JP2016103036A - Display device driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce noise arising from a display panel surface.SOLUTION: A driver has: a frame memory that stores display data to be externally input; a plurality of first latch circuits that reads the display data by one display line from the frame memory to latch the display data thereby; a plurality of second latch circuits that is provided for each of the plurality of first latch circuits, and latches the display data latched by the first latch circuit on the basis of a latch control signal; and a plurality of decoder circuits that is provided for each of the plurality of second latch circuits, and converts the display data latched by the second latch circuit into a picture voltage. A plurality of picture lines, and the second latch circuit and decoder circuit to be provided for each picture line are divided into a plurality of blocks, and a delay element is inserted into a boundary among the blocks of a propagation route of the latch control signal. In the second latch circuit, timing latching the display data latched by the first latch circuit is made different every each block.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a display device, and more particularly to a technique for reducing noise on the surface of a display panel.

In recent years, in the spread of mobile devices, touch panel technology supporting a “human friendly” graphical user interface has become important.
Also, a liquid crystal display panel with a touch panel that performs an operation corresponding to the menu by touching the menu screen displayed on the liquid crystal display panel with a finger by attaching the touch panel substrate to the surface of the liquid crystal display panel is also known. Yes.

JP 2000-231120 A

However, in a liquid crystal display panel with a touch panel, it is assumed that the touch panel malfunctions due to noise generated from the surface of the liquid crystal display panel.
The present invention has been made to solve the problems of the prior art, and an object of the present invention is to provide a technique capable of reducing noise generated from the display panel surface in a display device. It is in.
The above and other objects and novel features of the present invention will become apparent from the description of this specification and the accompanying drawings.

Of the inventions disclosed in this application, the outline of typical ones will be briefly described as follows.
(1) A display panel having a plurality of pixels, a plurality of video lines for inputting video voltages to the plurality of pixels, and a driver for supplying the video voltages to the video lines, wherein the drivers are externally provided. A frame memory for storing input display data; a plurality of first latch circuits for reading and latching display data for one display line from the frame memory; and provided for each of the plurality of first latch circuits; A plurality of second latch circuits for latching display data latched in the first latch circuit based on a latch control signal; and each of the plurality of second latch circuits. A display device having a plurality of decoder circuits for converting the latched display data into a video voltage, the plurality of video lines, and the second label provided for each of the video lines. And the decoder circuit is divided into a plurality of blocks, a delay element is inserted at the boundary of the block of the propagation path of the latch control signal, and is latched by the first latch circuit in the second latch circuit. The timing for latching the display data is made different for each block.
(2) In (1), the propagation path of the latch control signal has two propagation paths from the center of the driver toward the left and right sides.
(3) In (1), the display panel includes a plurality of scanning lines for inputting a scanning voltage to the plurality of pixels, and is provided on both left and right sides of a pixel portion configured by the plurality of pixels. The first scanning circuit supplies a scanning voltage to odd-numbered scanning lines among a plurality of scanning lines, and the second scanning circuit includes: A scanning voltage is supplied to an even-numbered scanning line among the plurality of scanning lines, and the propagation direction of the scanning voltage coincides with the propagation path of the latch control signal.

(4) In (1), each output amplifier circuit includes a plurality of output amplifier circuits provided for each of the plurality of decoder circuits, and each output amplifier circuit outputs a gradation voltage output from each decoder circuit in one horizontal scanning period. Before outputting to each video line, the precharge voltage is output to each video line, and the timing at which each output amplifier circuit outputs the precharge voltage to each video line in one horizontal scanning period is set for each block. Make it different.
(5) In (1), it has a plurality of output amplifier circuits provided for each of the plurality of decoder circuits, and a bias circuit for supplying a bias voltage to each of the output amplifier circuits, and each of the bias circuits has a current value. A plurality of constant current sources different from each other, and a switch element that selects any one of the plurality of constant current sources, and the bias circuit generates a bias voltage generated by the selected constant current source. To the output amplifier circuits.
(6) In (1), it includes a plurality of output amplifier circuits provided for each of the plurality of decoder circuits, and a bias circuit that supplies a bias voltage to each of the output amplifier circuits, and the plurality of output amplifier circuits include: A plurality of positive-polarity amplifier circuits for outputting positive-polarity gradation voltages and negative-polarity amplifier circuits for outputting negative-polarity gradation voltages; A constant current source, a plurality of constant current sources for a negative polarity amplifier circuit each having a different current value, and a switch element for selecting any one of the plurality of constant current sources for the positive polarity amplifier circuit, A switching element for selecting any one of a plurality of constant current sources for the negative polarity amplifier circuit, and the bias circuit is generated by the selected constant current source for the positive polarity amplifier circuit. Buy Supply a bias voltage generated by a constant current source for the selected negative amplifier circuit to the negative amplifier circuit of each output amplifier circuit. To do.

