Common voltage driving circuit and liquid crystal display device

Abstract

This application discloses a common voltage drive circuit and a liquid crystal display device. The common voltage drive circuit includes a voltage amplification module and an output control module. The voltage amplification module is configured to amplify an input voltage signal and output a common voltage in a first state. The output control module is connected to the output terminal of the voltage amplification module and is configured to convert the common voltage in the first state to a common voltage in a second state when a refresh of the image is completed. The common voltage drive circuit provided in this application can output the required common voltage according to the operating state of the display device, reduce manufacturing costs, and improve product competitiveness.

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 an LCD typically includes a common voltage driver module. This module applies a positive or negative common voltage (VCOM) to the LCD panel, creating a voltage differential between VCOM and the source voltage (Source) of the pixel unit. This controls the rotation angle of the liquid crystal molecules and drives the LCD panel to display color.

[0003] like Figure 1 As shown, the common voltage drive 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). When the liquid crystal display panel finishes refreshing the screen, the DAC converts VCOM to a ground voltage to reset the liquid crystal molecules. Since the DAC is a separate hardware component, it requires additional circuit design and material costs, which increases the manufacturing cost of the display device and affects the product's competitiveness 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 this 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 manufacturing costs, and improve product competitiveness.

[0005] To achieve the above objectives:

[0006] 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;

[0007] The voltage amplification module is used to amplify the input voltage signal and output a common voltage in a first state;

[0008] 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 refresh screen ends.

[0009] 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.

[0010] Optionally, the output control module includes a first switch unit and a second switch unit;

[0011] The control terminals of the first switch unit and the second switch unit are connected to a timing control signal;

[0012] 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.

[0013] Optionally, the first switch unit includes a first switch tube, the control end of the first switch tube serves as the control end of the first switch unit, the first path end of the first switch tube is connected to the second switch unit, and the second path end of the first switch tube is connected to the output end of the voltage amplification module.

[0014] Optionally, the second switch unit includes a second switch tube, a third switch tube and a fourth switch tube;

[0015] The control terminal of the third switch tube and the control terminal of the fourth switch tube are connected in parallel to serve as the control terminal of the second switch unit; the first path terminal of the third switch tube is connected to the first power supply voltage; the second path terminal of the third switch tube and the second path terminal of the fourth switch tube are connected in parallel to the control terminal of the second switch tube; the first path terminal of the fourth switch tube is connected to the second power supply voltage;

[0016] The first path end of the second switch tube is grounded, and the second path end of the second switch tube is connected to the first path end of the first switch tube.

[0017] Optionally, the first switching tube and the second switching tube have different conductivity types, and the third switching tube and the fourth switching tube have different conductivity types.

[0018] Optionally, the first switching tube, the second switching tube, the third switching tube and the fourth switching tube are transistors or field effect tubes.

[0019] 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 the output terminal of the voltage amplification module.

[0020] Optionally, 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.

[0021] 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.

[0022] The common voltage drive circuit and liquid crystal display device provided in the embodiments of the present application utilize a voltage amplifier module to amplify an input voltage signal and output a common voltage in a first state. An output control module is connected to the output terminal of the voltage amplifier module to convert the common voltage in the first state to a common voltage in the second state when the image refresh is complete. This allows the desired common voltage to be output based on the operating state of the display device, reducing manufacturing costs and improving product competitiveness. BRIEF DESCRIPTION OF THE DRAWINGS

[0023] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. 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 relevant drawings can be obtained based on these drawings without creative work.

[0024] Figure 1 It is a structural diagram of a common voltage driving module in the prior art.

[0025] Figure 2 This is a schematic diagram of the structure of the common voltage driving circuit provided in an embodiment of the present application.

[0026] Figure 3 A circuit diagram of a common voltage driving circuit provided in an embodiment of the present application.

[0027] Figure 4 This is a timing diagram of the operation of the common voltage driving circuit provided in an embodiment of the present application. DETAILED DESCRIPTION

[0028] Exemplary embodiments will be described in detail herein, with examples illustrated in the accompanying drawings. In the following description, when referring to the drawings, identical numerals in different figures represent identical or similar elements unless otherwise indicated. The embodiments described in the following exemplary embodiments are not intended to represent all embodiments consistent with the present application. Rather, they are merely examples of apparatus and methods consistent with certain aspects of the present application, as detailed in the appended claims.

