An LCD pixel driving circuit for field sequential display

Abstract

The application discloses an LCD pixel driving circuit for field sequential display, comprising a pre-storage unit and a driving unit, wherein the pre-storage unit comprises at least a first transistor and a pre-storage capacitor, and the driving unit comprises at least a second transistor and a pixel electrode; the first end of the first transistor is used for receiving a data signal, the control end is used for receiving a scanning signal, and the second end is coupled to the pre-storage capacitor; the other end of the pre-storage capacitor is coupled to a coupling voltage; the first end of the second transistor is coupled to the second end of the first transistor, the second end is coupled to the pixel electrode, and the control end is used for receiving a transfer signal.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of pixel driving, in particular to an LCD pixel driving circuit for field sequential display. BACKGROUND

[0002] In field sequential or color sequential display technology, the backlight needs to be turned on after all the liquid crystal deflection reaches a stable state to avoid the phenomenon of picture confusion, so how to speed up the liquid crystal driving time and increase the backlight on time is a problem to be solved in the field.

[0003] The pixel driving circuit of the traditional field sequential display technology LCD first charges each row of pixel electrodes in sequence within a frame, then waits for all the liquid crystal to deflect to a stable position, and finally turns on the backlight. If the liquid crystal is not waited to be stable, but the backlight is turned on immediately after the charging of the last row of pixels is completed, the liquid crystal corresponding to the pixels charged later will not be stable, which will cause differences in brightness and color between the upper and lower parts, and further cause picture confusion. Therefore, the time left for the backlight to turn on in the pixel driving circuit within a frame is very short, it is difficult to realize high brightness and high frequency display, and the backlight brightness specification and service life will be higher, which increases the product cost.

[0004] In summary, the traditional pixel driving circuit has the problem of being unable to balance the light output quality and light output brightness. SUMMARY

[0005] Therefore, the present application provides an LCD pixel driving circuit for field sequential display, which solves the problem of the traditional pixel driving circuit being unable to balance the light output quality and light output brightness by improving the circuit structure.

[0006] To solve the above problems, the technical scheme of the present application is to adopt an LCD pixel driving circuit for field sequential display, which comprises a pre-storage unit and a driving unit, the pre-storage unit at least comprises a first transistor and a pre-storage capacitor, and the driving unit at least comprises a second transistor and a pixel electrode, wherein the first end of the first transistor is used to receive a data signal, the control end is used to receive a scanning signal, the second end is coupled to the pre-storage capacitor, and the other end of the pre-storage capacitor is coupled to a coupling voltage; the first end of the second transistor is coupled to the second end of the first transistor, the second end is coupled to the pixel electrode, and the control end is used to receive a transfer signal.

[0007] Optionally, during the backlight-on time of the current frame, the first transistor is controlled to turn on based on the scanning signal. The first transistor outputs a pre-charge voltage based on the data signal and stores it in the pre-storage capacitor. When all pixels have completed voltage pre-storage, the coupling voltage jump is controlled based on the polarity of the data signal to achieve coupling of the pre-charge voltage on each pixel. Then, the second transistor is controlled to turn on based on the transfer signal. The second transistor outputs the voltage required by the pixel for the next frame to the pixel electrode based on the pre-charge voltage and forms a voltage difference with the common voltage to complete the deflection of the liquid crystal target angle.

[0008] Optionally, when the liquid crystal flip mode is row flip, the coupling voltage is configured such that the potential of the coupling voltage of each row of pixels is the same, and the potential of the coupling voltage of its adjacent row of pixels is opposite.

[0009] Optionally, when the liquid crystal flip mode is column flip, the coupling voltage is configured such that the potential of the coupling voltage of each column of pixels is the same, and the potential of the coupling voltage of its adjacent column of pixels is opposite.

[0010] Optionally, controlling the coupling voltage transition based on the polarity of the data signal includes: when the polarity of the data signal is positive, the coupling voltage transitions to a high potential; when the polarity of the data signal is negative, the coupling voltage transitions to a negative potential.

