This application claims priority to Chinese Patent Application No. 201711329200.1, filed on Dec. 13, 2017 and titled “PIXEL CIRCUIT AND DISPLAY DEVICE”, the disclosure of which is hereby incorporated by reference in its entirety.
The present disclosure relates to a pixel circuit and a display device.
A traditional active-matrix display device, either in a dynamic-picture display mode or a static-picture display mode, writes data into a pixel through a driver. In this case, during display of a static picture, the driver repeatedly writes the same data into the pixel. In view of this, a memory may be disposed in each pixel, such that during display of the static picture, data memorized by the memories may be written into the pixels to replace of driving by the driver and reduce power loss. To meet the application demands of high-PPI (Pixels Per Inch), low-power-consumption and low-cost of the display device, a latch circuit formed by transistors is disposed usually within the pixel to realize the function of the memory.
There is provided a pixel circuit and a display device in the present disclosure.
In an aspect, there is provided a pixel circuit in the present disclosure, comprising:
a first inverter circuit having an input terminal connected to a first node and an output terminal connected to a second node;
a second inverter circuit having an input terminal connected to the second node and an output terminal connected to a third node;
a switching circuit connected respectively to the first node and the third node and configured to disconnect a connection between the first node and the third node when a first scanning signal is at an active level; and
a control circuit connected to at least one of the first node and the second node and configured to control a level of at least one of the first node and the second node according to a level control signal when the first scanning signal is at an active level.
In a possible implementation, the pixel circuit further comprises:
a data writing circuit, connected to at least one of the first node and the second node, and configured to determine a data writing mode according to the level of at least one of the first node and the second node and to write a display data signal according to a currently determined data writing mode when the second scanning signal is at an active level.
In a possible implementation, the control circuit and the data writing circuit are both connected to a data line, and the level control signal and the display data signal are provided by the data line.
In a possible implementation, the data writing circuit comprises:
a gating sub-circuit connected to at least one of the first node and the second node and configured to provide a display data signal of one of a to-be-displayed picture and a normally-black picture for a fourth node according to the level of at least one of the first node and the second node; and
a scanning sub-circuit connected to the fourth node and configured to provide the display data signal at the fourth node for a pixel electrode when the second scanning signal is at an active level.
In a possible implementation, the scanning sub-circuit comprises a first transistor,
a gate of the first transistor is connected to the second scanning signal, one of a source and a drain of the first transistor is connected to the fourth node, and the other one is connected to the pixel electrode.
In a possible implementation, the gating sub-circuit comprises a second transistor and a third transistor;
a gate of the second transistor is connected to the second node, one of a source and a drain of the second transistor is connected to the display data signal of the to-be-displayed picture, and the other one is connected to the fourth node; and
a gate of the third transistor is connected to the first node, one of a source and a drain of the third transistor is connected to the display data signal of the normally-black picture, and the other one is connected to the fourth node.
In a possible implementation, the switching circuit and the control circuit are both connected to a first scanning line which provides the first scanning signal.
In a possible implementation, the switching circuit comprises a fourth transistor;
a gate of the fourth transistor is connected to the first scanning signal, one of a source and a drain of the fourth transistor is connected to the second node, and the other one is connected to the third node;
wherein the active level of the first scanning signal is within a range of a gate voltage that causes the fourth transistor to operate in a cut-off region.
In a possible implementation, the control circuit comprises a fifth transistor;
a gate of the fifth transistor is connected to the first scanning signal, one of a source and a drain of the fifth transistor is connected to the level control signal, and the other one is connected to the first node;
wherein the active level of the first scanning signal is within a range of a gate voltage that causes the fifth transistor to operate beyond a cut-off region.
