JP2002229507A - Matrix type display device and driving method therefor, and portable information terminal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent a screen from being burnt when a same picture is always displayed, in a display device performing gradation display by frame rate control(FRC). SOLUTION: To prevent burning, the display device is made to alternately display a video signal and a non-display signal at regular intervals. In this case, to prevent a period for replacing display from varying due to a difference between full screen display and partial display, a rate for varying a ratio of a non-display area to video display area is altered according to the number of display lines.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display having a matrix pixel structure.

[0002]

2. Description of the Related Art Liquid crystal display panels are widely used in portable devices and the like because of their thinness and low power consumption. Devices such as word processors, personal computers, televisions (TVs), viewfinders for video cameras, and monitors are also used. It is also used for In recent years, a reflective liquid crystal display panel using external light as a light source without using a backlight has been adopted.

[0003]

When ultra-low power consumption is required for a portable telephone or the like, there is a problem that the power consumption is large relative to the required power. Therefore, there is a partial display mode in which a minimum display is displayed on a part of the screen when the user does not perform a key operation or a call. However, in the case of this display method, there is a case where a video signal is not input in order to reduce power, and a change in a displayed image is small. There is a problem. This occurs regardless of a display material such as a CRT display or an organic light emitting element as well as a liquid crystal display.

[0004]

In order to solve these drawbacks, a display device according to the present invention is applied to a matrix type display device which performs gradation display by frame rate control (FRC). Signals are alternately applied to the segment signal lines using FRC processing so that the display state can be changed at certain intervals without exchanging signals with the outside.

[0005]

Embodiments of the present invention will be described below with reference to the drawings.

The contents described in each drawing and the like can be combined with other embodiments and the like without any particular notice. For example, a combination of the burning prevention methods shown in FIGS. 1 and 3 and a configuration in which the display device shown in the embodiment of FIG. 1 is introduced into the display unit of FIG. That is, the items described in the drawings and the specification of the display panel and the like of the present invention can be combined with each other without individually describing the display device and the like of the embodiment.

As described above, even if not specifically exemplified in the specification, the matters described or explained in the specification and drawings,
The contents and specifications can be described in the claims in combination with each other. This is because it is impossible to describe all combinations in a specification or the like.

(First Embodiment of the Invention) FIG. 1 shows a functional block diagram according to a first embodiment of the present invention. Reference numeral 20 denotes a gray scale register circuit. The output of the gray scale register is a result of frame rate control of each gray scale.
9 has been entered. This example shows an example of eight gradation display from 0 to 7, and data of gradations 1 to 6 excluding gradation 0 and gradation 7 is input. Gradation 0 and gradation 7
Is turned off all the time or turned on all the time, and can be handled by the gradation selection circuit 29. The gradation register performs shift operation processing by an amount stored in the shift amount holding RAM 22 in accordance with the horizontal synchronization signal 26 and the vertical synchronization signal 27. The input video signal 28, which is generally a multi-tone signal, is
Is converted to 1-bit on / off data. This conversion unit is a gradation selection circuit 29, which selects a corresponding gradation register output according to the gradation of the input video signal 28 and outputs FRC data. The output 18 of the gradation selection circuit 29 is supplied to a segment signal line or used as an input signal matrix in a matrix operation with an orthogonal function matrix in the case of multi-line select (MLS) driving.

FIG. 2 shows a method for preventing burn-in of the display section. FIG. 2A shows the case of full-screen display, and FIG. 2B shows the case of partial display, and changes to the pattern shown on the right over time. According to this, the display patterns are erased in order from the top (two from the left end), and when the whole is not displayed (third from the left), it is displayed again from the top (fourth and fifth from the left), Display the entire display area (right end).
In order to realize this, the frame count circuit 24 and the row number count circuit 25 shown in FIG. 1 are used. If the line count is changed every four frames by four lines, as shown in the example of FIG. 2A, when the frame count value is 0 to 3, the controller 23 selects the gradation only when the row count value is 0. The circuit 29 is controlled to output a non-display signal regardless of the input video signal 28. When the frame count value is 4 to 7, the non-display signal is selected when the row count value is 0 or 1, and otherwise, the output of the gradation register according to the gradation of the input video signal 28 is selected. Hereinafter, the same operation is repeated. The number of frames required for this series of operations is 160
The number of frames is 320 frames for a line panel, and 80 frames when a partial display of only 40 lines is displayed. If the frame frequency is 100 Hz, the displayed time is 1.6 seconds in FIG. 2A and 0.4 seconds in FIG. 2B.
At this speed, the display time is short and the display contents cannot be confirmed. Therefore, it was changed so that it changed by 4 lines every 32 frames. As a result, the display time (A) was 12.8 seconds, the display information could be confirmed, and burn-in could be prevented. The display time T of the display area is T = 1 / F × (N / 4 × A), assuming that the display area is changed by 4 lines per frame frequency F, the number of display rows N, and A frames.
It is represented by Assuming that the frame frequency F is specified as a constant value, if the display time is to be reduced to about 12 to 15 seconds, the number of frames A for changing the display area needs to be changed according to the number of display rows N. FIG. 6 shows the relationship between the number N of display rows and the display time T when the number of rows in the display area is changed for each A frame when the frame frequency is 100 Hz. In order to make the display time of the display area constant regardless of the number of display rows, the number of frames A required to change the display area is changed according to the number of display rows, and N × A = 4 × T × F = constant I just need to be. Therefore, information on the number of display rows N is input to the controller 23 as the display area signal 19, and the number of rows and the number of frames to which the gradation selection circuit 29 outputs the non-display signal are changed according to the display area signal 19. As a result, it is possible to realize a panel having different display areas and a burn-in prevention circuit corresponding to display switching of the entire screen.

