JP2011043767A - Conversion circuit, display drive circuit, electro-optical device, and electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a conversion circuit, a display drive circuit and the like, capable of achieving high-definition display without inducing a large increase in power consumption due to an increase in an operation speed. <P>SOLUTION: Matrix conversion circuits 22a, 22b are provided in a display drive circuit that performs digital driving for representing a plurality of grayscales by dividing a single frame into a plurality of sub frames and displaying an image. The matrix conversion circuits include: a shift register SR that sequentially outputs clock pulses WC1 to WC96 from one of output terminals each time when a write clock WC is input; a plurality of flip-flop groups comprising a plurality of flip-flops DF1-1 to DF1-48, ..., DF96-1 to DF96-48 respectively connected to output terminals of the shift register SR; a plurality of selectors SL1 to SL96 selecting any of a plurality of data output from the flip-flop groups; and a counter CT controlling the data selected by the plurality of selectors SL1 to SL96. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a conversion circuit that converts data used for image display, a display drive circuit including the conversion circuit, an electro-optical device including the display drive circuit, and an electronic apparatus including the electro-optical device.

  As is well known, the electro-optical device includes a plurality of scanning electrodes (scanning lines), a plurality of signal electrodes (data lines), and a plurality of pixels provided at positions where the scanning electrodes and the signal electrodes intersect. The gradation state (image data) corresponding to the gradation of each pixel is supplied to each pixel corresponding to the selected scanning electrode via the signal electrode, thereby changing the optical state of each pixel. Is. Such electro-optical devices are used not only in stationary electronic devices such as projectors and televisions but also in a wide variety of portable electronic devices.

  In recent years, in many electro-optical devices, a digital driving method has been adopted in which digitized image data is used to display a plurality of gradations by dividing one frame into a plurality of subframes and displaying an image. The following Patent Document 1 discloses a technique for increasing the number of gradations that can be expressed without increasing the number of subframes in one frame. Patent Document 2 below discloses a technique for realizing high gradation display without using a special high-speed circuit element.

JP 2006-215534 A JP 2001-209346 A

  By the way, if the resolution increases and the number of gradations increases, the amount of image data to be handled becomes enormous, and therefore it is necessary to process the image data at high speed. In order to process this enormous amount of image data at high speed, it is necessary to prepare not only a high-speed circuit element for processing the image data but also a high-speed data bus, which may increase the circuit scale. There is a problem that there is.

  In addition, since the electro-optical device adopting the above-described digital driving method becomes higher in definition as the number of subframes increases, the conventional analog driving method (method of driving without dividing into subframes) is adopted. The operation speed may be several tens of times higher than that of an electro-optical device. Then, the operation speed becomes as high as several gigahertz, which causes a problem that the design becomes difficult and the power consumption increases.

  One embodiment of the present invention includes a conversion circuit, a display driver circuit, an electro-optical device, and the electro-optical device that can realize high-definition display without causing an increase in operation speed and a significant increase in power consumption. An electronic device including the above is provided.

The conversion circuit according to the present invention is a conversion circuit provided in a display drive circuit that performs digital drive to express a plurality of gradations by dividing one frame into a plurality of subframes and displaying an image. A shift register having a predetermined number of output ends larger than the number, and outputting a clock pulse sequentially from any of the output ends each time a clock signal is input, and a plurality of bits indicating the luminance level for each subframe Each consisting of a plurality of flip-flops to which the value of each bit of data for each pixel is input, and a plurality of flip-flop groups connected to each of the output ends of the shift register, and the plurality of flip-flop groups, respectively A plurality of selectors for selecting one of a plurality of data output from a connected flip-flop group. When it is characterized in that it comprises a counter for controlling the data selected by the plurality of selectors.
According to the present invention, among the plurality of flip-flop groups connected to each of the output terminals of the shift register, only the flip-flops that form the flip-flop group connected to the output terminal to which the clock pulse is output are in the operating state. Thus, data for each pixel composed of a plurality of bits indicating the luminance level for each subframe is input. In addition, by selecting the input data with a selector under the control of the counter, the data is composed of bits indicating the luminance level of the same subframe in units of a predetermined number of pixels larger than the number of subframes. The converted data can be output at a slower speed than the input data. For this reason, high-definition display can be realized without causing an increase in operating speed and a significant increase in power consumption.
Here, the conversion circuit of the present invention is characterized in that the shift register has as many output terminals as the number of phase expansions.
In the conversion circuit of the present invention, the flip-flop may be a D flip-flop that maintains the output of the value that was input when the clock pulse was input until the next clock pulse is input. desirable.
According to another aspect of the present invention, there is provided a conversion circuit that outputs a first clock signal from a first output terminal and a second clock signal from a second output terminal; and The first and second flip-flops that are input, the third and fourth flip-flops to which the second clock signal is input, the output signal of the first flip-flop, and the A first selector to which an output signal of a third flip-flop is input; a second selector to which an output signal of the second flip-flop and an output signal of the fourth flip-flop are input; And a signal generator for generating a signal for controlling the operation of the second selector.
The display driving circuit of the present invention is a display driving circuit that performs digital driving to express a plurality of gradations by dividing one frame into a plurality of sub-frames and displaying an image, and indicates the gradation for each pixel in one frame. A generator configured to generate, for each pixel, data composed of a plurality of bits indicating a luminance level for each subframe based on gradation data; and the converter according to any one of the above, The data generated in step (b) is converted into data composed of bits indicating the luminance level of the same subframe in units of the predetermined number of pixels, and the data converted by the converter is stored. And a storage unit.
According to the present invention, based on the gradation data indicating the gradation for each pixel in one frame, data composed of a plurality of bits indicating the luminance level for each subframe is generated for each pixel, and the generated data is Using the above conversion circuit, the data is converted into data composed of bits indicating the luminance level of the same subframe in units of a predetermined number of pixels larger than the number of subframes and stored. Thereby, high-definition display can be realized without causing a significant increase in circuit scale and an increase in operation speed.
In the display drive circuit of the present invention, the generation unit includes a plurality of addresses whose addresses correspond to the gradation data and in which data stored in a storage area specified by the addresses indicates a luminance level for each subframe. It is characterized by comprising a non-volatile memory corresponding to data consisting of the bits.
According to the present invention, since the data stored in the storage area specified by the address corresponding to the gradation data is data composed of a plurality of bits indicating the luminance level for each subframe, the luminance level for each subframe is set. Data consisting of a plurality of bits can be generated at high speed with a simple configuration.
In the display drive circuit of the present invention, the conversion unit includes a plurality of the conversion circuits described above, and the input of the data generated by the generation unit and the output of the converted data are alternately performed. It is characterized by being performed.
According to the present invention, since the input of the data generated by the generation unit and the output of the converted data are alternately performed by the plurality of conversion circuits, the data generated by the generation unit can be converted continuously.
In the display drive circuit of the present invention, the storage unit includes a plurality of storage circuits capable of storing data for one frame converted by the conversion unit.
In addition, the display driving circuit of the present invention includes a writing control unit that writes data output from the conversion circuit to the storage unit in synchronization with a dot clock that is a unit for driving the pixel. .
The electro-optical device of the present invention is an electro-optical device having a pixel including a switching element provided corresponding to the intersection of a plurality of scanning lines and a plurality of data lines, and a pixel electrode connected to the switching element. Then, the display driving circuit according to any one of the above is provided, which drives the pixel based on data stored in the storage unit.
An electronic apparatus according to an aspect of the invention includes the above electro-optical device.