In a possible implementation, the first inverter circuit comprises a sixth transistor and a seventh transistor, and the second inverter circuit comprises an eighth transistor and a ninth transistor;
a gate of the sixth transistor is connected to the first node, one of a source and a drain of the sixth transistor is connected to the second node, and the other one is connected to a first level voltage line;
a gate of the seventh transistor is connected to the first node, one of a source and a drain of the seventh transistor is connected to a second level voltage line, and the other one is connected to the second node;
a gate of the eighth transistor is connected to the second node, one of a source and a drain of the eighth transistor is connected to the third node, and the other one is connected to the first level voltage line; and
a gate of the ninth transistor is connected to the second node, one of a source and a drain of the ninth transistor is connected to the second level voltage line, and the other one is connected to the third node;
wherein a level on the first level voltage line is within a range of a gate voltage that causes the sixth transistor and the eighth transistor to operate in a cut-off region, a level on the second level voltage line is within a range of a gate voltage that causes the seventh transistor and the ninth transistor to operate in a cut-off region, and the level on the first level voltage line is opposite to the level on the second level voltage line.
In another aspect, there is provided a display device, comprising a plurality of pixel circuits, wherein each pixel circuit comprises:
a first inverter circuit having an input terminal connected to a first node and an output terminal connected to a second node;
a second inverter circuit having an input terminal connected to the second node and an output terminal connected to a third node;
a switching circuit connected respectively to the first node and the third node and configured to disconnect a connection between the first node and the third node when a first scanning signal is at an active level; and
a control circuit connected to at least one of the first node and the second node and configured to control a level of at least one of the first node and the second node according to a level control signal when the first scanning signal is at an active level.
In a possible implementation, the pixel circuit further comprises:
a data writing circuit connected to at least one of the first node and the second node and configured to determine a data writing mode according to the level of at least one of the first node and the second node and to write a display data signal according to a currently determined data writing mode when the second scanning signal is at an active level.
In a possible implementation, the control circuit and the data writing circuit are both connected to a data line, and the level control signal and the display data signal are provided by the data line.
In a possible implementation, the data writing circuit comprises:
a gating sub-circuit connected to at least one of the first node and the second node and configured to provide a display data signal of one of a to-be-displayed picture and a normally-black picture for a fourth node according to the level of at least one of the first node and the second node; and
a scanning sub-circuit connected to the fourth node and configured to provide the display data signal at the fourth node for a pixel electrode when the second scanning signal is at an active level.
In a possible implementation, the scanning sub-circuit comprises a first transistor,
a gate of the first transistor is connected to the second scanning signal, one of a source and a drain of the first transistor is connected to the fourth node, and the other one is connected to the pixel electrode.
In a possible implementation, the gating sub-circuit comprises a second transistor and a third transistor;
a gate of the second transistor is connected to the second node, one of a source and a drain of the second transistor is connected to the display data signal of the to-be-displayed picture, and the other one is connected to the fourth node; and
a gate of the third transistor is connected to the first node, one of a source and a drain of the third transistor is connected to the display data signal of the normally-black picture, and the other one is connected to the fourth node.
In a possible implementation, the switching circuit and the control circuit are both connected to a first scanning line which provides the first scanning signal.
In a possible implementation, the switching circuit comprises a fourth transistor;
a gate of the fourth transistor is connected to the first scanning signal, one of a source and a drain of the fourth transistor is connected to the second node, and the other one is connected to the third node;
wherein the active level of the first scanning signal is within a range of a gate voltage that causes the fourth transistor to operate in a cut-off region.
In a possible implementation, the control circuit comprises a fifth transistor;
a gate of the fifth transistor is connected to the first scanning signal, one of a source and a drain of the fifth transistor is connected to the level control signal, and the other one is connected to the first node;
wherein the active level of the first scanning signal is within a range of a gate voltage that causes the fifth transistor to operate beyond a cut-off region.
