JP2009058694A - Display device and driving method for the same, electronic equipment - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a display device, a driving method of the device and electronic equipment capable of reducing power consumption within a panel and optimizing both of black luminance and white luminance. <P>SOLUTION: The display device has a multi-color display mode and a low color display mode, and carries out an AC inversion driving by applying a common voltage signal of a level varying in a predetermined period to a pixel electrode. An application voltage to a signal line in the low color display mode is set to be lower than an application voltage to a signal line in the multicolor display mode. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to an active matrix display device in which display elements (electro-optical elements) of pixels are arranged in a matrix in a display region, a driving method thereof, and an electronic apparatus.

  A display device, for example, a liquid crystal display device using a liquid crystal cell as a pixel display element (electro-optical element), is characterized by being thin and low power consumption, for example, a personal digital assistant (PDA), portable It is applied to a wide range of electronic devices such as telephones, digital cameras, video cameras, and display devices for personal computers.

FIG. 1 is a block diagram illustrating a configuration example of a liquid crystal display device (see, for example, Patent Documents 1 and 2).
As shown in FIG. 1, the liquid crystal display device 1 includes an effective pixel unit 2, a vertical drive circuit (VDRV) 3, and a horizontal drive circuit (HDRV) 4.

In the effective pixel portion 2, a plurality of pixel circuits 21 are arranged in a matrix.
Each pixel circuit 21 includes a thin film transistor (TFT) 21 as a switching element, a liquid crystal cell LC 21 having a pixel electrode connected to the drain electrode (or source electrode) of the TFT 21, and one electrode connected to the drain electrode of the TFT 21. Is constituted by a holding capacitor Cs21 connected thereto.
For each of these pixel circuits 21, scanning lines (gate lines) 5-1 to 5-m are wired along the pixel arrangement direction for each row, and signal lines 6-1 to 6-n are provided for each column. Wiring is performed along the pixel array direction.
The gate electrodes of the TFTs 21 of the pixel circuits 21 are connected to the same scanning lines 5-1 to 5-m in units of rows. The source electrode (or drain electrode) of each pixel circuit 21 is connected to the same signal line 6-1 to 6-n in each column unit.

Further, in a general liquid crystal display device, a storage capacitor line Cs is provided, and the storage capacitor line Cs21 is formed between the storage capacitor line Cs and the first electrode of the liquid crystal cell LC21. A common voltage VCOM and an in-phase pulse are input and used as a storage capacitor. In a general liquid crystal display device, the storage capacitors Cs21 of all the pixel circuits 21 in the effective pixel unit 2 are commonly connected to one storage capacitor line Cs.
The second electrode of the liquid crystal cell LC21 of each pixel circuit 21 is commonly connected to the supply line 7 of the common voltage Vcom whose polarity is inverted every horizontal scanning period (1H), for example.

  The scanning lines 5-1 to 5-m are driven by the vertical driving circuit 3, and the signal lines 6-1 to 6-n are driven by the horizontal driving circuit 4.

The vertical driving circuit 3 performs a process of sequentially selecting each pixel circuit 21 connected to the scanning lines 5-1 to 5-m in units of rows by scanning in the vertical direction (row direction) every field period.
That is, when the scanning pulse GP1 is applied to the scanning line 5-1 from the vertical drive circuit 3, the pixels in each column of the first row are selected, and the scanning pulse GP2 is applied to the scanning line 5-2. In this case, the pixels in each column of the second row are selected. Similarly, scanning pulses GP3,..., GPm are sequentially applied to the scanning lines 5-3,.

  2A to 2E are timing charts in the so-called 1HVcom inversion driving method of the general liquid crystal display device shown in FIG.

As another driving method, a capacitive coupling driving method is known in which the voltage applied to the liquid crystal is modulated using coupling from the storage capacitor wiring Cs (see, for example, Patent Document 3).
Japanese Patent Laid-Open No. 11-119746 JP 2000-298459 A Japanese Patent Laid-Open No. 2-157815

  In the meantime, the liquid crystal display device of FIG. 1 or the like, for example, level-shifts (boosts) the voltage supplied from the outside by a power supply circuit composed of a DC-DC converter in synchronization with a master clock MCK of a predetermined level from the outside, for example. A driving voltage is generated and configured to be supplied to a desired circuit formed on the insulating substrate.

One of the great values of portable devices (electronic devices) is the operating time.
With respect to liquid crystal display devices as well, it is required to reduce the power during driving in order to reduce battery power consumption.
The AC power consumption that occupies most of the power consumption can be expressed as P = C × V × f. Therefore, as a measure to reduce power consumption,
<1> Reduction of C: reduction of parasitic capacitance in the device,
<2> Reduction of V: Reduction of device drive voltage,
<3> Reduction of f: Reduction of device drive frequency,
Can be considered.

Regarding <1> above, since the process is changed, the change is extremely difficult. At the design level, it is important to obtain optimal solutions <2> and <3>.
However, as for <2>, as a side effect, it is not easy to reduce display image quality (brightness, contrast, etc.) and drive margin because <3> also causes display image quality to decline (flicker). .

  In addition, the capacitive coupling driving method described above can improve the response speed of the liquid crystal due to so-called overdrive as compared with the 1HVcom inversion driving method, can reduce the audio noise generated in the Vcom frequency band, and the contrast of the ultra-high definition panel. There are features such as compensation.

However, this capacitive coupling driving method described in Patent Document 3 is applied to a liquid crystal display device using a liquid crystal material (for example, normally white) having a characteristic of a liquid crystal dielectric constant ε with respect to an applied voltage as shown in FIG. If this is used, there is a disadvantage that the luminance change is large when the liquid crystal gap fluctuation / gate oxide film thickness fluctuation at the time of manufacturing or the relative permittivity fluctuation of the liquid crystal at the time of temperature environment change occurs when the effective pixel potential is considered. There is.
Further, when trying to optimize the black luminance, there is a disadvantage that the white luminance becomes black (sinks).

(Equation 1)
ΔVpix1 = Vsig + (Ccs / Ccs + Clc) * ΔVcs−Vcom (1)

In Expression (1), ΔVpix represents the effective pixel potential, Vsig represents the video signal voltage, Ccs represents the storage capacitor, Clc represents the liquid crystal capacitance, ΔVcs represents the potential of the signal CS, and Vcom represents the common voltage.
As described above, when the black luminance is optimized, the white luminance is sunk in the term (Ccs / Ccs + Clc) * ΔVcs in the above equation (1), and the nonlinearity of the liquid crystal dielectric constant is effective. This is because the pixel potential is affected.

  It is an object of the present invention to provide a display device capable of reducing power consumption inside the panel and optimizing both black luminance and white luminance, a driving method thereof, and an electronic apparatus. is there.

  A display device according to a first aspect of the present invention has a multi-color display mode and a low-color display mode, and applies a common voltage signal whose level is switched at a predetermined cycle to a pixel electrode to perform AC inversion driving. A plurality of pixel circuits for writing video pixel data through the switching elements are arranged corresponding to a row arrangement of the pixel circuits of the effective pixel unit and the pixel circuit of the effective pixel unit, and the switching A plurality of scanning lines for element conduction control; a plurality of capacitance lines arranged to correspond to the row arrangement of the pixel circuits; and the pixel data arranged to correspond to the column arrangement of the pixel circuits. A first drive circuit that selectively drives the plurality of scanning lines and the plurality of scanning lines and the plurality of capacitance lines, and a second drive circuit that drives the signal lines Has, the second driving circuit sets the signal line voltage applied at the time of low color display mode lower than the signal line voltage applied multicolor display mode.

  Preferably, when shifting from the low color display mode to the multicolor display mode, no voltage is applied to the pixels during a period in which the center voltage of AC inversion driving is changing.

  Preferably, when shifting from the low color display mode to the multicolor display mode, black or white is displayed during a period in which the center voltage of AC inversion driving is changing.

  Preferably, when shifting from the low-color display mode to the multi-color display mode, the low-color drive is performed while the multi-color display drive is performed during the period in which the center voltage of the AC inversion drive is changing.

  Preferably, the driving frequency at the time of low color display is lower than the driving frequency at the time of multicolor display mode.

  Preferably, when shifting from the low color display mode to the multicolor display mode, no voltage is applied to the pixels during a period in which the center voltage of AC inversion driving is changing.

  Preferably, when shifting from the low color display mode to the multicolor display mode, black or white is displayed in a period in which the center voltage of the AC inversion drive is changing, and the drive frequency is equal to that of the multicolor display mode. When shifting from the color display mode to the low color display mode, the drive frequency during the period in which the center voltage of the AC drive is changed is equal to that in the multicolor display mode although the display is in the low color display mode.

  Preferably, when shifting from the low color display mode to the multicolor display mode, low color driving is performed while the center voltage of AC inversion driving is changing while the multicolor display driving is performed, and the driving frequency is multicolor. Equal to the display mode, when shifting from the multicolor display mode to the low color display mode, the drive frequency during the period in which the center voltage of the AC drive is changed is the multicolor display mode while the display is in the low color display mode. equal.

  Preferably, the center value of the common voltage signal whose level is switched at a predetermined cycle can be corrected by detecting a potential obtained by averaging the detection potentials of the positive and negative monitor pixels formed separately from the effective pixel portion. Each pixel circuit arranged in the effective pixel section includes a display element having a first pixel electrode and a second pixel electrode, and a storage capacitor having a first electrode and a second electrode. A first pixel electrode of the display element, a first electrode of the storage capacitor, and one terminal of the switching element are connected, and a second electrode of the storage capacitor is connected to the capacitor wiring arranged in a corresponding row. A common voltage signal whose level is switched at a predetermined cycle is applied to the second pixel electrode of the display element.

  The second aspect of the present invention corresponds to an effective pixel portion in which a plurality of pixel circuits for writing video pixel data through switching elements are arranged in a matrix, and a row arrangement of the pixel circuits in the effective pixel portion. A plurality of scanning lines for controlling the conduction of the switching elements, a plurality of capacitance wirings arranged to correspond to the row arrangement of the pixel circuits, and arranged to correspond to the column arrangement of the pixel circuits. A plurality of signal lines for propagating the pixel data; a plurality of scanning lines; and a first driving circuit for selectively driving the plurality of capacitance lines; a second driving circuit for driving the signal lines; A display device having a multi-color display mode and a low-color display mode, and applying a common voltage signal whose level is switched at a predetermined cycle to the pixel electrode to perform AC inversion driving A is, it sets the signal line voltage applied at the time of low color display mode lower than the signal line voltage applied multicolor display mode.

  According to a third aspect of the present invention, there is provided an electronic apparatus including a display device, wherein the display device has a multicolor display mode and a low color display mode, and the pixel electrode has a common level that switches at a predetermined cycle. A display device that performs AC inversion driving by applying a voltage signal, wherein an effective pixel portion in which a plurality of pixel circuits for writing image pixel data through a switching element are arranged in a matrix, and the pixel circuit of the effective pixel portion A plurality of scanning lines for controlling the conduction of the switching elements, a plurality of capacitance lines arranged corresponding to the row arrangement of the pixel circuits, and the pixel circuits. A first drive circuit that is arranged so as to correspond to the column arrangement and selectively drives the plurality of signal lines that propagate the pixel data, the plurality of scan lines, and the plurality of capacitance lines. And a second drive circuit for driving the signal line, wherein the second drive circuit sets a signal line application voltage in the low color display mode to be lower than a signal line application voltage in the multicolor display mode. .

  According to the present invention, the signal line application voltage in the low color display mode is set lower than the signal line application voltage in the multicolor display mode by the second drive circuit.

  According to the present invention, it is possible to reduce the power consumption inside the panel, and it is possible to optimize both the black luminance and the white luminance.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

FIG. 4 is a diagram illustrating a configuration example of an active matrix display device according to an embodiment of the present invention using, for example, a liquid crystal cell as a pixel display element (electro-optical element).
FIG. 5 is a circuit diagram showing a specific configuration example of the effective pixel portion of the circuit of FIG.

  As shown in FIGS. 4 and 5, the display device 100 includes an effective pixel unit 101, a vertical drive circuit (V / CSDRV) 102, a horizontal drive circuit (HDRV) 103, and gate lines (scan lines) 104-1 to 104. -M, storage capacitor lines (hereinafter referred to as storage lines) 105-1 to 105-m, signal lines 106-1 to 106-n, first monitor (dummy) pixel unit (MNTP1) 107-1, second monitor image Part (MNTP2) 107-2, first monitor pixel part and monitor vertical drive circuit (V / CSDRVM) 108 also serving as the second monitor pixel part, first monitor horizontal drive circuit (HDRVM1) 109- dedicated for the first monitor pixel part 1, a second monitor horizontal drive circuit (HDRVM2) 109-2 dedicated to the first monitor pixel unit, a detection output circuit 110, and a correction circuit 111 are main components. Has Te.

In the present embodiment, the first monitor pixel unit 107-1 and the second monitor pixel unit 107-including one pixel or a plurality of pixels are provided adjacent to the effective pixel unit 101 independently (on the right side in FIG. 4). 2. A monitor vertical drive circuit (V / CSDRVM) 108 for driving monitor pixels, a first monitor horizontal drive circuit 109-1, a second monitor horizontal drive circuit (HDRVM2) 109-2, and a detection output circuit 110 A monitor circuit 120 is formed.
A horizontal drive circuit 103 and a vertical drive circuit 102 are formed adjacent to the effective pixel portion 101. In FIG. 4, a horizontal drive circuit 103 is formed on the upper side of the effective pixel unit 101, and a vertical drive circuit 102 is formed on the left side of the effective pixel unit 101.

