CN1588529A - Liquid crystal display and method for improving picture flickering during boot process - Google Patents

Abstract

The invention provides a liquid crystal display and a method for improving image flicker in a starting-up process, wherein the liquid crystal display with the flicker improving function comprises a liquid crystal display panel, a panel power supply, a video signal controller and a time schedule controller. The panel power supply supplies power for the LCD panel. The video signal controller controls the picture content input to the liquid crystal display panel. The time sequence controller is connected to the panel power supply and the video signal controller to control the operation sequence. The operation method is that at a preset time point after the power of the liquid crystal display is turned on, a preset picture with a preset time length is provided to the liquid crystal display panel so as to generate enough driving electric field to rapidly charge the liquid crystal capacitor.

Description

Liquid crystal display and method for improving picture flickering during boot process

technical field

The invention relates to a frame control technology of a liquid crystal display, in particular to a liquid crystal display and a method for improving the flickering of the frame during the booting process.

Background technique

Liquid Crystal Display (LCD) has gradually replaced the traditional Cathode Ray Tube (CRT) display due to its advantages of thinness, lightness, power saving, and radiation-free. Currently, LCDs are widely used in electronic products such as high-definition digital televisions, desktop computers, personal digital assistants, notebook computers, digital cameras, and mobile phones.

Fig. 1 shows the equivalent circuit diagram of a single pixel (Pixel) 1 in a liquid crystal display, which comprises a thin film transistor (ThinFilm Transitor, TFT) 2 and a liquid crystal capacitor 3, wherein the source electrode (Source) of the thin film transistor 2 is connected to the signal Lines (or data lines (Data Line)) 4 are connected, and the gate (Gate) is connected to the scan line 5. One end of the liquid crystal capacitor 3 is connected to the drain of the TFT 2 , and the other end is connected to a common voltage (CommonVoltage, Vcom).

The above-mentioned liquid crystal capacitor 3 is composed of a common electrode layer (not shown), a pixel electrode layer (not shown) and a liquid crystal layer (not shown) sandwiched therebetween, wherein the common electrode layer is connected to a constant The common voltage of the pixel electrode layer provides an operation voltage (Operation Voltage), and the voltage difference between the common voltage and the operating voltage can generate an electric field in the liquid crystal layer to drive the liquid crystal molecules to rotate. Generally speaking, in order to prevent the liquid crystal molecules from being fixed in the same direction and causing the liquid crystal molecules to rotate with the electric field, it is necessary to use voltages of different polarities to drive the liquid crystal molecules. Therefore, the above-mentioned operating voltage applied to the pixel electrode layer is an alternating voltage with positive and negative polarities appearing alternately.

When the liquid crystal display panel displays a static picture, as shown in Figure 2, the waveform of the operating voltage Vo presents alternate positive polarity (Positive Cycle) and negative polarity (Negative Cycle), where the positive polarity part refers to the operating voltage value Vo The part with a negative polarity greater than the common voltage Vcom means that the operating voltage Vo is less than the common voltage Vcom. In order to present this static picture, the absolute value of the voltage difference between the common voltage value and the operating voltage value must be kept constant. In this way, even if the direction of the liquid crystal molecules changes with the positive and negative polarities of the operating voltage, as long as the electric field driving the liquid crystal molecules to rotate remains constant, the liquid crystal layer can maintain a certain light transmittance.

As shown in FIG. 3 , if the common voltage Vcom' deviates from the default value Vcom, the absolute value of the voltage difference between the common voltage Vcom' and the operating voltage Vo cannot be kept constant. The figure shows the situation where the common voltage generates a positive bias (Positive bias). In the positive polarity part, the absolute value of the voltage difference between the operating voltage value Vo and the common voltage value Vcom' will be reduced, while in the negative polarity part, the operating voltage value The absolute value of the voltage difference between Vo and the common voltage value Vcom' will increase. Therefore, the magnitude of the electric field in the liquid crystal layer will change with the positive and negative polarity of the operating voltage Vo, so that the light transmittance of the liquid crystal layer cannot be maintained constant, resulting in flicker phenomenon.

Please refer to FIG. 1 at the same time. If there is residual charge in the liquid crystal capacitor 3 that has not been released (that is, there is a DC bias (DC-bias) between the common electrode layer and the pixel electrode layer), the level of the common voltage will be changed. Instead, the flickering phenomenon shown in FIG. 3 occurs. In addition, when the liquid crystal display is turned off, there is usually residual charge in the liquid crystal capacitor. If these charges cannot be completely discharged before the next activation of the liquid crystal display, a DC bias voltage will be generated in the liquid crystal capacitor. This will cause the liquid crystal display panel to flicker for a short time after the display is turned on next time.