In a possible implementation, the first inverter circuit comprises a sixth transistor and a seventh transistor, and the second inverter circuit comprises an eighth transistor and a ninth transistor;
a gate of the sixth transistor is connected to the first node, one of a source and a drain of the sixth transistor is connected to the second node, and the other one is connected to a first level voltage line;
a gate of the seventh transistor is connected to the first node, one of a source and a drain of the seventh transistor is connected to a second level voltage line, and the other one is connected to the second node;
a gate of the eighth transistor is connected to the second node, one of a source and a drain of the eighth transistor is connected to the third node, and the other one is connected to the first level voltage line; and
a gate of the ninth transistor is connected to the second node, one of a source and a drain of the ninth transistor is connected to the second level voltage line, and the other one is connected to the third node;
wherein a level on the first level voltage line is within a range of a gate voltage that causes the sixth transistor and the eighth transistor to operate in a cut-off region, a level on the second level voltage line is within a range of a gate voltage that causes the seventh transistor and the ninth transistor to operate in a cut-off region, and the level on the first level voltage line is opposite to the level on the second level voltage line.
To make the principles and advantages of the present disclosure clearer, the embodiments of the present disclosure will be described below in detail in conjunction with the accompanying drawings. It is obvious that the described embodiments are part rather than all of the embodiments of the present disclosure. All other embodiments derived by those of ordinary skill in the art based on the embodiments of the present disclosure without creative effort are within the protection scope of the present disclosure. Unless otherwise defined, technical terms or scientific terms used in the present disclosure shall be of ordinary meaning as understood by those of ordinary skill in the art to which the present disclosure pertains. The term “first” or “second” or a similar term used in the present disclosure does not denote any order, quantity, or importance, but is merely used to distinguish different components. The term “comprising” or a similar term means that elements or items which appear before the term include the elements or items listed after the term and their equivalents, and do not exclude other elements or items. The term “connection” or “connected to” or a similar term is not limited to a physical or mechanical connection but may include an electrical connection that is direct or indirect.
It can be noted that a traditional active-matrix display device, no matter in a dynamic-picture or static-picture display mode, writes data into a pixel through a driver. In this case, during display of a static picture, the driver repeatedly writes the same data into the pixel. In view of this, a memory may be disposed in each pixel, such that during display of the static picture, data memorized by the memories may be written into the pixels to replace of driving by the driver and reduce power loss. To meet the application demands of high-PPI (Pixels Per Inch), low-power-consumption and low-cost of the display device, a latch circuit formed by transistors is disposed within the pixel to realize the function of the memory. However, in practice, such a latch may easily cause an output signal abnormality during the reversing of an output level, leading to an unstable display state of a pixel circuit and other abnormities such as noise and a blurred screen, which seriously affects the performance of a display product.
It should be noted that an active level and an inactive level herein refer to two different pre-configured voltage ranges (both based on a common terminal voltage) in terms of a specific circuit node respectively. In an example, active levels of all circuit nodes are high levels in a digital circuit. In another example, active levels of all circuit nodes are low levels in a digital circuit. In still another example, active levels at the first node Q1 and the third node Q3 are high levels, and an active level of the first scanning signal G1 is a low level. Of course, the setting of the active level and the inactive level may not be limited to the above-mentioned examples.
It should be understood that the first inverter circuit 11 and the second inverter circuit 12 are both a circuit structure that can invert the level at the output terminal from the level at the input terminal. For example, a low level is output at the output terminal when the input terminal is at a high level, and a high level is output at the output terminal when the input terminal is at a low level. It should be noted that the inverting function of the first inverter circuit 11 and/or the second inverter circuit 12 may be unidirectional (the level at the output terminal may not affect the level at the input terminal, for example, the input terminal may be kept at a high level when the output terminal is at a high level) or bidirectional (the level at the output terminal and the level at the input terminal may affect each other, for example, the input terminal may also be at a low level when the output terminal is at a high level). When the bidirectional inverting function is provided, the input terminal and the output terminal are symmetrical, and a circuit function thereof is kept unchanged when they are exchanged. Besides, the first inverter circuit 11 and/or the second inverter circuit 12 may be provided with an enable terminal that controls the inverting function to be effective or not. The input terminal and the output terminal may be, for example, in a high-impedance state or an open-circuit state when the inverting function is not effective.