In the present embodiment, the power supply circuit (VDD2) 130 is provided.
When the power supply circuit 130 receives the liquid crystal voltage VDD1 from the outside at 0 to 3.5 V, it can obtain a dynamic range for gradation display of the liquid crystal. The power consumption is reduced by receiving the voltage VDD1 at 0 to 2.9V.
The power supply circuit 130 includes a DC-DC converter. For example, as shown in FIG. 6, a liquid crystal voltage VDD1 (eg, 2.9V) is supplied from the outside, and this voltage is supplied from an interface circuit (not shown). In synchronization with the horizontal synchronization signal Hsync, the voltage is boosted to a 5V panel voltage VDD2 (eg, 5.0V) and supplied to each circuit inside the panel. The power supply circuit 130 outputs the panel voltage VDD2 (for example, 5.0 V) to the regulator Reg outside the panel. The regulator Reg generates a 3.5 V system voltage used in a predetermined circuit inside the panel, and supplies it to the inside of the panel.
Further, the power supply circuit 130 generates VSS2 (for example, -1.9V) and VSS3 (for example, -3.8V), which are negative voltages, as an internal panel voltage, and supplies them to a predetermined circuit (an interface circuit or the like) inside the panel.

In addition, the power supply circuit 130 is connected to a reference voltage drive circuit (reference driver: REFDRV) 140 that generates an applied voltage to the signal lines 106-1 to 106-n through the horizontal drive circuit 103, for example. Supply 9V.
The configuration of the reference driver 140 will be described in detail later.

In this embodiment, basically, as described in detail later, after pixel data is written from the signal lines 106-1 to 106-n (the rise of the gate pulse to the gate lines 104-1 to 104-m). Driving method in which the pixel potential is changed by applying coupling from the storage lines 105-1 to 105-m independently wired to each row through the storage capacitor Cs201 and the liquid crystal applied voltage is modulated. Is adopted.
During actual driving by this driving method, positive and negative monitor pixel potentials of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 in the monitor circuit (in the monitor pixel, the connection node ND201 of the pixel circuit PXLC). Is detected, and the result is fed back to the optimum common voltage Vcom value or the reference driver to automatically adjust the center value of the common voltage Vcom.
In the present embodiment, as will be described later, the pixel potential of the effective pixel portion 101 becomes an arbitrary potential according to the monitor pixel potential detected from the first and second monitor pixel portions 107-1 and 107-2. As described above, the storage signal CS output from the CS driver is corrected.
A configuration function of the monitor circuit and a storage signal CS correction system will be described in detail later.

As shown in FIG. 5, the effective pixel unit 101 includes a plurality of pixel circuits PXLC arranged in an m × n matrix.
In FIG. 5, a 4 × 4 matrix arrangement is shown for simplification of the drawing.

As shown in FIG. 5, each pixel circuit PXLC includes a TFT (thin film transistor) 201 as a switching element, and a liquid crystal cell LC201 in which a first pixel electrode is connected to a drain electrode (or source electrode) of the TFT 201. The storage capacitor Cs201 includes a first electrode connected to the drain electrode of the TFT201.
Note that a node ND201 is formed by a connection point between the drain of the TFT 201, the first pixel electrode of the liquid crystal cell LC201, and the first electrode of the storage capacitor Cs201.

  For each of these pixel circuits PXLC, gate lines (scanning lines) 104-1 to 104-m and storage lines 105-1 to 105-m are wired along the pixel arrangement direction for each row, and the signal line 106 -1 to 106-n are wired along the pixel arrangement direction for each column.

The gate electrode of the TFT 201 of each pixel circuit PXLC is connected to the same gate line 104-1 to 104-m for each row.
The second electrode of the storage capacitor Cs201 of each pixel circuit PXLC is connected to the same storage line 105-1 to 105-m for each row.
In addition, the source electrode (or drain electrode) of each pixel circuit PXLC is connected to the same signal line 106-1 to 106-n for each column.
The second pixel electrode of the liquid crystal cell LC201 of each pixel circuit PXLC is connected in common to a supply line 112 of, for example, a small amplitude common voltage VCOM (Vcom) whose polarity is inverted during one horizontal scanning period (1H). Yes.
The common voltage Vcom will be described in detail later.

  Each of the gate lines 104-1 to 104-m is driven by a gate driver of the vertical drive circuit 102, and each of the storage lines 105-1 to 105-m is driven by a capacity driver (CS driver) of the vertical drive circuit 102. The signal lines 106-1 to 106-n are driven by the horizontal drive circuit 103.

The vertical drive circuit 102 basically scans in the vertical direction (row direction) for each field period and sequentially selects each pixel circuit PXLC connected to the gate lines 104-1 to 104-m in units of one row. Perform the process.
That is, the vertical driving circuit 102 applies the gate pulse GP1 to the gate line 104-1, selects the pixels in each column of the first row, and applies the gate pulse GP2 to the gate line 104-2. A pixel in each column in the second row is selected. Similarly, gate pulses GP3,..., GPm are sequentially applied to the gate lines 104-3,.

  Further, the vertical driving circuit 102 has a first level (CSH, for example, 3V to 4V) or a second level (CSL) for each storage line 105-1 to 105-m independently wired corresponding to each gate line. , For example, 0V), the capacitance signals (hereinafter referred to as storage signals) CS1 to CSm selected in order are given.

  7A to 7L are timing charts showing examples of driving the gate lines and the storage lines of the vertical drive circuit of this embodiment.

The vertical drive circuit 102 drives the gate lines 104-1 to 104-m and the storage lines 105-1 to 105-m in order from the first row, for example, but drives one gate line with a gate pulse. Later (after signal writing), the levels of the storage signals CS1 to CSm applied to the storage lines 105-1 to 105-m at the timing of the rise of the gate pulse of the next gate line are set to the first level CSH as follows. And the second level CSL are alternately selected and applied.
For example, when the vertical drive circuit 102 selects the first level CSH and applies the storage signal CS1 to the storage line 105-1 in the first row, the vertical drive circuit 102 applies the second level to the storage line 105-2 in the second row. The storage signal CS2 is selected by selecting CSL, the first level CSH is selected and applied to the storage line 105-3 in the third row, and the storage signal CS3 is applied to the storage line 105-4 in the fourth row. Selects the second level CSL, applies the storage signal CS4, and similarly selects the first level CSH and the second level CSL alternately to transfer the storage signals CS5-CSm to the storage lines 105-5-105-m. Apply to.
In addition, when the second level CS1 is selected and the storage signal CS1 is applied to the storage line 105-1 in the first row, the first level CSH is selected and stored in the storage line 105-2 in the second row. The signal CS2 is applied, the second level CSL is selected for the storage line 105-3 in the third row and the storage signal CS3 is applied, and the first level CSH is applied to the storage line 105-4 in the fourth row. The storage signal CS4 is selected and applied, the second level CSL and the first level CSH are alternately selected in the same manner, and the storage signals CS5 to CSm are applied to the storage lines 105-5 to 105-m.

In the present embodiment, after the fall of the gate pulse GP (after writing from the signal line), the storage lines 105-1 to 105-m are driven and coupled via the storage capacitor Cs201, thereby causing the pixel potential (node). The voltage applied to the liquid crystal is modulated by changing the potential of the ND 201.
During actual driving by this driving method, as described later, positive and negative monitor pixel potentials of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 in the monitor circuit (in the monitor pixel, the pixel circuit A potential obtained by averaging (corresponding to the potential of the connection node ND201 of PXLC) is detected, and the result is fed back to the optimum common voltage Vcom value or the reference driver to automatically adjust the center value of the common voltage Vcom. Has been.
In the present embodiment, the CS driver is configured so that the pixel potential of the effective pixel unit 101 becomes an arbitrary potential according to the monitor pixel potential detected from the first and second monitor pixel units 107-1 and 107-2. The storage signal CS output from is corrected.

FIG. 5 schematically illustrates an example of the level selection output unit of the CS driver 1020 of the vertical drive circuit 102.
The CS driver 1020 includes a variable power supply unit 1021, a first level supply line 1022 connected to the positive electrode side of the power supply unit 1021, a second level supply line 1023 connected to the negative electrode side of the power supply unit 1021, and a first level. It includes switches SW1 to SWm that selectively connect the storage lines 105-1 to 105-m in which the supply line 1022 or the second level supply line 1023 is wired for each row of the pixel array.

In FIG. 5, ΔVcs indicates a level difference (potential difference) between the first level CSH and the second level CSL.
As will be described in detail later, ΔVcs and the amplitude ΔVcom of the AC common voltage Vcom having a small amplitude are selected to values that can optimize both the black luminance and the white luminance.
For example, as will be described later, the effective pixel potential ΔVpix applied to the liquid crystal during white display. The values of ΔVcs and ΔVcom are determined so that W becomes a value of 0.5V or less.

The vertical drive circuit 102 includes a vertical shift register group, and a plurality of shifts provided corresponding to gate buffers to which gate lines 104-1 to 104-m arranged for each row corresponding to the pixel arrangement are connected. It has a register VSR. Each shift register VSR is supplied with a vertical start pulse VST for instructing the start of vertical scanning generated by a clock generator (not shown) and a vertical clock VCK (or vertical clocks VCK and VCKX having opposite phases to each other) as a reference for vertical scanning. The
For example, the shift register shifts the vertical start pulse VST in synchronization with the vertical clock VCK and supplies it to the corresponding gate buffer.
Further, the vertical start pulse VST is propagated from the upper side or the lower side of the effective pixel portion 101 and is sequentially shifted into each shift register.
Therefore, basically, the gate lines 104-1 to 104-m are sequentially driven through the gate buffers by the vertical clock supplied from the shift register VSR.

The horizontal drive circuit 103 receives an input video signal Vsig based on a horizontal start pulse HST for instructing the start of horizontal scanning and a horizontal clock HCK (or vertical clocks HCK and HCKX having opposite phases to each other) as a reference for horizontal scanning. Sampling is sequentially performed every 1H (H is a horizontal scanning period), and writing processing is performed on each pixel circuit PXLC selected in units of rows by the vertical driving circuit 102 via the signal lines 106-1 to 106-n.
The level of the video signal Vsig is formed by the reference driver 140 as a voltage corresponding to the gradation level.

  Here, the configuration and function of the reference driver 140 according to the present embodiment will be described.

  FIG. 8 is a block diagram showing a basic configuration of the reference driver according to the present embodiment.

  The reference driver 140 in FIG. 8 includes a digital-analog converter (DAC) 141, a booster 142, and an analog buffer 143.

  Since the reference driver 140 receives 0 to 2.9 V from the power supply circuit 130, as shown in FIG. 9, the gradation expression is reduced due to the reduction of the dynamic range as compared with the case where it receives 3.5 V. Therefore, the dynamic range is secured by the following method.

  FIGS. 10A and 10B are diagrams showing processing capable of maintaining the gradation expression of the reference driver 140 according to the present embodiment.

In this embodiment, the dynamic range is expanded by changing the drive only on the black side where the voltage change is large.
That is, the boosting process by capacitive coupling is not performed only for the 0 gradation.
For example, if the gradation expression is to be expressed by 8 bits of 64 gradations, as shown in FIG. 10A, only the 0 gradation is not used, and the booster 142 is used in the case of 1 to 63 gradations. 142 functions are used.

In this case, the reference voltage Vref is supplied with [0 gradation: 0 V], “1 gradation: 0 V”, 63 gradation: 2.9 V], and [dynamic range (D-range): 2.9 V]. The
The input voltage of the analog buffer of the reference driver 140 is [0 gradation: 0 V], [1 gradation: 0.72 V], [63 gradation: 3.69 V], [D-range: 3.69 V]. It becomes.
Thus, in this embodiment, even if it supplies with 2.9V, the dynamic range more than a power supply voltage is securable.
That is, the dynamic range can be ensured when the voltage is lowered.

FIG. 11 is a diagram showing a basic equivalent circuit of the reference driver according to the present embodiment.
FIG. 12 is a timing chart of the circuit of FIG. 13A and 13B are diagrams showing voltage waveforms when there is no boosting process and when there is no boosting process.

  The reference driver 140 includes switches SW1-1 to SW1-3 that are turned on and off at the same timing, switches SW2-1 and SW2-2 that are turned on and off at the same timing, an output side switch SW3, a charging capacitor C1, and a charge pump capacitor. C2, an n-channel (NMOS) transistor NT1 forming a source follower, and nodes ND1 to ND7.

The voltage Vin (0 to 2.9 V) is supplied to the node ND1, and the voltage V is supplied to the node ND2.
The fixed contact a of the switch SW1-1 is connected to the node ND2, and the operation contact b is connected to the node ND3.
The fixed contact a of the switch SW1-2 is connected to a reference potential (for example, the ground potential GND), and the operation contact b is connected to the node ND4.
The fixed contact a of the switch SW1-3 is connected to the node ND5, and the operation contact b is connected to the node ND1.
The fixed contact a of the switch SW2-1 is connected to the node ND3, and the operation contact b is connected to the node ND5.
The fixed contact a of the switch SW2-2 is connected to the node ND4, and the operation contact b is connected to the node ND6.
The first electrode of the capacitor C1 is connected to the node ND3, and the second electrode is connected to the node ND4.
A first electrode of the capacitor C2 is connected to the node ND5, and a second electrode is connected to the node ND6.
The drain of the NMOS transistor NT1 is connected to the supply line of the power supply voltage BVDD2, the source is connected to the ground potential GND, and a node ND7 is formed by the connection point. The gate of the NMOS transistor NT1 is connected to the node ND5.

The circuit 140A is configured for the purpose of suppressing the voltage applied to the drive circuit and the power consumption of the circuit.
However, if the drive voltage is suppressed as it is, the applied voltage to the liquid crystal also decreases, and the dynamic range cannot be secured as desired. In order to avoid this, the applied pressure of the liquid crystal is boosted by a booster circuit to secure a dynamic range as desired.
Therefore, a voltage applied to the liquid crystal is ensured with the booster circuit of the circuit of FIG.

In the equivalent circuit 140A, the switches SW1-1 to SW1-3, SW2-1, and SW2-2 control charging / discharging of the capacitor to boost the input voltage.
In operation, the switches SW2-1 and SW2-2 are off (OFF) while the switches SW1-1 to SW1-3 are on. Conversely, if the switches SW1-1 to SW1-3 are OFF, the switches SW2-1 and SW2-2 are ON.