[0011] Optionally, the magnitude of the coupling voltage is configured to be positively correlated with the ratio of the pixel capacitance to the pre-storage capacitance.

[0012] Optionally, the pixel driving circuit is configured such that after all pixels have completed voltage pre-storage, the scan signal returns to a low level, the first transistor is turned off, the transfer signal is changed to a high level, and the second transistor is turned on based on the transfer signal.

[0013] Optionally, the pixel driving circuit further includes a reset unit, which includes at least a third transistor. The first terminal of the third transistor is coupled to the pixel electrode, the control terminal is used to receive a reset signal, and the second terminal is coupled to a coupling voltage.

[0014] Optionally, the pre-storage capacitor is configured such that, in the vertical direction, it is formed by the overlapping region of the metal region of the control terminal of the first transistor and the heavily doped conductor region of the second terminal of the first transistor.

[0015] The primary improvement of this invention lies in the LCD pixel driving circuit for field-sequence display. By setting a pre-storage unit, a pre-charge voltage is stored in the pre-storage capacitor during the backlight emission time of the current frame. This allows all pixels to synchronously read the pre-charge voltage in the next frame, significantly reducing the pixel voltage write time and relatively increasing the backlight emission time. This, in turn, increases the emission brightness while maintaining light quality, solving the problem of traditional pixel driving circuits being unable to simultaneously achieve both light quality and brightness. Furthermore, by setting a coupling voltage line to the pre-storage capacitor, this invention increases the pixel electrode potential, thereby reducing the potential of the required data signal, further improving the emission brightness and reducing the power consumption and cost of the source IC. Attached Figure Description

[0016] Figure 1 This is a simplified circuit diagram of the LCD pixel driving circuit for field-sequence display according to the present invention;

[0017] Figure 2 This is a timing diagram of the LCD pixel driving circuit for field sequence display according to the present invention. Implementation

[0018] To enable those skilled in the art to better understand the technical solutions of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0019] To make the objectives, technical solutions, and advantages of the embodiments of this application clearer, the technical solutions of the embodiments of this application will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of this application, and not all embodiments. The components of the embodiments of this application described and shown in the accompanying drawings can generally be arranged and designed in various different configurations.

[0020] Therefore, the following detailed description of the embodiments of this application provided in the accompanying drawings is not intended to limit the scope of the claimed application, but merely to illustrate selected embodiments of the application. All other embodiments obtained by those skilled in the art based on the embodiments of this application without inventive effort are within the scope of protection of this application.

[0021] The embodiments of the technical solution of this application will now be described in detail with reference to the accompanying drawings. These embodiments are only used to more clearly illustrate the technical solution of this application and are therefore merely examples, and should not be used to limit the scope of protection of this application.

[0022] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application pertains; the terminology used herein is for the purpose of describing particular embodiments only and is not intended to limit the application; the terms “comprising” and “having”, and any variations thereof, in the specification, claims, and foregoing description of the drawings are intended to cover non-exclusive inclusion.

[0023] In the description of the embodiments of this application, technical terms such as "first" and "second" are used only to distinguish different objects and should not be construed as indicating or implying relative importance or implicitly specifying the number, specific order, or primary and secondary relationship of the indicated technical features. In the description of the embodiments of this application, "multiple" means two or more, unless otherwise explicitly defined.

[0024] In this document, the term "embodiment" means that a particular feature, structure, or characteristic described in connection with an embodiment may be included in at least one embodiment of this application. The appearance of this phrase in various places throughout the specification does not necessarily refer to the same embodiment, nor is it a separate or alternative embodiment mutually exclusive with other embodiments. It will be explicitly and implicitly understood by those skilled in the art that the embodiments described herein can be combined with other embodiments.

[0025] In the description of the embodiments in this application, the term "and / or" is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this document generally indicates that the preceding and following related objects have an "or" relationship.