It should be also understood that the first inverter circuit 11 and the second inverter circuit 12 in an operating state may form a latch structure when the first node Q1 and the third node Q3 are electrically connected to each other. That is, before the level of the first node Q1 or the level of the second node Q2 is changed by an external signal, the first node Q1 and the second node Q2 can stably maintain the levels inverted from each other. The levels of the first node Q1 and the second node Q2 are kept in the latch structure as stored data and may be used for controlling or triggering related operations.
In an exemplary implementation of the embodiments of the present disclosure, the control circuit 14 reverses the low level at the first node Q1 into the high level when the first scanning signal G1 is at an active level and the level control signal R1 is at the high level, such that the second node Q2 may be set to be at the low level under the action of the first inverter circuit 11, and the third node Q3 may be set to be at the high level under the action of the second inverter circuit 12. During this period, the switching circuit 13 disconnects a connection between the first node Q1 and the third node Q3, thereby completing the reversing of the latch level.
In a comparative example, the first node Q1 and the third node Q3 are always electrically connected. In a process of pulling-up a potential at the first node Q1 to a high level (the level at the first node Q1 is shifted into a high level) by the control circuit 14, the potentials at the third node Q3 and the first node Q1 may be pulled-down under the inverting function of the second inverter circuit 12. At this time, the pull-up function of the control circuit 14 may compete with the pull-down function of the second inverter circuit 12. For example, when the control circuit 14 provides a level shifting current that flows to the first node Q1, the second inverter circuit 12 may provide a competition current that flows from the first node Q1 to the low level. Although the pull-up function of the control circuit 14 may gain a competitive advantage by setting device parameters (for example, the level shifting current is higher than the competition current), a failure of level switching of the control circuit 14 is easily caused due to the level switching limited time, the device loss, or the device characteristic drift, etc., which is manifested as an abnormal output (the latch level cannot be flipped normally) of the latch structure, and the operations controlled or triggered by its output may be disordered, resulting in noise, dead pixels, a blurred screen and other abnormities.
In the embodiments of the present disclosure, it can be seen from comparison that the switching circuit 13 may disconnect a connection between the first inverter circuit 11 and the second inverter circuit 12 when the control circuit 14 shifts the level of the first node Q1, such that the control circuit 14 and the second inverter circuit 12 may not compete with each other when the level of the first node Q1 is shifted, thereby avoiding a consequent signal abnormity, enhancing the working stability of the pixel circuit, and contributing to improving the performance of the display product.
It should be understood that a control object of the control circuit 14 may not be limited to the first node Q1, and a control mode may not be limited to level shifting of a single node, it may also be that, for example, the second node Q2 is pulled-down while the first node Q1 is pulled-up, which is not limited thereto. In an example, the control circuit 14 is both connected to the first node and the second node, and is configured to control the levels at the first node and the second node in accordance with the level control signal when the first scanning signal is at an active level. It may also be understood that there are not limited in the embodiments of the present disclosure that how is the latch applied for the functional implementation of the pixel circuit, as well as the type of the applied pixel circuit. The working stability of any pixel circuit including the latch structure may be improved in the manner of the embodiments of the present disclosure. Thus, the display performance is improved.
The scanning sub-circuit 15b comprises a first transistor T1. A gate of the first transistor T1 is connected to a second scanning signal G2. One of a source and a drain of the first transistor T1 is connected to a fourth node P4, and the other one is connected to a pixel electrode. It should be noted that connection relationship between the source and the drain of the first transistor may be set in accordance with different specific types of the transistors, so as to match the direction of current that flows through the transistor. When the transistor adopts a structure that the source and the drain are symmetrical, the source and the drain may be regarded as two electrodes that are not specially distinguished. It also needs to be noted that
In
It should be understood that the gating sub-circuit 15a may determine whether the fourth node Q4 is connected to the display data signal D1 of the to-be-displayed picture or the display data signal D2 of the normally-black picture in accordance with which one of the first node Q1 and the second node Q2 is at the high level. The scanning sub-circuit 15b may provide the display data signal at the fourth node P4 for the pixel electrode when the active level of the second scanning signal G2 arrives. Thus, the data writing mode of the pixel may be controlled by the stable latch level. An MIP (Memory In Pixel) pixel structure having a latch structure therein can be realized.