Here, when the switches SW1-1 to SW1-3 are ON, the charge Q is charged in the capacitor C1 in order to generate the raised voltage ΔV. During this time, the input voltage Vin is applied to the gate of the transistor NT1 as Vg.
When the ON period of the switches SW1-1 to SW1-3 ends, the capacitors C1 and C2 are capacitively coupled by turning on the switches SW2-1 and SW2-2, and as a result, ΔV is generated.
Here, if the charge of the capacitor C1 is Q and the charge of the combined capacitance of C1 and C2 is Q ′, the following equation is established.

(Equation 2)
Q = C1 * Vin
Q ′ = (C1 + C2) * ΔV
Here, Vin is the input voltage, ΔV is the raised voltage, C1 is the capacity of the charging capacitor, and C2 is the capacity of the charge pump capacitor.

  Since Q = Q ′ according to the law of conservation of charge, the following equation is established. Therefore, solving the two equations yields the following.

(Equation 3)
ΔV = Vin * C1 / (C1 + C2).

  The generated voltage ΔV is applied to the gate of the source follower transistor NT1 in the sum with the input voltage V, and the voltage Vg is as follows.

(Equation 4)
Vg = Vin + ΔV

Since the voltage Vin is constantly applied regardless of the switches SW1-1 to SW1-3 and SW2-1 and SW2-2, Vout of the transistor nt1 is output as Vin and the dynamic range is narrowed.
When the source voltage of the transistor NT1 is Vin, that is, when the switches SW1-1 to SW1-3 are ON, the switch SW3 is turned OFF so that the potential of Vout does not become Vin (so that the dynamic range is not narrowed). It is necessary to control the switch SW3.

ΔV is a parameter for adjusting the voltage applied to the liquid crystal, and is a value determined by the ratio of C1 and C2.
However, if ΔV is increased, there is a concern that the voltage difference between the gradations becomes large and the color tone may be deteriorated during gradation expression.
If this circuit is used, a high voltage can be applied to the liquid crystal even at a low power supply voltage, a reduction in dynamic range can be avoided, and a reduction in power consumption is expected.

Furthermore, in the present embodiment, the following configuration is adopted in order to reduce low power consumption.
In other words, a system is employed that changes the drive frequency by changing the voltage applied to the signal line in accordance with the panel drive mode, and a system that does not cause image defects when the mode is changed.

This low power consumption technology is as follows.
There are mainly two display modes for portable devices that are electronic devices. One is a multicolor display mode in which image quality is given priority (typical examples: 16 bits, 18 bits, and 24 bits). In this case, high quality is required for both contrast and luminance.
The other is a low-color display mode (mostly 3-bit display) in which the image is confirmed with a reflection mode or a low-brightness backlight. Since the surface brightness of the display is low, image quality is not required, but in the standby mode. Since most of this is displayed, the demand for power is very high.

The liquid crystal device changes its optical characteristics depending on the voltage applied to the subpixel, and can display an image with high contrast and brightness when a high voltage is applied, but the driving power increases.
On the other hand, if the applied voltage is lowered, the power consumption can be reduced, but the image quality deteriorates.
Further, as shown in FIG. 14, flicker is not visually recognized even when the driving frequency is low because the VT characteristic of the liquid crystal is lying in a high voltage / low voltage region.

Utilizing this characteristic, as shown in FIG. 15, the signal line applied voltage and the driving frequency are slightly increased in the display mode. In the low color display mode, by reducing the signal line applied voltage and the driving frequency, it is possible to perform optimum power management in accordance with the usage status of the portable device.
For example, as shown in FIG. 15, the signal line application voltage is 3.5 V in the multicolor mode, and the signal application voltage is 2.9 V in the low color mode. This can be selected depending on whether or not the boosting function is used in the reference voltage driving circuit 140 described above, for example.
In this case, the center value in the multicolor mode is 3.5V, and the center value in the low color mode is 1.45V.
As described above, in the multi-color mode and the low-color mode, the Vsig center value is shifted by 0.3 V, so that the center value of the common voltage Vcom is also shifted by 0.3 V.

However, when the above drive system is employed, image quality problems occur when switching modes.
Due to the physical properties of the liquid crystal, there is a problem that a display image is burnt unless AC inversion driving is performed.
Since the center voltage at the time of AC inversion driving is half the value of the signal line applied voltage, the center voltage shifts between high voltage driving and low voltage driving. Therefore, when switching the drive mode, it is necessary to change the center voltage quickly and without image disturbance.

  Therefore, in the present embodiment, the frequency at the time of mode change is controlled, and the screen image holding control at the time of mode change is performed.

  FIG. 16 is a timing chart showing a specific example of sequence control from multicolor display (for example, 260,000 color display) to low color display (for example, eight color display).

At the time of low color display, as described above, since the signal line potential is written in the region where the VT characteristic is laid down, even if the center voltage at the time of AC inversion is slightly different from the ideal voltage, it is at a high frequency. If the drive is performed, the flicker is not visually recognized.
For this reason, low-color display and high-frequency driving are performed for several frame periods immediately after mode switching, and then the operating frequency is reduced when the AC inversion center voltage reaches the ideal voltage, so that the image quality is not degraded. Switching can be performed.

  FIG. 17 is a timing chart showing a specific example of sequence control from low color display to multicolor display.

  Since a slight center voltage shift is visually recognized during multicolor display, it is necessary to switch the mode when the voltage changes. For this purpose, for example, the following three methods can be employed.

<1> During the period when the center potential is changing, the potential application to the pixel is stopped, and the display is continued only with the potential stored in the liquid crystal.
<2> During the period in which the center potential is changing, the drive frequency is increased, the display is set to the all black (all white) state, and image disturbance is not caused by utilizing the fact that the VT characteristic is sleeping.
<3> While the center potential is changing, the image signal corresponding to the low color display mode is received in the multicolor display mode, and the same image as the low color display mode is output while increasing the drive frequency.

  In order to realize the above functions, in this embodiment, for example, as shown in FIG. 18, a timing generator (TG) 150 and a Vcom drive circuit 160 are provided in addition to the configuration of FIG. In the example of FIG. 18, the horizontal drive circuits 103 are provided above and below the effective pixel unit 101 in the drawing, for example, the odd lines are driven by the horizontal drive circuit 103-1, and the even lines are driven by the horizontal drive circuit 103-2. To drive.

  The timing generator 150 receives DATA (image signal), COL (low color / multicolor display mode switching signal), and Clock Pulse (in-panel reference clock) inputted into the panel, and drives signal line writing potential and AC inversion drive. The change of the center potential and the switching of the writing buffer circuit are controlled at the timing at which matching can be achieved within the panel.

The Vcom drive circuit 160 is a circuit for switching the center potential of AC inversion drive.
FIG. 19 is a circuit diagram showing an example of the Vcom drive circuit 160.
Resistance elements R161 to R163 and R164 to R166 and switches SW161 and SW162 connected in series are provided between the power supply potential and the reference potential. R162 is a variable resistor and has an independent adjustment circuit for multicolor display and low color display, and is configured to be switched by switches SW161 and SW162.

  The horizontal drive circuits 103-1 and 103-2 receive external input data, perform D / A conversion and write to the signal line, and use different buffers in the multi-color mode and the low-color mode. general.

  20 is a diagram illustrating a configuration example of the horizontal driving circuit 103 in the case of the three-line selector driving method, and FIG. 21 is a timing chart of FIG.

  FIG. 22 is a diagram illustrating a configuration example of the horizontal driving circuit 103 in the case of the 6-line selector driving method, and FIG. 23 is a timing chart of FIG.

The horizontal drive circuit 103 includes, for example, a horizontal shift register group 1031, a first latch group 1032, a second latch group 1033, a DAC and buffer unit 1034, and a switch group 1035.
Usually, the DAC section has two types of buffers for multicolor display and low color display.
The low color display buffer uses a CMOS inverter to reduce power consumption.

The low power consumption configuration described above has the following characteristics.
In a liquid crystal drive display having a multicolor display mode and a low color display mode, the signal line applied voltage in the low color display mode is lower than the signal line applied voltage in the multicolor display mode.
When shifting from the low color display mode to the multicolor display mode, no voltage is applied to the pixels during the period in which the center voltage of AC inversion driving is changing.
When shifting from the low color display mode to the multicolor display mode, black or white is displayed during a period in which the center voltage of AC inversion driving is changing. Here, black and white means that a section where the VT curve is sleeping is used.
When shifting from the low color display mode to the multicolor display mode, the low color drive is performed while the multicolor display drive is being performed during the period when the center voltage of the AC inversion drive is changing.
The drive frequency during low color display is lower than the drive frequency during multicolor display mode.
In this case, when shifting from the low color display mode to the multicolor display mode, no voltage is applied to the pixels during the period in which the center voltage of AC inversion driving is changing.
Also, when shifting from the low color display mode to the multicolor display mode, black or white is displayed during the period when the center voltage of the AC inversion drive is changing, and the drive frequency is equal to the multicolor display mode, and the multicolor display is performed. When shifting from the mode to the low color display mode, the drive frequency during the period in which the center voltage of the AC drive is changed is equal to that in the multicolor display mode, although the display is in the low color display mode.
In addition, when shifting from the low color display mode to the multicolor display mode, low color driving is performed while the center voltage of AC inversion driving is changing while the multicolor display driving is being performed, and the driving frequency is the multicolor display mode. When the transition from the multicolor display mode to the low color display mode is performed, the drive frequency during the period in which the AC drive center voltage is changing is the same as that in the multicolor display mode although the display is in the low color display mode.

  Next, the configuration and function of the monitor circuit 120 will be described in detail.

  As described above, the monitor circuit 120 is adjacent to the effective pixel unit 101 and independently (on the right side in the drawing in FIG. 4), the first monitor pixel unit 107-1, the second monitor including one pixel or a plurality of pixels. Pixel unit 107-2, monitor vertical drive circuit (V / CSDRVM) 108 for driving monitor pixels, first monitor horizontal drive circuit 109-1, second monitor horizontal drive circuit (HDRVM2) 109-2, and detection output The circuit 110 is configured.

One or a plurality of monitor (dummy) pixels constituting the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 have basically the same configuration as the pixels of the effective pixel unit 101.
24A and 24B show configuration examples of one monitor pixel of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2.

As shown in FIG. 24A, in the first monitor pixel circuit PXLCM1 of the first monitor pixel unit 107-1, the first pixel electrode is connected to the TFT 301 as a switching element and the drain electrode (or source electrode) of the TFT 301. The liquid crystal cell LC301 and the storage capacitor Cs301 in which the first electrode is connected to the drain electrode of the TFT 301.
Note that a node ND301 is formed by a connection point between the drain of the TFT 301, the first pixel electrode of the liquid crystal cell LC301, and the first electrode of the storage capacitor Cs301.

The gate electrode of the TFT 301 of the first monitor pixel circuit PXLCM1 is connected to the gate line 302.
The second electrode of the storage capacitor Cs301 of the first monitor pixel circuit PXLCM1 is connected to the same storage line 303 for each row.
Further, the source electrode (or drain electrode) of the first monitor pixel circuit PXLCM1 is connected to the signal line 304.
The second pixel electrode of the liquid crystal cell LC301 of the first monitor pixel circuit PXLCM1 is connected to a supply line 112 of, for example, a small amplitude common voltage VCOM (Vcom) whose polarity is inverted in one horizontal scanning period (1H). Yes.

  The gate line 302 is driven by the gate driver of the monitor vertical drive circuit 108, the storage line 303 is driven by the capacity driver (CS driver) of the monitor vertical drive circuit 108, and the signal line 304 is driven by the first monitor horizontal drive circuit 109-1. Driven.

In the second monitor pixel circuit PXLCM2 of the second monitor pixel unit 107-2, as shown in FIG. 7B, the first pixel electrode is connected to the TFT 311 as a switching element and the drain electrode (or source electrode) of the TFT 311. The liquid crystal cell LC311 and the storage capacitor Cs311 in which the first electrode is connected to the drain electrode of the TFT 311.
Note that a node ND311 is formed by a connection point between the drain of the TFT 311, the first pixel electrode of the liquid crystal cell LC311, and the first electrode of the storage capacitor Cs311.

The gate electrode of the TFT 311 of the monitor pixel circuit PXLCM2 is connected to the gate line 312.
The second electrode of the storage capacitor Cs311 of the second monitor pixel circuit PXLCM2 is connected to the same storage line 313 for each row.
The source electrode (or drain electrode) of the second monitor pixel circuit PXLCM2 is connected to the signal line 304.
The second pixel electrode of the liquid crystal cell LC311 of the second monitor pixel circuit PXLCM2 is connected to a supply line 112 of, for example, a small amplitude common voltage VCOM (Vcom) whose polarity is inverted in one horizontal scanning period (1H). Yes.

  The gate line 312 is driven by the gate driver of the monitor vertical drive circuit 108, the storage line 303 is driven by the capacity driver (CS driver) of the monitor vertical drive circuit 108, and the signal line 314 is driven by the second monitor horizontal drive circuit 109-2. Driven.

In the example of FIG. 4, the monitor vertical drive circuit 108 is also used. The basic function of the monitor vertical drive circuit 108 is the same as that of the vertical drive circuit 102 that drives the effective pixel unit 101.
The basic functions of the first monitor horizontal drive circuit 109-1 and the second monitor horizontal drive circuit 109-2 have the same functions as the horizontal drive circuit 103 that drives the effective pixel unit 101.

When one of the first monitor pixel circuit PXLCM1 of the first monitor pixel unit 107-1 and the second monitor pixel circuit PXLCM2 of the second monitor pixel unit 107-2 is driven as a positive pixel, the other is It is driven as a negative pixel.
The first monitor pixel circuit PXLCM1 and the second monitor pixel circuit PXLCM2 are driven and controlled so as to be alternately positive and negative pixels, for example, every horizontal scanning period (1H).