[0026] Specifically, such as Figure 1 As shown, an LCD pixel driving circuit for field-sequence display includes: a pre-storage unit and a driving unit. The pre-storage unit includes at least a first transistor M1 and a pre-storage capacitor Cst. The driving unit includes at least a second transistor M2 and a pixel electrode. The first terminal of the first transistor M1 (for any type of TFT, one of the two electrodes other than the gate is the source and the other is the drain; in this invention, they are referred to as the first terminal and the second terminal according to their spatial positions for distinction) is used to receive a data signal (Data signal), and the control terminal (gate) is used to receive a scan signal (Scan signal). The second terminal is coupled to the pre-storage capacitor Cst, and the other terminal of the pre-storage capacitor Cst is coupled to a coupling voltage (Vcouple). The first terminal of the second transistor M2 is coupled to one terminal of the pre-storage capacitor Cst, and the second terminal is coupled to the pixel electrode (Pixel ITO). The control terminal (gate) is used to receive a transfer signal (Tran signal).

[0027] Specifically, to facilitate understanding of the operating timing of the pixel driving circuit, as follows: Figure 2 As shown, during the backlight-on time of the current frame, the first transistor M1 is turned on based on the scanning signal. The first transistor M1 outputs a pre-charge voltage based on the data signal and stores it in the pre-storage capacitor Cst. When all pixels have completed voltage pre-storage, the coupling voltage jump is controlled based on the polarity of the data signal to achieve coupling of the pre-charge voltage on each pixel. Then, the second transistor M2 is turned on based on the transfer signal. The second transistor M2 outputs the voltage required by the pixel for the next frame to the pixel electrode based on the pre-charge voltage, and forms a voltage difference with the common voltage to complete the deflection of the liquid crystal target angle.

[0028] Furthermore, the pixel driving circuit may also include a reset unit, which includes at least a third transistor M3. The first terminal of the third transistor M3 is coupled to the pre-storage capacitor Cst, and its control terminal (gate) is used to receive a reset signal. The second terminal is coupled to a coupling voltage. The second terminal may also be directly coupled to a common electrode. When the reset signal is continuously high, the coupling voltage may be the same as the common voltage. When the reset signal is continuously high, the coupling voltage may be different from the common voltage. When the polarity of the data signal in the next frame of the pixel is positive, the coupling voltage is higher than the common voltage; when the polarity of the data signal is negative, the coupling voltage is lower than the common voltage. This reduces the voltage drop caused by charge sharing from the perspective of pixel voltage, further reducing the power consumption of the source IC.

[0029] Furthermore, when the pixel driving circuit includes a reset unit, a Reset signal is output before the transfer signal is output to reset the pixel voltage, thus preventing the pixel voltage from being affected by the previous frame.

[0030] This invention sets up a pre-storage unit so that during the backlight emission time of the current frame, a pre-charge voltage is stored using a pre-storage capacitor. This enables all pixels to synchronously read the pre-charge voltage in the next frame, greatly reducing the pixel voltage writing time and relatively increasing the backlight emission time. This increases the light emission brightness while ensuring the light emission quality, solving the problem that traditional pixel driving circuits cannot balance light emission quality and light emission brightness.

[0031] The inventors discovered in simulations that the measured pixel voltages were all lower than the pre-charge voltage. They further found the reason was that the pre-storage capacitor provides the required voltage to the first terminal of the second transistor M2, enabling the second terminal of M2 to output the voltage required for the next frame to the pixel electrode. This is done through charge sharing. Therefore, the pixel electrode potential after reading is lower than the potential of the pre-storage capacitor before reading, causing the potential required for complete liquid crystal deflection to exceed the voltage output range of the data signal. Therefore, this invention couples a voltage line to the pre-storage capacitor, increasing the potential of the pre-storage capacitor, thereby increasing the pixel electrode potential, reducing the potential of the required data signal, further improving the output brightness, and reducing the power consumption and cost of the source IC.