(Embodiment 2) In Embodiment 1 of the present invention, the time T during which a display area is displayed when a countermeasure against burning is performed is determined by the frame frequency F, the number of rows N in the display area, and the non-display time. It is shown that it depends on the number A of frames required to increase or decrease the area. Although the frame frequency is constant in the first embodiment, the frame frequency may be changed depending on the number of display gradations and a still image / moving image in order to prevent flicker during gradation display by FRC. In this case, the rate of increase / decrease of the non-display area changes depending on the number of display gradations and the still image / moving image, so that a countermeasure is required. Therefore, as shown in FIG. 3, information on the frame frequency is input to the controller 23, and the non-display signal output of the gradation selection circuit 29 is controlled by the frame frequency. Assuming that N and A are constant, T × F = N × A / 4
When the control is made constant, the time T during which the display area is displayed can be made constant regardless of the frame frequency. In addition, in FIG. 3 and this description, N and A were carried out while being fixed,
By the combination of the first and second embodiments, the time T during which the display area is displayed for any of N, A, and F can be constant.

(Embodiment 3) In the burn-in prevention method according to the present invention, the non-display portion as shown in FIG. 2 is controlled by the controller 23 in FIGS. For gradation, gradation 0 or 8
And outputs the non-display signal. During this time, the input video signal 2
8 has no effect on the operation. Since the video signal 28 is the output of the RAM storing the display data, the operation of the RAM may be stopped during this period. By stopping the RAM, power consumption can be reduced.

When the display device is driven by the n-row simultaneous selection method, the output 18 of the gradation selection circuit 29 becomes an element of the input signal matrix, and the voltage applied to the segment signal line is calculated by the matrix operation with the orthogonal function matrix. decide. The orthogonal function matrix has a value of 1 or -1 when the common signal line is selected, and has a value of 0 when it is not selected. Therefore, one row of the orthogonal function matrix has n
Since there are 1 or −1, at least n row data of the input signal matrix are required to output the product of the input signal matrix and the orthogonal function matrix corresponding to a certain horizontal scanning period, and n of the row data are It is necessary to correspond to the row selected by the common signal line. Therefore, it is necessary to simultaneously input n rows of the input video signals 28 within one horizontal scanning period. Therefore, n lines 28 are provided for each segment or one line is used for high-speed transfer. In the method of increasing the non-display area one by one, if at least one of the n rows selected at the same time occupies the display area, the other n−1
RAM must be moved even if the book is not displayed, but n
If the number is increased by n, the n sets are all divided into display or non-display, and the operation of the RAM can be controlled for each horizontal scanning period to enable the RAM to operate effectively.
Necessary information from the AM can be extracted with the least power consumption.

(Embodiment 4) In the third embodiment, the display area is changed by n rows in order to simplify the reading of the RAM and reduce the power consumption. 2 becomes steep, and the scroll operation of the non-display portion shown in FIG. 2 becomes unnatural. Therefore, the non-display portion is increased or decreased for each row. The control method from the controller 23 to the gradation selection circuit 29 in the increase / decrease for every n rows is either of selecting the output of the gradation register by the input video signal or forcibly outputting the non-display signal. In the case of each row, it is necessary to simultaneously perform the two different processing methods described above within the same horizontal scanning period.
As a method, a method of inserting black into a video signal corresponding to a non-display portion, or forcibly selecting a gradation indicating a non-display signal at a timing when row data of the non-display portion is sent. is there. In this method, the power consumption is increased as compared with the third embodiment. However, in the case of simultaneous selection of eight or more rows, if the non-display area is increased or decreased one line at a time, the scroll of the non-display part becomes smooth, and the effect is large.