(7) In (1), the plurality of video lines include a plurality of video lines of a first color, a plurality of video lines of a second color, and a plurality of video lines of a third color. And a switch circuit for outputting the gradation voltage output from each of the output amplifier circuits to the video lines of the first color to the third color within one horizontal scanning period. The switch circuit is controlled by a control signal and has a plurality of switch elements each having a different slew rate, and the switch circuit receives a switch control signal via a selected switching element among the plurality of switching elements. .
(8) In (7), each of the plurality of switching elements is constituted by a transfer gate circuit, and each of the transfer gate circuits is different in at least one of a gate length and a gate width.
(9) In (1), comprising: a display panel having a plurality of pixels; a plurality of video lines for inputting video voltages to the plurality of pixels; and a driver for supplying the video voltages to the video lines, A resistance element is inserted between the driver and each video line.
(10) In (9), the resistance element is formed of a polysilicon resistance layer.

The effects obtained by the representative ones of the inventions disclosed in the present application will be briefly described as follows.
According to the display device of the present invention, noise generated from the display panel surface can be reduced.

It is a block diagram which shows schematic structure of the liquid crystal display device of the Example of this invention. It is an internal block diagram of the driver (DRV) shown in FIG. 1 is a block diagram illustrating a schematic configuration of a driver (DRV) according to a first embodiment of the present invention, and is a diagram illustrating a peripheral circuit configuration of a final latch. FIG. It is a block diagram which shows schematic structure of the modification of the driver (DRV) of Example 1 of this invention, and is a figure which shows the circuit structure of the periphery of a last latch. It is a figure explaining the propagation direction of the scanning voltage by the gate circuit of Example 1 of this invention. It is a figure explaining the precharge circuit in the conventional liquid crystal display device. It is a figure which shows the relationship between the output waveform and noise in the conventional driver (DRV). It is a block diagram which shows schematic structure of the driver (DRV) of Example 2 of this invention, and is a figure which shows the circuit structure of a bias circuit. It is a figure explaining the positive polarity amplifier circuit and negative polarity amplifier circuit in the driver (DRV) of Example 2 of this invention. It is a figure explaining the control signal which controls the RGB switch circuit of the driver (DRV) of Example 3 of this invention. It is a figure explaining the liquid crystal display panel of Example 4 of this invention.

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.
In all the drawings for explaining the embodiments, parts having the same functions are given the same reference numerals, and repeated explanation thereof is omitted. Also, the following examples are not intended to limit the interpretation of the scope of the claims of the present invention.
FIG. 1 is a block diagram showing a schematic configuration of a liquid crystal display device according to an embodiment of the present invention.
The liquid crystal display panel is provided with a plurality of scanning lines (GL) and a plurality of video lines (DL) orthogonal to the plurality of scanning lines (GL). Pixels (PS) are provided at the intersections between the scanning lines (GL) and the video lines (DL). The plurality of pixels (PS) are arranged in a matrix to form a pixel area (AR).
Each pixel (PS) is provided with a pixel electrode (PX) and a thin film transistor (TFT). A counter electrode (CT) is provided so as to face each pixel electrode (PX), and a liquid crystal capacitor (not shown) and a holding capacitor (not shown) are provided between each pixel electrode (PX) and the counter electrode (CT). Cadd) is formed.
The thin film transistor (TFT) of each pixel (PS) has a source connected to the pixel electrode (PX), a drain connected to the video line (DL), and a gate connected to the scanning line (GL). The thin film transistor (TFT) functions as a switch for supplying a display voltage (gradation voltage) to the pixel electrode (PX).
Note that although the names of the source and the drain may be reversed due to the bias, the one connected to the video line (DL) is referred to as the drain here.

