In addition, the embodiment of the present disclosure further provides a display device including a display panel. The display panel includes a pixel circuit. The pixel circuit includes a driving transistor, a light emission control module, a first initialization module, a second initialization module, a threshold compensation module, a data writing module, a storage module and a light emitting device. The light emission control module is configured to provide a signal of a first voltage terminal to a first terminal of the driving transistor under the control of a first light emission control terminal and to make a connection between a second terminal of the driving transistor and an anode of the light emitting device conductive under the control of a second light emission control terminal. The first initialization module is configured to reset a gate of the driving transistor. The second initialization module is configured to enable the signal of the first voltage terminal to flow through the driving transistor before the light emitting device emits light. The threshold compensation module is configured to compensate a threshold voltage of the driving transistor. The data writing module is configured to write a data signal of a data signal terminal into the gate of the driving transistor. The storage module is configured to keep a gate voltage of the driving transistor stable. The driving transistor is configured to generate a driving current according to the data signal to drive the light emitting device to emit light.

In addition, the embodiment of the present disclosure further provides a method for driving a pixel circuit including a driving transistor, a light emission control module, a first initialization module, a second initialization module, a threshold compensation module, a data writing module, a storage module and a light emitting device, and the method includes the following operations.

At a first stage, providing a first potential signal to a first light emission control terminal and a first scanning signal terminal, and providing a second potential signal to a second light emission control terminal and a second scanning signal terminal. The light emission control module provides the signal of a first voltage terminal to a first terminal of the driving transistor under the control of the first light emission control terminal. The first initialization module provides the signal of a reference signal terminal to a gate of the driving transistor under the control of the first scanning signal terminal And the second initialization module cooperates with the light emission control module and the first initialization module to enable the signal of the first voltage terminal to flow to the reference signal terminal after flowing through the driving transistor under the control of the first scanning signal terminal.

At a second stage, providing a first potential signal to the first scanning signal terminal and providing a second potential signal to the first light emission control terminal, the second light emission control terminal and the second scanning signal terminal. The first initialization module provides the signal of the reference signal terminal to the gate of the driving transistor under the control of the first scanning signal terminal.

At a third stage, providing a first potential signal to the second scanning signal terminal, and providing a second potential signal to the first light emission control terminal, the second light emission control terminal and the first scanning signal terminal. The data writing module writes the signal of the data signal terminal into the first terminal of the driving transistor under the control of the second scanning signal, and the threshold compensation module makes the connection between the gate and a second terminal of the driving transistor conductive under the control of the second scanning signal terminal.

At a fourth stage, providing a first potential signal to the first light emission control terminal and the second light emission control terminal, and providing a second potential signal to the first scanning signal terminal and the second scanning signal terminal. The light emission control module provides the signal of the first voltage terminal to the first terminal of the driving transistor under the control of the first light emission control terminal, and makes the connection between the second terminal of the driving transistor and an anode of the light emitting device conductive under the control of the second light emission control terminal And the driving transistor drives the light emitting device to emit light.

FIG. 1 illustrates a circuit schematic diagram of a pixel circuit according to the embodiment of the present disclosure.

FIG. 2 illustrates a circuit schematic diagram of another pixel circuit according to the embodiment of the present disclosure.

FIG. 3 illustrates a specific circuit schematic diagram of a pixel circuit according to the embodiment of the present disclosure.

FIG. 4 illustrates a specific circuit schematic diagram of another pixel circuit according to the embodiment of the present disclosure.

FIG. 5 illustrates a circuit timing diagram corresponding to the pixel circuit illustrated in FIG. 3 .

FIG. 6 illustrates a circuit timing diagram corresponding to the pixel circuit illustrated in FIG. 4 .

FIG. 7 compares brightness values from the pixel circuit according to the embodiment of the present disclosure and corresponding to the existing pixel circuit after the pixel circuits have switched from displaying a low-grayscale image to displaying a high-grayscale image.

FIG. 8 illustrates a flowchart of a method for providing a pixel circuit according to the embodiment of the present disclosure.

FIG. 9 illustrates a structural schematic diagram of a display panel according to the embodiment of the present disclosure.

FIG. 10 illustrates a structural schematic diagram of a display device according to the embodiment of the present disclosure.

In order to make the purposes, technical solutions and advantages of the present disclosure clearer, specific implementation modes of a pixel circuit, a method for driving the same and an organic electroluminescent display panel according to an embodiment of the present disclosure is described below in detail with reference to the drawings. It should be understood that the optional embodiment described below is only used for describing and explaining the present disclosure instead of limiting the present disclosure. Besides, the implementation modes disclosed herein and features thereof can be combined in a case of no conflict.