1 is a block diagram illustrating a main configuration of an electro-optical device according to an embodiment of the invention. FIG. 3 is a circuit diagram illustrating a specific configuration example of a pixel 14. FIG. 3 is a diagram illustrating an example of a nonvolatile memory provided in a digital code conversion unit 21. FIG. It is a figure for demonstrating the process performed by the matrix conversion circuits 22a and 22b. It is a block diagram which shows the structural example of the matrix conversion circuits 22a and 22b. It is a figure which shows an example of the memory map of frame buffer 23a, 23b. 1 is a diagram illustrating an overall configuration of a liquid crystal device 1. It is a timing chart explaining the input timing of image data DATA. It is a timing chart explaining operation | movement of the matrix conversion circuit 22a. It is a timing chart explaining the operation | movement at the time of the display of the image according to the data for a display. It is a top view which shows the structure of the projector to which a liquid crystal device is applied. It is a perspective view which shows the structure of the personal computer to which the liquid crystal device is applied. It is a perspective view which shows the structure of the mobile telephone to which a liquid crystal device is applied.

  Hereinafter, a conversion circuit, a display drive circuit, an electro-optical device, and an electronic apparatus according to an embodiment of the invention will be described in detail with reference to the drawings. The embodiments described below show some aspects of the present invention and do not limit the present invention, and can be arbitrarily changed within the scope of the technical idea of the present invention.

  FIG. 1 is a block diagram illustrating a main configuration of an electro-optical device according to an embodiment of the invention. In the following description, a liquid crystal device is taken as an example of an electro-optical device. As shown in FIG. 1, the liquid crystal device 1 includes a liquid crystal panel 10, a display drive circuit 20, a level shifter 30, a data line drive circuit 40, a scanning line drive circuit 50, and a drive voltage generation circuit 60, and a control circuit ( A drive circuit such as the display drive circuit 20 drives the liquid crystal panel 10 under the control of (not shown).

  Note that the liquid crystal device 1 of the present embodiment divides one frame into a plurality of subframes as a gradation display method, and sets the luminance level of the pixels in each subframe to at least the first level or the second level. It is assumed that digital drive (digital time division drive) expressing a plurality of gradations is adopted, and common inversion drive is adopted as an AC drive method. In the present embodiment, the number of subframes is “48”. The display mode of the liquid crystal device 1 is normally white, black display with a voltage applied to the pixel (first level: luminance level 0), and white display with no voltage applied (second level). : The luminance level is other than 0).

  In the liquid crystal panel 10, the element substrate and the counter substrate are pasted with a certain gap therebetween, and liquid crystal as an electro-optic material is sandwiched between the gaps. In the liquid crystal panel 10, m scanning lines 11 and storage capacitor lines 12 (m is an integer of 2 or more) extending in the X direction are arranged in the Y direction, and n (n is (Integer of 2 or more) data lines 13 are arranged in the X direction. A plurality of pixels 14 are arranged in a matrix of m rows × n columns corresponding to each of the intersection positions where the scanning lines 11 and the data lines 13 intersect. In this embodiment, m = 1080 and n = 1920.

  FIG. 2 is a circuit diagram illustrating a specific configuration example of the pixel 14. As shown in FIG. 2, the pixel 14 includes a transistor (MOS type FET) 15 as a switching element, a pixel electrode 16, a counter electrode (common electrode) 17, a liquid crystal 18, and a storage capacitor 19. The transistor 15 has a gate connected to the scanning line 11, a source connected to the data line 13, and a drain connected to the pixel electrode 16. A liquid crystal layer is formed by sandwiching a liquid crystal 18 between the pixel electrode 16 and the counter electrode (common electrode) 17.

  The counter electrode 17 is a transparent electrode formed on the entire surface of the counter substrate so as to face the pixel electrode 16. In addition, the storage capacitor 19 is formed between the pixel electrode 16 and the storage capacitor line 12 and auxiliary charges are stored together with electrodes (pixel electrode 16 and counter electrode 17) sandwiching the liquid crystal layer. The common voltage VCOM is supplied from the drive voltage generation circuit 60 to the counter electrode 17 and the storage capacitor line 12 (see FIG. 1).

  Scanning signals G1, G2,..., Gm are supplied to the scanning lines 11 from the scanning line driving circuit 50, respectively. Each of the scanning signals G1, G2,..., Gm turns on the transistors 15 constituting the pixels 14 connected to the scanning lines 11, thereby supplying the data lines 13 from the data line driving circuit 40. Data signals d 1, d 2,..., Dn are supplied to the pixel electrode 16 and written in the liquid crystal 18 and the storage capacitor 19. In this embodiment, since the digital drive is adopted as described above, the data signals d1, d2,..., Dn are 2 corresponding to the first level (black) or the second level (white). Value voltage. In this way, the molecular orientation state of the liquid crystal 18 changes according to the voltage written to the pixel 14, that is, the potential difference between the pixel electrode 16 and the counter electrode 17, and the illumination light is modulated.

  The display drive circuit 20 includes a digital code conversion unit 21 (generation unit), a matrix conversion unit 22 (conversion unit), a frame buffer unit 23 (storage unit), a write timing controller 24, a write address controller 25 (write control unit), An oscillator 26, a read timing controller 27, and a read address controller 28 are provided. The display drive circuit 20 having such a configuration receives image data DATA, a dot clock signal DCLK, a vertical synchronization signal VSYNC, and a horizontal synchronization signal HSYNC output from a control circuit (not shown), and a liquid crystal panel based on these signals. 10 generates image display data (display data).

  Here, the image data DATA is data (gradation data) indicating the gradation for each pixel 14 in one frame. In the following, it is assumed that the number of bits of the image data DATA is 12 bits and 4096 gradations can be expressed. The dot clock signal DCLK is a signal that defines the transfer rate of image data DATA (the transfer timing of image data DATA for one pixel), and the vertical synchronization signal VSYNC is a signal that defines the start timing of one frame. The horizontal synchronization signal HSYNC is a signal that defines the start timing of one horizontal scanning period.

  In this embodiment, since the number of frames per second is “60”, the frequency of the vertical synchronization signal VSYNC is 60 Hz, and the number of scanning lines 11 is “1080”, so the frequency of the horizontal synchronization signal HSYNC is 64. .8 kHz (1080 × 60 Hz). Since the number of data lines 13 is “1920”, the frequency of the dot clock signal DCLK is approximately 124 MHz (1920 × 1080 × 60 Hz).

  Based on the input image data DATA, the digital code converter 21 generates data (hereinafter referred to as a digital code) composed of a plurality of bits indicating the luminance level for each subframe for each pixel. As shown in FIG. 3, the digital code conversion unit 21 has an address corresponding to a gradation, and data stored in a storage area specified by each address is a digital code such as a ROM (Read Only Memory). A non-volatile memory is provided, and image data DATA is converted into the digital code using the non-volatile memory.

  FIG. 3 is a diagram illustrating an example of a nonvolatile memory provided in the digital code conversion unit 21. As shown in FIG. 3, the non-volatile memory has 12 bits of addresses (0x000 to 0XFFF) that are the same as the number of bits of the image data DATA, and each address is a gradation (0 to 4095) of the image data DATA. Respectively. For example, in FIG. 3, the gradation “5” is associated with the address 0x005. In order to simplify the description, the case where the nonvolatile memory has an address corresponding to the number of bits of the image data DATA will be described as an example. Of course, the nonvolatile memory has an address corresponding to the number of bits of the image data DATA. It may be a thing.

  In addition, the storage area specified by each address stores a digital code for the gradation associated with each address. For example, in FIG. 3, a 48-bit digital code of 0x00000000000010C is stored in the storage area specified by the address 0x005 corresponding to the gradation “5”. Note that the digital code shown in FIG. 3 is merely an example, and the digital code stored in the nonvolatile memory is appropriately determined according to the characteristics of the liquid crystal panel 10.

  The number of bits of the digital code output from the digital code converter 21 is determined according to the number of subframes. In this embodiment, since the number of frames is “48”, a 48-bit digital code is used. Since the image data DATA for 1920 × 1080 pixels is input for 60 frames per second in synchronization with the dot clock signal DCLK, the digital code conversion unit 21 has an operating frequency of about 124 MHz. (1920 × 1080 × 60 Hz).

