JP2005070337A - Electro-optical device, electronic device, and method for controlling power source of the electro-optical device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To reduce the loads on a liquid crystal panel and a driving power circuit at actuation. <P>SOLUTION: A liquid crystal display device supplies electric power to a scanning line driving circuit 100 under the control of a microcomputer 10. Logic power VDDXY is supplied to a Y shift register and high-voltage power VHHXY and low-voltage power VLLXY are supplied to a level shifter. The microcomputer 10 controls the driving power circuit 30, to raise the high-voltage power VHHXY and low-voltage VLLXY a peroid of at least one frame, after the logic power VDDXY has started. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to an electro-optical device, an electronic apparatus, and a power control method for the electro-optical device.

  A display device, for example, a liquid crystal display device using a liquid crystal as an electro-optical material, is widely used as a display device in place of a cathode ray tube (CRT) in a display unit of various information processing devices, a liquid crystal television, and the like.

  The liquid crystal display device includes a liquid crystal panel and a peripheral circuit. The liquid crystal panel includes a pixel electrode arranged in a matrix, an element substrate provided with a switching element such as a TFT (Thin Film Transistor) connected to the pixel electrode, and a counter electrode facing the pixel electrode. And a liquid crystal which is an electro-optic material filled between the two substrates. A pixel is composed of a switching element, a pixel electrode, an electro-optic material, and a counter electrode, and is arranged in a matrix. Further, a scanning line driving circuit is formed in the liquid crystal panel, and the scanning line is selected according to each scanning signal sequentially output from the scanning line driving circuit.

  In the liquid crystal display device, the logic system power source of the peripheral circuit and the LCD system power source fed to the liquid crystal panel are provided in different systems. A technique for turning on the LCD system after turning on the logic system is known (for example, Patent Document 1). In addition, a technique of turning on the LCD system after the operation of the receiving circuit which is an interface of the liquid crystal panel is stabilized is also known (for example, Patent Document 2).

JP-A-7-104711 Japanese Patent Laid-Open No. 2001-100195

  Meanwhile, some scanning line driving circuits include a shift register and a level shifter. The level shifter converts the pulse transferred by the shift register into a large amplitude and outputs it as a scanning signal. In this case, the shift register and the level shifter are operated by different power sources. That is, a plurality of systems of power are supplied to the liquid crystal panel.

  However, in the conventional liquid crystal display device, the power supplied to the liquid crystal panel is regarded as one system, and control is performed to turn them all on and off. For this reason, there has been a problem that the amount of current at the time of startup becomes large. In addition, when power is supplied to the liquid crystal panel, whether each output signal becomes active or inactive at each stage of the shift register of the scanning line driver circuit depends on the gate potential of the transistor constituting the shift register. Because it depends, it is not a unique division. For this reason, since a plurality of scanning lines may be selected when the power is turned on, there is a problem that the screen at the time of startup is disturbed.

  SUMMARY OF THE INVENTION Accordingly, it is an object of the present invention to provide an electro-optical device, an electronic apparatus, and a power control method for the electro-optical device that reduce a current at startup and prevent disturbance of a display image at startup. .

  In order to solve the above-described problem, an electro-optical device according to the present invention includes a plurality of data lines, a plurality of scanning lines, and a plurality of switching elements provided corresponding to intersections of the data lines and the scanning lines. And a plurality of pixel electrodes connected to each switching element and a scanning line driving circuit for sequentially outputting each scanning signal for driving each scanning line, wherein the scanning line driving circuit includes a first power source. A shift register that sequentially shifts the transfer start pulse by receiving power from the second power supply, and a level shifter that receives power from the second power source and converts the level of the output signal of the shift register to output the respective scanning signals. Power supply means for generating one power supply and the second power supply, and control means for controlling the power supply means to start up the second power supply after the first power supply is turned on. That.

  According to the present invention, it is possible to turn on the second power supply to the level shifter after turning on the first power supply to the shift register of the scanning line driving circuit. For this reason, since the shift register and the level shifter are activated in stages, the current at the time of activation can be reduced. Further, although the scanning signal is output from the level shifter, an abnormal scanning signal may be output even if the level shifter is operated until the shift register operates normally. Therefore, it is preferable that the control means controls the power supply means to start up the second power supply after a predetermined period from when the first power supply is turned on until the shift register operates normally.