The video line (DL) is connected to a driver (DRV) via an RGB switch circuit (RGB-SW). The counter electrode (CT) is also connected to the driver (DRV).
The driver (DRV) is composed of a one-chip semiconductor integrated circuit (LSI) mounted on the first glass substrate (SUB1), and outputs a video signal output circuit to the video line (DL) and a counter electrode ( An output circuit that outputs a common electrode voltage to CT), and a circuit that outputs a gate control signal (S-GATE) to the gate circuits (L-GCS, R-GCS). Yes.
The scanning lines (GL) are connected to gate circuits (L-GCS, R-GCS) arranged on the left and right of the pixel region (AR) every other line. The gate circuit (L-GCS, R-GCS) is constituted by, for example, a circuit having a CMOS structure, or a circuit having a single channel structure in which a semiconductor layer is formed of a polysilicon thin film transistor made of polysilicon. The gate circuit (L-GCS, R-GCS) may be composed of an amorphous silicon thin film transistor whose semiconductor layer is made of amorphous silicon.
In any case, the thin film transistors constituting the gate circuits (L-GCS, R-GCS) are manufactured at the same time as the thin film transistors (TFTs) of the pixels (PS).

The liquid crystal display panel includes a first glass substrate (SUB1) provided with pixel electrodes (PX), thin film transistors (TFTs), and the like, and a second glass substrate (not shown) on which color filters and the like are formed. The two glass substrates are bonded together by a seal material provided in a frame shape in the vicinity of the peripheral edge between the two glass substrates while being spaced apart from each other, and between the two substrates from the liquid crystal sealing opening provided in a part of the seal material. A liquid crystal is sealed and sealed inside the sealing material, and a polarizing plate is attached to the outside of both glass substrates.
Since the present invention is not related to the internal structure of the liquid crystal display panel, a detailed description of the internal structure of the liquid crystal display panel is omitted. Furthermore, the present invention can be applied to a liquid crystal display panel having any structure. For example, in the case of the vertical electric field method, the counter electrode (CT) is formed on the second glass substrate. In the case of the horizontal electric field method, the counter electrode (CT) is formed on the first glass substrate (SUB1).

The gate circuits (L-GCS, R-GCS) are sequentially supplied to the scanning lines (GL) of the liquid crystal display panel every horizontal scanning time based on the gate control signal (S-GATE) input from the driver (DRV). Is supplied with a selection voltage (scanning signal) of “High” level. Thus, a plurality of thin film transistors (TFTs) connected to each scanning line (GL) of the liquid crystal display panel are electrically connected between the video line (DL) and the pixel electrode (PX) during one horizontal scanning period. Conduct.
The driver (DRV) outputs a gradation voltage corresponding to a gradation to be displayed by the pixel (PS) to the video line (DL). When the thin film transistor (TFT) is turned on (conductive), a gradation voltage (video signal) is supplied from the video line (DL) to the pixel electrode (PX). After that, when the thin film transistor (TFT) is turned off, the gradation voltage based on the image to be displayed by the pixel (PS) is held in the pixel electrode (PX).
In this embodiment, the driver (DRV) sequentially outputs gradation voltages of red (R), green (G), and blue (B) within one horizontal scanning time. Then, the RGB switch circuit (RGB-SW) receives red (R) sequentially output from the driver (DRV) within one horizontal scanning time based on the control signal (S-RGB) from the driver (DRV). The green (G) and blue (B) gradation voltages are output to the red (R), green (G), and blue (B) video lines (DL), respectively.
A counter electrode voltage is applied to the counter electrode (CT), and the liquid crystal display panel changes the orientation direction of the liquid crystal molecules sandwiched between them by the potential difference between the pixel electrode (PX) and the counter electrode (CT). The image is displayed by changing the light transmittance or reflectance.
In this embodiment, dot inversion is adopted as an alternating drive method. Therefore, the counter voltage (common voltage) on the counter electrode (CT) is a constant reference voltage, and the video line (DL) has a positive gradation voltage and a negative polarity every horizontal scanning time. Is output.

FIG. 2 is an internal block diagram of the driver (DRV) shown in FIG.
In the figure, reference numeral 11 denotes a timing generation circuit. Display data and a display control signal are input to the timing generation circuit 11 from the microcomputer or the graphic controller on the main body side via the interface circuit 10.
A system interface 31 in FIG. 1 is a system to which various control signals and images are input from a microcomputer or the like. Reference numeral 32 in FIG. 1 denotes a display data interface (RGB interface), which is a system in which image data generated by an external graphic controller and a data fetch clock are continuously input.
Display data input from the outside is stored in the frame memory 12.
The latch circuit 13 latches display data of 8 bits for each color by the number of outputs in synchronization with the clock (CL2) output from the timing generation circuit 11.
The final latch circuit 14 latches display data in the latch circuit 13 based on the output timing control clock (CL1) output from the timing generation circuit 11. The display data captured by the final latch circuit 14 is input to the decoder circuit 16 through the level shift circuit 15.