  The matrix conversion unit 22 includes matrix conversion circuits 22a and 22b (conversion circuits), a counter, and a frequency divider (the counter and the frequency divider are not shown), and the digital code output from the digital code conversion unit 21 Is converted into data in a predetermined format (display data). Specifically, the matrix conversion unit 22 generates a digital code, which is data for each pixel including a plurality of bits indicating a luminance level for each subframe, for the number of phase expansions of the phase expansion driving performed by the data line driving circuit 40. The data is converted into data composed of bits indicating the luminance level of the same subframe in units of pixels. The reason why such conversion processing is performed is mainly to suppress an increase in operating frequency of the display driving circuit 20 adopting digital driving without causing a significant increase in circuit scale.

Here, the phase expansion driving is a driving method for lowering the writing frequency of the data signal to the pixel 14 (frequency f _SCLK of a system clock signal SCLK described later), and phase expansion for each of the scanning lines 11. A driving method for sequentially writing data in units of numbers. For example, when there are 1920 pixels connected to one scanning line 11 and the number of phase expansions is “96”, the writing operation is performed only 20 times in one horizontal scanning period. On the other hand, when the phase development drive is not performed, 1920 writing operations are required in one horizontal scanning period. Therefore, the write frequency (f _SCLK ) can be drastically lowered by performing the phase expansion drive.

  The matrix conversion unit 22 performs conversion processing while switching the matrix conversion circuits 22a and 22b each time digital codes corresponding to the number of phase expansions are output from the digital code conversion unit 21. Such switching is performed in order to realize continuous conversion of the digital code by alternately reading the digital code output from the digital code conversion unit 21 and outputting the converted data by the matrix conversion circuits 22a and 22b. is there.

  Specifically, the matrix conversion unit 22 counts the dot clock signal DCLK output from the write timing controller 24 using a counter (not shown), and each time the count value becomes a multiple of the number of phase expansions, the matrix conversion circuit 22a. , 22b. Therefore, the switching frequency of the matrix conversion circuits 22a and 22b is 1.296 MHz (1920 × 1080 × 60/96 Hz) obtained by dividing the frequency of the dot clock signal DCLK by the number of phase expansions. The count value of the counter is reset every time the vertical synchronization signal VSYNC output from the write timing controller 24 is input.

  FIG. 4 is a diagram for explaining processing performed in the matrix conversion circuits 22a and 22b. Here, the processing performed in the matrix conversion circuit 22a will be described as an example. In FIG. 4, 48-bit data to which the code D1 is attached indicates a digital code output from the digital code converter 21, and 96-bit data to which the code D2 is attached is converted by the matrix conversion circuit 22a. Data are shown. The number of bits of the digital code D1 is the same as the number of subframes, and the number of bits of the data D2 is the same as the number of phase expansions.

  As shown in FIG. 4, the matrix conversion circuit 22a stores 96 digital codes D1 output from the digital code conversion unit 21 in the output order, the same as the number of phase expansions, and from the first bit of the stored data thereafter. In order up to the 48th bit, the same bit is converted into 96-bit data D2 and output in order. That is, of the 96 pieces of accumulated data from the matrix conversion circuit 22a, 96-bit data in which only the first bit is gathered, 96-bit data in which only the second bit is gathered,..., Only the 48th bit is gathered. The 96-bit data is sequentially output.

  Note that the matrix conversion circuit 22a is in a period from when the accumulation (reading) of the 96 digital codes D1 output from the digital code conversion unit 21 is completed until all the accumulated data is output as data D2. It is not possible to store a new digital code D1. For this reason, in this embodiment, a matrix conversion circuit 22b is provided in addition to the matrix conversion circuit 22a, and the digital code D1 is accumulated in the matrix conversion circuit 22b while the data D2 is output from the matrix conversion circuit 22a. While the data D2 is output from the matrix conversion circuit 22b, the digital conversion is performed by accumulating the digital code D1 in the matrix conversion circuit 22a.

  Here, the 48-bit digital code output from the digital code converter 21 having an operating frequency of about 124 MHz is input to the matrix converter 22. On the other hand, the digital code input to the matrix converter 22 is converted and output as 96-bit data. Therefore, the operating frequency (the frequency of the write clock) on the input side of the matrix conversion unit 22 (matrix conversion circuits 22a and 22b) is about 124 MHz, which is the same as the operating frequency of the digital code conversion unit 21, but the operating frequency on the output side. The (read clock frequency) is about 62.2 MHz (1920 × 1080 × 60 × 48/96 Hz), which is the same as a system clock SCLK described later.

  Next, specific circuit configurations of the matrix conversion circuits 22a and 22b will be described. FIG. 5 is a block diagram illustrating a configuration example of the matrix conversion circuits 22a and 22b. As shown in FIG. 5, the matrix conversion circuits 22a and 22b include one shift register SR, flip-flops (D flip-flops) DF1-1 to DF1-48 corresponding to the number of subframes × the number of phase expansions (48 × 96). ..., DF96-1 to DF96-48, selectors SL1 to SL96 corresponding to the number of phase expansions (96), and a counter CT, and a 48-bit digital code input from 48 input terminals A1 to A48 The data is converted into the above 96-bit data and output from the 96 output terminals B1 to B96.

  The shift register SR has one clock input terminal to which the write clock WC is input and 96 output terminals, and a clock pulse is output from any one of the 96 output terminals in synchronization with the write clock WC. Output sequentially. As the write clock WC, a dot clock signal DCLK (frequency about 124 MHz) output from the write timing controller 24 is used. Signal lines Q1 to Q96 for transmitting the clock pulse are connected to the output terminal of the shift register SR.

  The flip-flops DF1-1 to DF1-48,..., DF96-1 to DF96-48 each have one input terminal, one clock input terminal, and one output terminal, and receive data input from the input terminal. The signal is output from the output terminal in synchronization with the clock pulse input to the clock input terminal. The clock input terminals of the flip-flops DF1-1 to DF1-48 are connected to the signal line Q1. Similarly, clock input terminals of the flip-flops DF2-1 to DF2-48,..., And clock input terminals of the flip-flops DF96-1 to DF96-48 are connected to the signal lines Q2,. A flip-flop group is constituted by 96 flip-flops connected to each of the signal lines Q1 to Q96. In the example shown in FIG. 5, 96 flip-flop groups for each of the signal lines Q1 to Q96 are provided.

  The input terminals of the flip-flops DF1-1 to DF96-1 are connected to the input terminal A1, and the first bit of the digital code output from the digital code converter 21 is input thereto. Similarly, the input ends of the flip-flops DF1-2 to DF96-2,..., And the input ends of the flip-flops DF1-48 to DF96-48 are connected to the input ends A2,. The second bit,..., The 48th bit of the digital code output from the conversion unit 21 is input.

  The selectors SL1 to SL96 each include 48 input terminals and one output terminal, and 1-bit data input to each of the 48 input terminals based on the count signal SC output from the counter CT. One of these is selected and output from the output terminal. The output terminals of the flip-flops DF1-1 to DF1-48,..., DF96-1 to DF96-48 and the input terminals of the selectors SL1 to SL96 are connected to each other.

  For example, the output end of the flip-flop DF1-1 labeled with the symbol d1-1 is connected to the input end of the selector SL1 labeled with the same symbol d1-1. Accordingly, the output ends of the flip-flops DF1-1 to DF1-48 connected to the signal line Q1 are output to the input end of the selector SL1. Similarly, the output terminals of the flip-flops DF2-1 to DF2-48 connected to the signal line Q2 to the output terminals of the flip-flops DF96-1 to DF96-48 connected to the signal line Q96 are the input terminal to the selector of the selector SL2. Each is connected to the input terminal of SL96.

  In FIG. 5, in order to avoid complication, illustration of connection relations between the output terminals of the flip-flops DF1-1 to DF1-48,..., DF96-1 to DF96-48 and the input terminals of the selectors SL1 to SL96 is omitted. is doing. Further, from the output terminal B1 of the selector SL1, bits indicating the luminance level of the subframe for the first pixel among the pixels corresponding to the number of phase expansion are sequentially output. Similarly, from the output terminals of the selectors SL <b> 2 to SL <b> 96, bits indicating the luminance level of the subframe for the second to 96th pixels among the pixels corresponding to the number of phase expansions are output.