  In the electro-optical device described above, it is preferable that the voltage of the second power supply is higher than the voltage of the first power supply. As a result, the scanning line can be driven with a large amplitude so that the on / off state of the switching element can be controlled, and the current consumption of the shift register can be reduced.

  In the electro-optical device described above, it is preferable that the control unit controls the power source unit so that the second power source is started after at least one frame period has elapsed since the first power source was started. At startup, the logic level of the signal output from each stage of the shift register depends on the gate potential of the transistors constituting the shift register, and is not uniquely determined. Therefore, when the power supply of the shift register and the level shifter is turned on at the same time, a plurality of scanning lines are simultaneously selected, and a large current flows and an abnormal screen is displayed. On the other hand, the shift register is normally initialized as one frame period elapses. According to the present invention, since the second power source is turned on after at least one frame period has elapsed since the first power source was turned on, it is possible to prevent screen abnormalities at startup and to reduce the current. Thereby, the load of the electro-optical panel and the power supply means can be reduced.

  More specifically, in the above-described electro-optical device, the electro-optical device includes a timing generation unit that generates the transfer start pulse for each frame period, and the control unit starts the transfer after the first power supply is turned on. The timing generator is controlled to initialize a process for generating a pulse, and after the first transfer start pulse is generated after the initialization, at least the next transfer start pulse is generated and then the second power supply is turned on. It is preferable to control the power supply means to start up.

  In the electro-optical device described above, the element substrate on which the data line, the scanning line, the switching element, and the pixel electrode are formed, the counter substrate on which the counter electrode is formed, the element substrate, and the counter electrode An electro-optic material in the gap, the power supply means supplies a counter electrode potential to the counter electrode, and the control means supplies the counter electrode potential simultaneously with the start-up of the second power supply. It is preferable to control the power supply means. The gradation display in the electro-optical device may be determined by a voltage applied to an electro-optical material (for example, liquid crystal). In this case, it is necessary to apply some potential to the counter electrode and apply a voltage to the electro-optic material. However, it is not necessary to apply the counter electrode potential to the counter electrode until the scanning line is selected. According to the present invention, the counter electrode potential is raised at the same time as the second power supply is turned on, so that the counter electrode potential can be supplied after the preparation for image display is completed. In particular, when operating in normally black mode, it is possible to darken the screen by floating the counter electrode before starting the second power supply, and to display images normally at the same time the second power supply is turned on. Become.

  In the above-described electro-optical device, the second power supply includes a high potential and a low potential, and the power supply unit drives the counter electrode potential to be alternating-currentd at a predetermined cycle, and the high potential of the second power supply It is preferable that at least one of the low potentials is AC driven in synchronization with the predetermined period. There is a parasitic capacitance between the scanning line and the counter electrode. For this reason, the scanning line is a capacitive load. When the counter electrode potential is AC driven, the potential for making the scan line non-selected among the high potential and the low potential of the second power source is operated in synchronization with the counter electrode, thereby It is possible to reduce current consumption.

  Next, an electronic apparatus according to the present invention includes the above-described electro-optical device, and includes, for example, a liquid crystal projector, a personal computer, a mobile phone, an electronic camera, and a PDA.

  Next, the power control method for the electro-optical device according to the present invention includes a plurality of data lines, a plurality of scanning lines, and a plurality of switching elements provided corresponding to intersections of the data lines and the scanning lines, A plurality of pixel electrodes connected to each switching element; and a scanning line driving circuit for sequentially outputting each scanning signal for driving each scanning line, the scanning line driving circuit receiving power from a first power supply Assuming an electro-optical device comprising: a shift register that sequentially shifts transfer start pulses; and a level shifter that receives power from a second power supply and converts the level of an output signal of the shift register to output the scanning signals. The second power supply is started after the first power supply is started. In particular, it is preferable to start up the second power supply after at least one frame period has passed since the start of the first power supply from the viewpoint of preventing display of an abnormal screen and reducing current at startup.

