JP2008003347A - Electro-optical device drive circuit, electro-optical device drive method, electro-optical device, and electronic apparatus - Google Patents

Abstract

Power consumption is reduced in an electro-optical device such as a liquid crystal device.
An electro-optical device driving circuit includes a scanning line driving circuit for supplying a scanning signal Gi to a plurality of pixel portions via a scanning line, and an image signal VID for the plurality of pixel portions via a data line. A data line driving circuit 101 and a sampling circuit 7 to be supplied, and a DA conversion circuit 200 that performs DA conversion for converting the input image data DATA from a digital signal to an analog signal and outputs it as an image signal VID. Further, when the gradation values of the input image data DATA for one line corresponding to one scanning line 11a are the same, the control for controlling the DA conversion circuit 200 to stop the execution of the DA conversion. A circuit 300 is provided.
[Selection] Figure 3

Description

  The present invention relates to a driving circuit for an electro-optical device mounted on an electro-optical device such as a liquid crystal device, a driving method thereof, and the technical field of the electro-optical device and an electronic apparatus including the electro-optical device. About.

  This type of drive circuit is built as a data line drive circuit for driving data lines, a scan line drive circuit for driving scan lines, or the like on a substrate of an electro-optical device such as a liquid crystal device. During the operation, the data line driving circuit is configured to sample the image signal supplied to the image signal line at the timing of the sampling pulse and supply it to the data line.

  Here, in the electro-optical device, it is necessary to supply an image signal corresponding to the display gradation to each data line. In general, the display gradation is often given as image data (that is, a digital image signal), and this type of drive circuit converts the image data from a digital signal to an analog signal by DA (Digital to Analog). In many cases, a DA conversion circuit that outputs an image signal is provided. For example, Patent Document 1 discloses a voltage division type DA converter circuit including a plurality of resistors connected in series.

JP 2000-305527 A

  However, if all the image data is DA-converted by the DA conversion circuit as described above and supplied to the data line as an image signal, power consumption may increase due to current flowing through the resistor in the DA conversion circuit. There is a technical problem.

  The present invention has been made in view of the above-described problems, for example, and a driving circuit for an electro-optical device and a driving method for an electro-optical device capable of reducing power consumption, and an electro-optical device and an electronic apparatus to which these are applied. It is an issue to provide.

  In order to solve the above-described problem, the electro-optical device driving circuit according to the present invention is electrically connected to the data lines and the scanning lines, and to the data lines and the scanning lines. An electro-optical device driving circuit that drives an electro-optical device including a plurality of pixel units, the scanning line driving circuit supplying a scanning signal to the plurality of pixel units via the scanning lines, and the plurality of the plurality of pixel units An image signal supply circuit that supplies an image signal to the pixel portion via the data line; and DA conversion that converts the image data from a digital signal to an analog signal, and the image data converted into the analog signal is converted into the image signal When the tone value of the image data for one line corresponding to one scanning line and the DA conversion circuit that outputs the signal to the image signal supply circuit are the same, the DA conversion To stop the line, and a control means for controlling the DA converter.

  According to the electro-optical device driving circuit of the present invention, during the operation, the scanning line driving circuit is configured by, for example, a data line driving circuit, a sampling circuit, or the like in the pixel unit column selected by scanning the scanning line horizontally. An image signal supply circuit supplies an image signal via the data line. As a result, it is possible to display an image in a display area in which a plurality of pixel portions are arranged in a matrix, for example.

  Each pixel unit includes a display element such as a liquid crystal element and an organic EL element, a switching element such as a switching TFT (Thin Film Transistor), an electronic element such as a storage capacitor, and various wirings and various electrodes. Consists of.

  In the present invention, for example, image data supplied as a digital signal from an external circuit is converted into an analog signal by a DA conversion circuit and then supplied as an image signal to the image signal supply circuit. The DA conversion circuit can be configured as, for example, a voltage division type (or resistance division type) circuit, that is, can include a ladder circuit including a plurality of resistors connected in series. The DA conversion circuit may be provided as a built-in circuit on a substrate constituting the electro-optical device, or may be provided as, for example, an external IC (Integrated Circuit) chip separate from such a substrate.

  In the present invention, in particular, when the gradation values of image data for one line corresponding to one scanning line are the same, execution of DA conversion by the DA conversion circuit is stopped under the control of the control means. The In other words, a plurality of pixel portions for one line electrically connected to one scanning line (in other words, a plurality of pixel portions for one row arranged in the row direction along the direction in which the scanning line extends) are mutually connected. During a period in which image signals having the same gradation value are to be supplied (in other words, during a period in which lines corresponding to scanning lines on the display screen are displayed with the same luminance or the same color, for example, the aspect ratio is 4: 3. When a wide-size image with an aspect ratio of 16: 9 is displayed on the display screen, a plurality of lines positioned on the top and bottom of the display screen are displayed in black). Is not executed. Typically, power supply to the DA converter circuit is stopped during a period in which one or more lines are displayed with the same gradation. Even if the execution of DA conversion is stopped in this way, for example, an image signal that exists on the supply path from the DA conversion circuit to the image signal supply circuit and that has an invariable or the same gradation value is used as described above. Sampling repeatedly during the same gray scale display period, or, for example, a predetermined potential equal to the image signal that remains unchanged or has the same gray scale value (specifically, (i) fixed) Instead of an image signal, a power supply signal (such as a potential or (ii) a rectangular potential that is inverted with respect to a reference potential) is displayed on the supply path from the DA converter circuit to the image signal supply circuit in the same gradation as described above. It is possible to supply image signals of the same gradation by the image signal supply circuit by continuing to supply during the period. That is, for one line having the same gradation value, an image signal can be supplied in the same way as when DA conversion is performed normally even if execution of DA conversion is stopped. For this reason, the display for one line having the same gradation value is performed without any problem as corresponding to the image data.