  The counter CT counts a read clock RC input from the outside, and outputs the count value as a count signal SC. This counter CT is a 6-bit counter capable of counting the number of subframes (48), and repeats counting between “1” and “48”. The read clock RC is generated by dividing the dot clock signal DCLK (frequency about 124 MHz) output from the write timing controller 24 by two by a frequency divider (not shown) provided in the matrix conversion circuit 22. Therefore, the frequency of the read clock RC is about 62.2 MHz, which is half the frequency of the write clock WC.

  The frame buffer unit 23 includes two frame buffers 23a and 23b, and temporarily stores 96-bit data converted by the matrix conversion unit 22, that is, display data for an image to be displayed on the liquid crystal panel 10. . The frame buffer 23a is used, for example, for temporarily storing display data for odd frames, and the frame buffer 23b, for example, is used for temporarily storing display data for even frames. The writing of display data to the frame buffers 23a and 23b is switched every time the vertical synchronization signal VSYNC from the write timing controller 24 is input.

  FIG. 6 is a diagram showing an example of a memory map of the frame buffers 23a and 23b. Each of the frame buffers 23a and 23b has a capacity capable of storing display data for one frame, and as shown in FIG. 6, 48 areas each storing luminance data of the first to 48th subframes. It is divided into R1 to R48. The capacity of each of the regions R1 to R48 is set to a capacity capable of storing display data for at least one subframe.

  In the present embodiment, it is assumed that the liquid crystal device 1 has 1920 pixels connected to one scanning line 11, the total number of scanning lines 11 is 1080, and the number of phase expansions is “96”. . In order to perform writing to 1920 pixels connected to one scanning line 11, 20 pieces of 96-bit display data are required. Accordingly, the areas R1 to R48 are set to capacities capable of storing at least 96 bits of display data 21600 (= 20 × 1080). In the example shown in FIG. 6, the storage area specified by the addresses “1” to “21600” of the frame buffers 23a and 23b is set as the area R1, and the storage area specified by the addresses “21601” to “43200” is the area. R2 is set. Further, the storage area specified by the addresses “1015201” to “1036800” is set in the area R48.

  The write timing controller 24 operates based on the dot clock signal DCLK, the horizontal synchronization signal HSYNC, and the vertical synchronization signal VSYNC output from a control circuit (not shown), and the display timing for the frame buffers 23a and 23b. Controls the writing timing of data. The write timing controller 24 outputs the dot clock signal DCLK and the vertical synchronization signal VSYNC to the matrix conversion circuit 22, and outputs the vertical synchronization signal VSYNC to the frame buffer unit 23. Based on the control signal output from the write timing controller 24, the write address controller 25 generates and outputs a write address for writing display data to the frame buffers 23a and 23b.

The oscillator 26 generates a system clock signal SCLK having a predetermined frequency and outputs it to the read timing controller 27. Here, when the frame frequency f _FM is 60 Hz, the number of subframes in one frame is “48”, the number of scanning lines 11 is 1080, the number of data lines 13 is 1920, and the number of phase expansions is “96” The frequency f _SCLK of the system clock signal SCLK is about 62.2 MHz (1920 × 1080 × 60 × 48/96 Hz).

  The read timing controller 27 controls the read timing of display data from the frame buffers 23a and 23b based on a system clock signal SCLK output from the oscillator 26 and a vertical synchronization signal VSYNC output from a control circuit (not shown). . Specifically, the read timing controller 27 generates a polarity inversion signal FR, a scan start pulse YSP, a scan transfer clock YCLK, and a data transfer start pulse XSP to control the read timing.

  The polarity inversion signal FR is a signal that defines the polarity inversion period of the write voltage of the pixel 14 (in other words, a signal that defines the common inversion operation period). In the present embodiment, the polarity inversion period is determined so that the polarity is inverted once per frame. That is, the polarity inversion signal FR is a pulse signal whose level changes once per frame. In the present embodiment, a positive voltage is written to the pixel 14 when the polarity inversion signal FR is at a high level, and a negative voltage is written to the pixel 14 when the polarity inversion signal FR is at a low level.

The scan start pulse YSP is a signal that defines the start timing of each subframe, and is generated by dividing the system clock signal SCLK. When the frame frequency f _FM is 60 Hz and the number of subframes in one frame is “48”, the frequency f _YSP of the scan start pulse _YSP is 2.88 kHz (60 × 48 Hz).

The scanning transfer clock YCLK is a signal that defines the scanning speed (Y side) (in other words, a signal that defines the output timing of the scanning signals G1, G2,..., Gm), and divides the system clock signal SCLK. To be generated. Frequency _{f YSP} is 2.88KHz scanning start pulse YSP, when the number of scanning lines 11 is 1080, the frequency _{f YCLK} scanning transfer clock YCLK is to 1.5552MHz (2.88kHz × 1080/2) Become.

The data transfer start pulse XSP is a signal that defines the start timing of one horizontal scanning period, and is generated by dividing the system clock signal SCLK. Frequency _{f YSP} is 2.88KHz scanning start pulse YSP, when the number of scanning lines 11 is 1080, the frequency _{f XSP} of the data transfer start pulse XSP becomes 3.1104MHz (2.88kHz × 1080).

  The read timing controller 27 outputs the vertical synchronization signal VSYNC to the read address controller 28, outputs the system clock signal SCLK to the read address controller 28 and the data line drive circuit 40, and outputs the polarity inversion signal FR to the drive voltage generation circuit 60 and the level. Output to the shifter 30. Further, the scan start pulse YSP and the scan transfer clock YCLK are output to the scan line driving circuit 50, and the data transfer start pulse XSP is output to the data line drive circuit 40.

  The read address controller 28 generates a read address for reading display data from the frame buffers 23 a and 23 b based on the system clock signal SCLK and the vertical synchronization signal VSYNC output from the read timing controller 27.

  The level shifter 30 is based on the value of the display data (digital code for each subframe of 96 pixels) read from the frame buffer unit 23 and the level of the polarity inversion signal FR. The voltage level is shifted to the voltage level to be supplied to the pixel 14. Then, the code for 96 pixels after the voltage level shift is output to the data line driving circuit 40 as display data XDATA (96 bits).

  Specifically, in the level shifter 30, each code Ci (i is an integer satisfying 1 ≦ i ≦ 96) constituting the display data is “1” designating the first level, and the polarity inversion signal FR is high. If it is level (positive polarity), the voltage level of the code Ci is shifted to the maximum voltage VD1. The level shifter 30 sets the voltage level of the code Ci to the minimum voltage when the code Ci is “1” designating the first level and the polarity inversion signal FR is at the low level (negative polarity). Shift to VD2.

  On the other hand, the level shifter 30 sets the voltage level of the code Ci to the minimum voltage when the code Ci is “0” designating the second level and the polarity inversion signal FR is high level (positive polarity). Shift to VD2. Further, the level shifter 30 sets the voltage level of the code Ci to the maximum voltage VD1 when the code Ci is the code “0” designating the second level and the polarity inversion signal FR is the low level (negative polarity). Shift to.

  The voltage level shift operation by the level shifter 30 and the common voltage inversion operation by the drive voltage generation circuit 60 described above cause the pixel 14 to have a positive polarity with respect to the common voltage VCOM during the period in which the polarity inversion signal FR is at a high level. Voltage is written. In addition, a negative voltage with respect to the common voltage VCOM is written into the pixel 14 during a period in which the polarity inversion signal FR is at a low level.

  The data line driving circuit 40 grasps the start timing of one horizontal scanning period from the data transfer start pulse XSP, and in synchronization with the system clock SCLK, the display data XDATA (96 bits) is used as 96 pixel data signals for 96 data. Output simultaneously to line 13. The data line driving circuit 40 repeats the above-described operation of outputting data signals for 96 pixels 20 times while shifting the data line 13 in units of 96 pixels in synchronization with the system clock SCLK, thereby 1920 data in one horizontal scanning period. The output operation of data signals for pixels is completed. The scanning line driving circuit 50 grasps the start timing of each subframe from the scanning start pulse YSP, and scan signals G1, G2, G3 having a voltage VG on each scanning line 11 in synchronization with the scanning transfer clock YCLK. ..., Gm are sequentially output.