Therefore, how to prevent the residual charge in the liquid crystal capacitor from interfering with the screen when the liquid crystal display is turned on will have a very important impact on improving the quality of the liquid crystal display.

Contents of the invention

The main purpose of the present invention is to use the startup process of the liquid crystal display to quickly charge the liquid crystal capacitor, so as to improve the problem of flickering of the screen when the liquid crystal display is turned on.

According to a characteristic of the present invention, the liquid crystal display for improving screen flickering in the boot process includes a liquid crystal display panel, a panel power supply, a video signal controller and a timing controller. Among them, the liquid crystal display panel has a plurality of liquid crystal capacitors to display pictures; the panel power supply is to supply the power required by the liquid crystal display panel; the video signal controller is used to control the content of the input liquid crystal display panel picture; the timing controller is respectively connected with the video The signal controller is connected with the liquid crystal display panel to control the operation sequence of the video signal controller and the liquid crystal display panel. When starting up, the timing controller notifies the liquid crystal display panel to activate at a first preset time point, and then notifies the video signal controller to provide a preset picture (Predetermined Pattern) to the liquid crystal display panel at a second preset time point, so as to Quickly charge these liquid crystal capacitors.

The above-mentioned method for improving the flickering of the picture in the starting process of the liquid crystal display includes the following steps: a step of turning on the power supply, a step of activating the panel and a step of providing a preset picture. Wherein, the step of turning on the power supply is to activate the power supply of the liquid crystal display. The step of activating the panel is to turn on the liquid crystal display panel at a first preset time point after the step of turning on the power. The step of providing a preset image is to provide a preset image to the liquid crystal display panel at a second preset time point after the power-on step, so as to rapidly charge the liquid crystal capacitor in the liquid crystal display panel to activate the liquid crystal layer in the liquid crystal capacitor.

Description of drawings

Fig. 1 is the equivalent circuit diagram of the single pixel of a typical liquid crystal display;

Fig. 2 is a waveform diagram of its operating voltage when the liquid crystal display displays a static picture;

FIG. 3 is a waveform diagram of the operating voltage when the liquid crystal display flickers;

FIG. 4 is a schematic diagram of a preferred embodiment of the liquid crystal display for improving startup flickering of the present invention;

Fig. 5 is the flow chart of a preferred embodiment of the method for improving the flickering of the liquid crystal display screen of the present invention;

Fig. 6 is a waveform diagram corresponding to panel power supply and picture signal in the operation process of Fig. 5;

FIG. 7 is a flow chart of another embodiment of the method for improving the screen flickering of the liquid crystal display according to the present invention;

Fig. 8 is a waveform diagram corresponding to panel power supply and screen signal in the operation process of Fig. 7;

9A and 9B are waveform diagrams of operating voltages of the liquid crystal display of the present invention before and after providing preset images.

Symbol Description:

Pixel 1 Thin Film Transistor 2

LCD Capacitor 3 Signal Line 4

Scanning line 5 LCD display 10

LCD panel 20 Video signal controller 40

Timing controller 50 Picture generator 42

Multi-tasker 44 Clock generator 46

Detailed ways

The advantages and spirit of the present invention can be further understood through the following detailed description of the invention and the accompanying drawings.

4 is a functional block diagram of a preferred embodiment of the liquid crystal display 10 of the present invention, the liquid crystal display 10 has a liquid crystal display panel 20, a video signal controller 40 and a timing controller (Timing Controller) 50. Wherein, the liquid crystal display panel 20 has a plurality of liquid crystal capacitors (not shown) to display the picture, the video signal controller 40 is connected to the liquid crystal display panel 20 to provide picture content, and the timing controller 50 is connected with the liquid crystal display panel 20 and the video signal control The driver 40 is connected to transmit control signals to the drivers on the liquid crystal display panel 20 (for example: data driver (Source Driver) and scan driver (Gate Driver)), so as to determine the charge and discharge of each liquid crystal capacitor on the liquid crystal display panel 20 (also That is, the order and timing of each pixel display).

The video signal controller 40 has a frame generator 42 , a multiplexer 44 and a clock generator 46 . Wherein, the frame generator 42 is used to generate a preset frame F. As shown in FIG. The multiplexer 44 receives the preset frame F generated by the frame generator 42 and the normal frame A input from the outside, and selects one of the frames to output to the liquid crystal display panel 20 . The clock generator 46 is connected with the picture generator 42 to provide the clock signal S corresponding to the aforementioned preset picture F, so that the preset picture F can be controlled to appear on the liquid crystal display through the clock signal S Scanning speed and duration on panel 20.

Since the liquid crystal capacitor in the liquid crystal display panel 20 has residual charge after the liquid crystal display 10 is turned off, the liquid crystal display 10 is prone to short-lived flicker when it is turned on next time. Therefore, if the liquid crystal capacitor can be quickly charged immediately after the liquid crystal display 10 is turned on to activate the liquid crystal layer in the liquid crystal capacitor, the flickering phenomenon can be improved.