  Therefore, the power consumption consumed in the DA converter circuit during the period of displaying one or a plurality of lines with the same gradation can be eliminated almost or completely. Therefore, it is possible to reduce the power consumption of the entire apparatus.

  Note that during the period in which one or a plurality of lines are displayed with the same gradation, a power supply potential or a precharge potential having a potential corresponding to the gradation is supplied to the pixel portion through the data line. , Lines of the same gradation (that is, lines of the same luminance or the same color) may be displayed.

  In one aspect of the electro-optical device drive circuit according to the present invention, the DA converter circuit is connected in series between a high potential reference power source having a potential higher than the first predetermined potential and a low potential reference power source having a low potential. A plurality of resistors connected to each other, and conversion means for outputting the image signal having a potential corresponding to the gradation value of the image data from each connection point between the plurality of resistors, and the control means includes When the gradation values of the image data for one line are the same, the DA converter circuit is controlled so that no current flows through the plurality of resistors.

  According to this aspect, during the period when one or a plurality of lines are displayed with the same gradation, the control means controls so that no current flows through the plurality of resistors in the DA conversion circuit. Therefore, the power consumption of the plurality of resistors included in the DA converter circuit can be almost or completely eliminated.

  In another aspect of the electro-optical device drive circuit according to the present invention, a precharge signal for precharging the data line is supplied to the data line in a period preceding the supply of the image signal to the data line. A precharge circuit for outputting is provided.

  According to this aspect, a precharge signal for precharging the data line is supplied to the data line in a period preceding the supply of the image signal to the data line, for example, a horizontal blanking period in one horizontal scanning period. The Therefore, the potential of the precharge signal is adjusted in advance to a potential corresponding to a gradation to be displayed during a period in which one or a plurality of lines are displayed with the same gradation (for example, a potential corresponding to black). Thus, it is possible to display lines with the same gradation during a period in which execution of DA conversion is stopped.

  In another aspect of the drive circuit for an electro-optical device according to the present invention, the DA conversion circuit may be configured such that the image signal has a positive polarity on the higher side and a negative polarity on the lower side with respect to the second predetermined potential in a predetermined cycle. The high potential power source having a higher potential than the second predetermined potential and the low potential power source having a lower potential are alternately passed through the data line in the predetermined cycle. Power supply potential supply means that can be supplied to the pixel portion is provided.

  According to this aspect, in the period in which the execution of the DA conversion is stopped, instead of the image data being DA converted and supplied to the pixel unit as an image signal, the image signal is, for example, a ground potential, or A high potential power source and a low potential power source are alternately supplied to the pixel portion in a predetermined cycle in which the polarity is inverted with respect to a second predetermined potential which is a positive or negative reference potential with respect to the ground potential. Lines with the same gradation can be displayed.

  In another aspect of the electro-optical device drive circuit according to the present invention, a potential signal having one of a plurality of potentials corresponding to a gradation value of the image data can be supplied to the data line. Supply means are provided.

  According to this aspect, a potential signal having an arbitrary potential corresponding to the gradation value of the image data can be supplied to the data line during a period in which one or more lines are displayed with the same gradation.

  In another aspect of the drive circuit for an electro-optical device according to the present invention, storage means capable of storing at least one line of the image data, and a rank of the image data for the one line stored by the storage means. Determination means for determining whether or not the tone values are the same.

  According to this aspect, the determination unit determines whether or not the gradation values of the image data for one line are the same. For this reason, the control means can control the execution and stop of the DA conversion at least for each line based on the determination result by the determination means.

  In order to solve the above problems, an electro-optical device according to the present invention includes the above-described electro-optical device drive circuit according to the present invention (including various aspects), the plurality of data lines, and the plurality of scanning lines. And the plurality of pixel portions.

  The electro-optical device according to the present invention includes the above-described drive circuit for an electro-optical device according to the present invention, so that power consumption can be reduced. This electro-optical device realizes various display devices such as a liquid crystal device, an organic EL device, an electrophoretic device such as electronic paper, and a display device (Field Emission Display and Surface-Conduction Electron-Emitter Display) using electron-emitting elements. Is possible.

  In order to solve the above problems, an electronic apparatus according to the present invention includes the above-described electro-optical device according to the present invention.

  The electronic apparatus according to the present invention includes the above-described electro-optical device according to the present invention, so that power consumption can be reduced. Examples of the electronic apparatus include a projection display device, a television receiver, a mobile phone, an electronic notebook, a word processor, a viewfinder type or a monitor direct-view type video tape recorder, a workstation, a video phone, a POS terminal, a touch panel, and the like. It can be applied to other electronic devices.

  In order to solve the above problem, the electro-optical device driving method according to the present invention is electrically connected to the data lines and the scanning lines, and the data lines and the scanning lines that extend across each other. An electro-optical device driving method for driving an electro-optical device including a plurality of pixel units, the step of supplying a scan signal to the pixel unit via the scan line, and image data from a digital signal to an analog signal A DA conversion step of performing DA conversion to convert the image data into the analog signal and outputting the image data as an image signal; and supplying the image signal to each of the plurality of pixel portions via the data line The DA conversion step stops execution of the DA conversion when the gradation values of the image data for one line corresponding to one scanning line are the same.

