JP2017167406A - Liquid crystal display device and television apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a technique capable of efficiently reducing after-image after turning off the power in a television apparatus.SOLUTION: A drive part is a circuit that drives a liquid crystal which is configured, when a power supply control part detects the power off the main power supply, to write a piece of first black data from a writing position when the power is turned off stored in a storage part. The power supply control part is configured, when the writing of the first black data reaches the point when the power supply is turned off and the writing of the first black data is written on all over a liquid crystal display panel, to shut-off a backup power supply. There is also provided a television apparatus on which the liquid crystal drive circuit is mounted.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a liquid crystal display device and a television device.

  A liquid crystal display device mounted on a television device is a flat and thin viewing angle display device that uses liquid crystal elements, has low power consumption per screen size, and can be configured to be lightweight and thin. It is used in various electronic devices as an information display device and an image display device for video.

  In such a liquid crystal display device, after the power source is shut off, charges may remain in the storage capacitor or the liquid crystal capacitor, and an image immediately before the shut-off may be displayed as an afterimage. In particular, in recent years, the number of liquid crystal display devices such as iridium gallium zinc oxide (IGZO) that easily retains electric charges has increased, and afterimages are easily displayed. Since this afterimage affects the life of the liquid crystal display device, it is required to be reduced.

  Thus, as a technique for reducing afterimages, for example, a technique for detecting power-off and writing a black image for one frame is known (see Patent Document 1). In addition, a technique has been proposed in which after the power supply to the liquid crystal display device is interrupted, two discharge processes for discharging the charges in the display panel are performed to remove residual charges (see Patent Document 2).

JP 2012-133182 A International publication WO2013 / 088779

  The technique disclosed in Patent Document 1 writes a black image by sending a gate start pulse signal (GSP) to the top line of the display panel when the power is shut off. In this technique, when the power is turned off while writing a normal image, GSP is asserted, so that a black image is written from the writing middle position and the first line. As a result, the black video writing from the first line may superimpose the line on which the black video has already been written. This also leads to an increase in the time for writing a black image, which may increase power consumption.

  Further, the technique disclosed in Patent Document 2 may cause an overcurrent in order to bring all the gate lines into a selected state.

  The present invention has been made in view of these circumstances, and an object of the present invention is to provide a technique for efficiently reducing afterimages after power-off in a liquid crystal display device.

  The first technical means of the present invention includes a liquid crystal display panel, a drive unit that drives the liquid crystal display panel, a main power source that supplies power to the liquid crystal display panel, and the liquid crystal display when the main power source is off. A backup power source that supplies power to the panel; a power source control unit that shuts off the backup power source; and a storage unit that stores a writing position of a horizontal line of the liquid crystal display panel. When detecting the off, the first black data is written from the writing position stored when the power is turned off stored in the storage unit, and the power control unit writes the first black data when the power is turned off. The liquid crystal display device is characterized in that the backup power supply is shut off when the writing position is reached and the first black data is written on the entire liquid crystal display panel.

  According to a second technical means of the present invention, in the first technical means, the first black data is written from a writing position when the power is turned off toward a leading line or toward a trailing line. It is characterized by this.

  According to a third technical means of the present invention, in the first or second technical means, the driving unit writes the first black data from a writing position stored in the storage unit when the power is turned off, and the writing is performed. According to the position, the second black data is written from the head line or the tail line toward the writing position when the power is turned off.

  According to a fourth technical means of the present invention, in the third technical means, when the writing position is the upper half of the liquid crystal panel, the gate start pulse signal is output to the end line, and the head line is output. When the second black data is written toward the lower half of the liquid crystal panel, the gate start pulse signal is output to the first line, and the second black data is output toward the last line. It is characterized by writing black data.

  A fifth technical means of the present invention is a television device equipped with the liquid crystal display device of any one of the first to fourth technical means.