  Embodiments according to the present invention will be described below with reference to the drawings. In the present embodiment, a liquid crystal panel using liquid crystal as an electro-optical material will be described as an example of an electro-optical panel, and a liquid crystal display device using the liquid crystal panel will be described as an example of an electro-optical device.

<1. Overall configuration of liquid crystal display device>
FIG. 1 shows the overall configuration of the liquid crystal display device. As shown in this figure, the liquid crystal display device includes a microcomputer 10, a system power supply circuit 20, a drive power supply circuit 30, a main switch SW, a data line drive circuit 200, and a liquid crystal panel AA. The microcomputer 10 functions as a control unit that controls the entire liquid crystal display device. When the user operates the main switch SW, the main switch SW outputs a signal corresponding to the operation. The system power supply circuit 20 is activated in response to this signal and supplies the system power supply VS to the microcomputer 10 and the drive power supply circuit 30. When the system power supply VS starts up, the microcomputer 10 detects this and executes a power supply startup sequence.

  The drive power supply circuit 30 outputs various power supply voltages under the control of the microcomputer 10. The power supply voltage output from the drive power supply circuit 30 includes the following. The high voltage power supply VHHXY and the low voltage power supply VLLXY are supplied to the level shifter of the scanning line driving circuit 100. The high voltage power supply VHHXY is, for example, 8V, and the low voltage power supply VLLXY is, for example, 0V. The logic power supply VDDXY is supplied to the shift register of the scanning line driving circuit 100. The logic power supply VDDXY is, for example, 4.8V. The interface power supply VCC is used as an interface between the scanning line driving circuit 100 and the data line driving circuit 200, and is, for example, 3V. The analog power supply VDDHS is supplied to the DA converter of the data line driving circuit 200, and is 4.8V, for example. The gradation reference power supplies V0 and V15 are used in a reference voltage generation circuit that generates a reference voltage corresponding to each gradation in the DA converter. The logic power supply VDD is supplied to the logic circuit of the data line driving circuit 200 and is, for example, 2.5V. The counter electrode potential LCCOM is supplied to a counter electrode of the liquid crystal panel AA described later. The corresponding electrode potential LCCOM may be a constant potential, or may be converted into a high potential and a low potential in a predetermined cycle. The high potential in the case of alternating current is, for example, 4.6V, and the low potential is, for example, 0V.

  The liquid crystal panel AA includes a scanning line driving circuit 100 and an image display area A. FIG. 2 shows a detailed configuration of the image display area A. In the image display area A, m (m is a natural number of 2 or more) scanning lines 2 are formed in parallel along the X direction, while n (n is a natural number of 2 or more) data. Lines 3 are formed in parallel along the Y direction. In the vicinity of the intersection of the scanning line 2 and the data line 3, the gate of the TFT 50 is connected to the scanning line 2, while the source of the TFT 50 is connected to the data line 3 and the drain of the TFT 50 is connected to the pixel electrode 6. Connected. Each pixel includes a pixel electrode 6, a counter electrode (described later) formed on the counter substrate, and a liquid crystal sandwiched between the two electrodes. As a result, the pixels are arranged in a matrix corresponding to each intersection of the scanning line 2 and the data line 3.

  Further, scanning signals Y1, Y2,..., Ym are applied to each scanning line 2 to which the gate of the TFT 50 is connected in a pulse-by-line manner. Therefore, when a scanning signal is supplied to a certain scanning line 2, the TFT 50 connected to the scanning line is turned on, so that the data line signals X1, X2,..., Xn supplied from the data line 3 at a predetermined timing. Are sequentially written in the corresponding pixels and then held for a predetermined period.

  Since the orientation and order of liquid crystal molecules change according to the potential level applied to each pixel, gradation display by light modulation becomes possible. For example, in the normally white mode, the amount of light passing through the liquid crystal is limited as the applied potential is increased. In the normally black mode, the amount of light is reduced as the applied potential is increased. As a whole, light having contrast according to the image signal is emitted for each pixel. For this reason, a predetermined display becomes possible.