The decoder circuit 16 has one gradation voltage corresponding to display data based on the positive 256 gradation gradation voltage or the negative 256 gradation gradation voltage input from the gradation voltage generation circuit 19. (One gradation voltage in 256 gradations) is selected and output to the output amplifier circuit 17.
The output amplifier circuit 17 amplifies the gradation voltage and outputs it to each video line (DL). The bias voltage is input from the bias circuit 20 to the output amplifier circuit 17.
The gradation voltage generation circuit 19 adjusts the γ characteristic of the output gradation voltage based on the output from the γ adjustment circuit 18.
A gate control signal (S-GATE) for controlling the gate circuit generated by the timing generation circuit 11 is output to the gate circuits (L-GCS, R-GCS) via the level shift circuit 22 and the panel interface circuit 23. The The gate control signal (S-GATE) includes a frame start instruction signal (FLM) and a shift clock (CL3).
Here, the control signal (S-RGB) generated by the timing generation circuit 11 and controlling the RGB switch circuit (RGB-SW) is also transmitted via the level shift circuit 22 and the panel interface circuit 23. -SW).
Further, the booster circuit 21 of FIG. 1 generates various drive voltages used inside the liquid crystal display panel based on the clock output from the timing generation circuit 11.

As described above, in this embodiment, dot inversion is adopted as an alternating drive method. In the dot inversion, the counter voltage (common voltage) is constant, and the gradation voltage on the video line also has a positive gradation voltage and a negative gradation voltage. Was thought to be small.
However, as a result of investigations by the inventors of the present application, it has been found that noise generated from the surface of the liquid crystal display panel is greatly affected by voltage fluctuation on the video line (DL).
In this embodiment, in order to reduce noise peaks generated from the surface of the liquid crystal display panel, the video lines (DL) are divided into a plurality of blocks (for example, blocks for every 10 video lines (DL)), and the video is displayed. The output timing of the gradation voltage output to the line (DL) is different for each block.
In the conventional liquid crystal display panel, the voltage fluctuation occurs at the same timing in all the video lines (DL). In the liquid crystal display panel of the present embodiment, the voltage fluctuation timing is generated for each video line (DL) in each block. Since they are different, it is possible to reduce the peak of noise generated from the surface of the liquid crystal display panel.

FIG. 3 is a block diagram showing a schematic configuration of the driver (DRV) of this embodiment, and is a diagram showing a peripheral circuit configuration of the final latch 14.
As shown in FIG. 3, in this embodiment, a delay element is provided for each of the plurality of latch circuits 140 in the final latch circuit 14 to the signal line through which the output timing control clock (CL1) from the timing generation circuit 11 propagates. (DDL) is inserted, and the latch operation of each latch circuit 140 is performed in a time-sharing manner in units of blocks.
Accordingly, the gradation voltage output from the latch circuit 140 to each video line (DL) is also in units of blocks (for example, in units of 10 video lines (DL)). In addition, since the timing of voltage fluctuation is different, it is possible to reduce the peak of noise generated from the surface of the liquid crystal display panel.
In FIG. 3, the latch circuit 13 is divided into two, and the output timing control clock (CL1) from the timing generation circuit 11 is propagated from the central portion of the final latch circuit 14 to both the left and right sides. Yes. That is, the output timing control clock (CL1) input to each latch circuit 140 of the final latch circuit 14 is input earliest in the latch circuit 140 near the center of the final latch circuit 14, and both left and right sides of the final latch circuit 14 The input is delayed as the latch circuit 140 becomes.

