CN102867491A - LCD (Liquid Crystal Display) panel drive circuit and method as well as display unit - Google Patents

Abstract

The invention provides an LCD (Liquid Crystal Display) panel drive circuit and method as well as a display unit. The LCD panel drive circuit comprises a control unit and a charge release module. The LCD panel drive method comprises the steps that a control signal is generated by the control unit when the LCD panel is shut down and output to the charge release module; and the charge release module leads residual charge on a pixel electrode and a public electrode to a ground terminal according to the control signal. According to the LCD panel drive circuit and method as well as the display unit provided by the invention, charge on the pixel electrode and the public electrode is led to the ground terminal when the LCD panel is shut down, so that no residual charge is left in the whole panel, the occurrence of abnormal pictures in shutdown is eliminated, the polarized probability of liquid crystals is reduced simultaneously, and the service life of the LCD panel is prolonged.

Description

A liquid crystal panel driving circuit and method, and display device

technical field

The invention relates to the field of flat panel display technology, in particular to a liquid crystal panel driving circuit and method, and a display device.

Background technique

In recent years, TFT-LCD (Thin Film Transistor-Liquid Crystal Display) has gradually replaced cathode ray tube CRT (Cathode Ray Tube) display and has become the mainstream of the new generation of display. Since LCDs are widely used in electronic products closely related to life, such as notebook computers, mobile phones, and TVs, people have higher and higher requirements for image quality, so the improvement of image quality has always been the goal pursued by related fields.

Specifically, when the power supply (VDD) of the thin film transistor liquid crystal display is turned off, due to charging, after the display displays images for a long time, charges will be accumulated in the liquid crystal capacitance between two opposite electrodes, and this The accumulated charge cannot be released immediately after the power is turned off, so a part of the previous image will still remain on the momentary screen. Obviously, if there is no additional control circuit to exert influence, the LCD can only gradually achieve the purpose of pixel potential discharge through the leakage current of the thin film transistor corresponding to each pixel, which results in a relatively long-lasting afterimage after shutdown.

As shown in FIG. 1 , it is a schematic structural diagram of a liquid crystal panel driving circuit in the prior art. The liquid crystal panel driving circuit includes a pixel area 500, which includes a data line 510, a gate line 520, a common electrode (VCOM), a gate line 520 and a data line. For the TFT at the intersection of 510, the gate of the TFT is electrically connected to the gate line 520, the source of the TFT is electrically connected to the data line 510, and the drain of the TFT is connected to the pixel electrode; The data line 510 provides the data voltage; the gate voltage generation module 200 is used to provide the gate voltage to the gate line 520 of the pixel area 500, and an XON function circuit is usually set in the gate voltage generation module 200, where the XON function refers to , when the VDD of the liquid crystal panel is powered down to a certain extent, after the XON pin of the gate voltage generating module 200 receives the shutdown signal of the panel, the gate voltage generating module 200 outputs a VGH signal to turn on the gates of all TFTs in the display panel, In order to eliminate the screen abnormality and image after-image during shutdown, but it requires a long shutdown time, there will always be charge residue on the pixel capacitor, and you can still see abnormality or after-image when you turn on immediately after shutdown.

For a normally white LCD panel, the general data voltage generating module 100 outputs a white screen voltage (about 0.5V); for a normally black LCD panel, the general data voltage generating module 100 outputs a black screen voltage (about 0.4V) , so that all the pixels are at the same voltage level, the voltage is about a few tenths of a volt, and the voltage of the common electrode is still the voltage at design time, about 5~7V, then the VGH voltage drops to 0V, and the charge on the pixel The leakage can only disappear slowly, and the charge on the common electrode also loses power slowly, generally greater than 50ms. At this time, the voltage difference between the two ends of the liquid crystal is always the voltage difference of the same polarity. If the voltage difference exceeds the threshold voltage of the liquid crystal and remains If it takes a long time, it will cause the liquid crystal to be polarized, destroy the display performance of the liquid crystal, and affect the life of the LCD.