(Fifth Embodiment of the Invention) A fifth embodiment of the present invention is provided with a circuit which allows the user to select whether or not to apply the burn-in prevention method as shown in FIG. 2 by using an external switch or the like. It is a form of. A manual changeover switch 71 is connected to the controller 23 of FIG. 7, and the output of the changeover switch 71 allows the user to select whether or not to prevent burn-in. As a method of realizing this, as shown in FIG.
The operation of [1] can be set so that the display of burn-in prevention can be set on or off. The present invention can be similarly applied to a television, a PDA, and the like as well as the portable information terminal.

(Embodiment 6) In the non-display section, white or black is displayed on the screen. This is because when the controller 23 controls the gradation selection circuit 29, the gradation 0 in the case of M gradation display is selected as the non-display signal or the gradation (M
-1) is determined. The controller 23 refers to the non-display-portion black-and-white selection signal 51 and, based on the result of the signal 51, transmits to the gradation selection circuit 29 which gradation is to be inserted in the non-display portion. In general, the display at the time of non-display is gradation 0
Alternatively, white or black display of gradation (M-1) is conceivable, but the present invention is not limited to this, and display may be performed with gradation changed according to halftone or display color. If this method is applied, it can be applied to the case of displaying a single gradation (displaying wallpaper). As shown in FIG. 8, a wallpaper gradation designation signal 81 is input to the controller 23, and the controller 2
Reference numeral 3 controls the gradation selection circuit 29 so that a wallpaper having a desired gradation value can be displayed. When the wallpaper is displayed in this manner, if only the wallpaper is displayed, the output from the RAM is not required, and the signal and clock for reading the RAM can be stopped, and low power consumption can be realized. The wallpaper gradation specifying signal 81 may specify a different gradation for each display primary color. For example, different gray levels may be set for each of the three primary colors of light, red, green, and blue. In an inorganic electroluminescent element, different gray levels may be specified for each of the red, green, and yellow signal lines. Although it is possible to specify a different gradation for each pixel, the controller 23
This is not preferable because the area required for wiring to the gradation selection circuit 29 increases. At best, each display primary color is appropriate.

(Embodiment 7) When a liquid crystal display is used as a display device, whether to display white or black when no voltage is applied differs depending on the liquid crystal material used. Therefore, the NWNB signal 58 shown in FIG.
Are set to white on a white panel when no voltage is applied and black on a black panel. From the output of the gradation register circuit 20, the input signal of the voltage selection circuit 57 is expressed as 1 on and 0 off. Therefore, when the gradation 0 representing black is output, 0 is always output. This can be output as it is in a black display device when no voltage is applied, but white is displayed in a white display device when no voltage is applied. Therefore, the NWNB signal 58
When it is determined that the white display device is connected when no voltage is applied, the bit inversion is performed, and the output of gradation 0 is set to 1,
Enable to display black. This bit inversion operation is realized by inverting the value of the orthogonal function 53 by the inversion processing circuit 54. After the inversion processing, a matrix operation is performed by passing the output of the gradation selection circuit 29 and the MLS operation unit 55 and the addition circuit 56 to perform voltage selection.

The reason why the negative / positive reversal can be performed in this way is explained as follows. The matrix operation is represented as follows by using the symbols shown in FIG.

B [3] × H [3] + B [2] × H [2] + B [1]
× H [1] + B [0] × H [0] Since each bit of B and H is 1 or 0, the multiplication can be replaced with exclusive OR. The negative / positive inversion can be realized by taking the bit inversion of the video signal B. Further B
The value of the exclusive OR of the signal after inversion of H and H is equal to the exclusive OR of the signal after inversion of H and B. Therefore, instead of inverting B, the inversion processing circuit 54 inverts the orthogonal function H to realize negative / positive inversion. As a result, not only the display portion but also the non-display portion provided for preventing burning can be inverted at the same time, and the display color of the non-display portion (13 in FIG. 2) can be made the same regardless of the voltage-luminance characteristics of the panel. Becomes possible. Further, by combining the non-display part with the sixth embodiment, it is possible to perform the negative / positive reversal only in the non-display part.

In the above description, the number of display gradations is eight.
Although the gradation is used, the present invention is not limited to this, and a multi-gradation display (about 1 to 64 gradations) can be provided by preparing (gradation number−2) gradation registers and connecting to the gradation selection circuit 29. It is possible to

FIG. 4 shows a display device using at least one of the first to eighteenth embodiments. A demodulation device is provided inside a casing 43, an antenna 41 and a button 44 are attached, and It is a portable information terminal.