FIG. 4 is a block diagram showing a schematic configuration of a modified example of the driver (DRV) of the present embodiment, and is a diagram showing a peripheral circuit configuration of the final latch 14.
As shown in FIG. 4, in the modification of the present embodiment, the output timing control clock (CL1) is propagated from the left end to the right end of the semiconductor chip constituting the driver (DRV) (CL1-L), and the semiconductor Two types (CL1-R) that propagate from the right end to the left end of the chip are prepared.
As shown in FIG. 5, in the present embodiment, gate circuits (L-GCS, R-GCS) are arranged on the left and right sides of the pixel area (AR) of the liquid crystal display panel, and the scanning voltage propagates from right to left (FIG. 5). 5A) and the scanning voltage propagating from left to right (B in FIG. 5) are alternately output from the left and right gate circuits (L-GCS, R-GCS) for each scanning line.
When the scanning voltage propagates from right to left, the waveform of the scanning voltage is less dull at the right end of the liquid crystal display panel, and the waveform of the scanning voltage becomes dull at the left end of the liquid crystal display panel. Therefore, in this embodiment, the output timing control clock (CL1) propagating in the driver is also delayed from the right end of the semiconductor chip to the left end so that the output of the driver (DRV) is delayed at the left end where the waveform of the scanning voltage is greatly dull. Control to propagate to.
On the other hand, when the scanning voltage propagates from left to right, the waveform of the scanning voltage is less dull at the left end of the liquid crystal display panel, and the waveform of the scanning voltage becomes dull at the left end of the liquid crystal display panel. In this case, the output timing control clock (CL1) propagating in the driver is also propagated from the left end to the right end of the semiconductor chip so that the output of the driver (DRV) is delayed at the right end where the waveform of the scanning voltage is greatly dull. To control.

Conventionally, in order to reduce the time until the gradation voltage corresponding to the display data is output to each video line (DL) (hereinafter referred to as output delay time), as shown in FIG. Is provided with a precharge circuit 171, and the precharge circuit 171 is inserted in the subsequent stage of each amplifier circuit 172 of the output amplifier circuit 17.
The precharge circuit 171 pre-defines each video line (DL) by the switching element (SW1) before outputting the gradation voltage corresponding to the display data to each video line (DL) every horizontal scanning period. A charge voltage (Vpre; for example, in the case of a normally black type liquid crystal display panel, a voltage corresponding to an intermediate potential between white and black) is input, and each video line (DL) is set to a precharge voltage (Vpre). By charging, the output delay time can be reduced.
As described above, the video line (DL) is divided into a plurality of blocks (for example, blocks for every 10 video lines (DL)), and the operation of the precharge circuit 171 is also performed in a time-sharing manner. The output timing of the precharge voltage (Vpre) output to each video line (DL) is varied for each block.
Also in this case, it is possible to reduce noise peaks generated from the surface of the liquid crystal display panel.

FIG. 9 is a diagram illustrating a positive polarity amplifier circuit and a negative polarity amplifier circuit in the driver (DRV) of this embodiment.
As shown in FIG. 9, the decoder circuit 16 shown in FIG. 2 selects a positive polarity decoder circuit 16p that selects a positive gray scale voltage corresponding to display data output from each latch circuit 140 in the final latch circuit 14. And a negative decoder circuit 16n for selecting a negative gradation voltage corresponding to the display data.
The amplifier circuit 172 shown in FIG. 6 includes a positive polarity amplifier circuit 172p and a negative polarity amplifier circuit 172n. The positive amplifier circuit 172p amplifies and outputs a positive gradation voltage. The negative amplifier circuit 172n amplifies and outputs a negative gradation voltage.
In the dot inversion method, the gradation voltages of adjacent video lines (DL) have opposite polarities, and the positive polarity decoder circuit 16p and the positive polarity amplifier circuit 172p are adjacent to the negative polarity decoder circuit 16n and the negative polarity amplifier circuit 172n. Therefore, the display data is input to the adjacent latch circuit 13 as it is or after replacement by the switch unit (CSW1), and is output from the positive amplifier circuit 172p and the negative amplifier circuit 172n accordingly. By switching the output voltage using the switch unit (CSW2), a positive grayscale voltage is output to the Y1 video line and a negative grayscale voltage is output to the Y2 video line in any one horizontal scanning period. In the next one horizontal scanning period, it is possible to output a negative gradation voltage to the Y1 video line and a positive gradation voltage to the Y2 video line.