In the present embodiment, basically, after the pixel data is written from the signal lines 106-1 to 106-n (the gate pulse is applied to the gate lines 104-1 to 104-m) as the driving method of the effective pixel unit 101. After the fall, the pixel potential is changed by applying coupling from the storage lines 105-1 to 105-m independently wired to each row through the storage capacitor Cs201, and the liquid crystal applied voltage is modulated. The method is adopted.
The monitor circuit 120 includes a positive (or negative) first monitor pixel unit 107-1 and a negative (or positive) second monitor pixel unit 107-2 during actual driving by this driving method. The detection output circuit 110 detects an intermediate potential obtained by averaging the positive and negative monitor pixel potentials (corresponding to the potentials of the connection nodes ND301 and ND311 in the monitor pixel).
The monitor circuit 120 outputs the result from the output circuit of the detection output circuit 110, and automatically adjusts the center value of the common voltage Vcom.

FIG. 25 is a diagram showing a basic concept of the monitor circuit 120 according to the present embodiment.
In FIG. 25, the monitor vertical drive circuit 108, the first monitor horizontal drive circuit 109-1, and the second monitor horizontal drive circuit 109-2 are omitted for the sake of simplification of the drawing.
FIG. 25 shows an example in which the first monitor pixel unit 107-1 is driven as a positive pixel and the second monitor pixel unit 107-2 is driven as a negative pixel.

In FIG. 25, the detection output circuit 110 constituting the monitor circuit 120 includes switches 121 and 122 and a comparison output unit 123.
Further, a smoothing capacitor C120 having a common voltage Vcom connected to the output terminal TO and the input terminal TI is disposed outside the liquid crystal display panel (the liquid crystal display device 100 in FIG. 4).
In the monitor circuit 120, the first monitor pixel unit 107-1, the second monitor pixel unit 107-2, the switch 121, and the switch 122 constitute an intermediate potential detection circuit 124, and the comparison output unit 123 forms an output circuit 125. It is configured.

The fixed contact a of the switch 121 is connected to the output of the detection potential of the first monitor pixel unit 107-1, and the operation contact b is connected to the first input of the comparison output unit 123.
The fixed contact a of the switch 122 is connected to the detection potential output of the second monitor pixel unit 107-2, and the operation contact b is connected to the first input of the comparison output unit 123.
That is, the output side of the operation contact b of the switch 121 and the switch 122 is connected, and the connection point (node ND121) is connected to the first input of the comparison output unit 123.

A second input of the comparison output unit 123 is connected to a connection point (node ND122) between the input terminal TI and the supply line 112 of the common voltage Vcom.
The comparison output unit 123 outputs the common voltage Vcom whose center value is automatically adjusted to the output terminal TO.

  FIG. 26 is a circuit diagram illustrating a specific configuration example of the comparison output unit in the monitor circuit according to the present embodiment.

  26 includes a comparator (comparator) 1231, an inverter 1232 with a constant current source, a source follower 1233, and a smoothing capacitor C123.

  The comparator 1231 compares the intermediate potential VMHL of the node ND121 with the output of the source follower 1233, and outputs the result (difference potential) to the inverter 1232 with a constant current source.

The inverter with constant current source 1232 includes constant current sources I121 and T122, a p-channel MOS (PMOS) transistor PT121, and an n-channel MOS (NMOS) transistor NT121.
The gate of the PMOS transistor PT121 and the gate of the NMOS transistor NT121 are commonly connected to the output of the comparator 1231. The drain of the PMOS transistor PT121 and the drain of the NMOS transistor NT121 are connected to each other, and the connection point (node ND123) is connected to the input of the source follower 1233.
The source of the PMOS transistor PT121 is connected to the constant current source I121, and the constant current source I121 is connected to the power supply potential VDD2.
The source of the NMOS transistor NT121 is connected to the constant current source I122, and the constant current source I122 is connected to the reference potential VSS (for example, the ground potential GND).
The constant current source-equipped inverter 1232 forms a CMOS inverter, and constant current sources I121 and I122 for supplying a constant current of, for example, about 500 nA are connected to the power supply potential side (source side) and the reference potential side (source side). ing.

The source follower 1233 includes an NMOS transistor NT122 and a constant current source I123.
The gate of the NMOS transistor NT122 is connected to the node ND123 which is the output of the inverter 1232 with a constant current source. The drain of the NMOS transistor NT122 is connected to the power supply potential VDD2, the source is connected to the constant current source I123, and the connection point (node ND124) is a connection point between the second input of the comparator 1231 and the output terminal TO. It is connected to the.
A constant current source I123 is connected to a reference potential VSS (for example, ground potential GND).

  By such a comparison output unit 123, the center value of the common voltage Vcom is automatically adjusted so as to follow the intermediate potential VMHL detected by the intermediate potential detection circuit 124.

  FIG. 27 is a waveform diagram showing a flow of temporal processing in the driving method according to the present embodiment.

As shown in FIG. 27, pixel data is written from the signal lines 106-1 to 106-n at time t1, and the gate pulse to the gate lines 104-1 to 104-m is lowered at time t2 after a predetermined time has elapsed. Then, the TFT 201 of the pixel circuit PXLC is turned off.
At time t3, coupling is applied from the storage lines 105-1 to 105-m independently wired to each row through the storage capacitor Cs201, thereby changing the pixel potential and modulating the liquid crystal applied voltage.
After holding the potential for a predetermined time, when the switches 121 and 122 of the intermediate potential detection circuit 124 are turned on at time t4, both potentials are short-circuited at the node ND121 and are averaged as a result.
In the example of FIGS. 25 and 26, the pixel potential VpixlH of the first monitor pixel circuit PXLCM1 of the first monitor pixel unit 107-1 which is a positive pixel is 5.9V, and the second monitor pixel unit 107 which is a negative pixel. The pixel potential VpixL of the second monitor pixel circuit PXLCM2 of −2 is −2.8V.
Therefore, 1.55 V is detected as the intermediate potential VMHL, and is input to the comparison output unit 123 at time t4.
Then, the center value of the common voltage Vcom is automatically adjusted by the comparison output unit 123 so as to follow the intermediate potential VMHL detected by the intermediate potential detection circuit 124.

  Next, the reason why the liquid crystal display panel is provided with a system for automatically adjusting the center value of the common voltage Vcom will be described.

When the center value of the common voltage Vcom is not adjusted, there is a problem that flicker occurs on the front screen. In addition, since the voltage applied to the liquid crystal layer differs depending on the positive and negative polarity, a problem of image sticking occurs.
As measures against these, it is necessary to adjust the center value of the optimum common voltage Vcom in the inspection process at the time of shipment before shipping. In this inspection process, it is necessary to separately provide an adjustment circuit or the like, which requires troublesome work.
In addition, even if the common voltage Vcom center value is optimally adjusted in the inspection process, due to changes in temperature, drive method, drive frequency, backlight (B / L) brightness, external light brightness during continuous use, and continuous use The center value of the common voltage Vcom shifts from the optimum value, and the same problem occurs.

  Since the liquid crystal display device 100 according to the present embodiment has a system for automatically adjusting the center value of the common voltage Vcom formed in the liquid crystal display panel, an inspection process at the time of shipping which requires complicated work is unnecessary, and the liquid crystal display device 100 is in use. Even if the center value of the common voltage Vcom is shifted from the optimum value due to changes in temperature, drive system, drive frequency, backlight (B / L) brightness, and external light brightness, the center value of the common voltage Vcom depends on the usage situation. Therefore, there is an advantage that the occurrence of flicker can be adaptively suppressed.

In addition, the effective pixel potential of the effective pixel portion 101 varies due to coupling at the time of falling of the gate line or due to current leakage in the TFT 201 which is a pixel transistor, and as a result, the optimum center value of the common voltage Vcom varies. To do.
However, as in the present embodiment, by adjusting the center value of the common voltage Vcom to an optimum value, it is possible to suppress the influence on the image quality due to the effective pixel potential fluctuation.

  Hereinafter, the mechanism of the potential fluctuation of the effective pixel will be considered.

FIG. 28 is a diagram illustrating an ideal state according to the driving method of the present embodiment.
Note that the voltage values and the like shown in FIG. 28 are shown for ease of understanding, and may differ from actual driving.

As shown in FIG. 28, if the pixel potential is ideal, the amplitude is symmetrical with respect to the center potential of the video signal Sig.
If the pixel potential Pix vs. Vcom potential difference is equal between the positive (+) polarity and the negative (−) polarity, the luminance difference does not occur and the flicker becomes invisible.
That is, the Pix vs. Vcom potential is equal to both +/− polarity, and the center value of the video signal Sig should be the optimum Vcom value.
However, the actual optimum Vcom value is lower than the center value of the video signal Sig. This is considered to be due to coupling at the fall of the gate line or due to current leakage in the TFT 201 which is a pixel transistor.

<Gate coupling>
FIGS. 29A and 29B are diagrams illustrating the relationship between the pixel potential Pix and the Vcom potential difference between the positive (+) polarity and the negative (−) polarity in the driving method according to the present embodiment.
The coupling in the + direction of the gate (Gate) of the TFT 201 is canceled because the pixel transistor TFT 201 is on, but the coupling in the − direction is not canceled and the pixel potential is dropped.
Then, if Vcom potential = Sig center potential, the Pix-to-Vcom potential becomes non-uniform with +/− polarity and is not the optimum common voltage Vcom.

<Leakage of pixel transistor>
FIG. 30 is a diagram schematically illustrating a leak factor of the pixel transistor.
The pixel transistor leak includes a leak to the signal line (TFT source (S) -drain (D) leak) and a gate line charge / discharge (TFT source (S) -gate (G) leak). Leak).
As a result of combining the S-D leak and the S-G leak, the pixel potential (Pix potential) drops.
As a result, the pixel potential (Pix potential) is affected by an increase in the current Ioff due to light and a change in the holding period due to the frequency.

FIGS. 31A and 31B are diagrams collectively showing states due to gate coupling and pixel transistor leakage in the positive (+) polarity and the negative (−) polarity in the driving method according to the present embodiment.
In FIGS. 31A and 31B, broken lines indicate waveforms when there is no gate coupling and pixel transistor leakage, and solid lines indicate waveforms when there is gate coupling and pixel transistor leakage.
-On the polar side, the direction of the leak between S-D and the leak between S-G is opposite, so the actual direction depends on which leak is more.
On the + polar side, both the S-D leak and the S-G leak are directed in the same direction in which the pixel potential drops.
In this manner, the pixel potential drops (drops) due to gate coupling and / or pixel transistor leakage, and the optimum Vcom value shifts downward.

  In the present embodiment, by automatically adjusting the center value of the common voltage Vcom to the optimum value, it is possible to suppress the influence on the image quality due to the effective pixel potential fluctuation.

FIG. 32 is a diagram illustrating items in which the influence of the pixel potential variation factor can be suppressed by automatically adjusting the center value of the common voltage Vcom according to the present embodiment. In FIG. 32, items to be suppressed by the inspection process are shown for comparison and comparison.
According to the present embodiment, even in the inspection process, it is possible to suppress the influence of fluctuations in driving frequency, temperature, and aging during actual use due to off-leakage of pixel transistors that cannot be suppressed.
In addition, according to the present embodiment, even in the inspection process, it is possible to suppress the influence of fluctuations in driving frequency, temperature, backlight luminance, and external light luminance during actual use due to light leakage of pixel transistors that cannot be suppressed.

The automatic adjustment of the center value of the common voltage Vcom has been described above.
Next, the pixel arrangement of the monitor pixel unit according to this embodiment will be considered.

In the present embodiment, as described above, the first monitor pixel unit 107-1 and the second monitor that include one pixel or a plurality of pixels independently adjacent to the effective pixel unit 101 (on the right side in FIG. 4). Pixel unit 107-2, monitor vertical drive circuit (V / CSDRVM) 108 for driving monitor pixels, first monitor horizontal drive circuit 109-1, second monitor horizontal drive circuit (HDRVM2) 109-2, and detection output A monitor circuit 120 constituted by the circuit 110 is formed.
The reason is shown below.

As shown in FIG. 33, the monitor pixel is formed as a part of the effective pixel portion 101 so as to include, for example, one row or one pixel, and the vertical drive circuit 102 and the horizontal drive circuit 103 that are the same as the effective pixel portion 101 are used as gate lines. Further, it is possible to form a monitor pixel potential equivalent to that of the effective display pixel by driving the storage line and the signal line.
However, in this configuration, the monitor pixel requires the same potential as the display pixel, so the configuration of the monitor pixel portion cannot be changed greatly, and it is arranged only at the upper end or lower end of the effective pixel portion (effective display area) (horizontal placement). Cannot be placed).
Further, since the same drive signal (control signal) as that of the display pixel is used, the degree of freedom of the control signal is low. Further, since the signal line is also shared with the display area, there is a problem that the influence of the coupling from the signal line cannot be ignored.
According to the driving method of this embodiment, it is possible to perform optimum correction by performing detection in the middle of one frame period after writing to the monitor pixel.
However, as shown in FIG. 34, since the monitor pixel potential fluctuates due to the influence of the signal line that fluctuates depending on the display pixel in the middle of one frame period, the blanking period of the video signal must be corrected. .
In addition, it is difficult to dispose the positive and negative polar pixels necessary for the above-described system for automatically adjusting the center value of the common voltage Vcom.
Therefore, in the present embodiment, the first monitor pixel unit 107-1, the second monitor pixel unit 107-2, the monitor vertical drive circuit 108, and the monitor horizontal drive circuit 109-1 are provided adjacent to the effective pixel unit 101 independently. , 109-2, the monitor circuit 120 is formed.

