JP5017810B2 - Display driving device and display device - Google Patents

Description

  The present invention outputs gradation voltages corresponding to display data to a plurality of signal lines of a display panel including a plurality of display pixels arranged in a matrix in the vicinity of intersections of a plurality of scanning lines and a plurality of signal lines. The present invention relates to a display driving device and a display device including the display driving device and a display panel.

  As a typical example of a display panel, an active matrix liquid crystal display panel is known. In this active matrix type liquid crystal display panel, a pixel electrode (display pixel) connected to a signal line via a switching element (for example, a thin film transistor (TFT)) is disposed opposite to the pixel electrode. Liquid crystal is filled between the common electrode and an electric field is formed between the two electrodes, thereby driving the liquid crystal.

  FIG. 10 is a block diagram showing a schematic configuration of a conventional active matrix type liquid crystal display device 100. In FIG. 10, the display panel 110 includes a pixel-side substrate 200 made of a transparent substrate such as glass, a counter substrate 210 made of a transparent substrate such as glass provided opposite to the display region 150 of the pixel-side substrate 200, and a display region. 150 and a liquid crystal sandwiched between the counter substrate 210. A signal driver 120 and a scanning driver 130 are provided around the display area 150 of the pixel-side substrate 200, and a plurality of signal lines S connected to the signal driver 120 are arranged in the column direction in the display area 150. In addition, a plurality of scanning lines (gate lines) G connected to the scanning driver 130 are arranged in the row direction so as to be orthogonal to the signal lines S. In addition, pixel electrodes are connected near the intersections of the scanning lines G and the signal lines S via TFTs.

  On the other hand, a common electrode 140 made up of one sheet-like electrode is formed on almost the entire surface of the counter substrate 210 facing the pixel side substrate 200. The pixel-side substrate 200 and the counter substrate 210 are arranged to face each other with a predetermined interval, and the periphery thereof is sealed with a sealing material containing a spacer such as glass, and liquid crystal is held in the gap. Yes. A common voltage Vcom for forming an electric field with the pixel electrode is supplied to the common electrode 140 from the pixel side substrate 200 side. The supply of the common voltage Vcom to the common electrode 140 is, for example, as shown in FIG. This is performed from the power feeding units 141 to 144 provided at the four corners of the common electrode 140. As described above, Patent Documents 1 and 2 are known as examples of liquid crystal display devices having power feeding portions at the four corners of the common electrode.

  When the common voltage Vcom inverted at a predetermined cycle is applied from the power feeding units 141 to 144 to the common electrode 140, the peripheral part of the common electrode 140 close to the power feeding units 141 to 144 (for example, points A and C shown in FIG. , The waveform of the common voltage Vcom is hardly deteriorated, but the central portion of the screen away from the power supply portions 141 to 144 (for example, point B shown in FIG. ”), The waveform of the common voltage Vcom becomes dull due to the resistance component of the common electrode 140, and VcomDC (direct current component) decreases.

FIG. 11 is a graph showing an outline of the waveform of the common voltage Vcom at the points A to C and the DC component VcomDC thereof. FIG. 4A shows the point A, FIG. 2B shows the point B, and FIG. 4C shows the common voltage Vcom and the DC component VcomDC at the point C. FIGS. As shown in FIG. 4, the waveforms of the common voltages Vcom _A and Vcom _C at the points A and C are hardly deteriorated, and the direct current components VcomDC _A and VcomDC _C are not lowered. On the other hand, as shown in FIG. 5B, at the point B, the waveform of the common voltage Vcom _B becomes dull and the DC component VcomDC _B decreases.

Since the deterioration of the common voltage Vcom is caused by the resistance value of the sheet-like common electrode 140, the degree of deterioration becomes prominent in proportion to the separation distance from the supply units 141 to 144. Therefore, the larger the screen, the larger the difference between VcomDC at the power feeding peripheral part and the screen central part.
JP 2000-162629 A JP-A-6-194679

  As described above, since the waveform of the common voltage Vcom deteriorates in accordance with the separation distance from the supply units 141 to 144, a difference occurs in the DC component VcomDC of the common voltage Vcom between the power feeding peripheral portion and the screen center portion. When there is a difference in VcomDC in the display panel, there is a problem that flicker occurs in the screen.

  That is, in the liquid crystal display device, inversion driving is generally performed. The inversion driving is a driving method in which the electric field (polarity) between the pixel electrode and the common electrode is inverted at a predetermined period. As described above, the liquid crystal determines the alignment (or more precisely, the direction) according to the electric field between the electrodes. However, if an electric field is applied only in one direction, the two glass substrates that sandwich the liquid crystal may be baked. Since this causes deterioration and breakage of the liquid crystal, the electric field is periodically reversed to prevent these problems.

  In this case, the voltage applied to the liquid crystal is a value based on the potential difference between the signal voltage Vsig applied from the signal line to the pixel electrode and the common voltage Vcom applied to the common electrode 140, and thus the direct current of the common voltage Vcom If the value of the component VcomDC is constant, the center level of the signal voltage Vsig supplied from the signal driver (hereinafter referred to as “signal voltage Vsig / c”) and the DC component VcomDC of the common voltage Vcom are applied to the liquid crystal. By adjusting the values so that the positive voltage component and the negative voltage component are substantially equal, flicker can be prevented from occurring on the screen. However, if there is a difference in VcomDC in the display panel, the signal voltage Vsig / c is constant in each signal line, so that flicker can be prevented from occurring in a part of the screen. It was not possible to prevent flicker from occurring as a whole.