Contents of the invention

The invention provides a liquid crystal panel drive circuit and method, and a display device, which are used to solve the problem that the residual charge on the pixel capacitor cannot be quickly released when the display device is turned off, resulting in polarization of the liquid crystal, destroying the display performance of the liquid crystal, and affecting the life of the LCD.

In order to solve the above technical problems, the technical solutions provided by the embodiments of the present invention are as follows:

A liquid crystal panel drive circuit, comprising:

The control device generates a control signal and outputs it to the charge release module when the machine is turned off;

The charge release module guides the residual charge on the pixel electrode and the common electrode into the ground terminal according to the control signal output by the control device.

Preferably, the control device includes a grid voltage generation module and a control voltage module, the input terminal of the control voltage module is connected to the grid voltage generation module, and the output terminal is connected to the charge release module, for receiving the The gate voltage generating module generates a signal, and generates a driving voltage according to the signal to provide to the charge releasing module.

Specifically, the control voltage module includes an operational amplifier and a NAND gate, the input terminal of the operational amplifier receives the XON signal, the output terminal of the operational amplifier is connected to one input terminal of the NAND gate, and the other input terminal of the NAND gate receives the gate voltage The high-voltage signal VGH generated by the generating module, and the output terminal of the NAND gate outputs the driving voltage signal VOUT.

Preferably, the charge release module includes a plurality of switch units, and the charge release module includes a plurality of switch units, and each switch unit is connected to one end of a data line or a common electrode line.

Specifically, each switching unit includes a thin film transistor, the gate of which is connected to the control voltage module, the source is connected to the data line or the common electrode line, and the drain is grounded.

A method for driving a liquid crystal panel driving circuit, comprising:

The control device generates a control signal to output to the charge release module when the machine is turned off;

The charge releasing module guides the residual charge on the pixel electrode and the common electrode into the ground terminal according to the control signal.

Preferably, the control device includes a gate voltage generation module and a control voltage module, and the control device generates a control signal to output to the charge release module when the power is turned off, specifically:

The gate voltage generating module outputs a voltage signal to the control voltage module when the power is turned off;

The control voltage module generates a driving voltage according to the voltage signal, and provides it to the charge release module.

Specifically, the output voltage signals of the gate voltage generating module are high voltage signals VGH and XON signals, and the control voltage module receives the high voltage signal VGH generated by the gate voltage generating module and the XON signal generated by the XON functional circuit, and outputs the driving voltage signal VOUT.

Preferably, the charge release module includes a plurality of switch units, which are turned on according to the driving voltage signal VOUT outputted by the control voltage module, so as to guide the residual charge on the pixel electrode and the common electrode into the ground terminal.

The present invention also provides a display device comprising the above-mentioned liquid crystal panel driving circuit.

Embodiments provided by the invention have the following beneficial effects:

By adding a control device and a charge release module, the charge on the pixel electrode and the common electrode can be introduced into the ground terminal when the liquid crystal panel is turned off, so that there is no charge remaining on the entire panel, eliminating the abnormal screen that appears when the liquid crystal panel is turned off, and reducing the The probability of liquid crystal being polarized improves the life of the liquid crystal panel.

Description of drawings

In order to more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the following will briefly introduce the drawings that need to be used in the description of the embodiments or the prior art. Obviously, the accompanying drawings in the following description are only These are some embodiments of the present invention. Those skilled in the art can also obtain other drawings based on these drawings without creative work.

FIG. 1 is a schematic structural diagram of a liquid crystal panel driving circuit in the prior art;

Fig. 2 is a schematic structural diagram of a liquid crystal panel driving circuit of the present invention;

Fig. 3 is a schematic circuit diagram of the charge releasing module of the present invention;

Fig. 4 is the circuit schematic diagram of control voltage module of the present invention;

FIG. 5 is a flowchart of a method for driving a liquid crystal panel of the present invention.