  According to the electro-optical device driving method of the present invention, as described above in the section of the electro-optical device driving circuit according to the present invention, when the gradation values of the image data for one line are the same, Since the execution of DA conversion is stopped, the power consumption accompanying the execution of DA conversion can be reduced. Therefore, it is possible to reduce the power consumption of the entire electro-optical device.

  The operation and other advantages of the present invention will become apparent from the best mode for carrying out the invention described below.

Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the following embodiments, a driving circuit built-in type TFT active matrix driving type liquid crystal device, which is an example of the electro-optical device of the present invention, is taken as an example.
<First Embodiment>
The liquid crystal device according to the first embodiment and the driving method thereof will be described with reference to FIGS.

  First, an overall configuration of a liquid crystal panel as an example of an electro-optical panel in the liquid crystal device according to the present embodiment will be described with reference to FIGS. 1 and 2. FIG. 1 is a plan view showing the configuration of the liquid crystal panel according to the present embodiment, and FIG. 2 is a cross-sectional view taken along the line HH ′ of FIG.

  1 and 2, in the liquid crystal panel 100, the TFT array substrate 10 and the counter substrate 20 are arranged to face each other. A liquid crystal layer 50 is sealed between the TFT array substrate 10 and the counter substrate 20, and the TFT array substrate 10 and the counter substrate 20 are provided with a sealing material 52 provided in a seal region positioned around the image display region 10a. Are bonded to each other.

  In FIG. 1, a light-shielding frame light-shielding film 53 that defines the frame area of the image display region 10a is provided on the counter substrate 20 side in parallel with the inside of the seal region where the sealing material 52 is disposed. A data line driving circuit 101 and an external circuit connection terminal 102 are provided along one side of the TFT array substrate 10 in a region located outside the sealing region in which the sealing material 52 is disposed in the peripheral region. The sampling circuit 7 is provided so as to be covered with the frame light shielding film 53 on the inner side of the seal region along the one side. The data line driving circuit 101 and the sampling circuit 7 constitute an example of the “image signal supply circuit” according to the present invention. The scanning line driving circuit 104 is provided so as to be covered with the frame light-shielding film 53 inside the seal region along two sides adjacent to the one side. Further, a precharge circuit 60 is provided along the remaining side of the TFT array substrate 10 so as to be covered with the frame light shielding film 53. On the TFT array substrate 10, vertical conduction terminals 106 for connecting the two substrates with the vertical conduction material 107 are arranged in regions facing the four corner portions of the counter substrate 20. Thus, electrical conduction can be established between the TFT array substrate 10 and the counter substrate 20.

  On the TFT array substrate 10, a lead wiring 90 is formed for electrically connecting the external circuit connection terminal 102 to the data line driving circuit 101, the scanning line driving circuit 104, the vertical conduction terminal 106, and the like. .

  In FIG. 2, on the TFT array substrate 10, there is formed a laminated structure in which pixel switching TFTs (Thin Film Transistors), which are driving elements, and wirings such as scanning lines and data lines are formed. In the image display area 10a, pixel electrodes 9a are provided in a matrix on the upper layer of wiring such as pixel switching TFTs, scanning lines, and data lines. An alignment film is formed on the pixel electrode 9a. On the other hand, a light shielding film 23 is formed on the surface of the counter substrate 20 facing the TFT array substrate 10. The light shielding film 23 is formed of, for example, a light shielding metal film or the like, and is patterned, for example, in a lattice shape in the image display region 10a on the counter substrate 20. On the light shielding film 23, a counter electrode 21 made of a transparent material such as ITO is formed in a solid shape so as to face the plurality of pixel electrodes 9a. An alignment film is formed on the counter electrode 21. Further, the liquid crystal layer 50 is made of, for example, a liquid crystal in which one or several types of nematic liquid crystals are mixed, and takes a predetermined alignment state between the pair of alignment films.

  Although not shown here, in addition to the data line driving circuit 101 and the scanning line driving circuit 104, the TFT array substrate 10 is used for inspecting the quality, defects, etc. of the liquid crystal panel during manufacturing or at the time of shipment. An inspection circuit, an inspection pattern, or the like may be formed.

  Next, the overall configuration of the liquid crystal device according to the present embodiment will be described with reference to FIG. FIG. 3 is a block diagram showing the overall configuration of the liquid crystal device.

  As shown in FIG. 3, the liquid crystal device according to the present embodiment includes a liquid crystal panel 100 and a memory 320 provided as an external drive circuit, a DA converter circuit 200, a control circuit 300, a determination circuit 310, and a timing control circuit 400. , And a power supply circuit 700.

  The memory 320 is an example of the “storage unit” according to the present invention, and temporarily stores one set of input image data DATA input as a digital signal from the outside.

  The DA conversion circuit 200 reads the input image data DATA from the memory 320, converts the input image data DATA from a digital signal to an analog signal (that is, executes DA conversion), generates an image signal VID, and generates the image signal VID. (More specifically, to an image signal line 91 described later via the external circuit connection terminal 102). At this time, the input image data DATA is converted so that the potential is inverted to a positive polarity and a negative polarity with respect to a predetermined reference potential every horizontal scanning period, and an image signal VID is generated. A specific configuration of the DA conversion circuit 200 will be described later. Further, the DA conversion circuit 200 performs serial-parallel conversion on one system of input image data DATA, and outputs an n-phase image signal VID1 such as 6-phase, 9-phase, 12-phase, 24-phase, 48-phase, 96-phase,. ~ VIDn may be generated.