  FIG. 3 shows a detailed configuration of the scanning line driving circuit 100. As shown in this figure, the scanning line driving circuit 100 includes a Y shift register 102 and a level shifter 103. A logic power supply VDDXY is supplied to the Y shift register 102, while a high voltage power supply VHHXY and a low voltage power supply VLLXY are supplied to the level shifter 103. That is, the scanning line driving circuit 100 is driven by a plurality of power sources. The power supply on the low potential side of the Y shift register 102 may also be used as the low voltage power supply VLLXY.

  The Y transfer start pulse DY, the Y clock signal YCK, and the inverted Y clock signal YCKB are supplied to the Y shift register 102. The Y shift register 102 sequentially transfers the Y transfer start pulse DY in synchronization with the Y clock signal YCK and the inverted Y clock signal YCKB, and outputs signals y1, y2,.

  The level shifter 103 converts the signal amplitude. The level shifter 103 converts the signal amplitudes of the signals y1, y2,..., Ym into VHHXY-VLLXY. Each output signal of the level shifter 103 is output to each scanning line 2 as scanning signals Y1, Y2,.

  Returning to FIG. The data line driving circuit 200 includes a plurality of DA converter DACs that convert image data from digital signals to analog signals, and a reference voltage generation circuit. One DA converter DAC corresponds to one data line. On the other hand, the reference voltage generation circuit is common to a plurality of DA converters DAC. A plurality of data line driving circuits 200 may be provided corresponding to a predetermined number of data lines 3.

  Next, the timing generation circuit 300 is initialized by a reset signal R supplied from the microcomputer 10. The timing generation circuit 300 generates control signals such as a Y clock signal YCK, an inverted Y clock signal YCKB, and a Y transfer start pulse DY in synchronization with input image data, and controls various image processing circuits (not shown). A timing signal is generated and output. The Y clock signal YCK specifies a period for selecting the scanning line 2, and the inverted Y clock signal YCKB is obtained by inverting the logic level of the Y clock signal YCK. Also, the Y transfer start pulse DY is a pulse that becomes active at the beginning of one frame, and the cycle thereof coincides with the frame cycle.

<2. Power-on sequence for LCDs>
Next, a power supply startup sequence of the liquid crystal display device will be described. FIG. 4 is a timing chart of a power supply startup sequence executed under the control of the microcomputer 10. First, when the system power supply VS starts up at time t1, the microcomputer 10 is activated. The microcomputer 10 controls the drive power supply circuit 30 to start up the logic power supplies VDD and VDDXY, the interface power supply VCC, the analog power supply VDDHS, and the gradation reference power supplies V0 and V15 at time t2. Among these, the logic power supply VDDXY is supplied to the Y shift register 102 of the scanning line driving circuit 100. That is, in the scanning line driving circuit 100, first, the shift register 102 is activated prior to the level shifter 103. Further, the logic power supply of the timing generation circuit 300 is also turned on at the time t2, and the Y clock signal YCK and the inverted Y clock signal YCKB are supplied to the Y shift register 102.

  Then, at time t3, the microcomputer 10 activates the reset signal R to initialize the timing generation circuit 300. Thereafter, at time t 4, the Y transfer start pulse DY is supplied from the timing generation circuit 300 to the Y shift register 102 of the scanning line driving circuit 100. The logic power supply VDDXY of the Y shift register 102 rises at time t2, but at this time, whether each output signal of the plurality of unit shift registers constituting the Y shift register 102 is high level or low level is It depends on the probability. However, when the Y transfer start pulse DY is supplied at time t4, and these pulses are sequentially transferred by the Y shift register 102 and output from the unit shift register at the final stage, the abnormality at the rise of the logic power supply VDDXY is eliminated. . The Y transfer start pulse DY first input at time t4 has already been output from the unit shift register at the final stage at time t5 when one frame period 1tv has elapsed from time t4.

