Common voltage driving circuit and liquid crystal display device

Abstract

The invention discloses a common voltage driving circuit and a liquid crystal display device, the common voltage driving circuit comprises a voltage amplification module and an output control module, the voltage amplification module is used for amplifying an input voltage signal and outputting a common voltage in a first state; the output control module is connected with the output end of the voltage amplification module and used for converting the common voltage in the first state into the common voltage in the second state when picture refreshing is finished. According to the common voltage driving circuit provided by the invention, the required common voltage can be output according to the working state of the display device, the manufacturing cost can be reduced, and the product competitiveness can be improved.

Description

Technical Field

[0001] The present application relates to the field of display technology, and in particular to a common voltage driving circuit and a liquid crystal display device. Background Art

[0002] The driving system of a liquid crystal display usually includes a common voltage driving module, through which a positive or negative common voltage (VCOM) is applied to the liquid crystal display panel, so that a certain voltage difference is formed between VCOM and the source voltage (Source) of the pixel unit, thereby controlling the rotation angle of the liquid crystal molecules and driving the liquid crystal display panel to display color.

[0003] like Figure 1 As shown, the common voltage driving module in the prior art generally uses a microcontroller unit (MCU) to control a digital-to-analog converter (DAC), and outputs the VCOM required for the operation of the liquid crystal display panel through an operational amplifier (OPA), and when the liquid crystal display panel finishes refreshing the screen, the VCOM is converted to a ground voltage through the DAC to reset the liquid crystal molecules. Since the DAC is a separate hardware component, it requires additional circuit design and material costs, which will increase the manufacturing cost of the display device and affect the competitiveness of the product in the market. Therefore, it is necessary to provide an improved technical solution to overcome the above technical problems existing in the prior art. Summary of the invention

[0004] The purpose of the present application is to provide a common voltage driving circuit and a liquid crystal display device, which can output the required common voltage according to the working state of the display device, reduce the manufacturing cost and improve the product competitiveness.

[0005] To achieve the above objectives: In a first aspect, an embodiment of the present application provides a common voltage driving circuit, including a voltage amplification module and an output control module; The voltage amplification module is used to amplify the input voltage signal and output a common voltage in a first state; The output control module is connected to the output end of the voltage amplification module, and is used to convert the common voltage in the first state into the common voltage in the second state when the picture refresh ends.

[0006] Optionally, the common voltage in the first state is a square wave signal including a first level state and a second level state, and the common voltage in the second state is a ground voltage.

[0007] Optionally, the output control module includes a first switch unit and a second switch unit; The control ends of the first switch unit and the second switch unit are connected to a timing control signal; When the first switch unit and the second switch unit are in the on state under the control of the timing control signal, they are used to convert the common voltage in the first level state or the common voltage in the second level state output by the voltage amplification module to the ground voltage.

[0008] Optionally, the first switch unit includes a first switch tube, a control end of the first switch tube serves as the control end of the first switch unit, a first passage end of the first switch tube is connected to the second switch unit, and a second passage end of the first switch tube is connected to the output end of the voltage amplification module.

[0009] Optionally, the second switch unit includes a second switch tube, a third switch tube and a fourth switch tube; The control end of the third switch tube is connected in parallel with the control end of the fourth switch tube, serving as the control end of the second switch unit; the first path end of the third switch tube is connected to the first power supply voltage; the second path end of the third switch tube is connected in parallel with the second path end of the fourth switch tube, and connected to the control end of the second switch tube; the first path end of the fourth switch tube is connected to the second power supply voltage; The first passage end of the second switch tube is grounded, and the second passage end of the second switch tube is connected to the first passage end of the first switch tube.

[0010] Optionally, the first switch tube and the second switch tube have different conductivity types, and the third switch tube and the fourth switch tube have different conductivity types.

[0011] Optionally, the first switch tube, the second switch tube, the third switch tube and the fourth switch tube are transistors or field effect tubes.