  INDUSTRIAL APPLICABILITY The present invention can provide a technique for a liquid crystal driving circuit that efficiently reduces an afterimage after power-off in a liquid crystal display device mounted on a television device or the like. That is, according to the present invention, black data writing is started from the final writing position of the normal video data, and writing is ended at the position, so that the black data is not overwritten and the backup power source is wasted. Power consumption can be reduced. Further, efficient black data can be written according to the normal video writing position. Furthermore, it is possible to shorten the time required for writing black data and suppress wasteful power consumption of the backup power supply. Thus, afterimage generation can be prevented with low power. And the liquid crystal drive circuit of the said aspect can be mounted in liquid crystal display devices, such as a liquid crystal television and a liquid crystal monitor.

It is a functional block diagram of the liquid crystal display device which concerns on embodiment of this invention. It is explanatory drawing which concerns on Example 1 of Embodiment 1 of this invention. It is a flowchart which concerns on Example 2 of Example 2 of Embodiment 2 and Example 3 of Embodiment 3. FIG. It is explanatory drawing which concerns on Example 2 of Embodiment 2 of this invention. It is explanatory drawing which concerns on Example 3 of Embodiment 3 of this invention.

(Embodiment 1)
Hereinafter, preferred embodiments according to a liquid crystal display device and a liquid crystal driving circuit of the present invention will be described with reference to the drawings. In the following description, the configurations denoted by the same reference numerals in different drawings are the same, and the description thereof may be omitted.

[overall structure]
FIG. 1 is a block diagram illustrating a schematic configuration of a liquid crystal display device 100 according to the first embodiment. Referring to FIG. 1, the liquid crystal display device 100 includes a liquid crystal driving circuit 10, a main control unit 20, and a power supply circuit unit 30. The liquid crystal display device 100 is, for example, a TFT (Thin Film Transistor) active matrix liquid crystal display device, and corresponds to a liquid crystal monitor or a liquid crystal television device.

  The liquid crystal driving circuit 10 includes a source driver 11, a gate driver 12, a display panel 13, an image data circuit 14, a timing controller 15, a counter 16, and a power supply control unit 17.

  The source driver 11 is a video signal driver for driving the source bus line by sending the drive voltage output from the panel power supply 32 to a common line (source bus line) connecting the liquid crystal groups of the display panel 13. The gate driver 12 is a scanning signal driver that drives the gate bus line by sending the drive voltage output from the panel power supply 32 to a common line (gate bus line) connecting the liquid crystal groups of the display panel 13.

  The display panel 13 is, for example, an active matrix type liquid crystal display panel, and cells (not shown) are arranged in a matrix.

  When a clock signal is input from the outside, the image data circuit 14 generates a signal related to a horizontal periodic signal, a vertical periodic signal, and luminance data based on the clock signal. The synchronization signal is sent to the timing controller 15 and the luminance data is sent to the source driver 11.

  The timing controller 15 controls the operation timing of the source driver 11 and the gate driver 12. From the timing controller 15 to the gate driver 12, the gate start pulse signal GSP indicating the start horizontal line where scanning starts within one frame period in which one screen is displayed and the timing at which the plurality of electronic circuits transmit and receive signals are aligned. In addition, a clock signal GCK, which is an electric signal that is regularly engraved, is transmitted.

  The counter 16 detects and stores the position of the horizontal writing line of the display panel 13 when the main power supply 31 is turned off from the gate start pulse signal GSP and the clock signal GCK. Further, the counter 16 sends a signal to the timing controller 15 when the main power supply 31 is turned off. Further, the counter 16 sends a signal to the power supply control unit 17 when the first black data (black video) is written on the entire screen of the display panel 13 in the operation of the present embodiment described later.

  The power supply control unit 17 shuts off the backup power supply 33 to the power supply circuit unit 30 when a signal indicating that the first black data (black video) is written on the entire screen of the display panel 13 is sent from the counter 16. Send a signal to that effect.

  The main control unit 20 generates a control signal for causing the display panel 13 to display an image corresponding to an input signal from the outside. The control signal is sent to the liquid crystal drive circuit 10 and the power supply circuit unit 30.