Detailed ways

The following will clearly and completely describe the technical solutions in the embodiments of the present invention with reference to the accompanying drawings in the embodiments of the present invention. Obviously, the described embodiments are only some, not all, embodiments of the present invention. Based on the embodiments of the present invention, all other embodiments obtained by persons of ordinary skill in the art without making creative efforts belong to the protection scope of the present invention.

The invention provides a liquid crystal panel driving circuit, comprising: a control device, which generates a control signal and outputs it to a charge release module when the machine is turned off; end.

There are many ways for the control device to generate the control signal. It can be a manual button or a trigger device set on the liquid crystal panel. When the machine is turned off, a control signal is generated by manual control or trigger and provided to the charge release module.

Preferably, the control device includes a grid voltage generating module and a control voltage module, the input end of the control voltage module is connected to the grid voltage generating module, and the output end is connected to the charge releasing module, for receiving the voltage generated by the grid voltage generating module when the power is turned off. signal, and generate a driving voltage according to the signal to provide to the charge releasing module.

As shown in FIG. 2 , it is a schematic structural diagram of the liquid crystal panel driving circuit of the present invention. The liquid crystal panel driving circuit includes a pixel area 500, which includes a data line 510, a gate line 520, a common electrode (VCOM), a gate line 520 and a data line 510. For the TFT at the intersection, the gate of the TFT is electrically connected to the gate line 520, the source of the TFT is electrically connected to the data line 510, and the drain of the TFT is connected to the pixel electrode; the data voltage generating module 100 is used to transfer data to the pixel area 500 The line 510 provides the data voltage; the gate voltage generation module 200 is used to provide the gate voltage to the gate line 520 of the pixel area 500; the control voltage module 300, the input end is connected to the gate voltage generation module 200, and the output end is connected to the charge discharge The module 400 is connected to receive the signal generated by the gate voltage generating module when the power is off, and generate a driving voltage according to the signal to the charge releasing module; the charge releasing module 400, under the action of the driving voltage, connects the pixel electrode and the The residual charge on the common electrode is led to the ground terminal.

As shown in FIG. 3 , it is a schematic circuit diagram of the charge releasing module of the present invention. The charge releasing module 400 includes a plurality of switch units, and each switch unit is connected to one end of the data line 510 or the VCOM line.

Specifically, each switch unit is a TFT switch, the gate of which is connected to the control voltage module 200 , the source is connected to the data line 510 or the VCOM line, and the drain is connected to the GND terminal.

As shown in Figure 4, it is a schematic circuit diagram of the control voltage module of the present invention, the control voltage module 300 includes an operational amplifier 301 and a NAND gate 302, and the operational amplifier 301 has two input terminals, a non-inverting input terminal and an inverting input terminal, one Output terminal, the used operational amplifier 301 of the present invention is the proportional circuit in the same direction, the noninverting input terminal of operational amplifier 301 is connected to the input voltage, the inverting input terminal is grounded, the output terminal signal is proportional to the voltage of the inverting input terminal signal, and the ratio can be set as required The NAND gate 302 is a combination of an AND gate and a NOT gate, with two inputs and one output, and an AND operation is performed first, and then a NOT operation is performed.

The XON control signal is generated by the XON functional circuit. When the LCD panel is working normally, the XON signal is at a high level, and its voltage value is similar to that of VCC (3.3V). level becomes low level, the input terminal of the operational amplifier 301 receives the panel shutdown signal XON, and the output terminal outputs the amplified signal XONN.

The non-inverting output terminal of the operational amplifier 301 is connected to one input terminal of the NAND gate 302, and the other input terminal of the NAND gate 302 is connected to the gate voltage generating module 200, and always receives the high voltage signal VGH generated by the gate voltage generating module 200, and the VGH signal is a TFT The gate turns on the voltage, and the output terminal outputs the driving voltage signal VOUT.