[0029] It should be noted that, in this document, the terms "include", "comprises" or any other variations thereof are intended to cover non-exclusive inclusion, so that a process, method, article or device comprising a series of elements includes not only those elements, but also 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 "comprising a ..." does not exclude the presence of other identical elements in the process, method, article or device comprising 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.

[0030] It should be understood that although the terms first, second, third, etc. may be used herein to describe various information, such information should not be limited to these terms. These terms are merely used to distinguish information of the same type from one another. For example, without departing from the scope of this document, first information may also be referred to as second information, and similarly, second information may also be referred to as first information. Depending on the context, the term "if" as used herein may be interpreted as "at the time of," "when," or "in response to a determination." Furthermore, as used herein, the singular forms "a," "an," and "the" are intended to include the plural forms as well, unless the context indicates otherwise. It should be further understood that the terms "comprising" and "including" indicate the presence of the described features, steps, operations, elements, components, items, types, and / or groups, but do not exclude the presence, occurrence, or addition of one or more other features, steps, operations, elements, components, items, types, and / or groups. The terms "or" and "and / or" as used herein are to be interpreted as inclusive, meaning any one or any combination. Thus, “A, B, or C” or “A, B, and / or C” means “any of: A; B; C; A and B; A and C; B and C; A, B, and C.” An exception to this definition occurs only when a combination of elements, functions, steps, or operations are inherently mutually exclusive in some manner.

[0031] It should be understood that the specific embodiments described herein are only used to explain the present application and are not intended to limit the present application.

[0032] In the subsequent description, the use of suffixes such as "module", "component" or "unit" to represent elements is only for the purpose of facilitating the description of the present application and has no specific meaning. Therefore, "module", "component" or "unit" can be used interchangeably.

[0033] Figure 2 A schematic diagram of the structure of the 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 .

[0034] 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.

[0035] In one embodiment of the present application, 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. 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 both be positive voltages or both be negative voltages.

[0036] Specifically, when the LCD device powers up the common electrode, the MCU inputs a preset voltage signal, such as a pulse width modulation (PWM) signal, to the voltage amplifier module 110. The voltage amplifier module 110 amplifies the input PWM signal to form a square wave signal with positive and negative voltage states. When the LCD device refreshes the display image, the common voltage drive circuit normally outputs the common voltage in the form of a square wave signal. After the LCD device finishes refreshing the image, the output control module 120 converts the common voltage output from the output end of the voltage amplifier module 110 to a ground voltage, allowing the liquid crystal molecules to quickly reset. In this way, the common voltage drive circuit can be controlled to output different common voltage states according to the operating state of the LCD device.

[0037] 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 in the first level state or the second level state output by the voltage amplification module 110 to the ground voltage.

[0038] Specifically, the first switch unit 121 includes a first switch transistor M1. The control terminal of the first switch transistor M1 serves as the control terminal of the first switch unit 121. The first channel terminal of the first switch transistor M1 is connected to the second switch unit 122, and the second channel terminal of the first switch transistor M1 is connected to the output terminal of the voltage amplification module 110. The second switch unit 122 includes a second switch transistor M2, a third switch transistor M3, and a fourth switch transistor M4. The control terminal of the third switch transistor M3 and the control terminal of the fourth switch transistor M4 are connected in parallel and serve as the control terminal of the second switch unit 122. The first channel terminal of the third switch transistor M3 is connected to the first power supply voltage half VGH. The second channel terminal of the third switch transistor M3 and the second channel terminal of the fourth switch transistor M4 are connected in parallel and connected to the control terminal of the second switch transistor M2. The first channel terminal of the fourth switch transistor M4 is connected to the second power supply voltage VGL. The first channel terminal of the second switch transistor M2 is grounded, and the second channel terminal of the second switch transistor M2 is connected to the first channel terminal of the first switch transistor M1.

[0039] In this embodiment, the first switch M1 and the second switch M2 have different conductivity types, and the third switch M3 and the fourth switch M4 have different conductivity types. The first switch M1, the second switch M2, the third switch M3 and the fourth switch M4 can be transistors or field effect transistors.