As illustrated in FIG. 4 , the pixel circuit according to the embodiment of the disclosure includes a driving transistor M 0 , a light emission control module 01 , a first initialization module 02 , a second initialization module 03 , a threshold compensation module 04 , a data writing module 05 , a storage module 06 and a light emitting device OLED.

The light emission control module 01 is configured to provide a signal of a first voltage terminal PVDD to a first terminal of the driving transistor M 0 under the control of a first light emission control terminal Emit 1 and to make a connection between a second terminal of the driving transistor M 0 and an anode of the light emitting device OLED conductive under the control of a second light emission control terminal Emit 2 .

The first initialization module 02 is configured to reset a gate of the driving transistor M 0 .

The second initialization module 03 is configured to enable the signal of the first voltage terminal PVDD to flow through the driving transistor M 0 before the light emitting device OLED emits light.

The threshold compensation module 04 is configured to compensate threshold voltage of the driving transistor M 0 .

The data writing module 05 is configured to drive a data signal of a data signal terminal Data into the gate of the driving transistor M 0 .

The storage module 06 is configured to keep a gate voltage of the driving transistor M 0 stable.

The driving transistor M 0 is configured to generate a driving current according to the data signal to drive the light emitting device OLED to emit light.

The pixel circuit according to the embodiment of the present disclosure utilizes the first initialization module to reset the gate of the driving transistor, utilizes the data writing module to write the data signal, utilizes the threshold compensation module to compensate for threshold voltage drift of the driving transistor, and utilizes the storage module to keep the gate voltage of the driving transistor stable when the light emitting device emits light, thereby improving display non-uniformity caused by the threshold voltage drift of the driving transistor due to manufacturing process and transistor aging through internal compensation. Besides, since the pixel circuit is further provided with the second initialization module and the second initialization module is configured to enable the signal of the first voltage terminal to flow through the driving transistor before the light emitting device emits light, after the pixel circuit displays a low-grayscale image and before the pixel circuit displays a high-grayscale image, a large current is enabled to flow through the driving transistor to compensate for a threshold voltage hysteresis effect of the driving transistor such that the driving transistor can response promptly to drive the light emitting device to emit light, thereby improving the problem that the brightness of a first frame is low after an existing pixel circuit has switched from displaying a low-grayscale image to displaying a high-grayscale image.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 4 , a cathode of the light emitting device OLED is connected with a second voltage terminal PVEE, and generally the voltage of the second voltage terminal PVEE is negative or grounded.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, generally, the light emitting device OLED is an organic light emitting diode, which is not limited herein.

The present disclosure is described below in detail in combination with specific implementation modes. It should be understood that the implementation modes are used for better explaining the present disclosure instead of limiting the present disclosure.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 4 , the first initialization module 02 is configured to provide a signal of a reference signal terminal Vref to the gate of the driving transistor M 0 under the control of a first scanning signal terminal Scan 1 .

The second initialization module 03 is configured to cooperate with the light emission control module 01 and the first initialization module to enable the signal of the first voltage terminal PVDD to flow to the reference signal terminal Vref after flowing through the driving transistor M 0 under the control of the first scanning signal terminal Scan 1 .

The data writing module 05 is configured to write a signal of the data signal terminal Data into the first terminal of the driving transistor M 0 under the control of a second scanning signal terminal Scan 2 .

The threshold compensation module 04 is configured to make the gate and the second terminal of the driving transistor M 0 under the control of the second scanning signal terminal Scan 2 .

In this way, the first initialization module 02 provides the signal of the reference signal terminal Vref to the gate of the driving transistor M 0 under the control of the first scanning signal terminal Scan 1 , while the light emission control module 01 provides the signal of the first voltage terminal PVDD to the first terminal of the driving transistor M 0 under the control of the first light emission control terminal Emit 1 , the second initialization module 03 cooperates with the light emission control module 01 and the first initialization module 02 to enable the signal of the first voltage terminal PVDD to flow to the reference signal terminal Vref after flowing through the driving transistor M 0 , so that a large current is enabled to flow through the driving transistor M 0 to compensate for the threshold voltage hysteresis effect of the driving transistor M 0 . Thereafter, the data writing module writes the signal of the data signal terminal Data into the first terminal of the driving transistor M 0 under the control of the second scanning signal terminal Scan 2 ; the threshold compensation module makes a connection between the gate and the second terminal of the driving transistor M 0 conductive to write the data signal and a threshold voltage of the driving transistor M 0 into the gate of the driving transistor M 0 , and makes the driving current generated by the driving transistor M 0 according to the data signal irrelevant with the threshold voltage of the driving transistor M 0 . Finally the light emission control module 01 enables the driving current of the driving transistor M 0 to flow to the light emitting device OLED to drive the light emitting device OLED to emit light under the control of the first light emission control terminal Emit 1 and the second light emission control terminal Emit 2 .