  The control circuit 300 controls the operations of the DA conversion circuit 200, the scanning line driving circuit 104, and the data line driving circuit 101.

  The determination circuit 310 is an example of the “determination unit” according to the present invention. The determination circuit 310 reads the input image data DATA from the memory 320, and the gradation value of the input image data DATA for every one line corresponding to one scanning line. Are the same as each other. The determination circuit 310 outputs the determination result to the control circuit 300.

  The timing control circuit 400 is configured to output various timing signals used in each unit. A timing signal output unit (not shown), which is a part of the timing control circuit 400, generates a dot clock for scanning each pixel, which is a minimum unit clock. Based on this dot clock, a Y clock signal CLY, an inverted Y clock signal CLYinv, an X clock signal CLX, an inverted X clock signal XCLinv, a Y start pulse DY and an X start pulse DX are generated and supplied to the liquid crystal panel 100 ( More specifically, the Y clock signal CLY, the inverted Y clock signal CLYinv, and the Y start pulse DY are supplied to the scanning line drive circuit 104, and the X clock signal CLX, the inverted X clock signal XCLinv, and the X start pulse DX are data Supplied to the line driver circuit 101). Further, the timing control circuit 400 generates a precharge circuit drive signal NRG that defines the timing at which the precharge signal NRS is supplied to the data line 6a by the precharge circuit 60 (see FIG. 1), and supplies the precharge circuit drive signal NRG to the liquid crystal panel 100.

  The power supply circuit 700 supplies a common power supply signal of a predetermined common potential LCCOM to be supplied to the counter electrode 21 (see FIG. 2) to the liquid crystal panel 100. Further, the power supply circuit 700 supplies the liquid crystal panel 100 with a power supply signal VDD having a potential higher than a predetermined potential, a power supply signal VSS having a lower potential, and a precharge signal NRS for writing a precharge signal. In addition, the power supply circuit 700 supplies a reference power supply signal VrefH having a potential higher than a predetermined potential and a reference power supply signal VrefL having a lower potential to the DA conversion circuit 200.

  Next, the electrical configuration of the liquid crystal panel will be described with reference to FIG. FIG. 4 is a block diagram showing the electrical configuration of the liquid crystal panel.

  As shown in FIG. 4, the liquid crystal panel 100 includes a scanning line driving circuit 104, a data line driving circuit 101, a sampling circuit 7, and a pre-arrangement in a peripheral area located around the image display area 10 a on the TFT array substrate 10. An internal drive circuit including a charge circuit 60 is provided.

  The scanning line driving circuit 104 is supplied with a Y clock signal CLY, an inverted Y clock signal CLYinv, and a Y start pulse DY from a timing control circuit 400 (see FIG. 3) via an external circuit connection terminal 102 (see FIG. 1). The When the Y start pulse DY is input, the scanning line driving circuit 104 sequentially generates the scanning signal Gi (where i = 1,..., M) at a timing based on the Y clock signal CLY and the inverted Y clock signal CLYinv. Output. The scanning line driving circuit 104 is supplied with power supply signals VDD and VSS from the power supply circuit 700 (see FIG. 3) via the external circuit connection terminal 102.

  The data line driving circuit 101 is supplied with an X clock signal CLX, an inverted X clock signal CLXinv, and an X start pulse DX from the timing control circuit 400 via the external circuit connection terminal 102. When the X start pulse DX is input, the data line driving circuit 101 sequentially receives the sampling signal Si (where i = 1, 2,..., N) at a timing based on the X clock signal CLX and the inverted X clock signal XCLXinv. Generate and output. The power supply signals VDD and VSS are supplied from the power supply circuit 700 to the data line driving circuit 101 via the external circuit connection terminal 102.

  The sampling circuit 7 includes a plurality of sampling switches 71 provided for each data line 6a. Each sampling switch 71 is supplied with the image signal VID from the DA conversion circuit 200 (see FIG. 3) via the external circuit connection terminal 102 and the image signal line 91, and the sampling signal Si output from the data line driving circuit 101. Thus, each sampling switch 71 is closed sequentially. That is, the image signal VID is sampled for each data line 6a in accordance with the sampling signal Si, and applied to the plurality of data lines 6a as data signals Di (where i = 1, 2,..., N), respectively. Has been.

  More specifically, the sampling switch 71 is composed of, for example, a P-channel or N-channel single-channel TFT or a complementary TFT, and the image signal line 91 is connected to the source electrode of the sampling switch 71. The sampling signal line 92 is connected to the gate electrode of the sampling switch 71. When the image signal VID is input via the image signal line 91 and the sampling signal Si is input from the data line driving circuit 101 via the sampling signal line 92, the image signal VID is sampled and each data line is sampled. 6a is applied as a data signal Di.

  The precharge circuit 60 includes a TFT 61 which is a switching element provided for each data line 6a. A precharge signal line 93 is connected to the source electrode of the TFT 61, and a precharge circuit drive signal line 94 is connected to the gate electrode of the TFT 61. The precharge signal NRS is supplied via the precharge signal line 93 and the precharge circuit drive signal NRG is supplied via the precharge circuit drive signal line 94. The precharge circuit 60 supplies the precharge signal NRS in a period defined by the precharge circuit drive signal NRG (that is, a blanking period in one horizontal scanning period in the present embodiment). In the present embodiment, as the precharge signal NRS, a signal having a predetermined potential level corresponding to black is supplied to the precharge signal line 93 and written to each data line 6a at a timing according to the precharge circuit drive signal NRG. .