[0040] Specifically, Figure 3In the example, 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). The first switch tube M1 and the fourth switch tube M4 are N-type MOSFETs, the control terminals of the first switch tube M1 and the fourth switch tube M4 are the gates of the N-type MOSFETs, the first channel terminals of the first switch tube M1 and the fourth switch tube M4 are the sources of the N-type MOSFETs, and the second channel terminals 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 terminals of the second switch tube M2 and the third switch tube M3 are the gates of the P-type MOSFETs, the first channel terminals of the second switch tube M2 and the third switch tube M3 are the sources of the P-type MOSFETs, and the second channel terminals of the second switch tube M2 and the third switch tube M3 are the drains of the P-type MOSFETs. The first channel terminal of the third switch M3 is connected to the first power supply voltage, half VGH, which is a positive voltage, and the first channel terminal of the fourth switch M4 is connected to the second power supply voltage, VGL, which is a negative voltage. In other embodiments, after slightly changing the circuit connection and timing control signals, the first switch M1 and the fourth switch M4 can also be configured as P-type MOSFETs, and the second switch M2 and the third switch M3 can be configured as N-type MOSFETs.

[0041] 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.

[0042] During the image refresh process of the liquid crystal display device, the timing control signal MCU CTRL connected to the control terminals of the first switch unit 121 and the second switch unit 122 is a low-level signal, which controls the third switch transistor M3 to be in the on state and the first switch transistor M1 and the fourth switch transistor M4 to be in the off state. Because the control terminal of the second switch transistor M2 is connected to the positive voltage of the first power supply voltage half VGH through the turned-on third switch transistor M3, the second switch transistor M2 is also in the off state. Therefore, the output control module 120 operates in an inactive state during the image refresh process, and the common voltage drive circuit can normally output the common voltage in the form of a square wave signal.

[0043] When the LCD device finishes refreshing its image, the timing control signal MCU CTRL connected to the control terminals of the first and second switch units 121 and 122 becomes a high-level signal, turning on the first and fourth switch transistors M1 and M4, and turning off the third switch transistor M3. At this time, because the control terminal of the second switch transistor M2 is connected to the negative second power supply voltage VGL through the turned-on fourth switch transistor M4, the second switch transistor M2 is also turned on. This connects the output terminal of the voltage amplification module 110 to ground, converting the output common voltage VCOM to a ground voltage.

[0044] It should be noted that in this 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 common voltage output.

[0045] In this embodiment, the voltage amplification module 110 includes an operational amplifier OPA, and the first input terminal of the operational amplifier OPA is connected to the input voltage signal, such as the PWM signal output by the MCU, and the second input terminal of the operational amplifier OPA is connected to the 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 with positive voltage state and 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 by 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 the non-working mode, thereby keeping the output common voltage at the ground voltage state. It should be noted that in the actual circuit, the OPA has an enable pin (EN pin), which is not required as Figure 3 Resistor R1 is shown for isolation.

[0046] To summarize, 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 at the end of the screen refresh. This 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 with a simple circuit structure, thereby improving the response speed of the liquid crystal molecules, reducing the manufacturing cost of the display device, and increasing the competitiveness of the product in the market.

[0047] 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.

[0048] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0049] As used herein, the terms "comprises," "comprising," or any other variation thereof, are intended to cover a non-exclusive inclusion of elements other than the listed elements and may also include additional elements not specifically listed.

[0050] The above description is merely a specific embodiment of the present invention, but the scope of protection of the present invention is not limited thereto. Any modifications or substitutions that can be easily conceived by a person skilled in the art within the technical scope disclosed in the present invention should be included in the scope of protection of the present invention. Therefore, the scope of protection of the present invention should be based on the scope of protection of the claims.

Claims

1. A common voltage driving circuit, characterized in that: Including voltage amplification module and 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 refresh screen is finished; 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; The output control module includes a first switch unit and a second switch unit; control terminals 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 a conducting 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; 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 path end of the first switch tube is connected to the second switch unit, and a second path end of the first switch tube is connected to the output end of the voltage amplification module; 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 a 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 a second power supply voltage; the first path end of the second switch tube is grounded, and the second path end of the second switch tube is connected to the first path end of the first switch tube.

2. The common voltage driving circuit according to claim 1, wherein: The first switching tube and the second switching tube have different conductivity types, and the third switching tube and the fourth switching tube have different conductivity types.

3. The common voltage driving circuit according to claim 2, wherein: The first switching tube, the second switching tube, the third switching tube and the fourth switching tube are transistors or field effect tubes.

4. The common voltage driving circuit according to claim 1, wherein: 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.

5. The common voltage driving circuit according to claim 4, 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.

6. A liquid crystal display device, characterized in that: The common voltage driving circuit comprises the common voltage driving circuit according to any one of claims 1 to 5.

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