  The power supply circuit unit 30 includes a main power supply 31, a panel power supply 32, a backup power supply 33, and a shutoff detection unit 34. The main power supply 31 distributes power supplied from the outside to each block of the liquid crystal display device 100 when the liquid crystal display device 100 is normally displaying. The panel power supply 32 converts the power supplied from the main power supply 31 into a voltage / current necessary for driving the liquid crystal drive circuit 10 and sends it to the liquid crystal drive circuit 10. The backup power supply 33 supplies power for writing the first black data (black video) according to the present embodiment when the main power supply 31 is turned off. For example, a capacitor or the like can be applied to the backup power source 33.

  The shutoff detection unit 34 detects that the main power supply 31 is turned off and transmits the power of the backup power supply 33 to the panel power supply 32. The detected result is sent to the main control unit 20.

[Description of operation]

  Next, an example of the operation in the first embodiment will be described. FIG. 2 is Example 1 of Embodiment 1, and is an explanatory diagram represented as a diagram when applied to a full high-definition (FHD) panel (number of vertical total lines 1125, number of effective lines 1080). In FIG. 2, together with Example 1 of Embodiment 1, a reference example referring to Patent Document 1 is also described. In the following description and FIG. 2, the black video is assumed to agree with the black data.

  Referring to FIG. 2, when the writing of the normal video A to the entire screen of the display panel 13 is completed, the gate start pulse signal GSP is sent, and then the video writing of the normal video B is started. The time required for full screen writing of normal video is about 16.67 ms. FIG. 2 shows a case of the panel state E10 in which the main power supply 31 is turned off after 8 ms from the start of the writing of the normal video B.

  Referring also to FIG. 1, when the main power supply 31 is turned off, the shutoff detection unit 34 detects that the main power supply 31 is turned off and sends the power of the backup power supply 33 to the panel power supply 32. The detection result signal is transmitted to the main control unit 20, and the main control unit 20 sends a reset signal RST to the timing controller 15 of the liquid crystal driving circuit 10 when the main power supply 31 is detected to be off and performs a data writing process. Force reset.

  The timing controller 15 that has received the horizontal line writing position (panel state E11) of the display panel 13 when the main power supply 31 is off stored in the counter 16 starts the black video writing process from the horizontal line writing position. (Panel state E12). After that, when the black video writing reaches the 1080 pixel line which is the last of the number of effective lines (panel state E13), the timing controller 15 sends the gate start pulse signal GSP to the first pixel line ( Panel state E14). The gate start pulse signal GSP may be sent to the head pixel line not at the end of the number of effective lines as described above but at the end of the number of vertical total lines.

  Thereafter, when the black video writing process reaches the horizontal line writing position of the display panel 13 when the main power supply 31 stored in the counter 16 is off (refer to the panel state E11), the counter 16 Is sent to the power control unit 17. Then, the power supply control unit 17 sends a signal to the power supply circuit unit 30 to cut off the backup power supply 33, and the backup power supply 33 is cut off.

  The time required for the black video writing process is about 4 ms in the case of 1/4 writing of the screen shown in the panel state E12, about 4 ms in the case of 1/2 writing of the screen shown in the panel state E13. In the case of writing shown in the state E12, the time is about 8 ms, and the total is about 16 ms.

  Next, a reference example will be described. The reference example refers to Patent Document 1 as described above. The configuration of the reference example does not include the counter 16 and the power supply control unit 17 in the present embodiment. Referring to FIG. 2, the reference example also shows the case of the panel state R10 in which the main power supply 31 is turned off 8 ms after the writing of the normal video B is started.

  When the main power supply 31 is turned off, the shutoff detection unit 34 detects that fact. The interruption detection unit 34 notifies the main control unit 20 of the detection result, and starts power supply processing from the backup power source 33 to the liquid crystal drive circuit 10. Further, the main control unit 20 starts a process of turning off the liquid crystal driving circuit 10, further superimposes the reset signal RST, and outputs the superimposed signal to the timing controller 15.

  When the backup power supply 33 is turned on and power supply is started, the image data circuit 14 and the source driver 11 end the normal video as a video signal and output a signal corresponding to the black video. Specifically, the timing controller 15 that has received the reset signal from the main control unit 20 forcibly resets the normal video writing process and sends a gate start pulse signal GSP for performing the black video writing process from the first line ( Panel state R11).