  That is, as shown in FIG. 12A, the value of VcomDC changes according to the position in the display panel with respect to a constant signal voltage Vsig / c. Differences Δa to Δc between Vsig / c and VcomDC vary depending on the position in the display panel. Therefore, even if the values of the signal voltages Vsig / c and VcomDC are adjusted to optimum values according to a certain place on the display panel, the values of the signal voltages Vsig / c and VcomDC are optimum values at other places. It will shift from. For example, as schematically shown in FIG. 12B, when the signal voltage Vsig / c at the point B in the center of the screen is adjusted to an optimum value, flicker at the point B can be eliminated, Flickers occur at points A and C of the section. On the other hand, as schematically shown in FIG. 12C, when the signal voltage Vsig / c at the point A in the periphery of the power feeding is adjusted to an optimum value, flicker at the points A and C can be eliminated. Flicker occurs at point B in the center of the screen.

  An object of the present invention is to improve the display quality by suppressing the flicker generated on the display panel due to the change in the difference between the DC component of the common voltage and the center level of the gradation voltage over the entire screen. is there.

In order to solve the above problems, the invention of claim 1 includes a plurality of pixel electrodes arranged in a matrix at intersections near the plurality of scan lines and a plurality of signal lines, facing the plurality of pixel electrodes a common electrode, a plurality of display pixels composed of a liquid crystal sandwiched between the pixel electrode and the common electrode, and a display panel comprising a, a signal voltage corresponding to the display data to each of said plurality of signal lines A plurality of signal side driving means to be applied; a scanning side driving means for sequentially outputting scanning driving signals to the plurality of scanning lines to sequentially set the display pixels to a selected state; and generating a common voltage that is inverted at a predetermined cycle. Te, in a display device and a common voltage generating means for applying to the common electrode to the common voltage from the power supply portion provided in at least one place of the common electrode, each of the plurality of signal-side drive means a predetermined Provided for in each of the signal lines, each of said signal-side drive means, at least, up to the switching either voltage obtained by correcting the predetermined maximum gradation reference voltage or outermost high gradation reference voltage, and outputs as the highest reference voltage by switching the gradation reference voltage correction means, one of the corrected voltage a predetermined minimum gradation reference voltage or outermost low gray scale reference voltages, and the lowest gradation reference voltage correction means for outputting a minimum reference voltage, the highest Means for generating and outputting a plurality of gradation voltages corresponding to the number of gradations of the display data based on a reference voltage and the minimum reference voltage; A gradation voltage selection unit that selects the gradation voltage according to the gradation value of the display data and outputs the gradation voltage to each signal line as the signal voltage; and the gradation voltage in each signal side driving unit Generation Stage, depending on the voltage value of the maximum reference voltage and the lowest reference voltage output from the maximum gray level reference voltage correction means and said minimum gradation reference voltage correction means, the center level of said plurality of gradation voltages The highest gradation reference voltage correction means and the lowest gradation reference voltage correction means are set individually, and the voltage values of the highest reference voltage and the lowest reference voltage are set to a distance from the power supply unit in the common electrode. Accordingly, the potential difference between the average voltage value of the signal waveforms of the different common voltages and the center level of the plurality of gradation voltages is set to a preset value so as to approach a constant value .

According to a second aspect of the invention, in the display device according to claim 1, wherein the maximum gradation reference voltage correction means includes means for outputting a voltage lower than the maximum gray-level reference voltage as the highest reference voltage The lowest gradation reference voltage correcting means has means for outputting a voltage higher than the lowest gradation reference voltage as the lowest reference voltage.

The invention according to claim 3, a common electrode facing the plurality of pixel electrodes arranged in a matrix at intersections near the plurality of scan lines and a plurality of signal lines, to the plurality of pixel electrodes, pixel electrodes a signal-side drive means for applying a plurality of display pixels composed of a liquid crystal sandwiched between the common electrodes, a display panel comprising a, a signal voltage corresponding to the display data to each of said plurality of signal lines and the Scanning-side driving means for sequentially outputting scanning driving signals to a plurality of scanning lines to sequentially set the display pixels in a selected state; and generating a common voltage that is inverted at a predetermined cycle, and the common voltage is at least supplied to the common electrode in the display device comprising: a common voltage generation means for applying to the common electrode from the feeding section provided in one place, the said signal-side drive means, at least, a predetermined maximum gradation reference voltage or outermost high tone By switching either voltage obtained by correcting the reference voltage, by switching the maximum gradation reference voltage correction means for outputting as the highest reference voltage, one of the predetermined minimum gradation reference voltage or outermost low gradation reference voltages corrected voltage a minimum gradation reference voltage correction means for outputting a minimum reference voltage, the maximum reference voltage and based on said minimum reference voltage, means for generating and outputting a plurality of gradation voltages corresponding to the gradation number of the display data And a gradation voltage generating means that selects the gradation voltage corresponding to the gradation value of the display data from the plurality of gradation voltages and outputs the gradation voltage to each signal line as the signal voltage a plurality selection means, to a predetermined number of signal lines in said plurality of signal lines, the gradation voltage generating circuit, the output from the highest gray level reference voltage correction means and said minimum gradation reference voltage correction means In accordance with the voltage value of the maximum reference voltage and the lowest reference voltage, the center level of said plurality of gradation voltages generated by the gradation voltage generating means, is set individually for each of the predetermined number of signal lines The highest gradation reference voltage correction means and the lowest gradation reference voltage correction means differ in the voltage values of the highest reference voltage and the lowest reference voltage according to the distance from the power supply unit in the common electrode. It characterized that you set the voltage value to a preset value so as to approach the potential difference at a constant value of the center level of said plurality of gray scale voltages of the average voltage of the signal waveform of the common voltage.