[0012] Optionally, the voltage amplification module includes an operational amplifier, a first input terminal of the operational amplifier is connected to the input voltage signal, a second input terminal of the operational amplifier is connected to a bias voltage, and an output terminal of the operational amplifier serves as an output terminal of the voltage amplification module.

[0013] Optionally, when refreshing the picture ends, a low-level control signal is connected to the enable terminal of the operational amplifier to put the operational amplifier into a non-operating mode.

[0014] In a second aspect, an embodiment of the present application provides a liquid crystal display device, comprising the common voltage driving circuit as described above.

[0015] The common voltage driving circuit and liquid crystal display device provided in the embodiment of the present application amplify the input voltage signal through the voltage amplification module and output the common voltage of the first state; the output control module is connected to the output end of the voltage amplification module, and when the screen is refreshed, the common voltage of the first state is converted into the common voltage of the second state. In this way, the required common voltage can be output according to the working state of the display device, reducing the manufacturing cost and improving the product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the drawings required for use in the embodiments will be briefly introduced below. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other related drawings can be obtained based on these drawings without paying creative work.

[0017] Figure 1 It is a structural schematic diagram of a common voltage driving module in the prior art.

[0018] Figure 2 A schematic diagram of the structure of a common voltage driving circuit provided in an embodiment of the present application.

[0019] Figure 3 A circuit diagram of a common voltage driving circuit provided in an embodiment of the present application.

[0020] Figure 4 This is a working timing diagram of the common voltage driving circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0021] Exemplary embodiments will be described in detail herein, examples of which are shown in the accompanying drawings. When the following description refers to the drawings, the same numbers in different drawings represent the same or similar elements unless otherwise indicated. The implementations described in the following exemplary embodiments do not represent all implementations consistent with the present application. Instead, they are merely examples of devices and methods consistent with some aspects of the present application as detailed in the appended claims.

[0022] It should be noted that, in this article, the terms "include", "comprises" or any other variants thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device including a series of elements includes not only those elements, but also includes other elements not explicitly listed, or also includes elements inherent to such process, method, article or device. In the absence of further restrictions, an element defined by the sentence "includes a ..." does not exclude the existence of other identical elements in the process, method, article or device including the element. In addition, components, features, and elements with the same name in different embodiments of the present application may have the same meaning or different meanings, and their specific meanings need to be determined by their explanation in the specific embodiment or further combined with the context of the specific embodiment.

[0023] It should be understood that, although the terms first, second, third, etc. may be used to describe various information in this article, these information should not be limited to these terms. These terms are only used to distinguish the same type of information from each other. For example, without departing from the scope of this article, the first information may also be referred to as the second information, and similarly, the second information may also be referred to as the first information. Depending on the context, the word "if" as used herein can be interpreted as "at the time of..." or "when..." or "in response to determination". Furthermore, as used in this article, the singular forms "one", "one" and "the" are intended to also include plural forms, unless there is an opposite indication in the context. It should be further understood that the terms "comprising", "including" indicate that there are described features, steps, operations, elements, components, projects, kinds, and / or groups, but do not exclude the existence, occurrence or addition of one or more other features, steps, operations, elements, components, projects, kinds, and / or groups. The terms "or" and "and / or" used herein are interpreted as inclusive, or mean any one or any combination. Thus, “A, B, or C” or “A, B and / or C” means “any of the following: A; B; C; A and B; A and C; B and C; A, B, and C.” An exception to this definition will occur only when a combination of elements, functions, steps, or operations are inherently mutually exclusive in some manner.

[0024] It should be understood that the specific embodiments described herein are only used to explain the present application and are not used to limit the present application.

[0025] In the subsequent description, the suffixes such as "module", "component" or "unit" used to represent elements are only used to facilitate the description of the present application, and have no specific meanings. Therefore, "module", "component" or "unit" can be used in a mixed manner.

[0026] Figure 2 A schematic diagram of the structure of a common voltage driving circuit provided in an embodiment of the present application; Figure 2 As shown, the common voltage driving circuit provided in the embodiment of the present application includes a voltage amplification module 110 and an output control module 120 .