  The drive voltage generation circuit 60 generates a voltage VG (gate-on voltage of the transistor 15) of the scanning signals G1, G2,..., Gm and outputs it to the scanning line driving circuit 50. Further, a reference voltage V0, a maximum voltage VD1 (black voltage in the case of positive polarity), and a minimum voltage VD2 (black voltage in the case of negative polarity) of the data signals d1, d2,. Output. Further, the common voltage VCOM is generated and output to the counter electrode 17 and the storage capacitor line 12 provided in the liquid crystal panel 10. The maximum voltage VD1 and the minimum voltage VD2 are set to values that are symmetrical about the reference voltage V0.

  The drive voltage generation circuit 60 has a function of inverting the polarity of the common voltage VCOM around the reference voltage V0 according to the level of the polarity inversion signal FR output from the read timing controller 27. That is, when the polarity inversion signal FR is at a high level (positive polarity), the common voltage VCOM is a negative value (minimum value) with respect to the reference voltage V0, and when the polarity inversion signal FR is at a low level (negative polarity), The common voltage VCOM is a positive-side value (maximum value) with respect to the reference voltage V0. The maximum value of the common voltage VCOM is set to be equal to the maximum voltage VD1 of the data signal, and the minimum value of the common voltage VCOM is set to be equal to the minimum voltage VD2 of the data signal.

   Next, the overall configuration of the liquid crystal device 1 will be described. 7A and 7B are diagrams showing the overall configuration of the liquid crystal device 1, wherein FIG. 7A is a plan view and FIG. 7B is a cross-sectional view taken along the line AA ′ in FIG. As shown in FIG. 7, in the liquid crystal device 1, the element substrate 101 on which the pixel electrode 16 or the like is formed and the counter substrate 102 on which the counter electrode 17 or the like is formed are attached to each other with a sealant 103 while maintaining a certain gap. In addition, the liquid crystal 18 as an electro-optical material is sandwiched between the gaps. Actually, the sealing material 103 has a cutout portion, and after the liquid crystal 18 is sealed through this, the sealing material 103 is sealed with a sealing material, but is omitted in these drawings.

  The element substrate 101 and the counter substrate 102 are transparent substrates made of glass or the like. In the case of a reflective liquid crystal device, the element substrate 101 can be a semiconductor substrate. In this case, since the semiconductor substrate is opaque, the pixel electrode 16 is formed of a reflective metal such as aluminum. In the element substrate 101, a light shielding film 104 is provided on the inner side of the sealing material 103 and on the outer side of the display region 101 a. In the region where the light shielding film 104 is formed, the scanning line driving circuit 50 is formed in the region 110a, and the level shifter 30 and the data line driving circuit 40 are formed in the region 120a.

  That is, the light shielding film 104 prevents light from entering the drive circuits formed in these regions 110a and 120a. A common voltage VCOM is applied to the light shielding film 104 together with the counter electrode 17. In the element substrate 101, a plurality of connection terminals are formed in the region 130a outside the region 120a where the data line driving circuit 40 is formed and separated from the sealing material 103, and external control signals and The power supply is input.

  On the other hand, the counter electrode 17 of the counter substrate 102 is electrically connected to the light shielding film 104 and the connection terminal of the element substrate 101 by a conductive material (not shown) provided at at least one of the four corners of the substrate bonding portion. Conduction is achieved. That is, the common voltage VCOM is applied to the light shielding film 104 via a connection terminal provided on the element substrate 101 and further applied to the counter electrode 17 via a conductive material.

  The counter substrate 102 is provided with a color filter arranged in a stripe shape, a mosaic shape, a triangle shape, or the like according to the use of the liquid crystal device 1, for example, in the case of a direct view type. Further, for example, a light shielding film (black matrix) made of a metal material, resin, or the like is provided. In the case of the use of color light modulation, for example, when used as a light valve of a projector described later, a color filter is not formed. In the case of the direct-view type, the liquid crystal device 1 is provided with a light for irradiating light from the counter substrate 102 side or the element substrate side as required.

  In addition, the electrode formation surfaces of the element substrate 101 and the counter substrate 102 are each provided with an alignment film (not shown) that is rubbed in a predetermined direction to define the alignment direction of the liquid crystal molecules when no voltage is applied. On the other hand, a polarizer (not shown) corresponding to the orientation direction is provided on the counter substrate 101 side. However, if a polymer-dispersed liquid crystal dispersed as fine particles in a polymer is used as the liquid crystal 18, the above-described alignment film, polarizer, etc. are not required. As a result, the light utilization efficiency is increased. This is advantageous in terms of low power consumption.

  Next, the operation of the liquid crystal device 1 having the above configuration will be described. FIG. 8 is a timing chart for explaining the input timing of the image data DATA. As shown in FIG. 8, the start timing of one frame is time t1 when the falling edge of the vertical synchronization signal VSYNC occurs, and scanning of the first (first line) scanning line 11 is started within this one frame. Is the time t2 when the first falling edge of the horizontal synchronization signal HSYNC occurs.

  The number of periods of the horizontal synchronization signal HSYNC within one frame is 1080 periods corresponding to the number of scanning lines 11, and the number of periods of the dot clock signal DCLK within one period of the horizontal synchronization signal HSYNC is one scanning line 11. This is 1920 cycles corresponding to the number of pixels connected to. When 12-bit image data DATA for each pixel is sequentially output from a control circuit (not shown), the image data DATA is sequentially input to the digital code converter 21 in synchronization with the dot clock signal DCLK as shown in FIG. Is done.

  The image data DATA input to the digital code conversion unit 21 is sequentially converted into a digital code composed of a plurality of bits indicating the luminance level for each subframe. Specifically, the digital code stored in the address corresponding to the gradation of the input image data DATA is sequentially read from the nonvolatile memory (see FIG. 3) provided in the digital code conversion unit 21. Image data DATA is converted into a digital code. For example, when image data DATA having a gradation of “5” is input, it is converted into a 48-bit digital code 0x0000001010C stored in the storage area specified by the address 0x005 of the nonvolatile memory. Since the image data DATA is input in synchronization with the dot clock signal DCLK (frequency about 124 MHz), the conversion process in the digital code conversion unit 21 is also performed at the same operating frequency as the dot clock signal DCLK.

  The digital code converted by the digital code conversion unit 21 is input to the matrix conversion unit 22. Here, in the initial state, it is assumed that the matrix conversion circuit 22a is selected as a circuit to convert the input digital code. FIG. 9 is a timing chart for explaining the operation of the matrix conversion circuit 22a. When the matrix conversion circuit 22a is in a selected state, the write clock WC is input to the matrix conversion circuit 22a, and any one of the 96 output terminals of the shift register SR is input each time the write clock WC is input. To sequentially output clock pulses.

  Now, assuming that the clock pulse WC1 is output from the output terminal to which the connection line Q1 of the shift register SR is connected, the 48 flip-flops DF1-1 to DF1-48 having the clock input terminal connected to the connection line Q1 operate. It becomes a state. Then, a 48-bit digital code input from the input terminals A1 to A48 is input to the input terminals of the flip-flops DF1-1 to DF1-48 and output from the output terminals.

  Next, when the clock pulse WC2 is output from the output terminal to which the connection line Q2 of the shift register SR is connected, the 48 flip-flops DF2-1 to DF2-48 having the clock input terminal connected to the connection line Q2 are connected. Becomes operating. Then, new 48-bit digital codes input from the input terminals A1 to A48 are input to the input terminals of the flip-flops DF2-1 to DF2-48 and output from the output terminals, respectively. Similarly, clock pulses WC3 to WC96 are sequentially output from the output terminal of the shift register SR, and the same operation as described above is performed.