According to a fourth aspect of the present invention, in the display device according to the third aspect , the highest gradation reference voltage correction means includes means for outputting a voltage lower than the highest gradation reference voltage as the highest reference voltage. The lowest gradation reference voltage correcting means has means for outputting a voltage higher than the lowest gradation reference voltage as the lowest reference voltage.

According to the present invention, the plurality of gradation voltages corresponding to the number of gradations of the display data are the highest reference voltage based on the highest gradation reference voltage or a corrected voltage, and the lowest gradation reference voltage or a corrected voltage. The center level of the gradation voltage can be changed by the correction of the highest gradation reference voltage and the correction of the lowest gradation reference voltage. Therefore, for example, when a plurality of signal lines of a display panel are driven by a plurality of signal side drive means, the center level of the gradation voltage in each signal side drive means is individually set to apply to the common electrode of the display panel. The difference between the average voltage and the center level of the grayscale voltage that differ depending on the distance from the power supply unit within the common electrode can be made substantially uniform regardless of the display position on the display panel. It becomes like this. Thereby, it is possible to improve the display quality by suppressing the occurrence of flicker in the entire screen of the display panel.

Hereinafter, embodiments in which the present invention is applied to a liquid crystal display device will be described in detail with reference to the drawings.
[First Embodiment]
FIG. 1 is a block diagram showing a configuration of a liquid crystal display device according to the present invention. The liquid crystal display device 1 includes a liquid crystal display panel 10, signal drivers 20a to 20c, a scanning driver 30, an RGB decoder 40, a VCOM generation circuit 50, an LCD controller 60, and a voltage generation circuit 70. The

  In the liquid crystal display panel 10, a plurality of signal lines S connected to the signal drivers 20a to 20c and a plurality of scanning lines G connected to the scanning driver 30 are arranged so as to be orthogonal to each other. Display pixels are two-dimensionally arranged in the vicinity of each intersection with the line S.

  FIG. 2 shows an equivalent circuit of the display pixel. In the figure, the display pixel includes a TFT 91 which is an active element, a pixel electrode 92 connected to the scanning line G and the signal line S via the TFT 91, and a counter electrode (common common to the pixel electrode 92). Electrode) 93, a pixel capacitor (liquid crystal capacitor) 94 in which liquid crystal is filled between the pixel electrode 92 and the counter electrode 93, and a signal voltage applied to the pixel capacitor 94 is provided in parallel with the pixel capacitor 94. And an auxiliary capacity 95 to be held.

  When a scanning signal (gate pulse) is sequentially applied to each scanning line G by the scanning driver 30 to be in a selected state (high potential state), the TFT 91 of each corresponding display pixel is turned on. Then, the signal voltage applied to each signal line S from the signal drivers 20 a to 20 c is applied to each pixel electrode 92 via the TFT 91, whereby the voltage between the signal voltage and the common voltage Vcom applied to the counter electrode 93. The difference is applied to and charged in the pixel capacitor 94 of each display pixel, and the alignment state of the liquid crystal molecules in each display pixel is controlled according to the voltage difference. As a result, a desired image is displayed on the liquid crystal display panel 10.

  The signal drivers 20a to 20c are configured by, for example, three driver LSIs connected in cascade. A plurality of signal lines S are connected to each of the signal drivers 20a to 20c. Various control signals such as a horizontal control signal, a timing signal M, and an amplifier operation control signal CAV input from the LCD controller 60, and a voltage generation circuit 70 are provided. A signal voltage based on display data input from the RGB decoder 40 is applied to each signal line S based on the supplied gradation reference voltages VH, VL and the like. Specifically, the display data is supplied as a digital signal, and corresponds to the gradation value of the display data from the gradation voltages generated based on the gradation reference voltages VH and VL by the gradation voltage generation circuit 26 described later. The selected gradation voltage is selected, and the selected gradation voltage is applied to each signal line S as a signal voltage.

  A plurality of scanning lines G are connected to the scanning driver 30, and a scanning signal is sequentially applied to each scanning line G based on a vertical control signal input from the LCD controller 60 to make a selection state.

  The RGB decoder 40 extracts a horizontal synchronization signal H, a vertical synchronization signal V, and a composite synchronization signal CSY from a video signal input from the outside of the liquid crystal display device 1 and outputs them to the LCD controller 60 and is included in the video signal. The display data of each color of RGB is extracted and output to the signal drivers 20a to 20c.