[0027] Among them, the voltage amplification module 110 is used to amplify the input voltage signal and output a common voltage in the first state; the output control module 120 is connected to the output end of the voltage amplification module 110 and is used to convert the common voltage in the first state into a common voltage in the second state when the screen refresh ends.

[0028] In one embodiment of the present application, the common voltage of the first state is a square wave signal including a first level state and a second level state, and the common voltage of the second state is a ground voltage. The first level state may be a positive voltage, and the second level state may be a negative voltage. In other embodiments, the first level state and the second level state may also be both positive voltages or both negative voltages.

[0029] Specifically, when the liquid crystal display device powers on the common electrode, the MCU inputs a preset voltage signal, such as a pulse width modulation (PWM) signal, to the voltage amplifier module 110, and the voltage amplifier module 110 amplifies the input PWM signal to form a square wave signal with a positive voltage state and a negative voltage state. When the liquid crystal display device is refreshing the display screen, the common voltage driving circuit normally outputs a common voltage in the form of a square wave signal; after the liquid crystal display device finishes refreshing the screen, the output control module 120 converts the common voltage output from the output end of the voltage amplifier module 110 into a ground voltage, so that the liquid crystal molecules can be quickly reset. In this way, the common voltage driving circuit can be controlled to output common voltages of different states according to the working state of the liquid crystal display device.

[0030] Figure 3 A circuit diagram of a common voltage driving circuit provided in an embodiment of the present application; Figure 3 As shown, the output control module 120 in this embodiment includes a first switch unit 121 and a second switch unit 122; the control ends of the first switch unit 121 and the second switch unit 122 are connected to the timing control signal MCU CTRL; when the first switch unit 121 and the second switch unit 122 are in the on state under the control of the timing control signal MCU CTRL, they are used to convert the common voltage of the first level state or the second level state output by the voltage amplification module 110 to the ground voltage.

[0031] Specifically, the first switch unit 121 includes a first switch tube M1, the control end of the first switch tube M1 serves as the control end of the first switch unit 121, the first channel end of the first switch tube M1 is connected to the second switch unit 122, and the second channel end of the first switch tube M1 is connected to the output end of the voltage amplification module 110. The second switch unit 122 includes a second switch tube M2, a third switch tube M3 and a fourth switch tube M4; the control end of the third switch tube M3 is connected in parallel with the control end of the fourth switch tube M4, serving as the control end of the second switch unit 122; the first channel end of the third switch tube M3 is connected to the first power supply voltage halfVGH; the second channel end of the third switch tube M3 is connected in parallel with the second channel end of the fourth switch tube M4, and connected to the control end of the second switch tube M2; the first channel end of the fourth switch tube M4 is connected to the second power supply voltage VGL; the first channel end of the second switch tube M2 is grounded, and the second channel end of the second switch tube M2 is connected to the first channel end of the first switch tube M1.

[0032] In this embodiment, the first switch tube M1 and the second switch tube M2 have different conductivity types, and the third switch tube M3 and the fourth switch tube M4 have different conductivity types. The first switch tube M1, the second switch tube M2, the third switch tube M3 and the fourth switch tube M4 can be transistors or field effect tubes.