  Here, details of the operations of the flip-flops DF1-1 to DF1-48,..., DF96-1 to DF96-48 will be described by taking the flip-flops DF1-1 to DF96-1 as an example. Now, as shown in FIG. 9, the flip-flops DF1-1 to DF96-1 have the first bit data “a1”, “a2” of the 48-bit digital code sequentially input to the matrix conversion circuit 22a. .., “A96” are sequentially input in synchronization with the write clock WC (“input data” in FIG. 9). First, when the first data “a1” is input to the flip-flops DF1-1 to DF96-1, this data is output from the flip-flop DF1-1 at the rising timing of the clock pulse WC1 output from the shift register SR. It is output from the end (time t21).

  When the next data “a2” is input, this data is output from the output terminal of the flip-flop DF2-1 at the rising timing of the clock pulse WC2 output from the shift register SR (time t22). Here, at time t22, since the clock pulse WC1 is not input to the clock input terminal of the flip-flop DF1-1, the output of the data “a1” is continued from the output terminal of the flip-flop DF1-1.

  Similarly, data “a3”, “a4”,... Are sequentially input and clock pulses WC3, WC4,... Are output from the shift register SR, and data “a3”, “a4”,. Are sequentially output from 1, DF4-1,. The outputs of the data “a3”, “a4”,... Are continued from the flip-flops DF3-1, DF4-1,.

  When the above operation is repeated and data “a96” is input, this data is output from the output terminal of the flip-flop DF96-1 at the rising timing of the clock pulse WC96 output from the shift register SR (time). t23). Here, at time t23, the clock pulses WC1 to WC95 are not input to the clock input terminals of the flip-flops DF1-1 to DF95-1 other than the flip-flop DF96-1, and the outputs of the flip-flops DF1-1 to DF95-1 are output. From the end, output of data “a1” to “a95” is continued. As a result, as shown in FIG. 9, at time t23, data “a1” to “a96” are output from the output terminals of the flip-flops DF1-1 to DF96-1, respectively.

  Data output from each of the output terminals of the flip-flops DF1-1 to DF96-1 (data output from each of the output terminals denoted by reference numerals d1-1 to d96-1) is output from the selectors SL1 to SL96. Each is input to an input terminal to which the same symbol is attached. Although the flip-flops DF1-1 to DF96-1 are exemplified here, the other flip-flops DF1-2 to DF96-2,..., DF1-48 to DF96-48 are similar to the operations described above. Is performed.

  When the above operation is completed, the matrix conversion circuit 22b is selected as a circuit to convert the input digital code, and the matrix conversion circuit 22a is in a non-selected state. Then, the write clock WC is input to the matrix conversion circuit 22b, and the same operation as that of the matrix conversion circuit 22a is performed by the matrix conversion circuit 22b. In parallel with this, the matrix conversion circuit 22a performs a read operation.

  That is, the read clock RC is input to the matrix conversion circuit 22a in the non-selected state, and counting by the counter CT is started. In each of the selectors SL1 to SL96, one of 48 input terminals is selected based on the count signal SC output from the counter CT, and the data input to the selected input terminal is 96-bit data. “B1” is output from the output terminals B1 to B96 (time t24).

  Each time the read clock RC is input, different selectors are sequentially selected by the selectors SL1 to SL96, and as a result, the converted 96-bit data “b2” is output from the outputs B1 to B96 as shown in FIG. ,..., “B48” are sequentially output (“output data” in FIG. 9). When the above operation is performed for the number of frames (48 times), the matrix conversion circuit 22a is again selected, the digital code writing operation to the matrix conversion circuit 22a is performed, and the matrix conversion circuit 22b is unselected. Thus, the operation of outputting 96-bit data from the matrix conversion circuit 22b is performed. Thereafter, the selection / non-selection states of the matrix conversion circuits 22a and 22b are alternately switched, and the same operation as described above is repeated.

  The 96-bit data (display data) output from the matrix conversion unit 22 (matrix conversion circuits 22a and 22b) is input to the frame buffer unit 23. In the initial state, it is assumed that the frame buffer 23a is selected. The display data input to the frame buffer unit 23 is sequentially input to the frame buffer 23 a and written to an address specified by the write address output from the write address controller 25.

  As described above, the display data output from the matrix conversion unit 22 is data including bits indicating the luminance level of the same subframe in units of pixels corresponding to the number of phase expansions. For this reason, the display data (data “b1” in FIG. 9) output first from the matrix conversion circuit 22 is controlled by the write address controller 25 and the leading address (address “1”) of the region R1 of the frame buffer 23a. ) Is stored in the storage area specified by Next, the display data (data “b2” in FIG. 9) output from the matrix conversion circuit 22 is controlled by the write address controller 25 at the head address (address “21601”) of the region R2 of the frame buffer 23a. It is stored in the specified storage area. In this way, the display data output from the matrix converter 22 is sequentially stored in the regions R1 to R48 shown in FIG.

  When display data for one frame is output from the matrix conversion unit 22, display data for each of the first to 48th subframes is stored in the regions R1 to R48 in the frame buffer 23a as shown in FIG. The The capacity of display data for one frame is 1920 × 1080 × 60 × 46 bits. When the display data for one frame is stored in the frame buffer 23a, the frame buffer 23b is selected and writing of the display data output from the matrix conversion unit 22 is started, and the read address controller 28 reads the read address. Is output, and reading of the display data stored in the frame buffer 23a is started.

  FIG. 10 is a timing chart for explaining the operation at the time of displaying an image according to the display data. As shown in FIG. 10, when the falling edge of the vertical synchronization signal VSYNC occurs at time t1 and one frame is started, the scan timing pulse YSP is sequentially generated by the read timing controller 27, and the first to 48th subframes are generated. Are sequentially displayed (time t1, t4,..., T48).

  Here, in FIG. 10, attention is paid to time t3 (start timing of the first subframe). The read address controller 28 generates a read address indicating the head address (address “1”) of the region R1 of the frame buffer 23a in synchronization with the rising edge of the system clock signal SCLK and outputs the read address to the frame buffer unit 23. Then, 96-bit display data stored in the storage area specified by the address “1” of the frame buffer 23 a is read and output to the level shifter 30.

  The level shifter 30 sets each voltage level of the code Ci to the pixel 14 based on the value of the code Ci (1 ≦ i ≦ 96) forming the input 96-bit display data and the level of the polarity inversion signal FR. The code Ci after the voltage level shift is output to the data line driving circuit 40 as display data XDATA (96 bits). For example, when the code Ci is “1” designating the first level (black) and the polarity inversion signal FR is at the high level (positive polarity), the voltage level of the code Ci is set to the maximum voltage VD1. (At this time, the common voltage VCOM generated by the drive voltage generation circuit 60 becomes a negative-side value (minimum value) with respect to the reference voltage V0).

  On the other hand, the scanning line driving circuit 50 grasps the start timing of the first subframe from the rising edge of the scanning start pulse YSP at time t3 and is synchronized with the rising edge of the scanning transfer clock YCLK in the first direction in the Y direction. A scanning signal G 1 having a voltage VG is output to the scanning line 11. As a result, the transistors 15 in the 1920 pixels 14 connected to the first scanning line 11 in the Y direction are turned on.

  Then, the data line driving circuit 40 grasps the start timing of the first horizontal scanning period from the rising edge of the data transfer start pulse XSP at time t3, and synchronizes with the rising edge of the system clock SCLK to display data XDATA (96 bits). ) Are output as data signals d1, d2,..., D96 for 96 pixels to 96 data lines 13, that is, the first to 96th data lines 13 in the X direction. As a result, the black / white voltage corresponding to the first subframe is written in the first to 96th pixels 14 connected to the first scanning line 11 in the Y direction.