When the liquid crystal panel is working normally, because the voltage of the VGH signal is relatively large, the voltage amplitudes of the XON signal and VGH must be the same. Therefore, the XON signal needs to be amplified by the operational amplifier 301 according to a set ratio. The amplified XONN signal and VGH are both high level, and the NAND output VOUT signal is low level, the TFT at the end of the data line 510 and the VCOM line are not turned on, and the pixel electrode voltage and common voltage are normal values.

When the LCD panel is turned off, XON changes from a high level of 3.3V to a low level of about 0.8V. After the XON pin of the gate voltage generation module 200 receives the shutdown signal of the panel, the gate voltage generation module 200 outputs a VGH signal to turn on the display Gates of all TFTs in the panel. After XON is amplified by the operational amplifier, the XONN signal voltage is still at low level, after the VGH signal and the VONN signal are NANDed, the VOUT signal is at high level, and the gate of the TFT at the end of the data line 510 and the VCOM line receives the VOUT voltage signal, Turn on the TFT, and at this time all the TFTs in the display panel have also been turned on, the charge on the pixel electrode is transferred to the TFT drain at the end of the data line 510 through the data line 510, and the charge on the common electrode is transferred to the drain at the end of the VCOM line through the VCOM line. The residual charge on the TFT drain, pixel electrode and common electrode are all led to the ground terminal, so that there is no charge remaining on the entire panel, eliminating the abnormal picture that appears when the power is turned off, reducing the probability of liquid crystal being polarized, and improving the life of the liquid crystal panel .

The shutdown state of the liquid crystal panel in the present invention refers to the state when the liquid crystal panel is not working and there is no picture output.

The TFT at the end of the data line and the VCOM line of the present invention can be a P-type or N-type TFT. When the TFT is P-type, the gate needs to receive a high potential signal to open the TFT; when the TFT is N-type, the gate needs to be opened to open the TFT. To receive a low potential signal, an inverter needs to be added to the XONN signal input terminal, and a gate voltage generation module is required to provide a low voltage signal VGL to the VGH signal input terminal.

The purpose of the gate voltage generation module in the embodiment provided by the present invention is to provide gate signals to the pixel area; it can be formed on the drive circuit of the liquid crystal display through an array process, namely (Gate driver On the Array, GOA). This integration process not only saves costs, but also achieves a symmetrical and beautiful design on both sides of the panel. At the same time, it also saves the bonding area of the gate line integrated circuit and the wiring space for fan-out. Therefore, the design of narrow frame can be realized; moreover, this integration process can also save the Bonding process in the direction of the gate line, thereby improving the production capacity and yield rate. Compared with the traditional thin film chip integration (Chip On Film, COF) and glass chip integration (Chip On Glass, COG) process, it not only saves the cost, but also improves the production capacity because it can save the bonding process in the direction of the gate line. more favorable.

The present invention also provides a method for driving a liquid crystal panel driving circuit, comprising: the control device generates a control signal to output to the charge release module when the power is turned off; the charge release module guides the residual charge on the pixel electrode and the common electrode into the ground according to the control signal end.

When the control device is turned off, a control signal can be generated by manual control or triggering and provided to the charge release module. Preferably, the control device includes a gate voltage generation module and a control voltage module, and the gate voltage generation module outputs a voltage signal when the power is turned off. For the control voltage module, the control voltage module generates a driving voltage according to the voltage signal, and provides it to the charge releasing module.

Specifically, as shown in FIG. 5, it is a flow chart of driving the above-mentioned liquid crystal panel driving circuit according to the present invention, including:

Step 501, the gate voltage generating module outputs a voltage signal to the control voltage module when the power is turned off;

As an embodiment, the gate voltage generation module is provided with an XON functional circuit. When the liquid crystal panel is working normally, the XON signal output by the XON functional circuit is a high-level signal VCC. level becomes low level, and the gate voltage generation module provides the gate turn-on voltage signal VGH and XON signal to the control voltage module.

Step 502, the control voltage module generates a driving voltage VOUT according to the voltage signal, and provides it to the charge release module;

Specifically, the control voltage module receives the high voltage signal VGH and the XON signal generated by the gate voltage generation module, and generates a driving voltage VOUT to provide to the charge release module.