It should be also understood that a combination of the display data signal D1 of the to-be-displayed picture and the display data signal D2 of the normally-black picture may realize the selection of the data writing mode between the normally-black picture and the to-be-displayed picture. In other implementations, selection of the data writing mode between other pictures may also be realized by other combinations. For example, the black and white display between a normally-black picture and a normally-white picture can be realized through a combination of a display data signal of the normally-white picture and a display data signal of the normally-black picture. Alternatively, the selection of the data writing mode between the normally-white picture and the to-be-displayed picture can be realized by a combination of the display data signal of the normally-white picture and the display data signal of the to-be-displayed picture, and the like. In an example, the display data signal D1 and the display data signal D2 are respectively a signal that is consistent with a common voltage signal and a signal that is inverted from the common voltage signal. In another example, the display data signal D1 and the display data signal D2 are respectively a signal that is consistent with the common voltage signal and a display data signal of a color to-be-displayed picture, so as to realize the color display with a maximum display color number of 8,262 K and even 16.7 M. Moreover, the data writing circuit may not only utilize the first node and the second node to control the selection of the data writing mode, but also utilize the first node or the second node for replacement. For example, the second transistor T2 may be replaced by a P-type transistor, and a gate thereof is changed to be connected to the first node Q1, or, the first transistor T1 is replaced by the P-type transistor, and a gate thereof is changed to be connected to the second node Q2, such that the functions of the gating sub-circuit 15a and the data writing circuit are kept unchanged. Of course, the optional data writing mode may not be limited to the above forms. The ways in which the data writing circuit utilizes the first node and/or the second node to determine the data writing mode may also not be limited to the above-mentioned ways.
In
In
It should be understood that the control circuit and the data writing circuit are both connected to the data line (for providing the display data signal D1), and both of the level control signal and the display data signal are provided by the data line, such that the level control signal and the display data signal may share the same line, which contributes to reducing the number of signal lines in a display region, simplifies the layout of traces in the display region, and increases the PPI. It also should be understood that the switching circuit and the control circuit are both connected to a first scanning line G1 (for providing the first scanning signal), and the design between the fourth transistor T4 and the fifth transistor T5, for example, can be utilized to avoid using more than one signal line, which contributes to reducing the number of the signal lines in the display region, simplifying the layout of traces in the display region and increasing the PPI.
n
It can be seen that the first inverter circuit 11 and the second inverter circuit 12 in an operating state may form the latch structure when the first node Q1 and the third node Q3 are electrically connected to each other. That is, before the level of the first node Q1 or the second node Q2 is changed by an external signal, the first node Q1 and the second node Q2 can stably maintain the levels inverted from each other. However, as the switching circuit 13 may disconnect a connection between the first inverter circuit 11 and the second inverter circuit 12 when the control circuit 14 shifts the level of the first node Q1, the control circuit 14 and the second inverter circuit 12 may not compete with each other in a level shifting process of the first node Q1. Thus, in the embodiments of the present disclosure, a consequent signal abnormity can be avoided, the working stability of the pixel circuit can be enhanced, and the performance of the display product can be improved.
It should be understood that the implementation illustrated by
Based on the same inventive concept, an embodiment of the present disclosure provides a display device which comprises any one of the above mentioned pixel circuits. The display device in the embodiments of the present disclosure may be a display panel, a mobile phone, a tablet computer, a television, a display, a laptop, a digital photo frame, a navigator or any other products or parts that have a display functions. As an example,
The foregoing descriptions are only exemplary embodiments of the present disclosure, and are not intended to limit the present disclosure. Within the spirit and principles of the disclosure, any modifications, equivalent substitutions, improvements, etc., are within the protection scope of the appended claims of the present disclosure.
Number | Date | Country | Kind |
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201711329200.1 | Dec 2017 | CN | national |