The present disclosure relates to the field of tablet display technology, and particularly, to a pixel circuit and a driving method thereof, a display panel and a display device.
Organic Light Emitting Diode (OLED) display technology is an important development direction in current display technologies. The OLED display technology uses self-luminous organic light emitting diodes (OLEDs) to display images without the use of backlight elements. Compared with the Liquid Crystal Display (LCD) including the liquid crystal structure and the backlight element, it has the advantages of simple structure, thin thickness, and fast response. It is possible to satisfy the user's demand for a lighter, thinner, and more convenient display.
In the OLED display technology, the Active Matrix Organic Light Emitting Diode (AMOLED) technology and the Passive Matrix Organic Light Emitting Diode (PMOLED) technology are included according to the driving mode. PMOLED simply forms a matrix shape with cathode and anode, and lights up pixels in the array in a scanning way, and each pixel operates in a short pulse mode and emits light for instant high luminance. Its advantage is in the simple structure, which can effectively reduce the manufacturing cost. A potential problem is that the high drive voltage renders PMOLED not suitable for large-size and high-resolution panels. AMOLED technology uses a separate thin film transistor to control each pixel, which can be driven continuously and independently to emit light and can be driven using a low-temperature polysilicon or oxide TFT, and has advantages of low drive voltage and long life of the light emitting components. As a result, AMOLED technology has become the focus of the next generation of display technology.
However, the circuit in the prior art is still insufficient for the control precision of the OLED. As shown in
Embodiments of the present disclosure provide a pixel circuit and a driving method thereof, a display panel and a display, so that the current flows through the drive module in the same direction in data writing and in light emission, improving the control precision of the organic light emitting diode OLED and solving the slight light emitting phenomenon caused by OLED leakage current.
According to a first aspect, the present disclosure provides a pixel circuit including a reset module, a storage module, a data write module, a drive module, a control voltage compensation module, a light emission control module, and a light emitting module. The reset module is connected to a third power source, a second scan line and the storage module, and configured to reset the voltage stored in the storage module. The storage module is connected to a first power source, and configured to store a control voltage for the drive module. The data write module is connected to a data line and a third scan line, and configured to supply a voltage required for the display of the pixel circuit to the drive module. The drive module is connected to the storage module, and configured to drive the light emitting module to emit light via the light emission control module, based on the control voltage stored in the storage module. The control voltage compensation module is connected to the third scan line and the drive module, and configured to compensate the voltage provided by the data write module to obtain the control voltage for the drive module. The light emission control module is connected to a first scan line and the first power source, and configured to control the provision of the voltage of the first power source to the drive module and control the driving of the drive module to the light emitting module. The light emitting module is configured to emit light, under the driving of the drive module.
In embodiments of the present disclosure, the drive module includes a control electrode, a first electrode, and a second electrode. The control electrode of the drive module is connected to the storage module. The first electrode of the drive module is connected to the data write module, and to the first power source via the light emission control module. The second electrode of the drive module is connected to the light emitting module via the light emission control module. The control voltage compensation module is connected to the control electrode and second electrode of the drive module.
In embodiments of the present disclosure, the drive module includes a second transistor. A control electrode, a first electrode, and a second electrode of the second transistor are connected to the control electrode, the first electrode and the second electrode of the drive module, respectively.
In embodiments of the present disclosure, the pixel circuit further includes a shunt module, the shunt module connected in parallel to the light emitting module, and configured to shunt the current flowing through the light emitting module.
In embodiments of the present disclosure, the shunt module includes a seventh transistor. A first electrode and a second electrode of the seventh transistor are connected to the light emitting module, and a control electrode of the seventh transistor is connected to the first scan line.
In embodiments of the present disclosure, the reset module, the data write module, the control voltage compensation module, and the light emission control module are implemented with transistors. In the pixel circuit, the seventh transistor is an N-type MOS transistor, and the remaining transistors are P-type MOS transistors.
According to a second aspect, the present disclosure provides a method for driving the pixel circuit, including a first phase, a second phase, a third phase, a fourth phase, and a fifth phase. In the first phase, the light emitting module is initialized. In the second phase, a voltage stored in the storage module is reset to be the voltage of the third power source. In the third phase, a control voltage for the drive module is stored in the storage module. In the fourth phase, the light emitting module is reset. In the fifth phase, the light emitting module is driven to emit light by the drive module based on the voltage stored in the storage module.
In embodiments of the present disclosure, the pixel circuit further includes a shunt module, connected in parallel to the light emitting module, and configured to shunt the current flowing through the light emitting module. The method also includes, in the first to fourth phases, shunting the current flowing through the organic light emitting diode, by the shunt module.
In embodiments of the present disclosure, the shunt module includes a seventh transistor. A first electrode and a second electrode of the seventh transistor are connected to the light emitting module. The method further includes turning on the seventh transistor in the first to fourth phases. In the fifth phase, the seventh transistor is turned off.