In order to effectively charge the liquid crystal layer of the liquid crystal capacitor, the video signal controller 40 provides a preset image F to the liquid crystal display panel 20 after power on. The preset frame F is to provide enough driving electric field for the liquid crystal capacitor to charge the liquid crystal capacitor in the liquid crystal display panel 20 in a short time. As far as a preferred embodiment is concerned, the sufficient driving electric field refers to 90% of the maximum driving electric field value set to drive liquid crystal molecules to turn in the data driver. As far as an 8-bit driven liquid crystal display panel is concerned, the maximum driving electric field refers to the driving electric field generated by the 255th order driving signal. Of course, the size of the sufficient driving electric field is different according to the characteristics of each liquid crystal display.

In order to fully activate the liquid crystal molecules in the liquid crystal capacitor, the video signal controller 40 can provide a number of preset frames F ranging from 1 to 100, or a preset frame length ranging from 10 ms to 1000 ms. In addition, in this embodiment, the preset picture F provides different picture signals according to the characteristics of the liquid crystal display panel 20 . For example: when the liquid crystal layer of the liquid crystal display panel 20 belongs to twisted nematic (Twisted Nematic, TN), then the preset picture F is a black picture signal, so as to provide enough driving electric field to quickly charge the liquid crystal capacitor; For Multi-domain Vertical Alignment (MVA) or In-Plain Switching (IPS), the preset picture F is a white picture signal to provide enough driving electric field to quickly charge the liquid crystal capacitor.

Please refer to FIG. 5 , which is a flowchart of a preferred embodiment of the operation method of the present invention. For its description, please refer to the functional block diagram in FIG. 4 and the action sequence diagram in FIG. 6 . When the power switch of the liquid crystal display is turned on (step 100 ), the timing controller 50 notifies the liquid crystal display panel 20 to activate at the first preset time point t1 (step 120 ), so as to supply the power required by the liquid crystal display panel 20 . Then, at the second preset time point t2, the multiplexer 44 in the video signal controller 40 is notified to select the preset frame F provided by the frame generator 42 and output to the liquid crystal display panel 20, so as to quickly charge the liquid crystal layer (step 140 ). After the playback of the preset picture F is finished, the timing controller 50 notifies the multiplexer 44 at the third preset time point t3 to select the externally provided normal picture A to output to the liquid crystal display panel 20 (step 160), to start the liquid crystal display panel 20. normal operation. As far as a preferred embodiment is concerned, the first preset time point t1 is within 100 ms after the power-on action, the time length d1 of the preset frame F is between 20 ms and 100 ms, and the second preset time point t2 is within 100 ms. The interval of the third preset time point t3 is equal to the duration d1 of the preset frame F. Of course, the values of these parameters t1, t2, t3 and d1 will also vary due to different display designs.

It should be noted that, in addition to the method of notifying the multiplexer 44 through the timing controller 50 to switch the signal source to the external normal frame A as described in the aforementioned step 160 . The multiplexer 44 can also directly detect the end signal of the preset frame F to switch the signal source of the video signal controller 40 to the external normal frame A to start the normal operation of the liquid crystal display panel 20 .

The foregoing embodiments are described for the case where the present invention is applied to a reflective liquid crystal display. Please refer to FIG. 7 and FIG. 8 , which show the operation process of the present invention applied to a transmissive or transflective liquid crystal display, that is, a liquid crystal display with a backlight. First, after activating a power-on action (step 200 ), the timing controller 50 notifies the liquid crystal display panel 20 to activate at a first preset time point t1 (step 220 ). Then, notify the multiplexer 44 in the video signal controller 40 at a second preset time point t2 to provide the preset frame F provided by the frame generator 42 to the liquid crystal display panel 20 so as to quickly charge the liquid crystal layer (step 240 ). After the playback of the preset frame F is finished, the multiplexer 44 provides the external normal frame A to the liquid crystal display panel 20 (step 260 ), so as to start the normal operation of the liquid crystal display panel 20 . Next, turn on the backlight again (step 280) to complete the booting process. As far as a preferred embodiment is concerned, after 50 ms from the start of providing the normal frame A to the liquid crystal display panel 20, the backlight is activated immediately.

Please refer to FIG. 9A and FIG. 9B , which show the improvement process of the preset frame F provided by the present invention for the DC bias voltage in the liquid crystal capacitor. Vo in the figure refers to the operating voltage, Vcom refers to the preset common voltage value, and Vcom” refers to the actual common voltage value. Figure 9A shows the common voltage value of the liquid crystal capacitor when the preset screen is not displayed Vcom" changes. And Fig. 9B shows the change situation of the common voltage value Vcom" of the liquid crystal capacitor when the default screen is entered immediately after starting up. As shown in the figure, the default screen is to quickly activate the liquid crystal molecules to accelerate the elimination of direct current Bias voltage, to shorten the screen flashing time after power on.