  The black video writing process starts from the writing position of the horizontal line of the display panel 13 when the leading line and the main power supply 31 are off (panel state R12). Thereafter, the black video writing process covers all the pixels of the panel (panel state R13). The black video writing process started from the first line is also performed on the lower half of the screen where black video writing has already been completed, and when the black video writing process reaches the last line of the vertical total line The black video writing process ends. However, the backup power source 33 is set so as to drive the liquid crystal driving circuit 10 for about 20 ms from the time when the main power source 31 is turned off in advance. What is the end of the black video writing process and the end of the power supply of the backup power source 33? Not linked. Therefore, it is necessary to store the power of the backup power supply 33 so that the supply can be held until the black video writing process is reliably completed.

  Example 1 according to Embodiment 1 is compared with a reference example. In the reference example, two lines of black video writing processing are performed at the same time. On the other hand, in the first embodiment, since writing is always performed on one line, peak power and power consumption can be suppressed. Further, in the reference example, a portion that becomes a duplicated black video writing process occurs. On the other hand, in the first embodiment, no overlap occurs, and unnecessary processing is eliminated. Furthermore, in the reference example, it takes about 20 ms to preset the timing for shutting off the backup power supply 33. On the other hand, in the first embodiment, the backup power supply 33 is shut off when the black video writing process is completed. The driving time is 16 ms. As described above, Example 1 according to Embodiment 1 can eliminate waste, reduce power consumption, and reduce processing time compared to the reference example.

(Other embodiments)
Next, Embodiments 2 and 3 according to the liquid crystal display device and the liquid crystal driving circuit of the present invention will be described. FIG. 3 is a flowchart according to Example 2 of Embodiment 2 of the present invention and Example 3 of Embodiment 3. FIG. 4 is an explanatory diagram according to Example 2 of Embodiment 2 of the present invention. FIG. 10 is an explanatory diagram according to Example 3 of Embodiment 3. FIG. In the following description, portions overlapping with the configuration / operation of the first embodiment are omitted as appropriate.

  Referring to FIG. 3, when the main power supply 31 is turned off, the shutoff detection unit 34 detects that the main power supply 31 is turned off (step S01). The counter 16 stores the counter value P of the writing position on the horizontal line of the display panel 13 when the main power supply 31 is turned off (step S02).

  Here, when the number of effective lines corresponding to the number of effective lines 1080 of the FHD panel is N, the counter value P of the writing position of the horizontal line is larger than ½ of N (in the case of the lower half of the FHD panel). If the number of effective lines is 1080, if the number is larger than 540, the flow proceeds to the flow of steps S10 to S17, which is the second embodiment, while if smaller than 1/2 of N (in the case of the upper half of the FHD panel), the third embodiment It progresses to the flow of step S20-step S27 which is (step S03). Each of Embodiments 2 and 3 will be described below.

(Embodiment 2, Example 2)
Referring also to FIG. 4, when it is determined that the counter value P of the writing position on the horizontal line is larger than ½ of N (panel state E20), the timing controller 15 applies a gate start pulse signal to the head pixel line. GSP is sent out (step S10, panel state E21). FIG. 4 shows a second embodiment in which the main power supply 31 is turned off about 12 ms after the normal video B is normally written (P = 810). Then, a forward black image writing process is instructed from the top to the bottom of the screen for both the head pixel line and the horizontal line writing position counter value P (step S11). This black video writing process corresponds to the writing of the first black data and the second black data.

  Then, the black video writing process is started downward from the counter value P of the writing position of the head pixel line and the horizontal line. The black video writing process started from the counter value P of the writing position of the horizontal line is performed until the end line is reached (steps S12 and 13, panel state E22). The process ends (step S14, panel state E22).