Optionally, as illustrated in FIG. 5 , the pixel circuit according to the embodiment of the present disclosure further includes an anode resetting module 07 . The anode resetting module 07 is configured to provide the signal of the reference signal terminal Vref to the anode of the light emitting device OLED under the control of the second scanning signal terminal Scan 2 . In this way, the light emitting device OLED, when emitting light at a current frame, is not influenced by a voltage of light emission at a previous frame.

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the light emission control module 01 includes a first switching transistor M 1 and a second switching transistor M 2 .

A gate of the first switching transistor M 1 is connected with the first light emission control terminal Emit 1 , a first terminal of the first switching transistor M 1 is connected with the first voltage terminal PVDD and a second terminal of the first switching transistor M 1 is connected with the first terminal of the driving transistor M 0 .

A gate of the second switching transistor M 2 is connected with the second light emission control terminal Emit 2 , a first terminal of the second switching transistor M 2 is connected with the second terminal of the driving transistor M 0 and a second terminal of the second switching transistor M 2 is connected with the anode of the light emitting device OLED.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, when the first light emission control terminal Emit 1 controls the first switching transistor M 1 to turn on, the signal of the first voltage terminal PVDD is transmitted to the first terminal of the driving transistor M 0 through the first switching transistor M 1 ; and when the second light emission control terminal Emit 2 controls the second switching transistor M 2 to turn on, the connection between the second terminal of the driving transistor M 0 and the light emitting device is conductive.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , the first switching transistor M 1 and the second switching transistor M 2 are P-type transistors, or as illustrated in FIG. 7 , the first switching transistor M 1 and the second switching transistor M 2 are N-type transistors, which are not limited herein.

The above-mentioned specific structure of the light emission control module in the pixel circuit is just an example. During actual implementation, the specific structure of the light emission control module is not limited to the above-mentioned structure and may also be another structure known by one skilled in the art, which is not limited herein.

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the first initialization module 02 includes a third switching transistor M 3 .

A gate of the third switching transistor M 3 is connected with the first scanning signal terminal Scan 1 , a first terminal of the third switching transistor M 3 is connected with the reference signal terminal Vref and a second terminal of the third switching transistor M 3 is connected with the gate of the driving transistor M 0 .

Specifically, in the pixel circuit according to the embodiment of the present disclosure, when the first scanning signal terminal Scant controls the third switching transistor M 3 to turn on, the signal of the reference signal terminal Vref is transmitted to the gate of the driving transistor M 0 through the third switching transistor M 3 to reset the gate of the driving transistor M 0 .

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , the third switching transistor M 3 is a P-type transistor, or as illustrated in FIG. 7 , the third switching transistor M 3 is an N-type transistor, which is not limited herein.

The above-mentioned specific structure of the first initialization module in the pixel circuit is just an example. During actual implementation, the specific structure of the first initialization module is not limited to the above-mentioned structure and may also be another structure known by one skilled in the art, which is not limited herein.

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the threshold compensation module 04 includes a fifth switching transistor M 5 .

A gate of the fifth switching transistor M 5 is connected with the second scanning signal terminal Scan 2 , a first terminal of the fifth switching transistor M 5 is connected with the first terminal of the driving transistor M 0 and a second terminal of the fifth switching transistor M 5 is connected with the gate of the driving transistor M 0 .

Specifically, in the pixel circuit according to the embodiment of the present disclosure, when the second scanning signal terminal Scan 2 controls the fifth switching transistor M 5 to be turn on, the connection between the gate and the second terminal of the driving transistor M 0 is conductive thereby compensating the threshold voltage.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , the fifth switching transistor M 5 is a P-type transistor, or as illustrated in FIG. 7 , the fifth switching transistor M 5 is an N-type transistor, which is not limited herein.

The above-mentioned specific structure of the threshold compensation module in the pixel circuit is just an example. During actual implementation, the specific structure of the threshold compensation module is not limited to the above-mentioned structure and may also be another structure known by one skilled in the art, which is not limited herein.

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the data writing module 05 includes a fourth switching transistor M 4 .

A gate of the fourth switching transistor M 4 is connected with the second scanning signal terminal Scan 2 , a first terminal of the fourth switching transistor M 4 is connected with the data signal terminal Data and a second terminal of the fourth switching transistor M 4 is connected with the first terminal of the driving transistor M 0 .

Specifically, in the pixel circuit according to the embodiment of the present disclosure, when the second scanning signal terminal Scan 2 controls the fourth switching transistor M 4 to turn on, the data signal of the data signal terminal Data is transmitted to the first terminal of the driving transistor M 0 through the fourth switching transistor M 4 to write data.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , the fourth switching transistor M 4 is a P-type transistor, or as illustrated in FIG. 7 , the fourth switching transistor M 4 is an N-type transistor, which is not limited herein.