In embodiments of the present disclosure, the drive module, the reset module, the data write module, the control voltage compensation module, and the light emission control module are implemented with transistors. In the first phase, the data write module is turned off, the driver module is turned off, the control voltage compensation module is turned off, the light emission control module is turned off, and the reset module is turned off. In the second phase, the data write module is turned off, the drive module is turned on, the control voltage compensation module is turned off, the light emission control module is turned off and the reset module is turned on. In the third phase, the data write module is turned on, the drive module is turned on, the control voltage compensation module is turned on, the light emission control module is turned off, and the reset module is turned off. In the fourth phase, the data write module is turned off, the drive module is turned off, the control voltage compensation module is turned off, the light emission control module is turned off, and the reset module is turned off. In the fifth phase, the data write module is turned off, the drive module is turned on, the control voltage compensation module is turned off, the light emission control module is turned on, and the reset module is turned off.
In embodiments of the present disclosure, in the pixel circuit, the seventh transistor is an N-type MOS transistor, and the remaining transistors are P-type MOS transistors. The method further includes, in a first phase, providing a high level voltage on the first scan line, providing a high level voltage on the second scan line, providing a high level voltage on the third scan line, and providing a low level voltage on the data line. In the second phase, a high level voltage is provided on the first scan line, a low level voltage is provided on the second scan line, a high level voltage is provided on the third scan line, and a low level voltage is provided on the data line. In the third phase, a high level voltage is provided on the first scan line, a high level voltage is provided on the second scan line, a low level voltage is provided on the third scan line, and a high level voltage is provided on the data line. In the fourth phase, a high level voltage is provided on the first scan line, a high level voltage is provided on the second scan line, a high level voltage is provided on the third scan line, and a low level voltage is provided on the data line. In the fifth phase, a low level voltage is provided on the first scan line, a high level voltage is provided on the second scan line, a high level voltage is provided on the third scan line, and a low level voltage is provided on the data line.
According to a third aspect, the present disclosure provides a display panel including a pixel circuit of any of the above.
According to a fourth aspect, the present disclosure provides a display device including the above-described display panel.
According to embodiments of the present disclosure, the wiring mode of the driving circuit is changed to optimize the current collecting manner of the capacitor C so that the current flows through the second transistor T2 in different phases always in the same direction, greatly improving uniformity and accuracy of turning on the second transistor T2. The overall contrast of the display panel can also be increased due to more precise control of each pixel. Also, the change in the wiring mode reduces the space required for the display panel layout, which is advantageous for the improvement in the resolution. In addition, the seventh transistor T7 connected to the organic light emitting diode OLED is added, to shunt the organic light emitting diode OLED out of the light emitting phase, eliminating the slight light emitting phenomenon caused by the leakage current. In the case of a black picture, a low luminance can be ensured. In the case of not affecting white picture, the contrast can be improved.
In order to more clearly illustrate the technical solution in the embodiments of the present disclosure, the drawings in the embodiments will be briefly described below. It should be understood that the drawings described below relate only to some embodiments of the present disclosure, instead of limiting the present disclosure, in which:
In order that the technical solutions and advantages of the embodiments of the present disclosure will become more apparent, the technical solutions of the embodiments of the present disclosure will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are a part of the embodiments of the present disclosure, but not all embodiments. Based on the described embodiments of the present disclosure, all other embodiments obtained by those skilled in the art without the need for creative work fall within the scope of the present disclosure.
The pixel circuit of the present embodiment may include a reset module 1, a storage module 2, a data write module 3, a drive module 4, a control voltage compensation module 5, a light emission control module 6, and a light emitting module 7. The reset module is connected to the third power source Vint, the second scan line Sn−1, and the storage module 2. The reset module 1 is controlled by a signal inputted from the second scan line Sn−1 for resetting the voltage stored in the storage module 2. The storage module 2 is connected to the first power source ELVDD and the drive module 4, for storing a control voltage for the drive module 4. The data write module is connected to the data line Data and the third scan line Sn, is connected to the storage module 2 via the drive module 4 and the control voltage compensation module 5, and is controlled by a signal inputted from the third scan line Sn, for providing the voltage required for displaying the pixel circuit to the drive module. The drive module 4 is connected to the light emission control module 6 and the storage module 2, for driving the light emitting module 7 to emit light via the light emission control module 6 according to the control voltage stored in the storage module 2. The control voltage compensation module 5 is connected to the third scan line Sn, the drive module 4 and the storage module 2, controlled by the signal inputted from the third scan line Sn, for compensating the voltage provided by the data write module 3 to obtain the control voltage for the drive module 4. The light emission control module 6 is connected to the first scan line En, the first power source ELVDD, the drive module 4, and the light emitting module 7, for controlling the connection between the drive module 4 and the first power source ELVDD and the connection between the drive module 4 and the light emitting module 7, based on the voltage inputted from the first scan line En, i.e., controlling the provision of the voltage of the first power source ELVDD to the drive module 4 and controlling the driving of the drive module 4 to the light emitting module 7. The light emitting module 7 is configured to emit light, under the driving of the drive module 4.