Further, when the monitor pixel portion is formed by a plurality of monitor pixel circuits, as shown in FIGS. 35A and 35B, when the gate lines are simply shared (shared) by the plurality of monitor pixels, The amount of gate coupling will change.
As shown in FIG. 35A, when the monitor pixel arrangement is set horizontally and the gate line is shared, it is affected by the gate coupling of adjacent pixels.
In addition, as shown in FIG. 35B, when the gate line is shared with the monitor pixel arrangement set vertically, not only the own pixel but also the gate coupling of the adjacent pixel is received at the same time, so that the amount of drop of the pixel potential is large. .
Therefore, in the present embodiment, as shown below, the gate lines are arranged so-called in a nested manner, so that even if the monitor pixels are placed vertically, the gate coupling is configured only for the own line. Is preferred.

  FIG. 36 is a diagram illustrating a pixel arrangement example in the monitor pixel unit according to the present embodiment. FIG. 37 is a diagram showing an example of drive waveforms of the monitor pixel portion of FIG.

  The monitor pixel unit 107A illustrated in FIG. 36 illustrates an example in which 16 pixel circuits PXLCM11 to PXLCM44 are arranged in a 4 × 4 matrix. The number of pixels arranged in a matrix is not limited to this.

In the monitor pixel portion 107A, regions ARA1 and ARA2 divided in the row direction in the matrix pixel array are formed.
In each row of the pixel array, a first monitor pixel circuit ARA11 for idle driving (indicated by pixA in the figure) that is not used for actual monitoring, and a second monitor pixel (in the figure, used as actual monitor pixels). A region ARA21 (shown by pixB) is formed.
In each of the binary regions ARA1 and ARA2, the first monitor pixel region ARA11 and the second monitor pixel region ARA21 are alternately arranged for each row in the column direction.
Therefore, the first monitor pixel pixA and the second monitor pixel pixB are arranged in a zigzag manner in the column direction of the pixel array.

As shown in FIG. 36, the first monitor pixel circuit pixA and the second monitor pixel circuit pixB of the monitor pixel unit 107 have the TFT 321 as a switching element and the first pixel electrode connected to the drain electrode (or source electrode) of the TFT 321. The liquid crystal cell LC321 thus formed and a storage capacitor Cs321 having a first electrode connected to the drain electrode of the TFT 321.
Note that a node ND321 is formed by a connection point of the drain of the TFT 321, the first pixel electrode of the liquid crystal cell LC321, and the first electrode of the storage capacitor Cs321.

In the monitor pixel unit 107A of FIG. 36, the first gate line GT1 and the second gate line GT2 are used as the gate lines, and the first monitor pixel area ARA11 in the first monitor line area ARA11 is used with respect to the first gate line GT1. The gate electrode of the TFT 321 of the monitor pixel pixA is connected, and the gate electrode of the TFT 321 of the second monitor pixel pixB of the second monitor pixel area ARA21 is connected to the second gate line GT2.
The node ND321 of the second monitor pixel pixB is connected by a conductive wiring such as ITO. The node ND321 of the second monitor pixel circuit PXLCM42 in the 4th row and the 2nd column is connected to the detection output circuit 110.
In the example of FIG. 36, pixel circuits PXLCM13, PXLCM22, PXLCM33, and PXLCM42 are allocated as actual monitor pixels.

The second electrodes of the storage capacitors Cs321 of the first monitor pixel pixA and the second monitor pixel pixB are connected to the same storage line L321 for each row.
The source electrodes (or drain electrodes) of the first monitor pixel pixA and the second monitor pixel pixB arranged in the same column are connected to signal lines L322-1 to L322-4, respectively.
The second pixel electrodes of the first monitor pixel pixA and the second monitor pixel pixB are connected to a supply line of, for example, a small amplitude common voltage VCOM (Vcom) whose polarity is inverted in one horizontal scanning period (1H). Yes.

As shown in FIG. 37, the monitor pixel unit 107 first drives the first gate line GT1, and the first monitor pixel pixA is driven idle. Here, the gate coupling for the adjacent line is received here, but it returns to the original timing at the fall of the first gate line GT1.
Next, the second gate line GT2 is driven, and the second monitor pixel pixB is fully driven. In this case, the gate coupling is only for the own pixel and does not receive the gate coupling of the adjacent pixel. Therefore, the amount of pixel potential dropped can be made equal to that of the pixel circuit PXLC of the effective pixel unit 101.
As described above, in this embodiment, the gate lines of the monitor pixels can be limited to the own line by arranging the gate lines in a so-called nested manner.

  The monitor pixel unit shown in FIG. 36 can be applied to the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 in FIG.

As described above, in the present embodiment, the first monitor pixel unit 107-1, the second monitor pixel unit 107-2, the monitor vertical drive circuit 108, and the monitor horizontal drive circuit 109 are independently adjacent to the effective pixel unit 101. -1, 109-2 are formed, and the gate lines are arranged so as to be nested, so that there is an advantage that the degree of freedom in panel design is increased.
This facilitates the arrangement of the constituent circuits of the monitor circuit 120, that is, the first monitor pixel unit 107-1, the second monitor pixel unit 107-2, the monitor vertical drive circuit 108, and the monitor horizontal drive circuits 109-1 and 109-2. It becomes.
As shown in FIG. 4, it is possible to arrange all the constituent circuits of the monitor circuit 120 on the right side in the drawing adjacent to the effective pixel portion 101, and it is possible to arrange them in various modes.
For example, as shown in FIG. 38A, the effective pixel portion 101 may be arranged separately on the right side and the upper side in the drawing. As shown in FIG. 38B, the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 can be arranged in parallel, and the monitor horizontal drive circuit can be arranged in parallel.

  In addition, it is possible to have the vertical and horizontal drive circuits dedicated to the monitor pixel unit separately from the effective pixel unit 101, which solves the above-described problem that the signal line amplitude problem can be detected only during the blanking period. it can.

By the way, as described above, when effective pixels (display pixels) and monitor pixels are individually arranged and driven, there is a concern about a shift from the target monitor pixel potential due to a structural difference.
Therefore, in this embodiment, a circuit that adjusts the shift of the monitor potential from the target potential is employed.

In the present embodiment, in the monitor circuit 120, a pair of monitor pixel units 107-1 and 107-2 having positive (+) / negative (-) polarity are arranged, and both monitor pixel units 107-1 and 107-2 are arranged. A system that adjusts (corrects) the potential (center value) of the common voltage Vcom by generating an average potential by short-circuiting the detection pixel potential is employed.
Although this potential should match the Vcom potential of the effective pixel, if the monitor pixel and the display pixel (effective pixel) are arranged independently, for example, as shown in FIG. 39, a liquid crystal cell gap, an interlayer insulating film, etc. There is a possibility that the difference between the display pixel and the physical property value is caused by the variation in the panel surface.
For example, variation in the liquid crystal cell gap affects the liquid crystal capacitance, and variation in the interlayer insulating film affects, for example, the storage capacitance, the gate parasitic capacitance of the TFT, and the transistor characteristics.
In such a case, an error may occur in the monitor circuit and the target value may be shifted.
This problem can be solved by, for example, the following two different methods and combinations thereof.
The first is a method in which signals having different amplitudes are written to the monitor pixels to correct the detected pixel potential by offsetting.
The second is a method of correcting by offsetting the detected pixel potential by adding a capacity to the monitor pixel.
In addition to these, the shift can be canceled by the first method, the second method, or a combination of both methods.

  First, offset correction by the potential of the signal Sig in the first method will be described.

  40A and 40B are diagrams for explaining offset correction based on the potential of the signal Sig.

In the first method, the solution is achieved by shifting the potential of the monitor pixel with respect to the above-mentioned shift.
In this embodiment, a pair of monitor pixel portions are provided, but signals having different amplitudes are written to the monitor pixel portions.
Since the detection pixel potential is generated by short-circuiting the output of the monitor pixel, it is possible to shift the detection pixel potential.
In this example, the case of shifting the writing on the negative side is described, but it is also possible to shift the detection potential by changing the amplitude of Sig +.

  FIG. 41 is a diagram illustrating a first configuration example of a circuit capable of realizing offset correction based on the potential of the signal Sig.

This circuit includes, for example, a first monitor horizontal drive circuit 109-1 and a second monitor horizontal drive circuit 109-2 provided corresponding to the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2, respectively. The write circuit 1091-1 exclusively for the positive polarity monitor pixel and the write circuit 1091-2 exclusively for the negative polarity monitor pixel are arranged at the output stage, and the amplitude of the video signal Sig is controlled independently.
The write circuits 1091-1 and 1091-2 include a digital / analog converter DAC and an amplifier amp.

  FIG. 42 is a diagram illustrating a second configuration example of the circuit capable of realizing the offset correction based on the potential of the signal Sig.

This circuit includes, for example, a first monitor horizontal drive circuit 109-1 and a second monitor horizontal drive circuit 109-2 provided corresponding to the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2, respectively. In the output stage, division resistor groups DRG1 and DRG2 are provided instead of the DAC, and the amplitude of the video signal Sig is independently controlled.
In the example of FIG. 42, the divided resistors of the divided resistor groups DRG1 and DRG2 are configured to be switched by the switch SW. However, it is also possible to adopt a method in which the resistors are separated and controlled by, for example, laser repair. It is.

  Note that these detection system and Sig writing system are not necessarily formed integrally in the LCD panel. For example, as shown in FIGS. 43 (A) and 43 (B), an external IC such as COG or COF is provided. It can also be realized.

  First, offset correction by the additional capacity of the second method will be described.

  FIG. 44 is a diagram for explaining an outline of offset correction by an additional capacitor.

In the second method, an additional capacitor COFS is added to the potential detection node ND321 of the monitor pixel PXLCM to adjust the charge amount of the monitor pixel.
A detection pixel offset can be achieved by attaching a capacitance COF to both the positive monitor pixel and the negative monitor pixel and adjusting the additional capacitance by laser repair or switching.
The example of FIG. 44 shows an example in which a capacitor is added by switching of the offset switch SWOF.

  FIG. 45 is a circuit diagram showing a configuration example of an intermediate potential detection circuit that employs offset correction using an additional capacitor.

The intermediate potential detection circuit 124A of FIG. 45 has an additional capacitance COF107 composed of a plurality of capacitance elements (capacitors) arranged in parallel to the node ND301 of the first monitor pixel unit 107-1 via a switch SW107-1 by an NMOS transistor. -1 is connected to the node ND311 of the second monitor pixel unit 107-2 and an additional capacitor COF107-2 including a plurality of capacitors (capacitors) arranged in parallel via a switch SW107-2 by a PMOS transistor is connected. Has been.
The gate electrode (control electrode) of the switch SW107-1 is connected to the supply line of the offset signal SOFST via the inverter INV107, and the gate electrode (control electrode) of the switch SW107-2 is connected to the supply line of the offset signal SOFST. ing.
In the example of FIG. 35, the first monitor pixel unit 107-1 is shown as a positive pixel, and the second monitor pixel 107-2 is shown as a negative pixel. In the example of FIG. 35, the switches 121 and 122 for short-circuiting and averaging the detection pixel potential are formed by transistors.

  FIG. 46 is a timing chart illustrating an example of connection timing of additional capacitors.

As shown in FIG. 46, during the pixel potential detection period, the offset signal SOFST is set to an active low level, and the additional capacitors COF 107-1 and COF 107-2 are connected to nodes ND301 and ND311 for potential detection.
On the other hand, during the non-detection period, the offset signal SOFST is set to the high level, and the additional capacitors COF 107-1 and COF 107-2 are not connected to the nodes ND301 and ND311.
In addition, since the additional capacitor is connected during the additional capacitor connection period, the CS coupling amount decreases.

  FIG. 47 is a diagram showing a pixel potential short model of the detection pixel potential offset correction circuit, and a model expression of the detection pixel potential offset correction circuit based on this model is shown below.

Below is an example of a model formula.
48 (1) and 48 (2) are diagrams showing pixel potential waveforms when the additional capacitance value is changed.
The following equation shows the center value of the common voltage Vcom when the additional capacitance is changed using the above equation (2).

  From the results of [1] and [2], the offset of the detected pixel potential can be corrected from the offset of the detected pixel potential.

  FIG. 49 is a diagram illustrating a configuration example in which the constant of the additional capacitor COF is changed.

The constant of the additional capacitor COF can be controlled by turning on and off the switch SWOF by the control signal CTL as shown in FIG.
Alternatively, it is possible to set the constant of the additional capacity COF by physically separating with a laser.

Further, as described above, the effective pixel (display pixel) and the monitor pixel are individually arranged and driven, the monitor pixel potential is detected, and the detection pixel potential is short-circuited through the switches 121 and 122. It is configured to average.
In this configuration, after the short-circuiting operation, there is a possibility that the potential of the pixel may be deteriorated such as burn-in, depending on whether the detection pixel potential of the monitor pixel is short-circuited or not.
Therefore, in the present embodiment, rewriting is performed after the detection pixel potential is short-circuited to correct the potential deviation and to perform electrical protection.

In the present embodiment, an average potential is generated by adjusting the center value of the common voltage Vcom by short-circuiting the detection pixel potential of the monitor pixel having the positive (+) / negative (−) polarity.
As shown in FIG. 50A, the liquid crystal is normally driven by alternating current so as not to cause a potential bias.
However, in a system that repeatedly repeats the short and open states of the switches that alternately detect monitor pixel potentials, there is a concern that potential bias may occur, as shown in FIG.
When short-circuited, the potential is biased because the period of negative polarity is shortened.
In the example of FIG. 50, the negative polarity side is short, but the detection pixel that is paired has a short positive polarity.

  FIG. 51 is a diagram for explaining a method of preventing potential bias from being caused by monitor pixel potential short processing.

If the detection system (detection output circuit 110) reads a desired potential, it is not necessary to maintain the short state.
Therefore, the same potential as before the short circuit is written again after the detection is completed.
Before rewriting, it is necessary to prepare for rewriting. This system will be described later.

  FIG. 52 is a diagram for more specifically explaining a method for preventing the potential bias caused by the short process of the monitor pixel potential.