  Thus, in the present embodiment, at time t5 when the second Y transfer start pulse DY becomes active, the high voltage power supply VHHXY, the low voltage power supply VLLXY, and the counter electrode potential LCCOM are raised. That is, the high voltage power supply VHHXY and the low voltage power supply VLLXY of the level shifter 103 rise after at least one frame period has elapsed since the logic power supply VDDXY of the Y shift register 102 has risen. The microcomputer 10 may detect the second Y transfer start pulse DY and start up the high voltage power supply VHHXY and the low voltage power supply VLLXY.

  As a result, after the abnormality at the start of the Y shift register 102 is resolved, the level shifter 103 operates and the scanning line 2 is selected. For this reason, it is possible to prevent an abnormal screen from being displayed immediately after the user operates the main switch SW.

  Since the scanning line 2 has a parasitic capacitance, it is a capacitive load. Therefore, when the level shifter 103 activates the scanning signal, the level shifter 103 writes a charge in the parasitic capacitance. According to the present embodiment, since the operation of the level shifter 103 is delayed, two or more scanning lines 2 are not simultaneously selected. Therefore, it is possible to prevent overcurrent at startup. In addition, since the logic power supply and the actual drive power supply are started up step by step, an overcurrent can be prevented. Thus, by reducing the current at startup, the load on the liquid crystal panel AA and the driving power supply circuit 30 can be reduced.

<3. Mechanical configuration of LCD panel>
Next, the mechanical configuration of the liquid crystal panel AA will be described with reference to FIGS. Here, FIG. 4 is a perspective view showing the configuration of the liquid crystal panel AA, and FIG. 6 is a sectional view taken along the line ZZ ′ in FIG.

  As shown in these figures, the liquid crystal panel AA includes an element substrate 151 such as glass or semiconductor on which the pixel electrode 6 or the like is formed, and a transparent counter substrate 152 such as glass on which the counter electrode 158 or the like is formed. In addition, the sealing material 154 mixed with the spacer 153 is bonded so that the electrode forming surfaces face each other while maintaining a certain gap, and a liquid crystal 155 as an electro-optical material is sealed in the gap. Note that the sealant 154 is formed along the periphery of the counter substrate 152, but a part thereof is opened to enclose the liquid crystal 155. Therefore, after the liquid crystal 155 is sealed, the opening is sealed with the sealing material 156.

  Here, on the opposite surface of the element substrate 151 and on the outer side of the sealing material 154, the scanning line driving circuit 100 is formed to drive the data lines 3 extending in the X direction. In addition, a plurality of input terminals 157 are formed on one side adjacent to the one side, and a driving signal is supplied to the scanning line driving circuit 100 and an image signal is supplied to the data line 3 as a data line signal. It has become.

  The counter electrode 158 of the counter substrate 152 is electrically connected to the element substrate 151 by a conductive material provided in at least one of the four corners of the bonding portion with the element substrate 151. The counter electrode 158 is supplied with the counter electrode potential LCCOM. In addition, the counter substrate 152 is provided with, for example, 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 panel AA. And a black matrix such as resin black in which carbon or titanium is dispersed in a photoresist, and third, a backlight for irradiating the liquid crystal panel AA with light. Particularly in the case of color light modulation, a black matrix is provided on the counter substrate 152 without forming a color filter.

  In addition, the opposing surfaces of the element substrate 151 and the counter substrate 152 are each provided with an alignment film or the like that is rubbed in a predetermined direction, and a polarizing plate (not shown) corresponding to the alignment direction on each back side. Are provided respectively. However, if a polymer-dispersed liquid crystal dispersed as fine particles in a polymer is used as the liquid crystal 155, the above-described alignment film, polarizing plate, and the like are not required. This is advantageous in terms of reducing power consumption.