  As shown in FIG. 4, each of a plurality of pixels formed in a matrix that forms the image display region 10a of the TFT array substrate 10 has a pixel electrode 9a and a TFT 30 for controlling the switching of the pixel electrode 9a. The data line 6 a formed and supplied with the data signal Di is electrically connected to the source of the TFT 30. The data signal Di written to the data line 6a may be supplied line-sequentially in this order, or may be supplied for each of a plurality of adjacent data lines 6a.

  Further, the scanning line 11 a is electrically connected to the gate of the TFT 30. The scanning signals G1, G2,..., Gm are applied to the scanning line 11a in a line-sequential order in this order from the scanning line driving circuit 104 at a predetermined timing. In this embodiment, for the sake of simplicity of explanation, the scanning signals G1, G2,..., Gm are applied to the scanning line 11a in this order in a line sequential manner. = 1, 2,..., M) may be applied to the scanning line 11a in any order. The pixel electrode 9a is electrically connected to the drain of the TFT 30, and the data signal Di supplied from the data line 6a is written at a predetermined timing by closing the switch of the TFT 30 as a switching element for a certain period.

  A predetermined level of data signal Di (where i = 1, 2,..., N) written to the liquid crystal via the pixel electrode 9a is applied to the counter electrode 21 (see FIG. 2) formed on the counter substrate 20 (see FIG. 2). For a certain period. The liquid crystal modulates light and enables gradation display by changing the orientation and order of the molecular assembly depending on the applied voltage level. In the normally white mode, the transmittance for incident light is reduced according to the voltage applied in units of each pixel, and in the normally black mode, the light is incident according to the voltage applied in units of each pixel. The light transmittance is increased, and light having a contrast corresponding to an image signal is emitted from the liquid crystal device as a whole.

  In order to prevent the image signal held here from leaking, a storage capacitor 70 is added in parallel with the liquid crystal capacitor formed between the pixel electrode 9 a and the counter electrode 21. One electrode of the storage capacitor 70 is connected to the drain of the TFT 30 in parallel with the pixel electrode 9a, and the other electrode is connected to the capacitor wiring 400 with a fixed potential so as to have a constant potential.

  Next, the electrical configuration of the DA converter circuit will be described with reference to FIG. FIG. 5 is an equivalent circuit diagram of the DA conversion circuit.

  As shown in FIG. 5, the DA conversion circuit 200 performs DA conversion using a so-called R-2R ladder circuit, and is a voltage division type circuit. The DA conversion circuit 200 is configured to input each bit of input image data DATA which is a digital signal in an 8-bit format (in other words, 28 = 256 gradations) (the most significant bit is MSB, hereinafter 2SB, 3SB,..., 7SB, least significant bit). The switches Sw1 to Sw8 are provided corresponding to LSB). Each of the switches Sw1 to Sw8 is connected to the terminal a when the corresponding bit is “1”, and is connected to the terminal b when the corresponding bit is “0”. Here, for convenience of explanation, it is assumed that the switch is on when connected to the terminal a, and the switch is off when connected to the terminal b. The terminals a of the switches Sw1 to Sw8 are connected to a signal line to which a reference potential VrefH is supplied, while the terminal b is connected to a signal line to which a reference potential VrefL is supplied.

  The common terminals of the switches Sw1 to Sw8 are connected to the connection points A to H via the resistors 220 having a resistance value of 2R. In addition, at each of the connection points A to H, connection points adjacent to each other are connected via a resistor 210 having a resistance value R. For this reason, in a ladder circuit composed of a resistor 220 having a resistance value 2R and a resistor 210 having a resistance value R, the upper bit direction, the lower bit direction, In addition, the resistance value is 2R in any of the switch directions. The connection point A is connected to the line L and serves as the output terminal Eout of the DA conversion circuit 200.

  In such a configuration, when the switch corresponding to the input bit “1” among the switches Sw1 to Sw8 is turned on, a voltage corresponding to the weight of each bit is output to the output terminal Eout. That is, the image signal VID having a voltage corresponding to the gradation of the input image data DATA is output from the output end Eout of the DA conversion circuit 200, that is, the input image data DATA is DA-converted from a digital signal to an analog signal, The image signal VID is output from the output terminal Eout. For example, if the most significant bit MSB is “1”, the switch Sw1 is turned on, so that the voltage of ΔVref / 2 (where ΔVref = VrefH−VrefL) and the 3SB lower by 2 bits are “ If it is “1”, the voltage of ΔVref / 8 is generated at the output terminal Eout by turning on the switch Sw3.

  Next, a driving method for driving the liquid crystal device according to the present embodiment will be described with reference to FIG. 6 in addition to FIG. FIG. 6 is a schematic diagram showing a period during which the operation of the DA converter circuit is stopped.

  In FIG. 3, particularly in the present embodiment, when the gradation values of the input image data DATA for one line corresponding to one scanning line 11 a are the same, DA conversion is performed under the control of the control circuit 300. The execution of DA conversion by the circuit 200 is stopped. That is, DA conversion by the DA conversion circuit 200 is not executed during the period in which the image signals VID having the same voltage level are to be supplied to the n pixel electrodes 9a electrically connected to one scanning line 11a. .