The pixel potential is written through a TFT (pixel transistor), and then a desired potential is obtained by CS coupling.
Since coupling is performed once at the time of the first writing, it is necessary to devise in order to provide this CS coupling at the time of rewriting.
For this reason, the preparatory operation is once swung in the direction opposite to the CS coupling direction (the H / L direction changes depending on the pixel polarity). That is, as a preparatory operation, CS coupling is once performed in the direction opposite to the CS coupling direction.
Of course, the pixel potential is also affected by swinging in the reverse direction, but if it is performed immediately before the gate pulse for rewriting comes, it is rewritten with a normal signal, so the influence can be canceled.

FIG. 53 is a diagram illustrating a first configuration example of a potential bias suppression circuit that does not cause potential bias due to a short process of the monitor pixel potential.
54A and 54B are timing charts of the circuit of FIG.

53 has a two-input ORG gate 401 that inputs and outputs a normal write transfer pulse (vertical start pulse) VST or a rewrite transfer pulse VST2, and an output from the OR gate 401. It is set by cascaded shift registers (SRG) 402 to 403 and a normal write transfer pulse VST, reset by a pulse V3 by the last stage shift register 404, and is active at a low level from the inverted output XQ. SR-type flip-flop (SRFF) 405, a 3-input AND gate 406 that takes the logical product of the output pulse V2, the masking signal MSK, and the enable signal ENB of the shift register 403 in the middle stage, and the polarity recognition pulse POL AND gate 406 CS reset signal Cs by entering the force signal S406 A CS reset circuit 407 that outputs reset and an output pulse V3 of the shift register 404 are latched in synchronization with the polarity recognition pulse POL, and a CS reset signal Cs It has a CS latch circuit 408 that resets latch data by reset, and an output buffer 409 that outputs the output of the CS latch circuit 408 as a storage signal CS.

As described above, the potential deviation suppression circuit 400 of FIG. 53 includes the CS reset circuit 407 so that rewriting can be prepared.
The CS reset circuit 407 recognizes the polarity of the storage signal CS and performs reset (preparation for rewriting) in the direction opposite to the current direction. At this time, the pulse V2 of the preceding shift register 403 is used so that preparation can be made immediately before rewriting.
Also, it is necessary to determine the current polarity in order to swing in the reverse direction. For this purpose, a polarity recognition pulse POL synchronized with the polarity is input.
During the masking, the CS reset signal Cs The reset is not output.
In this example, pixel writing is performed at the timing of the pulse V3.

FIG. 55 is a diagram illustrating a second configuration example of the potential deviation suppression circuit that does not cause potential deviation due to the short process of the monitor pixel potential.
56A and 56B are timing charts of the circuit of FIG.

In the potential bias suppression circuit 400A of FIG. 55, the SRFF for masking is deleted from the potential bias suppression circuit 400 of FIG. 53 in order to simplify the circuit configuration, although it is not immediately before preparation for rewriting. In this case, it is possible to prepare for rewriting at the timing of the transfer pulse VST2.
The potential bias suppression circuit 400A of FIG. 55 is useful if the reset period is long but negligible.

  It should be noted that it does not matter whether these potential deviation suppression circuits are integrally molded by LTPS or externally attached such as COG and COF.

  Next, the gate line wiring in the monitor circuit 120 will be considered.

As described above, in the present embodiment, the gate line in which the gate lines are arranged so as to be nested is employed, but basically the time constants of the display pixel (effective pixel) and the monitor pixel gate line are set. If they do not match, there is a difference between the pixel potentials of the two. Assuming that the pixel potentials of both are equal, the Vcom center value and the output of the correction circuit of CS and Sig described later may be shifted.
Therefore, an adjustment resistor is provided on the monitor pixel side having a small time constant. More specifically, the shape of the gate line of the monitor pixel is devised so that it becomes a resistor. Thereby, the effective pixel and the time constant are matched to solve the above problem.

57A to 57C are diagrams for explaining the cause of the time constant deviation of the gate line, and FIG. 57A is a diagram showing an equivalent circuit of the pixel, and FIG. ) Is a diagram comparing gate waveforms, and FIG. 57 (C) is a diagram for explaining the cause of the time constant deviation in time series.
As shown in FIGS. 57A to 57C, due to the rounding of the gate waveform, charge reinjection occurs from the liquid crystal capacitance Ccl, and the pixel potential shifts.
If the gate waveform is different, the monitor pixel (detection pixel) potential shifts. As a result, the correction function may not operate normally.

  58A and 58B are diagrams showing a layout model of effective pixels and a layout model of monitor pixels (detection pixels) in the present embodiment.

  In the present embodiment, the gate lines GT2 and GT1 on the monitor circuit 120 side are arranged by bending (meandering) the wires as shown in FIG. 57B in order to adjust the time constant. In this case, the time constant is adjusted by the number of bendings.

  FIGS. 59A and 59B are diagrams showing an example of a method for matching the time constants of the gate lines.

  In this example, the resistor wiring layout is devised so that the time constants of the measurement points MPNT1 and MPNT2 of the effective pixel load model and the monitor pixel (detection pixel) load model coincide.

  FIGS. 60A to 60C are diagrams illustrating an example in which layout options are used in the method of matching the time constants of the gate lines.

  In this example, the normal layout can be changed to option layouts 1 and 2 or parallel wiring. If the detection potential becomes abnormal after manufacturing, the time constant can be adjusted by laser repair.

The automatic adjustment (correction) system for the center value of the common voltage Vcom has been described above.
Next, the value of the common voltage Vcom according to the present embodiment will be described.

  In the present embodiment, for example, the second pixel electrode of the liquid crystal cell LC201 of all the pixel circuits PXLC of the effective pixel unit 101 is supplied through the supply line 112 as a common voltage Vcom having a small amplitude whose polarity is inverted every horizontal scanning period (1H). , And supplied to the second electrodes of the liquid crystal cells LC301 and LC311 of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 of the monitor circuit 120.

The value of the amplitude ΔVcom of the amplitude of the common voltage Vcom is selected such that the black luminance and the white luminance can be optimized together with the difference ΔVcs between the first level of the storage signal CS and the CSH and the second level CSL.
For example, as will be described later, the effective pixel potential ΔVpix applied to the liquid crystal during white display. The values of ΔVcs and ΔVcom are determined so that W becomes a value of 0.5V or less.

  As the common voltage generation circuit, a configuration provided in the liquid crystal panel may be employed, or the common voltage generation circuit may be disposed outside the panel and supplied with the common voltage Vcom from the outside of the panel.

Small amplitudes can be used using capacitive coupling (digital coupling) or digitally generated.
The value of the small amplitude ΔVcom is preferably as small as possible, for example, about 10 mV to 1.0 V. The reason is that otherwise, effects such as improvement of response speed by overdrive and reduction of acoustic noise are reduced.

As described above, in the liquid crystal display device 100, when performing capacitive coupling drive using capacitive coupling, the value of the amplitude ΔVcom of the amplitude of the common voltage Vcom, the first level, the CSH, and the second level of the storage signal CS. The value of the difference ΔVcs from the CSL is selected to be a value that can optimize both the black luminance and the white luminance.
For example, the effective pixel potential ΔVpix applied to the liquid crystal during white display The values of ΔVcs and ΔVcom are determined so that W becomes a value lower than 0.5V.
Hereinafter, the capacitive coupling driving method according to the present embodiment will be described in more detail.

61A to 61E are timing charts showing driving waveforms of main liquid crystal cells of this embodiment.
FIG. 61A shows the gate pulse GP. N, FIG. 61B shows the common voltage Vcom, and FIG. 61C shows the storage signal CS. N, FIG. 61D shows the video signal Vsig, and FIG. 61E shows the signal Pix applied to the liquid crystal cell. N is shown respectively.

In the capacitive coupling driving according to the present embodiment, the common voltage Vcom is not a constant DC voltage but is generated as a small amplitude AC signal whose polarity is inverted every horizontal scanning period (1H), and the liquid crystal of each pixel circuit PXLC. The voltage is applied to the second pixel electrode of the cell LC201 and the second electrodes of the liquid crystal cells LC301 and LC311 of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 of the monitor circuit 120.
The storage signal CS N is a first level (CSH, for example, 3V to 4V) or a second level (CSL) for each storage line 105-1 to 105-m independently wired corresponding to each gate line of the effective pixel unit 101. For example, 0V).
The effective pixel potential ΔVpix applied to the liquid crystal when driven in this way is given by the following equation.

As shown in FIG. 62, in the equation (7), Vsig is a video signal voltage, Ccs is a holding capacitor, Clc is a liquid crystal capacitor, Cg is a capacitor between the node ND201 and the gate line, and Csp is between the node ND201 and the signal line. The capacitance, ΔVcs indicates the potential of the signal CS, and Vcom indicates the common voltage.
In Equation (7), the second term {(Ccs / Ccs + Clc) * ΔVcs} of the approximate expression is a term that causes the white luminance side to become black (sink) due to the nonlinearity of the liquid crystal dielectric constant, and the third term of the approximate expression. {(Ccl / Ccs + Clc) * ΔVcom / 2} is a term for making the white luminance side white (floating) due to the nonlinearity of the liquid crystal dielectric constant.
That is, the second potential of the approximate expression is compensated for by the function of making the low potential side white (floating) according to the third term.
The optimum contrast can be obtained by selecting values that can optimize both the black luminance and the white luminance.

63A and 63B show the effective pixel potential ΔVpix applied to the liquid crystal during white display when the liquid crystal material (normally white liquid crystal) used in the liquid crystal display device is used. It is a figure for demonstrating the selection criteria of W. FIG. 63A is a diagram showing the characteristic of the relative dielectric constant ε with respect to the applied voltage, and FIG. 63B is an enlarged diagram showing a region where the characteristic of FIG. 63A greatly changes.

As shown in the figure, in the liquid crystal characteristics used in the liquid crystal display device, when a voltage of about 0.5 V or more is applied, white luminance is reduced.
Therefore, in order to optimize the white luminance, the effective pixel potential ΔVpix applied to the liquid crystal at the time of white display. W needs to be 0.5V or less. Therefore, the effective pixel potential ΔVpix The values of ΔVcs and ΔVcom are determined so that W is 0.5V or less.

  As a result of actual evaluation, an optimum contrast was obtained when ΔVcs = 3.8V and ΔVcom = 0.5V.

FIG. 64 is a diagram showing the relationship between the video signal voltage and the effective pixel potential in the driving method, the related capacitive coupling driving method, and the normal 1HVcom driving method according to the embodiment of the present invention.
In FIG. 64, the horizontal axis represents the video signal voltage Vsig, and the vertical axis represents the effective pixel potential ΔVpix. In FIG. 54, the line indicated by A indicates the characteristic of the driving method according to the embodiment of the present invention, the characteristic indicated by C indicates the characteristic of the capacitive coupling driving method, and the line indicated by B indicates the normal 1HVcom driving method. The characteristics are shown.

  As can be seen from FIG. 64, according to the driving method according to the present embodiment, a sufficient characteristic improvement is obtained as compared with the related capacitive coupling driving method.

FIG. 65 is a diagram showing the relationship between the video signal voltage and the luminance in the driving method according to the embodiment of the present invention and the related capacitive coupling driving method.
In FIG. 65, the horizontal axis represents the video signal voltage Vsig, and the vertical axis represents the luminance. In FIG. 65, the line indicated by A indicates the characteristic of the driving method according to the embodiment of the present invention, and the characteristic indicated by the line B indicates the characteristic of the capacitive coupling driving method.

  As can be seen from FIG. 65, in the related capacitive coupling driving method, when the black luminance (2) was optimized, the white luminance (1) was sunk. On the other hand, according to the driving method according to the present embodiment, both black luminance (2) and white luminance (1) can be optimized by setting Vcom to a small amplitude.

In the following number (5), the effective pixel potential ΔVpix during black display and black display when a specific numerical value is set in the number (4) of the driving method according to the present embodiment. Effective pixel potential ΔVpix when displaying B and white The value of W is shown.
Further, the effective pixel potential ΔVpix at the time of black display and the black display when a specific numerical value is set to the above-described number (1) of the capacitive coupling driving method related to the number (6). B and effective pixel potential ΔVpix The value of W is shown.

As shown in the equations (8) and (9), in the case of black display, the effective pixel potential ΔVpix is used for both the driving method and the driving method according to the present embodiment. B is 3.3 V, and the black luminance is optimized.
At the time of white display, as shown in the equation (9), the effective pixel potential ΔVpix of the related driving method. W becomes 0.8V of 0.5V or more, and the white luminance is reduced as described in relation to FIG.
On the other hand, the effective pixel potential ΔVpix of the driving method according to the present embodiment. W becomes 0.4V which is 0.5V or less, and the white luminance is optimized as described with reference to FIG.

  Next, the potential Vcs of the storage signal CS, which is one of the features of this embodiment, is applied to the positive or negative first monitor pixel unit 107-1 of the monitor circuit 120 and the negative or negative polarity by the correction circuit 111. A specific configuration example will be described in which correction is made in accordance with the detected pixel potential of the positive second monitor pixel unit 107-2 and the optical characteristics are optimized.

  In this embodiment, the applied voltage of the liquid crystal is changed due to a change in the dielectric constant of the liquid crystal due to a change in driving temperature, a change in the film thickness of the insulating film forming the storage capacitor Cs201 due to variations in mass production, and a change in the liquid crystal cell gap. It will fluctuate. This change is detected electrically (detected as a change in the potential of the monitor pixel), and the change due to variations in display temperature and mass production is suppressed by suppressing the change in the liquid crystal applied voltage.

  That is, in the present embodiment, a dummy pixel (sensor pixel) that monitors variation variation during mass production or temperature variation is arranged in the liquid crystal panel, and the potential of the capacitance line or the reference driver is detected by detecting the variation. A liquid crystal display device capable of optimizing the brightness and optimizing (correcting) the luminance is realized.

Note that the reference driver not shown in FIG. 4 functions as a gradation voltage generation circuit that generates video pixel data to be propagated to the signal line.
That is, the reference driver is corrected according to the detection pixel potential of the first monitor pixel unit 107-1 having the positive or negative polarity of the monitor circuit 120 and the second monitor pixel unit 107-2 having the negative or positive polarity. The system functions as a correction system for the potential Vsig of the signal Sig.