  The VCOM generation circuit 50 generates a common voltage Vcom applied to the common line C and the counter electrode 93 commonly connected to the auxiliary capacitance 95 of each display pixel in the liquid crystal display panel 10, and a timing signal input from the LCD controller 60. According to M, the polarity of the common voltage Vcom is inverted at a predetermined period and output.

  The LCD controller 60 generates a timing signal M based on the horizontal synchronization signal H, the vertical synchronization signal V, and the composite synchronization signal CSY input from the RGB decoder 40, and outputs them to the signal drivers 20a to 20c and the VCOM generation circuit 50. Also, a horizontal control signal and an amplifier operation control signal CAV including a clock signal SCK, a composite synchronization signal CSY, a shift start signal STH, and a latch operation control signal STB are generated and output to the signal drivers 20a to 20c to generate a vertical control signal. And output to the scanning driver 30. In addition, the LCD controller 60 generates a switching control signal ST for each of the signal drivers 20a to 20c and outputs the switching control signal ST to each of the signal drivers 20a to 20c. Then, the display pixels of the liquid crystal display panel 10 are sequentially selected at a predetermined timing, and a signal voltage is applied to the display pixels in the selected state to display a predetermined image based on the display data.

  The voltage generation circuit 70 generates various voltages necessary for each part of the liquid crystal display device 1. For example, the highest gray scale reference voltage VH and the lowest gray scale reference voltage VL necessary for generating the gray scale voltages in the signal drivers 20a to 20c (the "gray scale reference voltages VH, VL are appropriately and collectively used in this specification"). Is generated and supplied to the signal drivers 20a to 20c.

  FIG. 3 is a block diagram showing a schematic configuration of the signal driver according to the first embodiment of the present invention. Note that the signal drivers 20a to 20c all have the same configuration, and therefore the signal driver 20a will be described below as an example.

  In FIG. 3, the signal driver 20 a includes a shift register 21, a data register 22, a latch circuit 23, a selection circuit 24, an output buffer 25, and a gradation voltage generation circuit 26.

  The shift register 21 sequentially shifts the input shift register signal STR according to the clock signal CLK and outputs it. The data register 22 captures and outputs display data input at the timing of the signal input from the shift register 21.

  The latch circuit 23 captures and holds the display data output from the data register 22 in accordance with the input latch operation control signal STB, and outputs it as display data D1, D2,..., Dn. Here, “n” is the number of signal lines S.

  The selection circuit 24 selects a gradation voltage corresponding to each of the display data D1, D2,..., Dn input from the latch circuit 23 from the gradation voltages input from the gradation voltage generation circuit 26. And output as a signal voltage. The output buffer 25 outputs the signal voltages output from the selection circuit 24 to the signal lines S as source outputs Vsig1, Vsig2,..., Vsign.

  The gradation voltage generation circuit 26 generates and outputs a gradation voltage corresponding to the number of gradations of display data based on the gradation reference voltages VH and VL supplied from the voltage generation circuit 70.

  FIG. 4 is a diagram showing a circuit configuration of the gradation voltage generation circuit 26 in the present embodiment. The gradation voltage generation circuit 26 includes gradation reference voltage correction circuits 261A and 261B, an overall resistor Rt, and a voltage level generation circuit 262. The gradation reference voltage correction circuit 261A is supplied with the highest potential maximum gradation reference voltage VH from the voltage generation circuit 70, and is either the highest gradation reference voltage VH or a voltage obtained by correcting the highest gradation reference voltage VH. (The highest reference voltage) is supplied to the voltage level generation circuit 262. Further, the gradation reference voltage correction circuit 261B is supplied with the lowest gradation reference voltage VL having a low potential from the voltage generation circuit 70, and either the lowest gradation reference voltage VL or a voltage obtained by correcting the lowest gradation reference voltage VL. (The minimum reference voltage) is supplied to the voltage level generation circuit 262. The voltage level generation circuit 262 divides between the highest reference voltage and the lowest reference voltage supplied from the gradation reference voltage correction circuits 261A and 261B according to the number of gradations of display data (for example, 11 in FIG. 4), The gradation voltages V0, V1,..., V10 are generated and output.

  The gradation reference voltage correction circuit 261A is provided with one correction resistor Rs1 and two switches 263A and 264A constituting a switching circuit. One end of the correction resistor Rs1 is connected to the terminal VH1 to which the highest gradation reference voltage VH is supplied, and the other end is connected to one end of the total resistor Rt. One end of the switch 263A is connected to the terminal VH1, one end of the switch 264A is connected to the other end of the correction resistor Rs1, and the other end of the switch 263A and the other end of the switch 264A are connected to the output terminal of the gradation voltage V0. . Depending on the open / closed state of the switches 263A and 264A, the terminal VH1 and the voltage level generating circuit 262 are connected with the correction resistor Rs1 interposed or without the correction resistor Rs1 interposed.

  For example, in FIG. 4, when the switch 263A is closed and the switch 264A is opened, the terminal VH1 is directly connected to the voltage level generation circuit 262 without the correction resistor Rs1. On the other hand, when the switch 263A is opened and the switch 264A is closed, the terminal VH1 is connected to the voltage level generation circuit 262 via the correction resistor Rs1.