  More specifically, in FIG. 3, input image data DATA input as a digital signal from the outside is temporarily stored in the memory 320. Next, the input image data DATA is read from the memory 320 by the determination circuit 310 for each line. The determination circuit 310 determines whether or not the gradation values of the read input image data DATA for one line are the same. The determination circuit 310 outputs the determination result to the control circuit 300. When the determination circuit 310 determines that the gradation values of the input image data DATA for one line are the same, the control circuit 300 controls the DA conversion circuit 200 so as to stop the DA conversion. To do. On the other hand, when the determination circuit 310 determines that the gradation values of the input image data DATA for one line are not the same, the control circuit 300 performs the DA conversion as usual. 200 is controlled.

  That is, as shown in FIG. 6, for example, when displaying a wide-size image with an aspect ratio of 16: 9 in an image display area 10a with an aspect ratio of 4: 3, Scanning in the image display area 10a, such as during a period during which black areas 10c (that is, lines GL1 to GL4 and GLm-3 to GLm) positioned above and below the image area 10b (that is, lines GL5 to GLm-4) are displayed in black. During the period in which the line GLi (i = 1, 2,..., M) corresponding to the line 11a is displayed with the same luminance or the same color (black in this embodiment), DA conversion is performed under the control of the control circuit 300. The DA conversion by the circuit 200 is stopped. Even when the execution of DA conversion is stopped in this manner, prior to the supply of the image signal VID from the DA conversion circuit 200, the precharge signal NRS corresponding to black is supplied to each data line 6a by the precharge circuit 60. Therefore, black is displayed in the black area 10c in the image display area 10a as in the case where the DA conversion is performed as usual. That is, the display of one line having the same gradation value (in this embodiment, black lines GL1 to GL4 and GLm-3 to GLm) is performed without any problem as corresponding to the input image data DATA. become.

  Therefore, the power consumption consumed in the DA converter circuit 200 during the period during which the black region 10c (that is, the lines GL1 to GL4 and GLm-3 to GLm) is displayed in black can be almost or preferably completely eliminated. Therefore, the power consumption of the entire liquid crystal device can be reduced.

3 and 5, in the present embodiment, the DA conversion by the DA conversion circuit 200 is stopped during the period in which the black region 10c (that is, the lines GL1 to GL4 and GLm-3 to GLm) is displayed in black. Therefore, the control circuit 300 controls so that no current flows through the plurality of resistors 210 and 220 in the DA conversion circuit 200. Therefore, the power consumption in the plurality of resistors 210 and 220 included in the DA converter circuit 200 can be almost or completely eliminated.
<Second Embodiment>
Next, a liquid crystal device according to a second embodiment will be described with reference to FIG. FIG. 7 is a block diagram showing circuits and wirings related to driving of the data lines in the second embodiment. In FIG. 7, the same reference numerals are given to the same components as the components according to the first embodiment shown in FIGS. 1 to 5, and description thereof will be omitted as appropriate.

  As shown in FIG. 7, the liquid crystal device according to this embodiment is described above in that it further includes a plurality of switches 81, a power supply potential supply line 95, a switch 85, and a control signal line 96 on the TFT array substrate 10. Unlike the liquid crystal device according to the first embodiment, the other configuration is substantially the same as the liquid crystal device according to the first embodiment described above. The plurality of switches 81, the power supply potential supply line 95, the switch 85, and the control signal line 96 constitute an example of “power supply potential supply means” according to the present invention.

  Similarly to the sampling switch 71, the switch 81 is configured by, for example, a P-channel or N-channel single-channel TFT or a complementary TFT, and is provided for each data line 6a. A power supply potential supply line 95 is connected to the source electrode of the switch 81, a control signal line 96 is connected to the gate electrode of the switch 81, and a data line 6 a is connected to the drain electrode of the switch 81. Has been. The switching operation of the switch 85 is configured to be controllable by the control circuit 300. The power supply potential supply line 95 is configured to be supplied with the power supply signal VDD or VSS according to the switching operation of the switch 85. More specifically, the power supply signals VDD and VSS are alternately supplied to the power supply potential supply line 95 in accordance with a predetermined cycle in which the polarity of the image signal VID is inverted. The control signal line 96 is supplied from the control circuit 300 via the external circuit connection terminal 102 with a control signal CS1 for turning on the switch 81 during the period in which the DA conversion in the DA conversion circuit 200 is stopped. It is comprised so that. That is, during the period when the DA conversion in the DA conversion circuit 200 is stopped, the switch 81 is supplied with the power supply signal VDD or VSS via the power supply potential signal line 99 and via the control signal line 96. The control signal CS1 is supplied. During the period when the DA conversion in the DA conversion circuit 200 is stopped, the sampling switch 71 may be in an off state (that is, a non-conduction state), and the image signal VID is not supplied to the image signal line 91. It may be.

  Since it is configured as described above, the power supply signals VDD and VSS are supplied to the data lines 6a via the switch 81 during the period in which the DA conversion in the DA conversion circuit 200 is stopped. VID can be applied alternately in accordance with a predetermined period in which the polarity is reversed. That is, instead of the input image data DATA being DA-converted and supplied as the image signal VID to the data line 6a (in other words, the pixel electrode 9a electrically connected to the data line 6a), the image signal VID is polarized. The power supply signals VDD and VSS can be alternately supplied to the pixel electrode 9a at a predetermined cycle of inversion. Therefore, it is possible to reliably display lines of the same gradation corresponding to the power supply signals VDD and VSS during the period in which the DA conversion in the DA conversion circuit 200 is stopped. At this time, since the DA conversion in the DA conversion circuit 200 is stopped, the power consumption of the apparatus can be reduced.