The above-mentioned specific structure of the data writing module in the pixel circuit is just an example. During actual implementation, the specific structure of the data writing module is not limited to the above-mentioned structure and may also be another structure known by one skilled in the art, which is not limited herein.

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the storage module 06 includes a capacitor C 1 . One terminal of the capacitor C 1 is connected with the first voltage terminal PVDD and the other terminal is connected with the gate of the driving transistor M 0 .

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the second initialization module 03 includes a sixth switching transistor M 6 .

A gate of the sixth switching transistor M 6 is connected with the first scanning signal terminal Scan 1 , a first terminal of the sixth switching transistor M 6 is connected with the first terminal of the driving transistor M 0 and a second terminal of the sixth switching transistor M 6 is connected with the gate of the driving transistor M 0 .

Specifically, in the pixel circuit according to the embodiment of the present disclosure, when the first scanning signal terminal Scan 1 controls the sixth switching transistor M 6 to turn on, the connection between the gate and the second terminal of the driving transistor M 0 is conductive, the sixth switching transistor M 6 cooperates with the third switching transistor M 3 and the first switching transistor M 1 to enable the signal of the first voltage terminal PVDD to pass through the first switching transistor M 1 , then the driving transistor M 0 , then the sixth switching transistor M 6 and then the third switching transistor M 3 to flow to the reference signal terminal, so that a large current could flow through the driving transistor M 0 before the light emitting device OLED emits light to compensate for the threshold voltage hysteresis effect of the driving transistor M 0 .

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , the sixth switching transistor M 6 is a P-type transistor, or as illustrated in FIG. 7 , the sixth switching transistor M 6 is an N-type transistor, which is not limited herein.

The above-mentioned specific structure of the second initialization module in the pixel circuit is just an example. During actual implementation, the specific structure of the second initialization module is not limited to the above-mentioned structure and may also be another structure known by one skilled in the art, which is not limited herein.

Optionally, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , the anode resetting module 07 includes a seventh switching transistor M 7 .

A gate of the seventh switching transistor M 7 is connected with the second scanning signal terminal Scan 2 , a first terminal of the seventh switching transistor M 7 is connected with the reference signal terminal Vref and a second terminal of the seventh switching transistor M 7 is connected with the anode of the light emitting device OLED.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, when the second scanning signal terminal Scan 2 controls the seventh switching transistor M 7 to turn on, the signal of the reference signal terminal Vref is transmitted to the anode of the light emitting device OLED through the seventh switching transistor M 7 to reset the anode of the light emitting device OLED.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , the seventh switching transistor M 7 is a P-type transistor, or as illustrated in FIG. 7 , the seventh switching transistor M 7 is an N-type transistor, which is not limited herein.

The above-mentioned specific structure of the anode resetting module in the pixel circuit is just an example During actual implementation, the specific structure of the anode resetting module is not limited to the above-mentioned structure and may also be another structure known by one skilled in the art, which is not limited herein.

Specifically, in order to unify manufacturing processes, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 , all the transistors are P-type transistors; or as illustrated in FIG. 7 , all the transistors are N-type transistors.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, an N-type transistor turns on under the influence of a high-potential signal and is cut off under the influence of a low-potential signal. And a P-type transistor turns on under the influence of a low-potential signal and is cut off under the influence of a high-potential signal.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, the first terminal of the transistor may be a source and the second terminal thereof is a drain, or the first terminal of the transistor may be a drain and the second terminal thereof is a source, which are not specifically distinguished herein.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, in order to reduce the leakage current, any of the switching transistors may be configured to have a dual-gate structure, which is not limited herein.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, the width-length ratio of the channel of the driving transistor is smaller than the width-length ratio of the channel of any switching transistor.

During actual implementation, in the display panel according to the embodiment of the present disclosure, the driving transistor M 0 is a P-type transistor. In a case where the driving transistor M 0 is an N-type transistor, the design principle is the same as the present disclosure and it is also included in the protection scope of the present disclosure.

Specifically, in the pixel circuit according to the embodiment of the present disclosure, as illustrated in FIG. 6 and FIG. 7 , it is specified that the gate of the driving transistor M 0 is a first node N 1 , the first terminal of the driving transistor M 0 is a second node N 2 and the second terminal of the driving transistor M 0 is a third node N 3 .

The operation process of the pixel circuit according to the embodiment of the present disclosure is described below with reference to the circuit timing diagram. In the description below, 1 represents high potential and 0 represents low potential. 1 and 0 are logical potentials and are just used for better explaining the specific operation process of the embodiment of the present disclosure instead of representing specific voltage values.