FIG. 7 is a diagram illustrating a relationship between an output waveform and noise in a conventional driver (DRV).
In FIG. 7, VPW is a positive “white” gradation voltage, and VNW is a negative “white” gradation voltage.
As shown in FIG. 7, when “white” is displayed on the liquid crystal display panel by the dot inversion method, the voltage on the video line (DL) is a positive “white” gradation voltage for each display period. From (VPW) to negative “white” gradation voltage (VNW), or from negative “white” gradation voltage (VNW) to positive “white” gradation voltage (VPW) Will do.
In this case, noise (NOIZ) is generated as shown in FIG. 7 due to the slew rate difference (rising characteristic difference) between the positive amplifier circuit 172p and the negative amplifier circuit 172n in the output amplifier circuit 17.
The second embodiment of the present invention is an embodiment for reducing the noise (NOIZ) shown in FIG.
FIG. 8 is a block diagram illustrating a schematic configuration of the driver (DRV) according to the second embodiment of the present invention, and illustrates a circuit configuration of the bias circuit 20.
As shown in FIG. 8, in order to make the slew rate difference between the 17 positive amplifier circuits 172p and the negative amplifier circuit 172n in the output amplifier circuit match, the current flowing through the positive amplifier circuit 172p of the output amplifier circuit 17 The current flowing through the negative polarity amplifier circuit 172n is adjusted.
Therefore, as shown in FIG. 8, a plurality of current sources (Io1 to Io3) having different current values are prepared in the bias circuit 20, and are switched by the switching element (SW2), so that the current source at the time of selection is selected. Is output to the output amplifier circuit 17.
As a result, the amplifier output of various slew rates is enabled from the positive polarity amplifier circuit 172p and the negative polarity amplifier circuit 172n of the output amplifier circuit 17. Here, the circuit shown in FIG. 8 is prepared for each of the positive polarity amplifier circuit 172p and the negative polarity amplifier circuit 172n of the output amplifier circuit 17.

As shown in FIG. 1, in a liquid crystal display panel having an RGB switch circuit (RGB-SW), noise is generated by ON / OFF of a control signal (S-RGB). However, since the control signal (S-RGB) has no canceling waveform, the ON / OFF waveform propagates as noise as it is.
Therefore, in the third embodiment of the present invention, as shown in FIG. 10, as a gate circuit that outputs the control signal (S-RGB) in the panel interface circuit 23 of FIG. 2, at least one of the channel width and the channel length is different. A plurality of transfer gate circuits (TG1 to TG3) are prepared. Then, by selecting the transfer gate circuit, the slew rate of the transfer gate circuit is reduced, the control signal (S-RGB) ON / OFF waveform is blunted, and noise is reduced.
Normally, as the definition becomes higher, the writing time becomes more severe, so that the slew rate of the transfer gate circuit is improved. However, in order to prevent noise, the slew rate of the transfer gate circuit is adjusted to be rather deteriorated.

Since the generation principle of noise generated from the surface of the liquid crystal display panel is coupling of signal transitions such as video lines (DL), noise can be reduced if the voltage transitions on the video lines (DL) are slow. .
Therefore, as shown in FIG. 11, in the fourth embodiment of the present invention, the RGB switch circuit (RGB-SW) of the driver (DRV) of the liquid crystal display panel and the pixel are within the range satisfying the writing time of the gradation voltage. By inserting the resistance element (R) between the video line (DL) in the region (AR), the slew rate can be reduced and noise can be reduced.
In the present embodiment, as in the first embodiment, the time point at which the gradation voltage is written to the video line (DL) is not different for each block.
When the thin film transistor (TFT) of each pixel has a semiconductor layer made of polysilicon, the resistance element (R) can be easily formed of a polysilicon resistance layer.
As mentioned above, the invention made by the present inventor has been specifically described based on the above embodiments. However, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the scope of the invention. Of course.

DESCRIPTION OF SYMBOLS 10 Interface circuit 11 Timing generation circuit 12 Frame memory 13, 140 Latch circuit 14 Final latch circuit 15, 22 Level shift circuit 16 Decoder circuit 17 Output amplifier circuit 18 Gamma adjustment circuit 19 Gradation voltage generation circuit 20 Bias circuit 21 Booster circuit 23 Panel Interface circuit 171 Precharge circuit 172 Amplifier circuit 172p Positive amplifier circuit 172n Negative amplifier circuit DL Video line GL Scan line CT Counter electrode PX Pixel electrode Cadd Holding capacitor PS Pixel AR Pixel area TFT Thin film transistor RGB-SW RGB switch circuit CSW1, CSW2 Switch part DRV driver SUB1 1st glass substrate L-GCS, R-GCS Gate circuit DDL Delay element Io1-Io3 Current source TG1-TG3 Transfer gate circuit S 1, SW2 switching element R resistive element

Claims (8)