  In this embodiment, the polarity of the image signal VID is inverted at a predetermined cycle, the power signal VDD corresponds to black on the positive polarity side, and the power signal VSS corresponds to black on the negative polarity side. .

As a modification, the power supply signals VDD and VSS are alternately output from the power supply circuit 700 at a predetermined cycle in which the polarity of the image signal VID is inverted, and supplied to the power supply potential supply line 95 via the external circuit connection terminal 102. You may do it. Also in this case, the same gradation line can be displayed reliably.
<Third Embodiment>
Next, a liquid crystal device according to a third embodiment will be described with reference to FIG. FIG. 8 is a block diagram having the same concept as FIG. 7 in the third embodiment. In FIG. 8, the same components as those in the first embodiment shown in FIGS. 1 to 5 are denoted by the same reference numerals, and description thereof will be omitted as appropriate.

  As shown in FIG. 8, a plurality of switches 83, a potential signal supply line 97, and a control signal line 98 are further provided on the TFT array substrate 10, and a potential signal supply circuit 600 is provided separately from the liquid crystal panel. Thus, the liquid crystal device according to the first embodiment described above is different from the liquid crystal device according to the first embodiment in other respects and is configured in substantially the same manner as the liquid crystal device according to the first embodiment described above. The plurality of switches 83, the potential signal supply line 97, the control signal line 98, and the potential signal supply circuit 600 constitute an example of the “potential signal supply unit” according to the present invention.

  Similarly to the sampling switch 71, the switch 83 is composed of, for example, a P-channel or N-channel single-channel TFT or a complementary TFT, and is provided for each data line 6a. A potential signal supply line 97 is connected to the source electrode of the switch 83, a control signal line 98 is connected to the gate electrode of the switch 83, and a data line 6a is connected to the drain electrode of the switch 83. Has been. The potential signal supply line 97 is electrically connected to the potential signal supply circuit 600 via the external circuit connection terminal 102.

  The potential signal supply circuit 600 is configured to be able to output a potential signal Vs having one of a plurality of potentials corresponding to the gradation value of the input image data DATA. That is, the potential signal supply circuit 600 is configured as a voltage control or power supply control circuit, and is configured to be able to generate a plurality of necessary voltage levels according to the gradation value.

  The control signal line 98 is supplied with a control signal CS2 from the control circuit 300 via the external circuit connection terminal 102 to turn on the switch 83 during the period in which the DA conversion in the DA conversion circuit 200 is stopped. It is comprised so that. That is, during the period when the DA conversion in the DA conversion circuit 200 is stopped, the potential signal Vs is supplied to the switch 83 via the potential signal supply line 97 and the control signal via the control signal line 96. CS2 is configured to be supplied. It should be noted that the sampling switch 71 may be turned off or the image signal VID may not be supplied to the image signal line 91 while the DA conversion in the DA conversion circuit 200 is stopped.

Since it is configured as described above, an arbitrary potential signal Vs is applied to each data line 6a via the switch 83 during a period in which execution of DA conversion in the DA conversion circuit 200 is stopped. Can do. That is, instead of the input image data DATA being DA-converted and supplied as the image signal VID to the data line 6a (in other words, the pixel electrode 9a electrically connected to the data line 6a), an arbitrary potential signal Vs. Can be supplied to the pixel electrode 9a. Therefore, during the period when the DA conversion in the DA conversion circuit 200 is stopped, the same gradation line corresponding to the arbitrary potential signal Vs can be reliably displayed. At this time, since the DA conversion in the DA conversion circuit 200 is stopped, the power consumption of the apparatus can be reduced.
<Electronic equipment>
Next, a case where the above-described liquid crystal device which is an electro-optical device is applied to various electronic devices will be described.

  A projector using this liquid crystal device as a light valve will be described with reference to FIG. FIG. 9 is a plan view showing a configuration example of the projector.

  As shown in FIG. 9, a projector 1100 includes a lamp unit 1102 made of a white light source such as a halogen lamp. The projection light emitted from the lamp unit 1102 is separated into three primary colors of RGB by four mirrors 1106 and two dichroic mirrors 1108 arranged in the light guide 1104, and serves as a light valve corresponding to each primary color. The light enters the liquid crystal panels 1110R, 1110B, and 1110G.

  The configuration of the liquid crystal panels 1110R, 1110B, and 1110G is the same as that of the above-described liquid crystal device, and is driven by primary color signals of R, G, and B, respectively. The light modulated by these liquid crystal panels enters the dichroic prism 1112 from three directions. In the dichroic prism 1112, R and B light is refracted at 90 degrees, while G light travels straight. Therefore, as a result of the synthesis of the images of the respective colors, a color image is projected onto the screen or the like via the projection lens 1114.

  The projector 1100 can reduce power consumption by using the liquid crystal device described above.

  In addition to the electronic device described with reference to FIG. 9, a mobile personal computer, a mobile phone, a liquid crystal television, a viewfinder type, a monitor direct view type video tape recorder, a car navigation device, a pager, and an electronic notebook , Calculators, word processors, workstations, videophones, POS terminals, devices with touch panels, and the like. Needless to say, the present invention can be applied to these various electronic devices.