As described above, the liquid crystal display device 100 of the present embodiment includes the positive or negative first monitor pixel unit 107-1 and the negative or positive second monitor pixel unit 107-2 of the monitor circuit 120. As shown in FIG. 56, a correction system that receives and detects the detected pixel potential is a Vcom correction system 110A (detection output circuit 110 of the monitor circuit 120) as a first correction system, and a second correction system. Vcs correction system 111A (correction circuit 111) and a Vsig correction system 113 as a third correction system.
The Vcom correction system 110A includes a comparator (Cmp) 1101 and an amplifier (Amp) 1102 as main components.
The Vcs correction system 111A includes a comparator (Cmp) 1111 and an amplifier (Amp) 1112 as main components.
The Vsig correction system 113 includes a comparator (Cmp) 1131 and a reference driver 1132 including an amplifier as main components.
Note that the detection pixel portions (monitor pixel portions) 107A, 107B, and 107C shown in FIG. 56 are the positive or negative first monitor pixel portion 107-1 of the monitor circuit 120 and the negative or positive second. A functional configuration equivalent to that of the monitor pixel unit 107-2 is included.

The configuration of FIG. 66 is an example in which three systems of detection pixel units 107A, 107B, and 107C are provided corresponding to each correction system.
However, this causes an increase in circuit area.
Therefore, in the present embodiment, as shown in FIG. 57, one detection pixel unit 107 is formed, and this detection pixel potential output is switched by the switch circuit 114, and each Vcom correction system 110A, Vcs correction system 111A, and The signal is selectively input to the Vsig correction system 113.
FIG. 67 is a diagram illustrating a configuration example in which one detection pixel unit (monitor pixel unit) is shared by a plurality of correction systems according to the present embodiment.

  In the switch circuit 114, the fixed contact a is connected to the detection pixel potential output line of the detection pixel unit 107, the operation contact b is connected to the input of the Vcom correction system 110A, and the operation contact c is connected to the input of the Vsig correction system 113. The operating contact d is connected to the input of the Vcs correction system 111A.

In this case, memories 1103, 1113 and 1133 for holding detection results (comparison results) are arranged on the output sides of the comparators 1101, 1111 and 1131 of each Vcom correction system 110A, Vcs correction system 111A, and Vsig correction system 113. Thus, the detection pixel can be switched. The memory is not particularly limited, such as DRAM or SRAM.
As a result, it is possible to perform correction for a plurality of systems with only one detection pixel unit 107, and independent arrangement of each correction system is possible.

  Further, the switching timing of the switch circuit 114 does not need to be performed in particular order and can be arbitrarily weighted.

  68A to 68D are diagrams illustrating a switching example in the case where one detection pixel unit (monitor pixel unit) is shared by a plurality of correction systems.

FIG. 68A shows an example of switching in order.
FIG. 68B shows an example in which switching is performed by arbitrarily weighting, and this example is a case where Vcom is weighted.
In this case, the detection pixel potential of the detection pixel portion is input to the Vcom correction system 110A twice or three times continuously, and then switched to be input to the Vcs correction system 111A and the Vsig correction system 113.
FIG. 68C shows an example of switching every field.
FIG. 68D shows an example of switching every 1/2 field.

  Note that if a desired pixel potential is obtained, the driving method such as field driving or line driving is not limited.

It does not matter whether these correction systems are integrally molded by LTPS or externally attached such as COG and COF.
FIG. 69 shows an example in which each Vcom correction system 110A, Vcs correction system 111A, and Vsig correction system 113 are mounted on an external IC 170.

Further, the correction system need not be three systems, and can be configured to select two systems each.
FIGS. 70A to 70C are diagrams illustrating a configuration example in which two correction systems are selected.

In the example of FIG. 70A, two correction systems of a Vcs correction system 111A and a Vsig correction system 113 are provided, and the detection pixel potential of the detection pixel unit 107 is selectively input to each correction system by the switch circuit 114A.
In the example of FIG. 70B, two correction systems of a Vcom correction system 110A and a Vcs correction system 111A are provided, and the detection pixel potential of the detection pixel unit 107 is selectively input to each correction system by the switch circuit 114A.
In the example of FIG. 70C, two correction systems of a Vcom correction system 110A and a Vsig correction system 113 are provided, and the detection pixel potential of the detection pixel unit 107 is selectively input to each correction system by the switch circuit 114A.

FIG. 71 is a diagram showing a more specific configuration example in the case where two correction systems of a Vcom correction system 110A and a Vsig correction system 113 are provided.
FIG. 72 is a diagram illustrating an example of switching timing of the circuit of FIG.
FIG. 71 shows an example in which the first monitor pixel unit 107-1 is driven as a positive pixel and the second monitor pixel unit 107-2 is driven as a negative pixel.

Two switches SW10-1, SW10-2, SW20-1, and SW20-2 are provided in parallel with the detection pixel potential output lines of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2, respectively. .
The switches SW10-1 and SW20-1 are connected to the Vcom adjustment pixel (pix) potential processing unit 115, and the output of the pixel potential processing unit 115 is supplied to the comparator 1101 of the Vcom correction system 110A.
Further, the switches SW10-2 and SW20-2 are connected to the Vcs adjustment pixel (pix) potential processing unit 116, and the output of the pixel potential processing unit 116 is supplied to the comparator 1111 of the Vcs correction system 111A.
The switches SW10-1 and SW20-1 and the switches SW10-2 and SW20-2 are alternately turned on and off.
In such a configuration, detection for Vcom and detection for Vcs are alternately performed for each field (F) from the detection pixel potentials of both polarities, and the comparison results are input to the Vcom correction system 110A and the Vcs correction system 111. Let

  Next, the operation according to the above configuration will be described.

The shift register of the vertical drive circuit 102 is supplied with a vertical start pulse VST generated by a clock generator (not shown) for instructing the start of vertical scanning, and vertical clocks VCK and VCKX having opposite phases as a reference for vertical scanning.
In the shift register, the level shift operation of the vertical clock is performed, and each is delayed by a different delay time. For example, in the shift register, the vertical start pulse VST is shifted in synchronization with the vertical clock VCK and supplied to the corresponding gate buffer.
Further, the vertical start pulse VST is propagated from the upper side or the lower side of the effective pixel portion 101 and is sequentially shifted into each shift register.
Therefore, basically, the gate lines 104-1 to 104-m are sequentially driven through the gate buffers by the vertical clock supplied from the shift register VSR.

As described above, the gate lines 104-1 to 104-m are sequentially driven from the first row by the vertical drive circuit 102, for example, and the storage lines 105-1 to 105-m are driven accordingly. To go. At this time, after driving one gate line with the gate pulse, the level of the storage signals CS1 to CSm applied to the storage lines 105-1 to 105-m at the timing of the rise of the gate pulse of the next gate line is the first level. The first level CSH and the second level CSL are alternately selected and applied.
For example, when the first level CSH is selected for the storage line 105-1 of the first row and the storage signal CS1 is applied, the second level CSL is selected for the storage line 105-2 of the second row. The storage signal CS2 is applied, the first level CSH is selected and applied to the storage line 105-3 in the third row, the storage signal CS3 is applied, and the second level CSL is applied to the storage line 105-4 in the fourth row. The storage signal CS4 is selected and the first level CSH and the second level CSL are alternately selected in the same manner, and the storage signals CS5 to CSm are applied to the storage lines 105-5 to 105-m.
In this storage signal, the pixel potentials of the monitor pixel units 107-1 and 107-2 of the monitor circuit 120 are detected, and the Vcs correction type 111 </ b> A is corrected to an arbitrary potential based on the detected potential.

Further, an alternating common voltage Vcom having a small amplitude ΔVcom is commonly applied to the second pixel electrodes of the liquid crystal cells LC201 of all the pixel circuits PXLC of the effective pixel unit 101.
The center value of the common voltage Vcom is adjusted to an optimum value in the Vcom correction system 110A based on the detected pixel potentials of the monitor pixel units 107-1 and 107-2 of the monitor circuit path 120.

The horizontal driving circuit 103 receives the horizontal start pulse HST for instructing the start of horizontal scanning generated by a clock generator (not shown) and the horizontal clocks HCK and HCKX having opposite phases as the reference for horizontal scanning to generate sampling pulses. Then, the input video signal is sequentially sampled in response to the generated sampling pulse and supplied to each signal line 106-1 to 106-n as a data signal SDT to be written to each pixel circuit PXLC.
For example, first, the R corresponding selector switch is driven and controlled to be conductive, R data is output to each signal line, and R data is written. When the writing of R data is completed, only the selector switch corresponding to G is driven and controlled so that the G data is output and written to each signal line. When the writing of the G data is completed, only the selector switch corresponding to B is driven and controlled so that the B data is output to each signal line and written.

In the present embodiment, after writing from the signal line (after the fall of the gate pulse GP), coupling is performed from the storage lines 105-1 to 105-m via the storage capacitor Cs201, thereby causing the pixel potential (of the node ND201). The voltage applied to the liquid crystal is modulated by changing the potential.
At this time, the common voltage Vcom is supplied as an alternating signal with a small amplitude ΔVcom (10 mV to 1.0 V) instead of a constant value.
Thereby, not only the black luminance but also the white luminance is optimized.

  As described above, according to the present embodiment, only the 0 gradation is boosted by receiving the input voltage when the dynamic range is insufficient for gradation expression and changing the driving only on the black side where the voltage change is large. The function of the booster 142 is used in the case of 1 to 63 gradations without using the function of 142. As a result, it is possible to obtain a dynamic range sufficient for gradation expression while realizing low power consumption.

  In addition, according to the present embodiment, after writing pixel data from the signal lines 106-1 to 106-n (after falling of the gate pulse to the gate lines 104-1 to 104-m), each row is independent. In this case, a driving method is used in which the pixel potential is changed by applying coupling from the storage lines 105-1 to 105-m wired through the storage capacitor Cs201 to modulate the liquid crystal applied voltage. During driving, positive and negative monitor pixel potentials of the first monitor pixel unit 107-1 and the second monitor pixel unit 107-2 in the monitor circuit (corresponding to the potential of the connection node ND201 of the pixel circuit PXLC in the monitor pixel). Since the average potential is detected and the center value of the common voltage Vcom is automatically adjusted, the following effects can be obtained. Rukoto can.

The inspection process at the time of shipment which requires troublesome work is not required, and the center value of the common voltage Vcom is the optimum value due to changes in temperature, driving method, driving frequency, backlight (B / L) luminance, and external light luminance during use. Even if shifted from, the center value of the common voltage Vcom can be held at an optimum value according to the use situation, and there is an advantage that the occurrence of flicker can be adaptively suppressed.
Further, by adjusting the center value of the common voltage Vcom to the optimum value, it is possible to suppress the influence on the image quality due to the effective pixel potential fluctuation.

In the present embodiment, the first monitor pixel unit 107-1, the second monitor pixel unit 107-2, the monitor vertical drive circuit 108, and the monitor horizontal drive circuit 109-1 are provided adjacent to the effective pixel unit 101 independently. , 109-2 are formed, and the gate lines are arranged so as to be nested, so that there is an advantage that the degree of freedom in panel design is increased.
This facilitates the arrangement of the constituent circuits of the monitor circuit 120, that is, the first monitor pixel unit 107-1, the second monitor pixel unit 107-2, the monitor vertical drive circuit 108, and the monitor horizontal drive circuits 109-1 and 109-2. It becomes.
In addition, it is possible to have the vertical and horizontal drive circuits dedicated to the monitor pixel unit separately from the effective pixel unit 101, which solves the above-described problem that the signal line amplitude problem can be detected only during the blanking period. it can.

  Further, in the present embodiment, a method of correcting by writing signals having different amplitudes to the monitor pixels and offsetting the detection pixel potential, a method of correcting by offsetting the detection pixel potential by adding capacitance to the monitor pixels, or The shift from the target value can be canceled by a combination of both methods.

Further, in the present embodiment, effective pixels (display pixels) and monitor pixels are individually arranged and driven, the monitor pixel potential is detected, and the detection pixel potential is short-circuited via the switches 121 and 122. However, by configuring the detection pixel potential to be rewritten after the shorting process, it is possible to correct the potential deviation and perform electrical protection.
Thus, after the short-circuiting operation, potential bias does not occur between the case where the detection pixel potential of the monitor pixel is short-circuited and the case where it is not performed, and the pixel function such as burn-in does not deteriorate.

  Further, in the present embodiment, an adjustment resistor is provided on the monitor pixel side having a small time constant. Specifically, the gate line of the monitor pixel is devised so as to become a resistor, whereby the effective pixel and the time constant are set. Therefore, the possibility that the potential of the monitor pixel (detection pixel) shifts is reduced, and as a result, the possibility that the correction function does not operate normally is eliminated.

  In this embodiment, one detection pixel unit 107 is formed, and this detection pixel potential output is switched by the switch circuit 114 to select each Vcom correction system 110A, Vcs correction system 111A, Vsig correction system 113, and the like. Therefore, it is possible to perform correction of a plurality of systems with only one detection pixel unit 107 without increasing the circuit area, and it is possible to arrange each correction system independently. .

  Each pixel circuit includes a liquid crystal cell LC201 having a first pixel electrode and a second pixel electrode, and a storage capacitor Cs201 having a first electrode and a second electrode, and the first pixel electrode and the storage capacitor of the liquid crystal cell. The first electrode of the TFT and one terminal of the TFT are connected, the second electrode of the storage capacitor is connected to the capacitor wiring arranged in the corresponding row, and the level of the second pixel electrode of the liquid crystal cell is switched at a predetermined cycle. Since a common voltage signal having an amplitude is applied, both black luminance and white luminance can be optimized. As a result, there is an advantage that the contrast can be optimized.