  Similarly, the gradation reference voltage correction circuit 261B is provided with one correction resistor Rs2 and two switches 263B and 264B that constitute a switching circuit. One end of the correction resistor Rs2 is connected to the terminal VL1 to which the lowest gradation reference voltage VL is supplied, and the other end is connected to one end of the total resistor Rt. One end of the switch 263B is connected to the other end of the correction resistor Rs2, one end of the switch 264B is connected to the terminal VL1, and the other end of the switch 263B and the other end of the switch 264B are connected to the output terminal of the gradation voltage V10. . Depending on the open / closed state of the switches 263B and 264B, the terminal VL1 and the voltage level generation circuit 262 are connected with the correction resistor Rs2 interposed or without the correction resistor Rs2.

  For example, in FIG. 4, when the switch 263B is closed and the switch 264B is opened, the terminal VL1 is connected to the voltage level generation circuit 262 via the correction resistor Rs2. When the switch 263B is opened and the switch 264B is closed, the terminal VL1 is directly connected to the voltage level generation circuit 262 without the correction resistor Rs2.

  In such a configuration, when the switches 263A and 263B are closed and the switches 264A and 264B are opened, the highest reference voltage supplied to the voltage level generation circuit 262 remains the highest gradation reference voltage VH and does not change. However, the lowest reference voltage is a voltage value that is changed from the lowest gradation reference voltage VL in the direction in which the potential is increased by the correction resistor Rs2. On the other hand, when the switches 264A and 264B are closed and the switches 263A and 263B are opened, the lowest reference voltage supplied to the voltage level generation circuit 262 remains the lowest gradation reference voltage VL, but the highest reference voltage is not changed. The voltage value is changed from the highest gradation reference voltage VH in the direction in which the potential decreases by the correction resistor Rs1.

  Therefore, the average level of the gradation reference voltage output from each of the gradation reference voltage correction circuits 261A and 261B is equal to that when the switches 263A and 263B are closed and the switches 264A and 264B are opened, the switches 264A and 264B. Is closed and is higher than when the switches 263A and 263B are opened.

  Hereinafter, the adjustment (including the case where the gradation reference voltage is not changed) of the gradation reference voltage by the gradation reference voltage correction circuits 261A and 261B is hereinafter referred to as “correction”.

  Here, opening / closing of the switches 263A, 263B, 264A, 264B is controlled in accordance with a switching control signal ST input from the LCD controller 60, for example. The switches 263A, 263B, 264A, 264B are controlled to be opened / closed according to the switching control signal ST. For example, the open / closed state of each switch 263A, 263B, 264A, 264B is set outside the signal drivers 20a-20c. A control terminal for setting may be pulled out, and the voltage level of the control terminal may be fixedly connected or opened by a jumper wire or the like.

  The voltage level generation circuit 262 includes, for example, ten resistors R0, R1,..., R9 connected in series. One end of the resistor R0 is connected to the terminal VH1 via the gradation reference voltage correction circuit 261A, and one end of the resistor R10 is connected to the terminal VL1 via the gradation reference voltage correction circuit 261B. Accordingly, the highest reference voltage having a voltage value corrected according to the open / closed state of the switches 263A and 264A is supplied to one end of the resistor R0. On the other hand, one end of the resistor R9 is supplied with a minimum reference voltage having a voltage value corrected according to the open / close state of the switches 263B and 264B.

  The voltage level generation circuit 262 divides the voltage difference between the highest reference voltage and the lowest reference voltage by resistors R0, R1,..., R9 corresponding to the number of gradations of the display data, and gradations the divided voltages. The voltages V0, V1,..., V9, V10 are applied to the gradation voltage application line.

  Here, as described above, the average level of the gradation reference voltage output from each of the gradation reference voltage correction circuits 261A and 261B is greater when the switches 263A and 263B are closed and the switches 264A and 264B are opened. , Higher than when switches 264A and 264B are closed and switches 263A and 263B are opened. Therefore, the potentials of the gradation voltages V0, V1,..., V10 generated and output by the voltage level generation circuit 262 change in the same direction by the correction by the gradation reference voltage correction circuits 261A and 261B. That is, when the switches 263A and 263B are closed and the switches 264A and 264B are opened, the generated gradation voltages are compared to when the switches 264A and 264B are closed and the switches 263A and 263B are opened. The average voltage level of V0, V1,..., V10 is high. The average voltage level of the gradation voltage corresponds to the center level (signal voltage Vsig / c) of the signal voltage Vsig supplied from the signal driver. That is, the gradation reference voltage correction circuits 261A and 261B generate a signal. The potential of the voltage Vsig / c is changed.

  Next, the operation of each switch of the gradation reference voltage correction circuits 261A and 261B of the signal drivers 20a to 20c will be described. As described above, the switching control signal ST is input from the LCD controller 60 to the signal drivers 20a to 20c, and the operations of the gradation reference voltage correction circuits 261A and 261B of the signal drivers 20a to 20c are controlled. Here, the switching control signal ST is set so that the switches 263A and 264A are closed and the 263B and 264B are opened for the signal drivers 20a and 20c, and the switches 263B and 264B are set for the signal driver 20b. It is set to close and open 263A and 264A.