[0032] Meanwhile, the inventors noted that in order to prevent liquid crystal molecules from aging due to long-term unidirectional bias, the voltage polarity of the data signals of different frames needs to be reversed. In order to avoid brightness differences between different frames caused by full-screen flipping, the art usually adopts a spatial alternating positive and negative flipping method. Therefore, the present invention provides a coupling voltage switching method. Specifically, when the liquid crystal flipping mode is column flipping, the coupling voltage is configured such that the potential of the coupling voltage of each column of pixels is the same, and the potential of the coupling voltage of its adjacent column of pixels is opposite (i.e., the coupling voltage lines are divided into odd and even columns, including Vcouple-odd and Vcouple-even).

[0033] In a preferred embodiment, when the liquid crystal flip mode is row flip, the coupling voltage is configured such that the potential of the coupling voltage of each row pixel is the same, and the potential of the coupling voltage of its adjacent row pixel is opposite.

[0034] As another preferred embodiment, when the liquid crystal flip mode is region flip, the coupling voltage is configured such that the potential of the coupling voltage of the pixels in each region is the same and the potential of the coupling voltage of the pixels in its adjacent regions is opposite. The region can be defined as N rows and / or M columns, where N and M are both positive integers.

[0035] Furthermore, the polarity-controlled coupling voltage transition based on the data signal includes: when the polarity of the data signal is positive, the coupling voltage transitions to a high potential; when the polarity of the data signal is negative, the coupling voltage transitions to a negative potential. This utilizes the potential change at the other end of the pre-storage capacitor to raise the pre-charge voltage through coupling, compensating for the voltage drop loss caused by the data transfer process. The magnitude of the coupling voltage is configured to be positively correlated with the ratio of the pixel capacitance to the pre-storage capacitor Cst. It should also be further explained that, for ease of understanding the coupling voltage transition principle, in practical applications, the polarity flipping timing of each pixel in the panel is preset on the hardware IC. Therefore, the timing of the coupling voltage transition corresponding to the polarity flipping timing is also programmed and fixed on the hardware IC, thus realizing the aforementioned polarity-controlled coupling voltage transition based on the data signal.

[0036] Furthermore, the pixel driving circuit is configured such that after all pixels have completed voltage pre-storage, the scanning signal returns to a low level, the first transistor M1 is turned off, the transfer signal is changed to a high level, and the second transistor M2 is turned on based on the transfer signal.

[0037] It should be noted that in some types of TFTs, the pixel driving circuit can be configured such that after all pixels have completed voltage pre-storage, the scan signal returns to a high level, the first transistor M1 is turned off, the transfer signal is changed to a low level, and the second transistor M2 is turned on based on the transfer signal.

[0038] Furthermore, the pre-storage capacitor Cst is configured such that, in the vertical direction, it is formed by the overlapping region of the metal region of the control terminal of the first transistor M1 and the heavily doped conductor region of the second terminal of the first transistor M1.

[0039] The above describes an LCD pixel driving circuit for field-sequence display provided by embodiments of the present invention. The various embodiments are described in a progressive manner, with each embodiment focusing on its differences from other embodiments. Similar or identical parts between embodiments can be referred to interchangeably. For the apparatus disclosed in the embodiments, since it corresponds to the method disclosed in the embodiments, the description is relatively simple; relevant parts can be referred to in the method section. It should be noted that those skilled in the art can make several improvements and modifications to the present invention without departing from the principles of the invention, and these improvements and modifications also fall within the protection scope of the claims of the present invention.