  Subsequently, when the rising edge of the next system clock SCLK occurs, the read address controller 28 generates a read address indicating the next address (address “2”) in the region R1 of the frame buffer 23a and outputs it to the frame buffer unit 23. Is done. Then, 96-bit display data stored in the storage area specified by the address “2” of the frame buffer 23 a is read and output to the level shifter 30. As a result, the code Ci for 96 pixels after the voltage level shift is output from the level shifter 30 to the data line driving circuit 40 as the next display data XDATA (96 bits).

  Then, the data line drive circuit 40 synchronizes the display data XDATA (96 bits) with the data signals d97, d98,..., D192 for the next 96 pixels in synchronization with the rising edge of the system clock SCLK. That is, the data is output to the 97th to 192th data lines 13 in the X direction. As a result, the black / white voltage corresponding to the first subframe is written into the 97th to 192nd pixels 14 connected to the first scanning line 11 in the Y direction. When the rising edge of the system clock SCLK occurs, the same operation as described above is repeated 20 times in total, so that all the 1920 pixels 14 connected to the first scanning line 11 in the Y direction have the first subframe. The black / white voltage corresponding to is written.

  Subsequently, the scanning line driving circuit 50 outputs the scanning signal G2 having the voltage VG to the second scanning line 11 in the Y direction in synchronization with the falling edge at the time t31 of the scanning transfer clock YCLK. As a result, the transistors 15 in the 1920 pixels 14 connected to the second scanning line 11 in the Y direction are turned on. The read address controller 28 generates a read address indicating the 21st address (address “21”) of the region R2 of the frame buffer 23a in synchronization with the falling edge of the system clock signal SCLK at time t31 to generate the frame buffer. To the unit 23. Then, 96-bit display data stored in the storage area specified by the address “21” is read and output to the level shifter 30. As a result, the code Ci for 96 pixels after the voltage level shift is output from the level shifter 30 to the data line driving circuit 40 as the next display data XDATA (96 bits).

Then, the data line driving circuit 40 grasps the start timing of the second horizontal scanning period from the rising edge of the data transfer start pulse XSP at time t31, and synchronizes with the rising edge of the system clock SCLK to display data XDATA (96 bits). ) Are output as data signals d1, d2,..., D96 for 96 pixels to the first to 96th data lines 13 in the X direction. As a result, the black / white voltage corresponding to the first subframe is written to the first to 96th pixels 14 connected to the second scanning line 11 in the Y direction.
Subsequently, when the rising edge of the next system clock SCLK occurs, the read address controller 28 generates a read address indicating the next address (address “22”) of the region R1 of the frame buffer 23a and outputs it to the frame buffer unit 23. Is done. Then, 96-bit display data stored in the storage area specified by the address “22” of the frame buffer 23 a is read and output to the level shifter 30. As a result, the code Ci for 96 pixels after the voltage level shift is output from the level shifter 30 to the data line driving circuit 40 as the next display data XDATA (96 bits).

  Then, the data line drive circuit 40 synchronizes the display data XDATA (96 bits) with the data signals d97, d98,..., D192 for the next 96 pixels in synchronization with the rising edge of the system clock SCLK. That is, the data is output to the 97th to 192th data lines 13 in the X direction. As a result, the black / white voltage corresponding to the first subframe is written to the 97th to 192st pixels 14 connected to the second scanning line 11 in the Y direction. When the rising edge of the system clock SCLK occurs, the same operation as described above is repeated 20 times in total, so that all the 1920 pixels 14 connected to the second scanning line 11 in the Y direction have the first subframe. The black / white voltage corresponding to is written.

  An operation similar to the operation described above is repeated from the third scanning line 11 to the 1080th scanning line 11, and the first pixel is applied to all of the 1920 pixels 14 connected to each of these scanning lines 11. The black / white voltage corresponding to the subframe is written. As a result, the black / white voltage is written in all the 1920 × 1080 pixels 14 and an image corresponding to the first sub-frame is displayed.

  Subsequently, when the rising edge of the scan start pulse YSP occurs at time t4 and the start timing of the second subframe arrives, the scanning line driving circuit 50 synchronizes with the rising edge of the scan transfer clock YCLK at time t4, A scanning signal G1 having a voltage VG is output to the first scanning line 11 in the Y direction. As a result, the transistors 15 in the 1920 pixels 14 connected to the first scanning line 11 in the Y direction are turned on.

  The read address controller 28 generates a read address indicating the head address (address “21601”) of the region R2 of the frame buffer 23a in synchronization with the rising edge of the system clock signal SCLK at time t4 and outputs the read address to the frame buffer unit 23. To do. Then, 96-bit display data stored in the storage area specified by the address “20601” of the frame buffer 23 a is read and output to the level shifter 30. As a result, the code Ci for 96 pixels after the voltage level shift is output from the level shifter 30 to the data line driving circuit 40 as the next display data XDATA (96 bits).

  Then, the data line driving circuit 40 grasps the start timing of the first horizontal scanning period from the rising edge of the data transfer start pulse XSP at time t4, and synchronizes with the rising edge of the system clock SCLK to display data XDATA (96 bits). ) Are output as data signals d1, d2,..., D96 for 96 pixels to the first to 96th data lines 13 in the X direction. As a result, the black / white voltage corresponding to the second subframe is written in the first to 96th pixels 14 connected to the first scanning line 11 in the Y direction.

  Subsequently, when the rising edge of the next system clock SCLK occurs, the read address controller 28 generates a read address indicating the next address (address “21602”) of the region R2 of the frame buffer 23a and stores it in the frame buffer unit 23. Output. Then, 96-bit display data stored in the storage area specified by the address “20602” of the frame buffer 23 a is read and output to the level shifter 30. As a result, the code Ci for 96 pixels after the voltage level shift is output from the level shifter 30 to the data line driving circuit 40 as the next display data XDATA (96 bits).

  Then, the data line drive circuit 40 synchronizes the display data XDATA (96 bits) with the data signals d97, d98,..., D192 for the next 96 pixels in synchronization with the rising edge of the system clock SCLK. That is, the data is output to the 97th to 192th data lines 13 in the X direction. As a result, the black / white voltage corresponding to the second subframe is written to the 97th to 192nd pixels 14 connected to the first scanning line 11 in the Y direction. When the rising edge of the system clock SCLK occurs, the same operation as described above is repeated 20 times in total, so that the second subframe is added to all 1920 pixels 14 connected to the first scanning line 11 in the Y direction. The black / white voltage corresponding to is written.

  The same operation as described above is repeated from the second scanning line 11 to the 1080th scanning line 11 and connected to each of these scanning lines 11 as in the case of the first subframe. A black / white voltage corresponding to the second subframe is written in all of the 1920 pixels 14. As a result, the black / white voltage is written to all the 1920 × 1080 pixels 14 and an image corresponding to the second subframe is displayed. The operation for each subframe described above is repeated up to the 48th subframe generated at time t48, whereby one frame of image display starting from time t1 is completed.

As described above, according to the liquid crystal device 1 according to the present embodiment, the gradation data indicating the gradation for each pixel in one frame is converted into digital data composed of a plurality of bits indicating the luminance level for each subframe by the digital code converter 21. The digital code is converted by the matrix converter 11 into data (display data) consisting of bits indicating the luminance level of the same subframe in units of pixels by the matrix converter 11, and the converted display code Data is stored in the frame buffer unit 23. Thereby, the operation frequency on the input side of the digital code conversion unit 21 and the matrix conversion unit 22 provided in the display drive circuit 20 is set to about 124 MHz equal to the frequency of the dot clock signal DCLK, and the output side of the matrix conversion unit 22 and the frame buffer unit. The operating frequency of 23 can be about 62.2 MHz which is equal to the frequency f _SCLK of the system clock signal SCLK. For this reason, it is possible to realize a high-definition display without causing a significant increase in circuit scale and an increase in operation speed.