A display driver for supplying a video voltage to each video line of a display panel,
A frame memory for storing display data input from the outside;
A plurality of first latch circuits for reading and latching display data for one display line from the frame memory;
A timing generation circuit for generating a latch control signal;
A plurality of second latch circuits provided for each of the plurality of first latch circuits and latching display data latched in the first latch circuit based on the latch control signal;
A plurality of decoder circuits for converting display data latched by the second latch circuit into video signal voltages;
A plurality of output amplifier circuits provided for each of the plurality of decoder circuits;
A bias circuit for supplying a bias voltage to each of the output amplifier circuits,
The bias circuit includes a plurality of constant current sources having different current values,
A switch element for selecting any one of the plurality of constant current sources;
The display device driver, wherein the bias circuit supplies a bias voltage generated by the selected constant current source to each of the output amplifier circuits. A display driver for supplying a video voltage to each video line of a display panel,
A frame memory for storing display data input from the outside;
A plurality of first latch circuits for reading and latching display data for one display line from the frame memory;
A timing generation circuit for generating a latch control signal;
A plurality of second latch circuits provided for each of the plurality of first latch circuits and latching display data latched in the first latch circuit based on the latch control signal;
A plurality of decoder circuits for converting display data latched by the second latch circuit into video signal voltages;
A plurality of output amplifier circuits provided for each of the plurality of decoder circuits;
A bias circuit for supplying a bias voltage to each of the output amplifier circuits,
The plurality of output amplifier circuits include a positive polarity amplifier circuit that outputs a positive gradation voltage;
A negative amplifier circuit that outputs a negative gradation voltage,
The bias circuit includes a plurality of constant current sources for positive polarity amplifier circuits each having a different current value,
A plurality of constant current sources for negative polarity amplifier circuits each having a different current value;
A switch element for selecting any one of the plurality of constant current sources for the positive polarity amplifier circuit, and a switch element for selecting any one of the plurality of constant current sources for the negative polarity amplifier circuit And
The bias circuit supplies a bias voltage generated by the constant current source for the selected positive amplifier circuit to the positive amplifier circuit of each of the output amplifier circuits, and for the selected negative amplifier circuit. A display driver, wherein a bias voltage generated by a constant current source is supplied to a negative polarity amplifier circuit of each output amplifier circuit. In the second latch circuit, the plurality of video lines are divided into a plurality of blocks, and a plurality of internal latch circuits are provided for each of the blocks,
A propagation path of the latch control signal from the timing generation circuit to the plurality of internal latch circuits;
A delay element for each internal latch circuit on the propagation path;
3. The display device according to claim 1, wherein in the second latch circuit, a timing at which display data latched in the first latch circuit is latched is different for each internal latch circuit. 4. Driver. The internal latch circuit is divided into first and second groups with a central position as a boundary in the second latch circuit,
4. The propagation path of the latch control signal has a first propagation path connected to the first group and a second propagation path connected to the second group. The display device driver described in 1. The display panel has a plurality of scanning lines for inputting a scanning voltage to the plurality of pixels,
A first scanning circuit and a second scanning circuit provided on the left and right sides of the pixel portion composed of the plurality of pixels;
The first scanning circuit supplies a scanning voltage to an odd-numbered scanning line among the plurality of scanning lines,
The second scanning circuit supplies a scanning voltage to an even-numbered scanning line among the plurality of scanning lines;
4. The propagation path of the latch control signal has a first propagation path corresponding to the first scanning circuit and a second propagation path corresponding to the second scanning circuit. The display device driver described in 1. A plurality of output amplifier circuits provided for each of the plurality of decoder circuits;
Each output amplifier circuit outputs a precharge voltage to each video line before outputting the gradation voltage output from each decoder circuit to each video line in one horizontal scanning period,
4. The driver for a display device according to claim 3, wherein a timing at which each output amplifier circuit outputs the precharge voltage to each video line in one horizontal scanning period is varied for each block. A switch circuit that outputs the gradation voltage output from each of the output amplifier circuits to the video lines of the first color to the third color within one horizontal scanning period;
The switch circuit is controlled by a switch control signal,
Each has a plurality of switching elements with different slew rates,
7. The display driver according to claim 6, wherein a switch control signal is input to the switch circuit via a selected switching element among the plurality of switching elements. Each of the plurality of switching elements is composed of a transfer gate circuit,
8. The display device driver according to claim 7, wherein each of the transfer gate circuits is different in at least one of a gate length and a gate width.

Images