  Accordingly, the center level (signal voltage Vsig / c) of the signal voltage Vsig output from the signal drivers 20a and 20c is higher than the center level (signal voltage Vsig / c) of the signal voltage Vsig output from the signal driver 20b. Thus, the potential of the signal voltage Vsig / c in the peripheral portion is higher than the potential of the signal voltage Vsig / c in the central signal line of the liquid crystal display panel 10. By setting the potential difference of the signal voltage Vsig / c by this signal line to a value corresponding to the difference of the DC component VcomDC of the common voltage Vcom in the display panel, VcomDC and the signal voltage Vsig / c Of the liquid crystal display panel 10 can be made substantially equal between the central portion and the peripheral portion.

  FIG. 5 is a diagram illustrating the relationship between the DC component VcomDC of the common voltage Vcom and the signal voltage Vsig / c in the present embodiment. As shown in FIG. 5, the potential of the signal voltage Vsig / c of the signal drivers 20a and 20c is changed to the signal voltage Vsig / c of the signal driver 20b so as to correspond to the change of the DC component VcomDC of the common voltage Vcom in the display panel. It is set to be higher than c.

  Thus, the potential of the signal voltage Vsig / c of each of the signal drivers 20a to 20c is set to be different. That is, whether or not to shift the overall level of the gradation voltage generated and output in each signal driver 20a to 20c is individually set for each signal driver 20a to 20c. The setting is determined according to which part of the signal line of the liquid crystal display panel 10 the signal driver applies the signal voltage to. Specifically, the signal voltage Vsig / c of the signal driver that applies the signal voltage to the signal line in the peripheral portion is greater than the signal voltage Vsig / c of the signal driver that applies the signal voltage to the signal line in the central portion of the liquid crystal display panel 10. Is set so that the potential is higher. Thereby, the change in the difference between VcomDC and the signal voltage Vsig / c due to the display position of the liquid crystal display panel is reduced, so that the difference between the VcomDC and the signal voltage Vsig / c becomes substantially uniform in the liquid crystal display panel. Therefore, flicker can be suppressed over the entire screen of the liquid crystal display panel 10 and display quality can be improved.

  In the present embodiment described above, the gradation voltage generation circuit 26 has been described as a configuration in which one correction resistor Rs1, Rs2 is provided in each of the gradation reference voltage correction circuits 261A, 261B. However, other configurations may be used. . FIG. 6 is a diagram showing a modification of the gradation voltage generation circuit in the present embodiment. For example, as in the gradation voltage generation circuit 27 shown in FIG. 6, the gradation reference voltage correction circuits 361A and 361B may be provided instead of the gradation reference voltage correction circuits 261A and 261B.

  In FIG. 6, the gradation reference voltage correction circuit 361A includes three correction resistors Rs11 to Rs13 connected in series, and each of the correction resistors Rs11 to Rs13 divides the highest gradation reference voltage VH applied to the terminal VH2. . The divided voltage is output to the voltage level generation circuit 262 via the switches 363A to 366A. Therefore, the potential of the highest reference voltage supplied to the voltage level generation circuit 262 can be changed to four potentials by switching between opening and closing of the switches 363A to 366A.

  Further, since the gradation reference voltage correction circuit 361B has substantially the same configuration as the gradation reference voltage correction circuit 361A, detailed description is omitted, but the voltage level is the same as in the case of the gradation reference voltage correction circuit 361A. The potential of the lowest reference voltage supplied to the generation circuit 262 can be changed to four potentials.

  Another modification of the gradation voltage generation circuit 26 will be described. FIG. 7 is a diagram showing another modification of the gradation voltage generation circuit in the present embodiment. Like the gradation voltage generation circuit 28 shown in FIG. 7, gradation reference voltage correction circuits 461A and 461B may be provided instead of the gradation reference voltage correction circuits 261A and 261B shown in FIG. In FIG. 7, the gradation reference voltage correction circuit 461A includes three correction resistors Rs31 to Rs33 in parallel, and is configured to be able to switch which correction resistors Rs31 to Rs33 are inserted by switches 465A to 467A. . In addition, the switch 464A can be switched so that the correction resistors Rs31 to Rs33 are not inserted.

  The correction resistors Rs31 to Rs33 are resistors having different resistance values. For example, only one of the switches 464A to 467A is closed according to the switching control signal ST.

  Therefore, depending on which of the switches 464A to 467A is closed, which of the plurality of parallel-connected correction resistors Rs31 to 33 having different resistance values is inserted between the terminal VH3 and the total resistor Rt, or between the terminal VH3 and the total resistor Rt. Can be selectively controlled, so that the potential of the highest gradation reference voltage output to the voltage level generation circuit 262 can be changed to four potentials. The gradation reference voltage correction circuit 461B has substantially the same configuration as the gradation reference voltage correction circuit 461A, and thus detailed description thereof is omitted.

  In the above-described embodiment, the case where the three signal drivers 20a to 20c are used as the signal driver for driving the display panel 10 has been described. However, other configurations may be used. For example, according to the gradation voltage correction circuit 27 shown in FIG. 6 and the gradation voltage correction circuit 28 shown in FIG. 7, the gradation reference voltages VH and VL can be changed to four different potentials. it can. Therefore, for example, the display panel 10 may be driven by nine signal drivers. That is, the switch of each signal driver is switched so that the potential of the signal voltage Vsig / c changes in four stages from the left and right ends of the screen to the center of the screen.