The drive module 4 includes a control electrode, a first electrode and a second electrode. The control electrode of the drive module 4 is connected to the storage module 2. The first electrode of the drive module 4 is connected to the data write module 3, and is connected to the first power source ELVDD via the light emission control module 6. The second electrode of the drive module 4 is connected to the light emitting module 7 via the light emission control module 6. The control voltage compensation module 5 is connected to the control electrode and the second electrode of the drive module 4. In this way, it may make the current flow through the drive module in different phases in the same direction.
The reset module 1 includes a sixth transistor T6. The storage module 2 includes a capacitor C. The data write module 3 includes a first transistor T1. The control voltage compensation module 5 includes a third transistor T3. The light emission control module 6 includes a fourth transistor T4 and a fifth transistor T5. The light emitting module 7 includes an organic light emitting diode OLED. The control electrode of the first transistor T1 is connected to the third scan line Sn, the first electrode of the first transistor T1 is connected to the data line Data, and the second electrode of the first transistor T1 is connected to the first electrode of the second transistor T2. The control electrode of the second transistor T2 is connected to the first electrode of the third transistor T3, and the second electrode of the second transistor T2 is connected to the second electrode of the third transistor T3. The control electrode of the third transistor T3 is connected to the third scan line Sn. The control electrode of the fourth transistor T4 is connected to the first scan line En, the first electrode of the fourth transistor T4 is connected to the first power source ELVDD, and the second electrode of the fourth transistor T4 is connected to the second electrode of the first transistor T1. The control electrode of the fifth transistor T5 is connected to the first scan line En, the first electrode of the fifth transistor T5 is connected to the second electrode of the second transistor T2, and the second electrode of the fifth transistor T5 is connected to the first electrode of the organic light emitting diode OLED. The control electrode of the sixth transistor T6 is connected to the second scan line Sn−1, and the second electrode of the sixth transistor T6 is connected to the third power source Vint. The capacitor C is connected between the first power source ELVDD and the first electrode of the sixth transistor T6.
As shown in
Hereinafter, the operation timing of the embodiment of the present disclosure will be described. Although with respect to the circuit in
Specifically, as shown in
As described above, the type of the level on the scan line is determined here depending on the type of transistor. In order to turn off the first transistor T1 to the sixth transistor T6, and turned on the seventh transistor T7, a high voltage is provided on the scan line. It will be appreciated by those skilled in the art that if the transistor type changes, the corresponding level type also changes accordingly.
Specifically, as shown in
Specifically, as shown in
Specifically, as shown in
According to the saturated current formula, the current flowing through the organic light emitting diode OLED is:
Where,
u μ and Cox are process constants, W is the channel width of the second transistor T2, L is the channel length of the second transistor T2, and W and L are both constants that can be selectively designed, so that K is a constant that can be determined in advance. From the above formula, it can be seen that the current Ioled flowing through the organic light emitting diode OLED is not affected by the threshold voltage Vth of the second transistor T2, but is only related to the voltage Vvdata transmitted by the data line and the voltage Velvdd of the first power source ELVDD. The pixel circuit thus can output a stable drive current without being affected by the threshold voltage Vth of the second transistor T2.
Since in the third phase t3 and the fifth phase t5, the current flows through the second transistor T2 in the same direction, it can be ensured that the organic light emitting diode OLED emits light accurately according to the data signal at the light emitting phase, and the accuracy of the display is ensured. In addition, the seventh transistor T7 is turned off, and the efficiency and characteristics of the organic light emitting diode OLED can be ensured.
The five phases abovementioned constitute a complete light emission control cycle, and after the completion of the fifth phase t5, it may proceed to a next light emission control cycle, to start a new first phase t1.
The pixel circuits in the embodiments of the present disclosure are arranged in a matrix form for use in a display panel. The display panel may be used for a display device. The display device may specifically be any product or component having display function, such as a liquid crystal display, an LCD TV, an OLED display, an OLED television, an electronic paper, a mobile phone, a tablet computer, and a digital photo frame.
Furthermore, although the description is made by example of the light emitting diode OLED, this is not a limitation of the present disclosure. The light emitting module 7 in the embodiment of the present disclosure may be another kind of light emitting element or display element.
It is to be understood that the above embodiments are merely exemplary embodiments employed for the purpose of illustrating the principles of the present disclosure, but the disclosure is not limited thereto. It will be apparent to those skilled in the art that various modifications and improvements can be made without departing from the spirit and essence of the present disclosure, and they are considered to be within the scope of the present disclosure.
Number | Date | Country | Kind |
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201610003811.6 | Jan 2016 | CN | national |
This application is a National Stage entry of PCT/CN2016/089070 filed Jul. 7, 2016, which claims the benefit and priority of Chinese Patent Application No. 201610003811.6, filed on Jan. 4, 2016, the entire contents of which are both incorporated by reference herein in their entirety as part of the present application.
Filing Document | Filing Date | Country | Kind |
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PCT/CN2016/089070 | 7/7/2016 | WO | 00 |