[0021]

As described above, according to the present invention, when a video signal and a non-display signal are alternately displayed in order to prevent burn-in in the simultaneous selection of n rows, an area where the non-display signal and the video signal are displayed is displayed. The rate of change can be changed according to the size of the display area, and the cycle of alternate display can always be constant. Further, it is possible to invert black and white of only the non-display area or the entire display unit of the display device by an external operation.

[Brief description of the drawings]

FIG. 1 is a diagram showing a gradation display unit and a non-display signal insertion unit of a display device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing an example of a display pattern when burn-in prevention is set according to the embodiment of the present invention.

FIG. 3 is a diagram showing a gradation display unit and a non-display signal insertion unit of a display device according to a second embodiment of the present invention.

FIG. 4 is a diagram showing an example in which the display device of the present invention is incorporated in a portable information terminal.

FIG. 5 is a diagram illustrating a gradation control unit, an MLS operation, and a segment voltage selection signal generation unit of a display device according to a sixth embodiment of the present invention.

FIG. 6 is a diagram showing a period during which an image is displayed in the first embodiment of the present invention.

FIG. 7 is a diagram illustrating a gradation display unit and a non-display signal insertion unit of a display device according to a fifth embodiment of the present invention.

FIG. 8 is a diagram illustrating a gradation control unit, an MLS operation, and a segment voltage selection signal generation unit of a display device according to a sixth embodiment of the present invention.

[Explanation of symbols]

 Reference Signs List 19 display area signal 20 gradation register circuit 21 gradation control unit 22 shift amount holding RAM 23 controller 24 frame count circuit 25 row count circuit 26 horizontal synchronization signal input 27 vertical synchronization signal input 28 input video signal 29 gradation selection circuit

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) G02F 1/133 545 G02F 1/133 545 575 575 G09G 3/36 G09G 3/36 5/00 550 5/00 550B (72) Inventor Atsuhiro Yamano 1006 Kazuma Kadoma, Osaka Pref. Matsushita Electric Industrial Co., Ltd. F term (reference) 2H093 NA47 NA55 NC11 NC22 NC27 ND06 ND12 ND39 ND60 5C006 AA14 AC24 AF42 AF44 AF59 BB11 BC03 BC11 BF08 BF22 FA47 5C080 AA10 BB05 DD18 DD26 EE26 EE29 FF12 JJ01 JJ02 JJ06 5C082 AA00 BA02 BA12 BB42 CA52 CB01 DA51 MM03

Claims (10)