[0033] Specifically, Figure 3In the embodiment, the first switch tube M1, the second switch tube M2, the third switch tube M3 and the fourth switch tube M4 are metal-oxide-semiconductor field-effect transistors (MOSFETs) as an example. The first switch tube M1 and the fourth switch tube M4 are N-type MOSFETs, the control ends of the first switch tube M1 and the fourth switch tube M4 are the gates of the N-type MOSFETs, the first channel ends of the first switch tube M1 and the fourth switch tube M4 are the sources of the N-type MOSFETs, and the second channel ends of the first switch tube M1 and the fourth switch tube M4 are the drains of the N-type MOSFETs; the second switch tube M2 and the third switch tube M3 are P-type MOSFETs, the control ends of the second switch tube M2 and the third switch tube M3 are the gates of the P-type MOSFETs, the first channel ends of the second switch tube M2 and the third switch tube M3 are the sources of the P-type MOSFETs, and the second channel ends of the second switch tube M2 and the third switch tube M3 are the drains of the P-type MOSFETs. The first power supply voltage half VGH connected to the first channel end of the third switch tube M3 is a positive voltage, and the second power supply voltage VGL connected to the first channel end of the fourth switch tube M4 is a negative voltage. In other embodiments, after slightly changing the circuit connection and the timing control signal, the first switch tube M1 and the fourth switch tube M4 can also be set as P-type MOSFETs, and the second switch tube M2 and the third switch tube M3 can be set as N-type MOSFETs.

[0034] Figure 4 The working timing diagram of the common voltage driving circuit provided in the embodiment of the present application; Figure 4 right Figure 3 The working process of the common voltage driving circuit shown in the example is described in detail.

[0035] During the process of refreshing the screen of the liquid crystal display device, the timing control signal MCU CTRL connected to the control end of the first switch unit 121 and the second switch unit 122 is a low-level signal, which controls the third switch tube M3 to be in the on state, and the first switch tube M1 and the fourth switch tube M4 to be in the off state. Since the control end of the second switch tube M2 is connected to the first power supply voltage half VGH in the positive voltage state through the turned-on third switch tube M3, the second switch tube M2 is also in the off state. Therefore, the output control module 120 works in an invalid state during the process of refreshing the screen, and the common voltage driving circuit can normally output the common voltage in the form of a square wave signal.

[0036] When the liquid crystal display device finishes refreshing the screen, the timing control signal MCU CTRL connected to the control end of the first switch unit 121 and the second switch unit 122 becomes a high-level signal, controlling the first switch tube M1 and the fourth switch tube M4 to be in a conducting state, and the third switch tube M3 to be in a cut-off state. At this time, since the control end of the second switch tube M2 is connected to the second power supply voltage VGL in a negative voltage state through the turned-on fourth switch tube M4, the second switch tube M2 is also in a conducting state, and then the output end of the voltage amplification module 110 is connected to the ground, and the output common voltage VCOM is converted into a ground voltage.

[0037] It should be noted that in the present embodiment, two MOSFETs of different conductivity types are used to control the output state of the common voltage. For example, the first switch tube M1 is set to an N-type MOSFET, and the second switch tube M2 is set to a P-type MOSFET. By utilizing the opposite directions of the body diodes of the N-type MOSFET and the P-type MOSFET, it is possible to avoid the output end of the voltage amplification module 110 being short-circuited to the ground when the switch tube operates abnormally, thereby causing abnormal output of the common voltage.

[0038] In the present embodiment, the voltage amplification module 110 includes an operational amplifier OPA, the first input terminal of the operational amplifier OPA is connected to an input voltage signal, such as a PWM signal output by the MCU, and the second input terminal of the operational amplifier OPA is connected to a bias voltage, so that the operational amplifier OPA amplifies the input PWM signal to output a common voltage in the form of a square wave signal having a positive voltage state and a negative voltage state. The output terminal of the operational amplifier OPA serves as the output terminal of the voltage amplification module 110, and the positive power input terminal and the negative power input terminal of the operational amplifier OPA are respectively connected to the corresponding positive power supply voltage V+ and negative power supply voltage V- to ensure the voltage swing required for the common voltage. When the display device finishes refreshing the screen, the enable terminal of the operational amplifier OPA is connected to a low-level control signal, so that the operational amplifier OPA enters a non-working mode, thereby keeping the output common voltage at a ground voltage state. It should be noted that in the actual circuit, OPA has an enable pin (EN pin), which is not required as Figure 3 Resistor R1 is shown for isolation.