<3. Application example>
<3-1: AC drive of counter electrode potential LCCOM>
In the above-described embodiment, the counter electrode potential LCCOM is described as a constant potential. However, the counter electrode potential LCCOM may be AC-driven. In this case, the parasitic capacitance generated between the counter electrode 158 and the scanning line 2 acts as a load when viewed from the drive power supply circuit 30. The scanning signals Y1 to Ym are active at a high level (VHHXY) and inactive at a low level (VLLXY). Here, if the potential of the scanning line 2 in the non-selected state is changed in synchronism with the AC drive of the counter electrode potential LCCOM, there is no charge of the parasitic capacitance of the scanning line 2, so that current consumption is reduced. Can do. Therefore, the potential of the low voltage power supply VLLXY may be changed in synchronization with the counter electrode potential LCCOM. In this case, the potential change width of the low voltage power supply VLLXY may be matched with the potential change width of the counter electrode potential LCCOM. Further, when the scanning signals Y1 to Ym become low level deactive, the potential of the high voltage power supply VHHXY may be changed in synchronization with the AC drive of the counter electrode potential LCCOM.

<3-2: Another example of electro-optical device>
In the above-described embodiment, the switching element of the pixel has been described as a three-terminal element typified by a TFT, but may be configured by a two-terminal element such as a diode. However, when a two-terminal element is used as a switching element of a pixel, the scanning line 2 is formed on one substrate, the data line 3 is formed on the other substrate, and the two-terminal element is connected to the scanning line 2 or the data line. 3 must be formed between the pixel electrode and the pixel electrode. In this case, the pixel is composed of a two-terminal element connected in series between the scanning line 2 and the data line 3 and a liquid crystal.

Although the present invention has been described as an active matrix liquid crystal display device, the present invention is not limited to this, and can also be applied to a passive type using STN (Super Twisted Nematic) liquid crystal. Furthermore, as an electro-optical material, in addition to liquid crystal, an electroluminescence element or the like can be used for a display device that performs display by the electro-optical effect. The electro-optical device also includes an electrophoretic device such as electronic paper, and a device using an electron-emitting device (Field Emission Display and Surface-Conduction Electron-Emitter Display).
That is, the present invention can be applied to all electro-optical devices having a configuration similar to that of the liquid crystal device described above.

<3-3: Electronic equipment>
Next, the case where the above-described liquid crystal display device is applied to various electronic devices will be described.
<3-3-1: Projector>
First, a projector using this liquid crystal device as a light valve will be described. FIG. 7 is a plan view showing a configuration example of the projector.

  As shown in this figure, a lamp unit 1102 including a white light source such as a halogen lamp is provided inside the projector 1100. 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 panel AA, and is driven by R, G, and B primary color signals supplied from an image signal processing circuit (not shown). The light modulated by these liquid crystal panels enters the dichroic prism 1112 from three directions. In this dichroic prism 1112, R and B light is refracted at 90 degrees, while G light travels straight. Accordingly, 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.

Here, paying attention to the display images by the liquid crystal panels 1110R, 1110B, and 1110G, the display image by the liquid crystal panel 1110G needs to be horizontally reversed with respect to the display images by the liquid crystal panels 1110R, 1110B.
Note that since light corresponding to the primary colors R, G, and B is incident on the liquid crystal panels 1110R, 1110B, and 1110G by the dichroic mirror 1108, it is not necessary to provide a color filter.

<3-5-2: Mobile computer>
Next, an example in which the liquid crystal panel AA is applied to a mobile personal computer will be described. FIG. 8 is a perspective view showing the configuration of this personal computer. In the figure, a computer 1200 includes a main body 1204 having a keyboard 1202 and a liquid crystal display unit 1206. The liquid crystal display unit 1206 is configured by adding a backlight to the back surface of the liquid crystal panel 1005 described above.

<3-5-3: Mobile phone>
Further, an example in which the liquid crystal panel AA is applied to a mobile phone will be described. FIG. 9 is a perspective view showing the configuration of this mobile phone. In the figure, a cellular phone 1300 includes a reflective liquid crystal panel 1005 together with a plurality of operation buttons 1302. In the reflective liquid crystal panel 1005, a front light is provided on the front surface thereof as necessary.

  In addition to the electronic devices described with reference to FIGS. 7 to 9, 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, a work Examples include a station, a videophone, a POS terminal, a device equipped with a touch panel, and the like. Needless to say, the present invention can be applied to these various electronic devices. The panel plate may be one using an organic LED instead of liquid crystal as an electro-optical material, one using plasma, or one using an inorganic electroluminescence element. Further, it can be applied to an electrophoretic panel such as electronic paper.