  In addition to the liquid crystal device described in the above embodiment, the present invention also includes a reflective liquid crystal device (LCOS) in which elements are formed on a silicon substrate, a plasma display (PDP), a field emission display (FED, SED), The present invention can also be applied to an organic EL display, a digital micromirror device (DMD), an electrophoresis apparatus, and the like.

  The present invention is not limited to the above-described embodiments, and can be appropriately changed without departing from the gist or concept of the invention that can be read from the claims and the entire specification. For electro-optical devices with such changes The driving circuit, the driving method for the electro-optical device, the electro-optical device, and the electronic apparatus are also included in the technical scope of the present invention.

It is a top view which shows the whole structure of the liquid crystal panel in the liquid crystal device which concerns on 1st Embodiment. It is the HH 'sectional view taken on the line of FIG. 1 is a block diagram illustrating an overall configuration of a liquid crystal device according to a first embodiment. It is a block diagram which shows the electric constitution of the liquid crystal panel which concerns on 1st Embodiment. FIG. 3 is an equivalent circuit diagram of a DA conversion circuit according to the first embodiment. It is a schematic diagram which shows the period which stops operation | movement of the DA converter circuit which concerns on 1st Embodiment. It is a block diagram which shows the circuit and wiring which concern on the drive of the data line in 2nd Embodiment. It is a block diagram with the same meaning as FIG. 7 in 3rd Embodiment. It is a top view which shows the structure of the projector which is an example of the electronic device to which the electro-optical apparatus is applied.

Explanation of symbols

  6a ... data line, 7 ... sampling circuit, 9a ... pixel electrode, 11a ... scanning line, 10 ... TFT array substrate, 10a ... image display area, 20 ... counter substrate, 21 ... counter electrode, 23 ... light shielding film, 50 ... liquid crystal Layer: 52 ... Sealing material, 53 ... Frame light shielding film, 60 ... Precharge circuit, 61 ... TFT, 71 ... Sampling switch, 81, 83 ... Switch, 91 ... Image signal line, 92 ... Sampling signal line, 93 ... Precharge Signal line 94... Precharge circuit drive signal line 95. Power supply potential supply line 96. Control signal line 97. Potential signal supply line 98. Control signal line 101... Data line drive circuit 102. Terminal 104, Scanning line drive circuit 106, Vertical conduction terminal 107, Vertical conduction material 200, DA converter circuit 210, 220 Resistance, 300 Control circuit 31 ... judgment circuit, 320 ... memory, 400 ... timing control circuit, 700 ... power supply circuit

Claims (9)

Electro-optical device drive for driving an electro-optical device including a plurality of data lines and a plurality of scanning lines extending so as to cross each other and a plurality of pixel portions electrically connected to the data lines and the scanning lines, respectively. A circuit,
A scanning line driving circuit for supplying a scanning signal to the plurality of pixel portions via the scanning line;
An image signal supply circuit for supplying an image signal to the plurality of pixel portions via the data line;
A DA conversion circuit for performing DA conversion for converting image data from a digital signal to an analog signal, and outputting the image data converted into the analog signal to the image signal supply circuit as the image signal;
Control means for controlling the DA conversion circuit to stop execution of the DA conversion when the gradation values of the image data for one line corresponding to one scanning line are the same; A drive circuit for an electro-optical device. The DA converter circuit
A plurality of resistors connected in series between a high potential reference power source having a potential higher than the first predetermined potential and a low potential reference power source having a low potential;
Conversion means for outputting the image signal having a potential corresponding to the gradation value of the image data from each connection point between the plurality of resistors,
The control means controls the DA converter circuit so that no current flows through the plurality of resistors when the gradation values of the image data for one line are the same. The drive circuit for an electro-optical device according to claim 1.   2. A precharge circuit that outputs a precharge signal for precharging the data line to the data line in a period preceding the supply of the image signal to the data line. Or a drive circuit for an electro-optical device according to 2; The DA conversion circuit outputs the image signal so that the potential is inverted between a positive polarity on the higher side and a negative polarity on the lower side with respect to the second predetermined potential in a predetermined cycle,
Power supply potential supply means capable of alternately supplying a high potential power source having a potential higher than the second predetermined potential and a low potential power source having a low potential to the pixel portion via the data line alternately in the predetermined cycle. The drive circuit for an electro-optical device according to any one of claims 1 to 3, wherein   5. A potential signal supply unit capable of supplying a potential signal having any one of a plurality of potentials corresponding to a gradation value of the image data to the data line. The drive circuit for an electro-optical device according to claim 1. Storage means capable of storing at least one line of the image data;
6. The determination unit according to claim 1, further comprising: a determination unit configured to determine whether or not the gradation values of the image data for the one line stored by the storage unit are the same. The drive circuit for an electro-optical device according to Item.   7. An electro-optical device comprising: the electro-optical device drive circuit according to claim 1; the plurality of data lines and the plurality of scanning lines; and the plurality of pixel units. apparatus.   An electronic apparatus comprising the electro-optical device according to claim 7. Electro-optical device drive for driving an electro-optical device including a plurality of data lines and a plurality of scanning lines extending so as to cross each other and a plurality of pixel portions electrically connected to the data lines and the scanning lines, respectively. A method,
Supplying a scanning signal to the pixel portion via the scanning line;
A DA conversion step of performing DA conversion for converting image data from a digital signal to an analog signal, and outputting the image data converted into the analog signal as an image signal;
Supplying the image signal to each of the plurality of pixel portions via the data line,
In the DA conversion step, the DA conversion is stopped when the gradation values of the image data for one line corresponding to one scanning line are the same. Device driving method.

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