Step 503 , the charge releasing module guides the residual charge on the pixel electrode and the common electrode into the ground terminal according to the driving voltage VOUT.

Specifically, the charge release module includes a plurality of switch units, and receives the driving voltage VOUT generated by the control voltage module. When the liquid crystal panel is working normally, the drive voltage VOUT is at a low level, the switch units of the charge release module are not turned on, and the pixel electrode voltage and The voltage of the common electrode is a normal value; when the liquid crystal panel is turned off, the driving voltage VOUT is high level, all the switch units of the charge release module are turned on, and the residual charge on the pixel electrode and the common electrode is introduced into the ground terminal.

The present invention also provides a display device, which includes a display panel, and adopts the liquid crystal panel drive circuit provided in this embodiment, so that the display device can quickly release the residual charge in the pixel area when the display device is turned off, so as to solve the problem of abnormal shutdown screen, and at the same time It can reduce the probability of liquid crystal being polarized and improve the life of the liquid crystal panel.

It can be understood that, the above embodiments are only exemplary embodiments adopted for illustrating the principle of the present invention, but the present invention is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and essence of the present invention, and these modifications and improvements are also regarded as the protection scope of the present invention.

Claims (10)

1. a liquid crystal panel drive circuit is characterized in that, comprising:

Control device produces control signal and exports to the electric charge release module when shutdown;

The electric charge release module, the control signal of exporting according to control device imports earth terminal with the residual charge on pixel electrode and the public electrode.

2. liquid crystal panel drive circuit according to claim 1, it is characterized in that, described control device comprises grid voltage generation module and control voltage module, described control voltage module input end is connected with described grid voltage generation module, output terminal is connected with the electric charge release module, be used for when shutdown, receiving the signal that described grid voltage generation module produces, and produce a driving voltage according to this signal and offer the electric charge release module.

3. liquid crystal panel drive circuit according to claim 2, it is characterized in that, described control voltage module comprises operational amplifier and Sheffer stroke gate, the operational amplifier input end receives the XON signal, operational amplifier output terminal is connected with described Sheffer stroke gate one input end, the high voltage signal VGH that another input end receiving grid pole tension generation module of Sheffer stroke gate produces, Sheffer stroke gate output terminal outputting drive voltage signal VOUT.

4. liquid crystal panel drive circuit according to claim 1 is characterized in that, described electric charge release module comprises a plurality of switch elements, and each switch element is connected to data line or public electrode wire one end.

5. liquid crystal panel drive circuit according to claim 4 is characterized in that, described each switch element comprises a thin film transistor (TFT), and its grid is connected with the control voltage module, and source electrode is connected grounded drain with data line or public electrode wire.

6. the method that liquid crystal panel drive circuit drives is characterized in that, comprising:

Control device produces control signal and exports to the electric charge release module when shutdown;

The electric charge release module imports earth terminal according to this control signal with the residual charge on pixel electrode and the public electrode.

7. method according to claim 6 is characterized in that, described control device comprises grid voltage generation module and control voltage module, and control device generation control signal when shutdown is exported to the electric charge release module and is specially:

Grid voltage generation module output voltage signal when shutdown is given the control voltage module;

The control voltage module produces a driving voltage according to this voltage signal, offers the electric charge release module.

8. method according to claim 7, it is characterized in that, the voltage signal of described grid voltage generation module output is high voltage VGH signal and XON signal, the XON signal that the high voltage signal VGH that described control voltage module receiving grid pole tension generation module produces and XON functional circuit produce, outputting drive voltage signal VOUT.

9. method according to claim 8, it is characterized in that, described electric charge release module comprises a plurality of switch elements, and the drive voltage signal VOUT that exports according to the control voltage module opens described a plurality of switch element, and the residual charge on pixel electrode and the public electrode is imported earth terminal.

10. a display device is characterized in that, comprises such as the arbitrary described liquid crystal panel drive circuit of claim 1 to 5.

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