In summary, the present invention has the following characteristics:

1. The present invention rapidly charges the liquid crystal capacitor by using a preset screen F through a given boot sequence, so as to avoid the interference of the residual charge in the liquid crystal capacitor to the normal display of the screen. Therefore, a stable and effective method can be provided to improve the image flicker phenomenon when the liquid crystal display is turned on, so as to improve the quality of the liquid crystal display and prolong the life of the liquid crystal display.

2. As shown in FIG. 8 , in the process of inputting the preset picture F, the backlight source of the liquid crystal display is turned off. Therefore, it is difficult for the user to notice the image afterimage that may appear during the charging process of the liquid crystal capacitor, and the quality of the booting image can be improved.

3. Since the present invention can prevent the residual charge in the liquid crystal capacitor from interfering with the normal display of the screen, it has an excellent improvement effect on the flicker phenomenon caused by reactivating the display in a short time.

4. Since the present invention controls the video signal controller and the liquid crystal display panel through the timing controller, it can control the video signal controller to provide the preset picture to the liquid crystal display panel at the preset time point without going through other Therefore, the present invention does not increase mass production cost.

Claims (13)

1. a liquid crystal display, can avoid the flicker phenomenon that picture produces when starting up, it is characterized in that described liquid crystal display comprises: A liquid crystal display panel with a plurality of liquid crystal capacitors for displaying images; A panel power supply, which supplies the power required by the liquid crystal display panel; A video signal controller, controlling the picture content input to the liquid crystal display panel; and a timing controller, respectively connected to the video signal controller and the liquid crystal display panel, to control the operation sequence of the video signal controller and the liquid crystal display panel; When starting up, the timing controller notifies the liquid crystal display panel to activate at a first preset time point, and then notifies the video signal controller to provide a preset picture to the liquid crystal display panel at a second preset time point, so as to Charge these liquid crystal capacitors quickly. 2. The liquid crystal display according to claim 1, wherein the timing controller notifies the video signal controller to provide a normal picture to the liquid crystal display panel at a third preset time point, and the second preset time The interval between the dot and the third preset time point is the duration of the preset frame. 3. The liquid crystal display according to claim 1, wherein the video signal controller provides a normal picture to the liquid crystal display panel after the preset picture ends. 4. The liquid crystal display according to claim 1 or 2, wherein the preset frame lasts for 1-100 frames or lasts for 10ms-1000ms. 5 . The liquid crystal display according to claim 1 , wherein in the preset frame, the driving electric field provided is more than 90% of the preset maximum driving electric field value for driving the liquid crystal capacitor. 6 . 6 . The liquid crystal display according to claim 1 , further comprising a backlight for providing illumination required by the liquid crystal display, and the backlight is activated after the preset frame ends. 7. The liquid crystal display according to claim 1, wherein the video signal controller comprises: a frame generator to generate the default frame; and A multiplexer receives the normal picture and the preset picture, and selects the picture content output to the liquid crystal display panel. 8. A method for improving the flickering of the screen when the liquid crystal display is turned on, the liquid crystal display has a liquid crystal display panel, and the liquid crystal display panel has a plurality of liquid crystal capacitors, the method comprises the following steps: A power-on step is to activate the power supply of the liquid crystal display; A step of activating the panel is to turn on the liquid crystal display panel at a first preset time point after the step of turning on the power; and A step of providing a preset image is to provide a preset image to the liquid crystal display panel at a second preset time point after the step of turning on the power, so as to quickly charge the liquid crystal capacitor to activate the liquid crystal layer in the liquid crystal capacitor . 9. The method according to claim 8 for improving the flickering of the screen when the liquid crystal display is turned on, after the step of providing a preset screen, further comprising a step of providing a normal screen, which is a third preset time point after the step of turning on the power A normal image is provided to the liquid crystal display panel. 10. The method according to claim 9, further comprising a step of turning on the backlight of the liquid crystal display after the step of providing a normal picture, to complete the start-up action of the display. 11. The method for improving the screen flickering when the liquid crystal display is turned on according to claim 8, wherein when the liquid crystal display panel is a twisted nematic type, the default screen is a black screen. 12 . The method for improving the screen flickering when the liquid crystal display is turned on according to claim 8 , wherein when the liquid crystal display panel is a multi-area vertical arrangement type, the default screen is a white screen. 13 . 13. The method for improving the picture flickering when the liquid crystal display is turned on according to claim 8, wherein when the liquid crystal display panel is a transverse electric field type, the default picture is a white picture.

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