[0040] Those skilled in the art will further recognize that the units and algorithm steps of the various examples described in connection with the embodiments disclosed herein can be implemented in electronic hardware, computer software, or a combination of both. To clearly illustrate the interchangeability of hardware and software, the components and steps of the various examples have been generally described in terms of functionality in the foregoing description. Whether these functions are implemented in hardware or software depends on the specific application and design constraints of the technical solution. Those skilled in the art can implement the described functions using different methods for each specific application, but such implementation should not be considered beyond the scope of the invention. The steps of the methods or algorithms described in connection with the embodiments disclosed herein can be implemented directly in hardware, software modules executed by a processor, or a combination of both. Software modules can be located in random access memory (RAM), main memory, read-only memory (ROM), electrically programmable ROM, electrically erasable programmable ROM, registers, hard disks, removable disks, CD-ROMs, or any other form of storage medium known in the art.

Claims

1. A pixel driving circuit for LCD for field-sequence display, characterized in that, include: The system includes a pre-storage unit and a driving unit. The pre-storage unit includes at least a first transistor (M1) and a pre-storage capacitor (Cst), and the driving unit includes at least a second transistor (M2) and a pixel electrode. The first transistor (M1) has a first terminal for receiving a data signal, a control terminal for receiving a scan signal, and a second terminal coupled to the pre-storage capacitor (Cst). The other terminal of the pre-storage capacitor (Cst) is coupled to a coupling voltage. The second transistor (M2) has a first terminal coupled to the second terminal of the first transistor (M1), a second terminal coupled to a pixel electrode, and a control terminal for receiving a transfer signal. When all pixels have completed voltage pre-storage, the polarity of the data signal controls the coupling voltage transition to achieve coupling of the pre-charge voltage on each pixel.

2. The LCD pixel driving circuit according to claim 1, characterized in that, During the backlight-on time of the current frame, the first transistor (M1) is turned on based on the scanning signal. The first transistor (M1) outputs a pre-charge voltage based on the data signal and stores it in the pre-storage capacitor (Cst). After coupling the pre-charge voltage on each pixel, the second transistor (M2) is turned on based on the transfer signal. The second transistor (M2) outputs the voltage required by the pixel for the next frame to the pixel electrode based on the pre-charge voltage, and forms a voltage difference with the common voltage to complete the deflection of the liquid crystal target angle.

3. The LCD pixel driving circuit according to claim 1, characterized in that, When the liquid crystal flip mode is row flip, the coupling voltage is configured such that the potential of the coupling voltage of each row of pixels is the same, and the potential of the coupling voltage of its adjacent row of pixels is opposite.

4. The LCD pixel driving circuit according to claim 1, characterized in that, When the liquid crystal flip mode is column flip, the coupling voltage is configured such that the potential of the coupling voltage of each column of pixels is the same, and the potential of the coupling voltage of its adjacent column of pixels is opposite.

5. The LCD pixel driving circuit according to claim 2, characterized in that, The polarity-controlled coupling voltage transition based on the data signal includes: When the polarity of the data signal is positive, the coupling voltage jumps to a high potential; When the polarity of the data signal is negative, the coupling voltage jumps to a negative potential.

6. The LCD pixel driving circuit according to claim 5, characterized in that, The magnitude of the coupling voltage is configured to be positively correlated with the ratio of the pixel capacitance to the pre-storage capacitance (Cst).

7. The LCD pixel driving circuit according to claim 2, characterized in that, The pixel driving circuit is configured such that after all pixels have completed voltage pre-storage, the scan signal returns to a low level, the first transistor (M1) is turned off, the transfer signal is changed to a high level, and the second transistor (M2) is turned on based on the transfer signal.

8. The LCD pixel driving circuit according to claim 1, characterized in that, The pixel driving circuit further includes a reset unit, which includes at least a third transistor (M3). The first terminal of the third transistor (M3) is coupled to the pixel electrode, the control terminal is used to receive a reset signal, and the second terminal is coupled to a coupling voltage.

9. The LCD pixel driving circuit according to claim 1, characterized in that, The pre-storage capacitor (Cst) is configured such that, in the vertical direction, it is formed by the overlapping region of the metal region of the control terminal of the first transistor (M1) and the heavily doped conductor region of the second terminal of the first transistor (M1).

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