  Here, in the matrix conversion circuit shown in FIG. 5, only the 96 flip-flops to which any one of the clock pulses WC1 to WC96 is input among the 48 × 96 flip-flops are in the operation state. Since the other flip-flops are in an inoperative state, power consumption can be reduced. Assuming that the current consumption of one flip-flop is 0.1 mA, the current consumption when all 48 × 96 flip-flops are in operation is 468.8 mA (4680 × 0.1 mA). . On the other hand, since the matrix conversion circuit shown in FIG. 5 has 48 flip-flops operating at a time, the current consumption is 4.8 mA (48 × 0.1 mA). As described above, the matrix conversion circuit shown in FIG. 5 can reduce the power consumption to about 1/90 compared to the case where all of the 48 × 96 flip-flops are in the operating state.

〔Electronics〕
Next, an example of an electronic apparatus including the liquid crystal device 1 (electro-optical device) described above will be described.
(1) Projector First, a projector using the liquid crystal device 1 according to the present embodiment as a light valve will be described. FIG. 11 is a plan view showing a configuration of a projector to which the liquid crystal device is applied. As shown in FIG. 11, a polarization illumination device 1110 is disposed inside the projector 1100 along the system optical axis PL. In this polarization illumination device 1110, the light emitted from the lamp 1112 becomes a substantially parallel light beam as reflected by the reflector 1114, and enters the first integrator lens 1120. Thereby, the emitted light from the lamp 1112 is divided into a plurality of intermediate light beams. The divided intermediate light beam is converted into one type of polarized light beam (s-polarized light beam) whose polarization directions are substantially aligned by a polarization conversion element 1130 having a second integrator lens on the light incident side, and the polarized illumination device 1110 It will be emitted from.

  The s-polarized light beam emitted from the polarization illumination device 1110 is reflected by the s-polarized light beam reflecting surface 1141 of the polarization beam splitter 1140. Of this reflected light beam, the blue light (B) light beam is reflected by the blue light reflecting layer of the dichroic mirror 1151 and modulated by the reflective liquid crystal device 1B. Of the light beams transmitted through the blue light reflection layer of the dichroic mirror 1151, the red light (R) light beam is reflected by the red light reflection layer of the dichroic mirror 1152 and modulated by the reflective liquid crystal device 1R. On the other hand, among the light beams transmitted through the blue light reflection layer of the dichroic mirror 1151, the green light (G) light beam is transmitted through the red light reflection layer of the dichroic mirror 1152 and modulated by the reflective liquid crystal device 1G.

  In this way, red, green, and blue lights that have been color-light modulated by the liquid crystal devices 1R, 1G, and 1B are sequentially synthesized by the dichroic mirrors 1152 and 1151, and the polarization beam splitter 1140, and then are projected by the projection optical system 1160. It is projected on the screen 1170. In addition, since the dichroic mirrors 1151 and 1152 enter the light fluxes corresponding to the primary colors R, G, and B, the liquid crystal devices 1R, 1B, and 1G do not need a color filter. In this embodiment, a reflective liquid crystal device is used. However, a projector using a transmissive display liquid crystal device may be used.

(2) Mobile Computer Next, an example in which the liquid crystal device 1 is applied to a mobile personal computer will be described. FIG. 12 is a perspective view illustrating a configuration of a personal computer to which the liquid crystal device is applied. In the drawing, a personal computer 1200 includes a main body 1204 provided with a keyboard 1202 and a display unit 1206. The display unit 1206 is configured by adding a front light to the front surface of the liquid crystal device 1 described above. In this configuration, since the liquid crystal device 1 is used as a reflection direct view type, it is desirable that the pixel electrode 16 has irregularities so that the reflected light is scattered in various directions.

(3) Mobile phone Further, an example in which the liquid crystal device 1 is applied to a mobile phone will be described. FIG. 13 is a perspective view illustrating a configuration of a mobile phone to which the liquid crystal device is applied. In the figure, a mobile phone 1300 includes a liquid crystal device 1 together with a mouthpiece 1304 and a mouthpiece 1306 in addition to a plurality of operation buttons 1302. The liquid crystal device 1 is also provided with a front light on the front surface as necessary. Also in this configuration, since the liquid crystal device 1 is used as a reflection direct view type, it is desirable that the pixel electrode 16 has irregularities.

  As electronic devices, in addition to those described with reference to FIGS. 11 to 13, a liquid crystal television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, an electronic notebook, a calculator, a word processor. , Workstations, videophones, POS terminals, devices with touch panels, and the like.

DESCRIPTION OF SYMBOLS 1 ... Liquid crystal device, 11 ... Scan line, 13 ... Data line, 14 ... Pixel, 15 ... Transistor, 16 ... Pixel electrode, 20 ... Display drive circuit, 21 ... Digital code conversion part, 22 ... Matrix conversion part, 22a, 22b ... Matrix conversion circuit, 23 ... Frame buffer unit, 23a, 23b ... Frame buffer, 25 ... Write address controller, CT ... Counter, DCLK ... Dot clock, DF1-1 to DF96-48 ... Flip-flop, SL1 to SL96 ... Selector, SR: Shift register, WC1-WC96: Clock pulse

Claims (11)

A conversion circuit provided in a display driving circuit that performs digital driving to express a plurality of gradations by dividing one frame into a plurality of sub-frames and displaying an image,
A shift register having a predetermined number of output ends larger than the number of subframes and sequentially outputting clock pulses from any of the output ends each time a clock signal is input;
A plurality of flip-flops each including a plurality of flip-flops to which the value of each bit of pixel data including a plurality of bits indicating the luminance level for each subframe is input, and connected to each of the output ends of the shift register Group,
A plurality of selectors connected to the plurality of flip-flop groups, respectively, for selecting any of a plurality of data output from the connected flip-flop groups;
And a counter that controls data selected by the plurality of selectors.   The conversion circuit according to claim 1, wherein the shift register has output terminals corresponding to the number of phase expansions.   2. The flip-flop according to claim 1, wherein the flip-flop is a D flip-flop that maintains an output of a value input at the time when the clock pulse is input until a next clock pulse is input. 2. The conversion circuit according to 2. A clock generation circuit for outputting a first clock signal from a first output terminal and outputting a second clock signal from a second output terminal;
A first flip-flop and a second flip-flop to which the first clock signal is input;
A third flip-flop and a fourth flip-flop to which the second clock signal is input;
A first selector to which an output signal of the first flip-flop and an output signal of the third flip-flop are input;
A second selector to which an output signal of the second flip-flop and an output signal of the fourth flip-flop are input;
A signal generator for generating a signal for controlling operations of the first selector and the second selector;
The conversion circuit characterized by including. In a display driving circuit that performs digital driving to express a plurality of gradations by dividing one frame into a plurality of sub-frames and displaying an image,
A generation unit that generates, for each pixel, data including a plurality of bits indicating a luminance level for each subframe, based on gradation data indicating a gradation for each pixel in one frame;
5. The conversion circuit according to claim 1, wherein the data generated by the generation unit is converted into luminance levels of the same subframe in units of the predetermined number of pixels. A conversion unit that converts the data into bits and outputs the data, and
A display drive circuit comprising: a storage unit that stores data converted by the conversion unit.   The generation unit is a nonvolatile memory in which an address corresponds to the gradation data, and data stored in a storage area specified by the address corresponds to data including a plurality of bits indicating a luminance level for each subframe. The display driving circuit according to claim 5, further comprising:   The conversion unit includes a plurality of conversion circuits according to any one of claims 1 to 3, and alternately performs input of data generated by the generation unit and output of converted data. 7. A display driving circuit according to claim 5, wherein   The display drive circuit according to any one of claims 5 to 7, wherein the storage unit includes a plurality of storage circuits capable of storing data for one frame converted by the conversion unit.   9. The display drive circuit according to claim 8, further comprising a write control unit that writes data output from the conversion circuit to the storage unit in synchronization with a dot clock that is a unit for driving the pixel. An electro-optical device having a pixel including a switching element provided corresponding to an intersection of a plurality of scanning lines and a plurality of data lines, and a pixel electrode connected to the switching element,
An electro-optical device comprising: the display drive circuit according to claim 5, wherein the pixel is driven based on data stored in the storage unit.   An electronic apparatus comprising the electro-optical device according to claim 10.

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