1 is a block diagram illustrating an overall configuration of a liquid crystal display device according to an embodiment of the present invention. 3 is a block diagram showing an electrical configuration of an image display area A. FIG. 2 is a block diagram showing a detailed configuration of a scanning line driving circuit 100. FIG. 4 is a timing chart of a power supply startup sequence executed under the control of a microcomputer 10. It is a perspective view which shows the mechanical structure of liquid crystal panel AA. FIG. 6 is a sectional view taken along line Z-Z ′ in FIG. 5. It is sectional drawing of the video projector which is an example of the electronic device to which the liquid crystal display device is applied. It is a perspective view which shows the structure of the personal computer which is an example of the electronic device to which the liquid crystal display device is applied. It is a perspective view which shows the structure of the mobile telephone which is an example of the electronic device to which the liquid crystal display device is applied.

Explanation of symbols

  2 ... scanning line, 3 ... data line, 10 ... microcomputer, 30 ... drive power supply, 100 ... scan line drive circuit, 200 ... data line drive circuit, AA ... liquid crystal panel, VDDXY ... logic power supply (first power supply), VLLXY ... low voltage power supply (second power supply), VHHXY ... high voltage power supply (first power supply).

Claims (9)

A plurality of data lines, a plurality of scanning lines, a plurality of switching elements provided corresponding to intersections of the data lines and the scanning lines, a plurality of pixel electrodes connected to the switching elements, and the scanning An electro-optical device including a scanning line driving circuit that sequentially outputs each scanning signal for driving a line,
The scanning line driving circuit receives a power supply from a first power supply and sequentially shifts a transfer start pulse, and receives a power supply from a second power supply and converts the level of an output signal of the shift register to convert each scanning signal. And a level shifter that outputs
Power supply means for generating the first power supply and the second power supply;
Control means for controlling the power supply means to start up the second power supply after starting up the first power supply;
An electro-optical device comprising:   The electro-optical device according to claim 1, wherein the voltage of the second power source is higher than the voltage of the first power source.   3. The control unit according to claim 1, wherein the control unit controls the power source unit to start up the second power source after at least one frame period has elapsed since the first power source was started up. Electro-optic device. Timing generating means for generating the transfer start pulse every frame period;
The control unit controls the timing generation unit to initialize the process of generating the transfer start pulse after the first power supply is turned on, and the first transfer start pulse is generated after the initialization. 4. The electro-optical device according to claim 3, wherein the power supply unit is controlled to start up the second power supply after at least the next transfer start pulse is generated. An element substrate on which the data line, the scanning line, the switching element, and the pixel electrode are formed;
A counter substrate on which a counter electrode is formed;
An electro-optic material is provided in the gap between the element substrate and the counter electrode,
The power supply means supplies a counter electrode potential to the counter electrode;
5. The control unit according to claim 1, wherein the control unit controls the power source unit so that the power source unit supplies the counter electrode potential simultaneously with the start-up of the second power source. The electro-optical device described. The second power source includes a high potential and a low potential;
The power supply means AC-drives the counter electrode potential in a predetermined cycle, and AC-drives at least one of the high potential and the low potential of the second power supply in synchronization with the predetermined cycle. The electro-optical device according to claim 5.   An electronic apparatus comprising the electro-optical device according to claim 1. A plurality of data lines, a plurality of scanning lines, a plurality of switching elements provided corresponding to intersections of the data lines and the scanning lines, a plurality of pixel electrodes connected to the switching elements, and the scanning A scanning line driving circuit for sequentially outputting each scanning signal for driving the line, the scanning line driving circuit receiving a power supply from a first power supply and sequentially shifting a transfer start pulse, and a power supply from a second power supply And a level shifter for converting the level of the output signal of the shift register and outputting the respective scanning signals, and a power control method for an electro-optical device comprising:
A power control method for an electro-optical device, wherein the second power supply is started after the first power supply is started.   9. The power control method for an electro-optical device according to claim 8, wherein the second power supply is started after at least one frame period has elapsed since the first power supply was started.

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