  As a result, the value of the signal voltage Vsig / c can be finely adjusted for each signal driver in accordance with the DC component VcomDC of the common voltage Vcom that varies depending on the portion of the display panel 10, and VcomDC and the signal voltage Vsig / c Can be made more uniform over the entire screen.

[Second Embodiment]
In the first embodiment described above, the liquid crystal display device 1 includes a plurality of signal drivers 20a to 20c, and the signal voltage Vsig / c is changed for each of the signal drivers 20a to 20c. 1 may include only one signal driver 220 as a signal driver, and the signal voltage Vsig / c may be changed for each predetermined number of signal lines S in the signal driver 220.

  FIG. 8 is a block diagram showing a schematic configuration of the signal driver according to the second embodiment of the present invention. In FIG. 8, the signal driver 220 includes a shift register 221, a data register 222, a latch circuit 223, three selection circuits 224a to 224c, an output buffer 225, and three gradation voltage generation circuits 226a to 226c. And is configured. The shift register 221, the data register 222, the latch circuit 223, and the output buffer 225 have the same configuration as that of the liquid crystal display device 1 described above, and thus detailed description thereof is omitted. In the following, the selection circuits 224a to 224c, The regulated voltage generation circuits 226a to 226c will be described.

  The gradation voltage generation circuits 226a to 226c are circuits that generate and output gradation voltages selected as signal voltages in the selection circuits 224a to 224c, respectively. The circuit configuration is the same as that of the gradation voltage generation circuit 26 described above. Circuit configuration. Of course, a circuit configuration similar to that of the gradation voltage generation circuits 27 and 28 may be used.

  The selection circuits 224a to 224c are circuits that output signal voltages to be applied to the signal lines at addresses 0 to β, β to γ, and γ to N, respectively, among the N signal lines of the liquid crystal display panel 10. This is a circuit that selects and outputs a gradation voltage corresponding to the gradation value of the display data from among the gradation voltages output from the voltage generation circuits 226a to 226c as a signal voltage.

  The grayscale voltage output levels from the grayscale voltage generation circuits 226a to 226c are higher in the grayscale voltage generation circuits 226a and 226c than in the grayscale voltage generation circuit 226b. The switches in the voltage generation circuits 226a to 226c are switched. Therefore, the signal voltage Vsig / c based on the gradation voltage output from the selection circuits 224a and 224c is higher than the signal voltage Vsig / c based on the gradation voltage output from the selection circuit 224b. Therefore, the signal voltage Vsig / c at the peripheral portion is higher than the signal voltage Vsig / c at the central signal line of the liquid crystal display panel 10. Also in this case, as in the case of the first embodiment, the potential difference of the signal voltage Vsig / c by the signal line is set to a value corresponding to the difference of the DC component VcomDC of the common voltage Vcom in the display panel. As a result, the difference between VcomDC and the signal voltage Vsig / c can be made substantially equal between the central portion and the peripheral portion of the liquid crystal display panel 10.

  FIG. 9 is a diagram illustrating the relationship between the DC component VcomDC of the common voltage Vcom and the signal voltage Vsig / c in the present embodiment. As shown in FIG. 9, the signal voltage Vsig / c at addresses 0 to β and addresses γ to N is a signal at addresses β to γ2 so as to correspond to the change in the DC component VcomDC of the common voltage Vcom in the display panel. It is set to be higher than the voltage Vsig / c.

  In the above-described modification, the configuration in which one signal driver 220 includes three gradation voltage generation circuits 226a to 226c has been described. However, the number of gradation voltage generation circuits 226a to 226c is limited to the above-described example. Not. By providing a large number of sets of gradation voltage generation circuits and selection circuits, the value of the signal voltage Vsig / c for each signal line can be finely adjusted, and flicker generated on the entire screen can be more effectively reduced. It is possible to suppress and improve display quality. Furthermore, the same number of sets of gradation voltage generation circuits and selection circuits as the plurality of signal lines S connected to the liquid crystal display panel 10 are provided, and the signal voltage Vsig / c can be changed for each signal line S. It may be a configuration.

  However, if the number of gradation voltage generation circuits provided in the signal driver is increased, it is effective for suppressing flicker, but disadvantages such as an increase in the size of the display device and improvement in power consumption of the signal driver also occur. It is desirable to select a suitable number according to the balance.

1 is a block diagram illustrating a configuration of a liquid crystal display device. Equivalent circuit of display pixel. 1 is a block diagram showing a schematic configuration of a signal driver according to a first embodiment. The figure which shows the circuit structure of the gradation voltage generation circuit in 1st Embodiment. The figure which shows the relationship between the direct current component of the common voltage in 1st Embodiment, and the center level of a signal voltage. The figure which shows the modification of the gradation voltage generation circuit in 1st Embodiment. FIG. 10 is a diagram illustrating another modification of the gradation voltage generation circuit according to the first embodiment. The block diagram which shows schematic structure in 2nd Embodiment of a signal driver. The figure which shows the relationship between the DC component of the common voltage in 2nd Embodiment, and the center level of a signal voltage. The block diagram which shows schematic structure of the conventional liquid crystal display device. The figure which shows the signal waveform and DC component of a common voltage. (A) The figure which shows the relationship between the conventional direct current component and signal voltage, (b) The schematic diagram at the time of adjusting flicker on the basis of the screen center part, (c) The flicker was adjusted on the basis of the feeding peripheral part Schematic diagram of the case.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Liquid crystal display device 10 Display panel 20a-20c Signal driver 21 Shift register 22 Data register 23 Latch circuit 24 Selection circuit 25 Output buffer 26 Gradation voltage generation circuit 30 Scan driver 40 RGB decoder 50 VCOM generation circuit 60 LCD controller 70 Voltage generation circuit