  The black video writing process corresponding to the second black data writing from the line of the first pixel is performed until the counter value P of the writing position of the horizontal line is reached (step S15, panel state E23). The black video writing process ends when the line P is reached (step S16, panel state E23). When the writing is completed, the counter 16 sends a signal to the power supply control unit 17. Then, the power supply control unit 17 sends a signal indicating that the backup power supply 33 is cut off to the power supply circuit unit 30, and the backup power supply 33 is cut off (step S17).

  According to the second embodiment related to the second embodiment, the time required for the black video writing process is 12 ms from when the main power supply 31 is turned off, thereby eliminating waste, reducing power consumption and shortening the processing time. Can do.

(Embodiment 3, Example 3)
Referring also to FIG. 5, when it is determined that the counter value P of the writing position of the horizontal line is smaller than ½ of N (panel state E30), the timing controller 15 applies a gate start pulse signal to the end pixel line. GSP is sent out (step S20, panel state E31). FIG. 4 shows a third embodiment in which the main power supply 31 is turned off about 4 ms after the normal writing of the normal video B (P = 270). Then, a reverse black image writing process is instructed from the bottom to the top of the screen for both the end pixel line and the horizontal line writing position counter value P (step S21). This black video writing process corresponds to the writing of the first black data and the second black data.

  Then, the black video writing process is started upward from the counter value P of the writing position of the end pixel line and the horizontal line. The black video writing process corresponding to the first black data writing started from the counter value P of the horizontal line writing position is performed until the head line is reached (steps S22 and 23, panel state E32). When the line is reached, the black video writing process ends (step S24, panel state E32).

  The black video writing process from the end pixel line is performed until the counter value P at the writing position of the horizontal line is reached (step S25, panel state E33). The video writing process ends (step S26, panel state E33). When the writing is completed, the counter 16 sends a signal to the power supply control unit 17. Then, the power supply control unit 17 sends a signal indicating that the backup power supply 33 is cut off to the power supply circuit unit 30, and the backup power supply 33 is cut off (step S27).

  According to Example 3 according to the third embodiment, the time required for the black video writing process is 12 ms from when the main power supply 31 is turned off, thereby eliminating waste, reducing power consumption, and shortening the processing time. Can do.

  In addition, the aspect of this invention is not restricted to the said embodiment, A deformation | transformation is possible in the range which does not deviate from the meaning.

DESCRIPTION OF SYMBOLS 10 ... Liquid crystal drive circuit, 11 ... Source driver, 12 ... Gate driver, 13 ... Display panel, 14 ... Image data circuit, 15 ... Timing controller, 16 ... Counter, 17 ... Power supply control part, 20 ... Main control part, 30 ... Power supply circuit unit 31... Main power supply 32. Panel power supply 33. Backup power supply 34. Cut-off detection unit 100.

Claims (5)

A liquid crystal display panel;
A drive unit for driving the liquid crystal display panel;
A main power supply for supplying power to the liquid crystal display panel;
A backup power source for supplying power to the liquid crystal display panel when the main power source is off;
A power control unit for cutting off the backup power;
A storage unit that stores a writing position of a horizontal line of the liquid crystal display panel,
When the driving unit detects that the main power supply is turned off, the driving unit writes first black data from the writing position stored in the storage unit when the power is turned off.
The power supply control unit includes the backup power supply when the writing of the first black data reaches the writing position when the power is turned off and the first black data is written on the entire liquid crystal display panel. A liquid crystal display device characterized by:   2. The liquid crystal display device according to claim 1, wherein the first black data is written toward a leading line or a trailing line from a writing position when the power is turned off.   The drive unit writes the first black data from the write position when the power is turned off stored in the storage unit, and the write position when the power is turned off from the head line or the tail line according to the write position. The liquid crystal display device according to claim 1, wherein the second black data is written toward When the writing position is the upper half of the liquid crystal panel, the gate start pulse signal is output to the tail line, and the second black data is written toward the head line,
When the writing position is the lower half of the liquid crystal panel, the gate start pulse signal is output to the leading line, and the second black data is written toward the trailing line. Item 4. A liquid crystal display device according to item 3. A television device on which the liquid crystal display device according to any one of claims 1 to 5 is mounted.

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