[Claims] In a matrix type display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing, a RAM for holding a shift amount, a frame count circuit for detecting the number of frames being scanned and the number of sets for each n rows by a horizontal synchronization signal and a vertical synchronization signal, a row number counting circuit, and a segment. A gray scale selection circuit provided for each signal line, wherein the gray scale selection circuit uses the output of the gray scale register at the same time according to the display area, the number of frames, and the number of sets for every n rows, and selects n rows. A matrix-type display device, which performs gradation processing, changes the output of a gradation selection circuit to a non-display signal, or changes the processing method. 2. A matrix display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, wherein a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing, a RAM for holding a shift amount, a frame count circuit for detecting the number of frames being scanned and the number of sets for every n rows by a horizontal synchronization signal and a vertical synchronization signal, a row number counting circuit, A gray scale selection circuit provided for each segment signal line, wherein the gray scale selection circuit uses the output of the gray scale register at the same time according to the frame frequency, the number of frames, and the number of sets of n rows, for n rows. A matrix-type display device, which performs gradation processing, changes the output of a gradation selection circuit to a non-display signal, or changes the processing method. 3. A gray scale display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, wherein a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing, a RAM for holding a shift amount, a frame count circuit for detecting the number of frames being scanned and the number of sets for every n rows by a horizontal synchronization signal and a vertical synchronization signal, a row number counting circuit, A gradation selection circuit provided for each segment signal line, wherein the frame count circuit and the row count circuit increase or decrease the display area by n rows for each of a plurality of frames; A matrix-type table for performing gradation processing of n rows using an output of a register and outputting a non-display signal in a non-display area. Apparatus. 4. A matrix type display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, wherein a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing, a RAM for holding a shift amount, a frame count circuit for detecting the number of frames being scanned and the number of sets for every n rows by a horizontal synchronization signal and a vertical synchronization signal, a row number counting circuit, A gradation selection circuit provided for each segment signal line; a display area is increased or decreased by one line for each of a plurality of frames by the frame count circuit and the row number count circuit; In the case of an area, gradation processing of n rows is performed using the output of the gradation register at the same time, and all n rows are not displayed in the non-display area. And outputs the issue,
When both the display area and the non-display area exist, only the row of the display area performs the gradation processing of n rows using the output of the gradation register at the same time, and the non-display area outputs a non-display signal. A matrix type display device characterized by the above-mentioned. 5. A matrix display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, wherein a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing, a RAM for holding a shift amount, a frame count circuit for detecting the number of frames being scanned and the number of sets for each n rows by a horizontal synchronization signal and a vertical synchronization signal, a row number counting circuit, and a segment. A gray scale selection circuit provided for each signal line, wherein the gray scale selection circuit uses the output of the gray scale register at the same time according to the display area, the number of frames, and the number of sets for every n rows, and selects n rows. You can select whether to perform gradation processing or use the output of the gradation selection circuit as a non-display signal, or change the processing method, and select whether to output a non-display signal with an external switch. Matrix display device is characterized in that the. 6. A gray scale display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, wherein a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing, a RAM for holding a shift amount, a frame count circuit for detecting the number of frames being scanned and the number of sets for every n rows by a horizontal synchronization signal and a vertical synchronization signal, a row number counting circuit, Switching means for displaying white or black on the non-display portion; and a gradation selection circuit provided for each segment signal line, wherein the gradation selection circuit has the same number of frames and n rows at the same time. The processing method is changed by performing the gray scale processing of n rows using the output of the gray scale register, or setting the output of the gray scale selection circuit as a non-display signal, and changing the processing method by the switching unit. Change processing of the gradation selection circuit, a matrix type display device, wherein a black and white hiding portion is to be inverted. 7. In a matrix type display device in which a plurality of rows (n rows) of common signal lines are selected at the same time, when displaying at least the same display primary color at the same gray scale, a gray scale register circuit and the gray scale register circuit A gray scale control unit that shifts the gray scale register with a horizontal synchronizing signal or a vertical synchronizing signal, a RAM that holds a shift amount, the number of frames being scanned by the horizontal synchronizing signal and the vertical synchronizing signal, and a set of n rows. A frame count circuit for detecting the number, a row number count circuit, a gray scale data input for performing the same gray scale display, and a gray scale selection circuit provided for each segment signal line. , N-row processing is performed using the output of the gray-scale register at the same time according to the number of sets of n rows, and the gray-scale register of the gray-scale register is processed according to the gray scale of the input video signal. In a region in which the same gradation is displayed in the same display primary color by selecting a force, a specific gradation can be selected regardless of an input video signal by a controller which refers to the gradation data input. apparatus. 8. A matrix display device for simultaneously selecting a plurality of rows (n rows) of common signal lines, wherein a gray scale register circuit and a gray scale register of the gray scale register circuit are shifted by a horizontal synchronization signal or a vertical synchronization signal. A gradation control unit for processing; a RAM for holding a shift amount; a frame count circuit for detecting the number of frames being scanned and the number of sets for every n rows by a horizontal synchronization signal and a vertical synchronization signal; Switching means for displaying white or black on the non-display portion; a gradation selection circuit provided for each segment signal line; a ROM holding an orthogonal function; an inversion processing circuit for inverting the sign of the orthogonal function; An MLS circuit and an addition circuit for calculating the orthogonal function and the video data to determine a voltage to be applied to the segment signal line; A voltage selection circuit for switching a voltage required for the connection signal line. The gradation selection circuit performs gradation processing of n rows by using the output of the gradation register at the same time according to the number of frames and the number of sets of n rows. A matrix type display device, wherein the processing method is changed, whether to perform the output or the output of the gradation selection circuit as a non-display signal, and inverting the display of the entire screen by the inversion processing circuit. 9. A portable information terminal comprising the display device according to claim 1, a demodulation circuit, and a key input circuit. 10. A frame rate control (FR)
In a matrix type display device for performing gray scale display by the method C), a gray scale register circuit, a gray scale control unit for shifting a gray scale register of the gray scale register circuit by a horizontal synchronizing signal or a vertical synchronizing signal, , A frame count circuit for detecting the number of frames and rows being scanned by the horizontal synchronization signal and the vertical synchronization signal, a row number counting circuit, and a gradation selection circuit provided for each segment signal line. The gradation selection circuit selects and outputs the output of the gradation register corresponding to the input video signal or outputs the non-display signal according to the display area, the number of frames and the number of rows during the previous scanning. Or a processing method is changed.