Claims (4)

Common electrode and, interposed between the respective pixel electrodes and the common electrode facing the plurality of pixel electrodes arranged in a matrix at intersections near the plurality of scan lines and a plurality of signal lines, to the plurality of pixel electrodes a plurality of signal-side drive means for applying a plurality of display pixels composed of a liquid crystal, a display panel comprising a, a signal voltage corresponding to the display data each of said plurality of signal lines, scanning the plurality of scan lines a scanning-side drive means for sequentially set to the selected state the display pixel drive signals are sequentially output, to generate a common voltage that is inverted at a predetermined period, provided the said common voltage to at least one portion of said common electrode A common voltage generating means applied to the common electrode from a power supply unit ;
In a display device comprising:
Each of the plurality of signal side driving means is provided for each predetermined number of the signal lines, and each signal side driving means has at least a predetermined highest gradation reference voltage or a voltage obtained by correcting the highest gradation reference voltage. Switch between either the highest gradation reference voltage correction means that outputs as the highest reference voltage and either the predetermined lowest gradation reference voltage or the voltage that has corrected the lowest gradation reference voltage, and output as the lowest reference voltage And a means for generating and outputting a plurality of gradation voltages corresponding to the number of gradations of the display data based on the highest reference voltage and the lowest reference voltage. Voltage generation means; and gradation voltage selection means for selecting the gradation voltage corresponding to the gradation value of the display data from the plurality of gradation voltages and outputting the selected voltage to each signal line as the signal voltage. ,
The gradation voltage generating means in each signal-side drive means, according to the voltage value of the maximum reference voltage and the lowest reference voltage output from the maximum gray level reference voltage correction means and said minimum gradation reference voltage correction means And individually setting the center level of the plurality of gradation voltages ,
The highest gradation reference voltage correction means and the lowest gradation reference voltage correction means are different in voltage values of the highest reference voltage and the lowest reference voltage depending on the distance from the power supply unit in the common electrode. A display device , wherein a potential difference between an average voltage value of a voltage signal waveform and a center level of the plurality of gradation voltages is set to a preset value so as to approach a constant value . The highest gradation reference voltage correction means has means for outputting a voltage lower than the highest gradation reference voltage as the highest reference voltage, and the lowest gradation reference voltage correction means is higher than the lowest gradation reference voltage. 2. The display device according to claim 1 , further comprising means for outputting a voltage as the lowest reference voltage. A plurality of pixel electrodes arranged in a matrix at intersections near the plurality of scan lines and a plurality of signal lines, a common electrode opposed to the plurality of pixel electrodes are sandwiched between the pixel electrode and the common electrode a plurality of display pixels composed of liquid crystals, a display panel and a signal side driving means for applying a signal voltage corresponding to display data to each of said plurality of signal lines, a scan drive signal to the plurality of scan lines a scanning-side drive means for sequentially set to output sequentially selects state the display pixels, generates a common voltage to be inverted at a predetermined period, the said common voltage from the power supply portion provided in at least one place of the common electrode Common voltage generating means applied to the common electrode ;
In a display device comprising:
The signal-side drive means, at least, by switching either the voltage obtained by correcting the predetermined maximum gradation reference voltage or outermost high gradation reference voltage, and the highest gradation reference voltage correction means for outputting as the highest reference voltage, a predetermined switching either the lowest gradation reference voltage or outermost low gradation reference voltages corrected voltage, and the lowest gradation reference voltage correction means for outputting a minimum reference voltage, based on the highest reference voltage and the lowest reference voltage, wherein Means for generating and outputting a plurality of gradation voltages according to the number of gradations of the display data; and the gradation voltage generation means having the gradation data according to the gradation values of the display data from the plurality of gradation voltages. A plurality of gradation voltage selection means for selecting a gradation voltage and outputting to each signal line as the signal voltage for each predetermined number of signal lines in the plurality of signal lines;
The gradation voltage generating circuit in accordance with the voltage value of the maximum gradation reference voltage correction means and said maximum reference voltage and the lowest reference voltage output from the minimum gradation reference voltage correction means, the gradation voltage generator Center levels of the plurality of gradation voltages generated by the means are individually set for each of the predetermined number of signal lines ,
The highest gradation reference voltage correction means and the lowest gradation reference voltage correction means are different in voltage values of the highest reference voltage and the lowest reference voltage depending on the distance from the power supply unit in the common electrode. display device comprising that you set the potential difference between the average voltage voltage value and the center level of said plurality of gradation voltages of the voltage of the signal waveform to a predetermined value so as to approach a constant value. The highest gradation reference voltage correction means has means for outputting a voltage lower than the highest gradation reference voltage as the highest reference voltage, and the lowest gradation reference voltage correction means is higher than the lowest gradation reference voltage. 4. The display device according to claim 3 , further comprising means for outputting a voltage as the minimum reference voltage.

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