[0039] In summary, the common voltage driving circuit provided in the embodiment of the present application constructs a voltage amplification module through an operational amplifier to amplify the input voltage signal to form the common voltage required for refreshing the screen, and constructs an output control module through four switching tubes of different conductivity types to pull the output common voltage to the ground voltage when the screen refresh is completed. It not only realizes the function of outputting common voltages in different states according to the working state of the display device, but also replaces the DAC module in the prior art through a simple circuit structure, thereby improving the response speed of liquid crystal molecules, reducing the manufacturing cost of the display device, and increasing the competitiveness of the product in the market.

[0040] Based on the same inventive concept as the above embodiments, an embodiment of the present invention further provides a liquid crystal display device, which includes the common voltage driving circuit as described in the above embodiments.

[0041] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0042] In this document, the terms "comprises," "comprising," or any other variations thereof, are intended to cover a non-exclusive inclusion of elements other than those listed and may also include additional elements not expressly listed.

[0043] The above is only a specific embodiment of the present invention, but the protection scope of the present invention is not limited thereto. Any person skilled in the art can easily think of changes or substitutions within the technical scope disclosed by the present invention, which should be included in the protection scope of the present invention. Therefore, the protection scope of the present invention should be based on the protection scope of the claims.

Claims

1. A common voltage driving circuit, characterized in that: It includes a voltage amplification module and an output control module; The voltage amplification module is used to amplify the input voltage signal and output a common voltage in a first state; The output control module is connected to the output end of the voltage amplification module, and is used to convert the common voltage in the first state into the common voltage in the second state when the picture refresh ends.

2. The common voltage control circuit according to claim 1, characterized in that: The common voltage in the first state is a square wave signal including a first level state and a second level state, and the common voltage in the second state is a ground voltage.

3. The common voltage driving circuit according to claim 2, characterized in that: The output control module includes a first switch unit and a second switch unit; The control ends of the first switch unit and the second switch unit are connected to a timing control signal; When the first switch unit and the second switch unit are in the on state under the control of the timing control signal, they are used to convert the common voltage in the first level state or the common voltage in the second level state output by the voltage amplification module to the ground voltage.

4. The common voltage driving circuit according to claim 3, characterized in that: The first switch unit includes a first switch tube, a control end of the first switch tube serves as the control end of the first switch unit, a first passage end of the first switch tube is connected to the second switch unit, and a second passage end of the first switch tube is connected to the output end of the voltage amplification module.

5. The common voltage driving circuit according to claim 4, characterized in that: The second switch unit includes a second switch tube, a third switch tube and a fourth switch tube; The control end of the third switch tube is connected in parallel with the control end of the fourth switch tube, serving as the control end of the second switch unit; the first path end of the third switch tube is connected to the first power supply voltage; the second path end of the third switch tube is connected in parallel with the second path end of the fourth switch tube, and connected to the control end of the second switch tube; the first path end of the fourth switch tube is connected to the second power supply voltage; The first passage end of the second switch tube is grounded, and the second passage end of the second switch tube is connected to the first passage end of the first switch tube.

6. The common voltage driving circuit according to claim 5, characterized in that: The first switch tube and the second switch tube have different conductivity types, and the third switch tube and the fourth switch tube have different conductivity types.

7. The common voltage driving circuit according to claim 6, characterized in that: The first switch tube, the second switch tube, the third switch tube and the fourth switch tube are transistors or field effect tubes.

8. The common voltage driving circuit according to claim 1, characterized in that: The voltage amplification module includes an operational amplifier, a first input terminal of the operational amplifier is connected to the input voltage signal, a second input terminal of the operational amplifier is connected to a bias voltage, and an output terminal of the operational amplifier serves as an output terminal of the voltage amplification module.

9. The common voltage driving circuit according to claim 8, characterized in that: When the refresh screen is finished, the enable terminal of the operational amplifier is connected to a low-level control signal, so that the operational amplifier enters a non-operating mode.

10. A liquid crystal display device, characterized in that: It comprises the common voltage driving circuit as claimed in any one of claims 1 to 9.

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