  Further, in this embodiment, liquid crystal application is caused by fluctuations in the dielectric constant of the liquid crystal due to changes in the driving temperature, fluctuations in the thickness of the insulating film forming the storage capacitor Cs201 due to variations during mass production, and fluctuations in the liquid crystal cell gap. The voltage will fluctuate. This variation is electrically detected, and the variation due to variations in display temperature and mass production is suppressed by suppressing variations in the liquid crystal applied voltage.

Further, the CS driver in the vertical drive circuit 102 of this embodiment determines the polarity of the CS signal only by the polarity at the time of pixel writing (indicated by POL) without depending on the polarity of the previous or next stage of the driver stage or the previous frame. Yes.
That is, it is possible to control only with the signal of its own stage without depending on the signals of the preceding and following stages of this embodiment.

  In the above embodiment, an analog video signal is input to the liquid crystal display device, and after latching the analog video signal, it is applied to a liquid crystal display device equipped with an analog interface driving circuit that writes the analog video signal to each pixel in a dot sequence. As described above, the present invention can be similarly applied to a liquid crystal display device equipped with a drive circuit that inputs a digital video signal and writes the video signal to pixels in a line-sequential manner using a selector method.

In the above embodiment, after writing pixel data from the signal lines 106-1 to 106-n (after the fall of the gate pulse to the gate lines 104-1 to 104-m), each row is independent. A capacitive coupling driving method is adopted in which the pixel potential is changed by applying coupling from the wired storage lines 105-1 to 105-m via the holding capacitor Cs201, and the liquid crystal applied voltage is modulated. The automatic adjustment system for the center value of the common voltage Vcom has been described.
The system for automatically adjusting the center value of the common voltage Vcom of the present invention can be applied not only to this capacitively coupled drive system but also to a normal 1HVcom inversion drive system.

FIG. 73 is a diagram showing a waveform example when the automatic adjustment system for the center value of the common voltage Vcom is adopted in the 1HVcom inversion driving method.
In this case, since the common pixel electrode (Vcom) is coupled to the TFT side pixel electrode in synchronization with 1H inversion, the positive (+) polarity and the negative (−) polarity do not exist at the same time.
Therefore, a device is required for detecting the pixel potential of the monitor pixel.

FIG. 74 is a diagram illustrating a configuration example of a detection circuit when the automatic adjustment system for the center value of the common voltage Vcom is employed in the 1HVcom inversion driving method.
FIG. 75 is a diagram showing a waveform example of the circuit of FIG.

74 includes switches 501 to 506, capacitors C501, C502, and C503, a comparison amplifier 501, a CMOS buffer 502, and an output buffer 503.
In the detection circuit 500, first, the switches SW505 and SW506 are turned on, the input and output of the comparison amplifier 501 are connected and reset, and the reference voltage Vref is charged in the capacitor C503. Then, the switches SW505 and SW506 are turned off.
Next, a (1/2) Sig voltage is applied to each of the positive (+) polarity and negative (−) polarity monitor pixel portions, and capacitively coupled at a timing shifted by 1H, and then the two capacitors are capacitively coupled again. Thus, the VcomDC value is determined.
The switch SW501 is turned on to store the capacitor C1A of the pixel PIXA in the capacitor C501 for a certain 1H period. When the next switch SW502 is turned on and the pixel PIXB performs the same operation at 1H, the capacitor C1B is stored in the capacitor C502.
Thereafter, the switches SW503 to SW504 are turned on, and the charges stored in the capacitors C501 and C502 are combined to perform averaging.

As a result, the automatic adjustment system for the center value of the common voltage Vcom can be employed in the 1HVcom inversion driving method.
Also in this case, a complicated inspection process is not required, and the center of the common voltage Vcom is changed due to changes in temperature, driving method, driving frequency, backlight (B / L) luminance, and external light luminance during use. Even if the value is shifted from the optimum value, the center value of the common voltage Vcom can be held at an optimum value according to the use situation, and there is an advantage that generation of flicker can be suppressed adaptively.
Further, by adjusting the center value of the common voltage Vcom to the optimum value, it is possible to suppress the influence on the image quality due to the effective pixel potential fluctuation.

In the above embodiment, the case where the present invention is applied to an active matrix liquid crystal display device using a liquid crystal cell as a display element (electro-optical element) of each pixel has been described as an example. The present invention is not limited, and the present invention can be applied to all active matrix display devices such as an active matrix EL display device using an electroluminescence (EL) element as a display element of each pixel.
The display device according to the embodiment described above is used as a display panel of a direct-view type video display device (liquid crystal monitor, liquid crystal viewfinder) and a projection type liquid crystal display device (liquid crystal projector), that is, an LCD (liquid crystal display) panel. Is possible.

  Furthermore, the active matrix type display device represented by the active matrix type liquid crystal display device according to the above embodiment is used as a display for OA equipment such as personal computers and word processors, television receivers, etc. It is suitable for use as a display unit of electronic devices (mobile terminals) such as mobile phones and PDAs that are being reduced in size and size.

  FIG. 76 is an external view showing a schematic configuration of a mobile terminal to which the present invention is applied, for example, a mobile phone.

A cellular phone 600 according to this example has a configuration in which a speaker unit 620, a display unit 630, an operation unit 640, and a microphone unit 650 are arranged in this order from the upper side on the front side of the apparatus housing 610.
In the mobile phone having such a configuration, for example, a liquid crystal display device is used as the display unit 630, and the active matrix liquid crystal display device according to the above-described embodiment is used as the liquid crystal display device.

As described above, in the mobile terminal such as a mobile phone, the use of the active matrix liquid crystal display device according to the above-described embodiment as the display unit 630 can accurately suppress the occurrence of flicker and obtain a high-quality image. There are advantages.
Further, the pitch can be narrowed, the frame can be narrowed, and the power consumption of the display device can be reduced. Therefore, the power consumption of the terminal body can be reduced.

It is a block diagram which shows the structural example of a general liquid crystal display device. 2 is a timing chart in the so-called 1HVcom inversion driving method of the general liquid crystal display device shown in FIG. It is a figure which shows the relationship between the applied voltage of a normally white liquid crystal, and a dielectric constant. It is a figure which shows the structural example of the active matrix type display apparatus which concerns on one Embodiment of this invention. FIG. 5 is a circuit diagram illustrating a specific configuration example of a pixel portion of the circuit of FIG. 4. It is explanatory drawing of a power supply circuit. 4 is a timing chart showing an example of driving a gate line and a storage line of the vertical drive circuit according to the embodiment. It is a block diagram which shows the basic composition of the reference driver which concerns on this embodiment. It is a figure for demonstrating a dynamic range. It is a figure which shows the process which can maintain the gradation expression of the reference driver 140 which concerns on this embodiment. It is a figure which shows the basic equivalent circuit of the reference driver which concerns on this embodiment. 12 is a timing chart of the circuit of FIG. It is a figure which shows a voltage waveform when there exists a case where there is no pressure | voltage rise processing. It is a circuit diagram which shows the specific structural example of the reference driver which concerns on this embodiment. It is a timing chart of the circuit of FIG. It is a figure which shows the structural example of the pulse generation circuit of the switch control of the circuit of FIG. It is a timing chart which shows the specific example of the sequence control from low color display to multicolor display. It is a figure which shows the example of a panel structure corresponding to the sequence control of low color display to multicolor display. It is a circuit diagram which shows an example of a Vcom drive circuit. It is a figure which shows the structural example of the horizontal drive circuit in the case of a 3 line selector drive system. It is a timing chart of FIG. It is a figure which shows the structural example of the horizontal drive circuit 103 in the case of a 6 line selector drive system. It is a timing chart of FIG. It is a figure which shows the structural example of one monitor pixel of a 1st monitor pixel part and a 2nd monitor pixel part. It is a figure which shows the basic concept of the monitor circuit which concerns on this embodiment. It is a circuit diagram which shows the specific structural example of the comparison output part in the monitor circuit which concerns on this embodiment. It is a wave form diagram which shows the flow of the time process in the drive system which concerns on this embodiment. It is a figure which shows the ideal state by the drive system of this embodiment. It is a figure which shows the relationship of pixel potential Pix versus Vcom potential difference by the positive (+) polarity and negative (-) polarity in the drive system which concerns on this embodiment. It is a figure which shows typically the leak factor of a pixel transistor. It is a figure which shows collectively the state by gate coupling and the leak of a pixel transistor by the positive (+) polarity and negative (-) polarity in the drive system which concerns on this embodiment. It is a figure which shows the item which can suppress the influence by a pixel electric potential fluctuation | variation factor by automatic adjustment of the center value of the common voltage Vcom which concerns on this embodiment. It is a figure which shows the example which forms a monitor pixel so that one line or one pixel may be included as a part of effective pixel part. It is a figure for demonstrating the example in which a monitor pixel electric potential changes by the influence of the signal line which changes with a display pixel in the middle of one frame period. It is a figure which shows the example which shares a gate line simply with a some monitor pixel. It is a figure which shows the example of a pixel arrangement | positioning in the monitor pixel part which concerns on this embodiment. It is a figure which shows the example of a drive waveform of the monitor pixel part of FIG. It is a figure which shows the other example of arrangement | positioning of the structural circuit of a monitor circuit. It is a figure for demonstrating that a display pixel and a physical-property value may be able to be made by the panel surface variations, such as a liquid crystal cell gap and an interlayer insulation film. It is a figure for demonstrating the offset correction by the electric potential of signal Sig. It is a figure which shows the 1st structural example of the circuit which can implement | achieve offset correction by the electric potential of signal Sig. It is a figure which shows the 2nd structural example of the circuit which can implement | achieve offset correction by the electric potential of signal Sig. It is a figure for demonstrating that a detection system and a Sig writing system are also realizable in external ICs, such as COG and COF. It is a figure for demonstrating the outline | summary of the offset correction by additional capacity. It is a circuit diagram which shows the structural example of the intermediate potential detection circuit which employ | adopted the offset correction by additional capacity | capacitance. It is a timing chart which shows the example of connection timing of additional capacity. It is a figure which shows the pixel electric potential short model of a detection pixel electric potential offset correction circuit. It is a figure which shows a pixel potential waveform at the time of changing an additional capacitance value. It is a figure which shows the structural example which changes the constant of additional capacity | capacitance COF. It is a figure for demonstrating the example which an electric potential bias produces in the system which repeats the short of a switch which performs monitor pixel electric potential detection alternately, and an open state. It is a figure for demonstrating the method which does not produce the bias of the electric potential by the short process of a monitor pixel electric potential. It is a figure for demonstrating more concretely the method which does not produce the bias of the electric potential by the short process of a monitor pixel electric potential. It is a figure which shows the 1st structural example of the electric potential deviation suppression circuit which does not produce the electric potential deviation by the short process of a monitor pixel electric potential. Fig. 54 is a timing chart of the circuit of Fig. 53. It is a figure which shows the 2nd structural example of the electric potential deviation suppression circuit which does not produce the electric potential deviation by the short process of a monitor pixel electric potential. 56 is a timing chart of the circuit of FIG. 55. It is a figure for demonstrating the factor of the time constant shift | offset | difference of a gate line. It is a figure which shows the layout model of the effective pixel in this embodiment, and the layout model of a monitor pixel (detection pixel). It is a figure which shows an example of the method of making the time constant of a gate line correspond. It is a figure which shows the example which uses a layout option in the method of making the time constant of a gate line correspond. It is a timing chart which shows the drive waveform of the main liquid crystal cells of this embodiment. FIG. 6 is a diagram illustrating each capacity of a liquid crystal cell in Formula 4. Effective pixel potential ΔVpix applied to the liquid crystal during white display when the liquid crystal material (normally white liquid crystal) used in the liquid crystal display device is used. It is a figure for demonstrating the selection criteria of W. It is a figure which shows the relationship between the video signal voltage and effective pixel electric potential of the drive system which concerns on embodiment of this invention, a related capacitive coupling drive system, and the normal 1HVcom drive system. It is a figure which shows the relationship between the video signal voltage of a drive system which concerns on embodiment of this invention, and a related capacitive coupling drive system, and a brightness | luminance. It is a figure which shows the example which provides three detection pixel parts corresponding to each correction system. It is a figure which shows the structural example which shares one detection pixel part (monitor pixel part) with the some correction system which concerns on this embodiment. It is a figure which shows the example of a switching in case one detection pixel part (monitor pixel part) is shared by several correction systems. It is a figure which shows the example which mounted each Vcom correction system, Vcs correction system, and Vsig correction system in external IC. It is a figure which shows the structural example which selects a correction | amendment system for every 2 systems. It is a figure which shows the more specific structural example at the time of providing the 2 type | system | group correction system of a Vcom correction system and a Vsig correction system. FIG. 62 is a diagram illustrating an example of switching timing of the circuit in FIG. 61. It is a figure which shows the example of a waveform at the time of employ | adopting the automatic adjustment system of the center value of the common voltage Vcom for the 1HVcom inversion drive system. It is a figure which shows the structural example of the detection circuit at the time of employ | adopting the automatic adjustment system of the center value of the common voltage Vcom to 1HVcom inversion drive system. FIG. 75 is a diagram showing a waveform example of the circuit of FIG. 74. 1 is an external view illustrating an outline of a configuration of a mobile phone that is an electronic apparatus to which the present invention is applied.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 100 ... Liquid crystal display device, 101 ... Effective pixel part, 102 ... Vertical drive circuit (VDRV), 103 ... Horizontal drive circuit (HDRV), 104-1 to 104-m ... Gate line , 105-1 to 105-m... Capacitance wiring (storage line), 106-1 to 106-n... Signal line, 107-1... First monitor (dummy) pixel unit (MNTP1), 107 -2 ... second monitor image part (MNTP2), 108 ... monitor vertical drive circuit (V / CSDRVM), 109-1 ... first monitor horizontal drive circuit (HDRVM1), 109-2 ... Second monitor horizontal drive circuit (HDRVM2), 110 ... detection output circuit, 110A ... Vcom correction system, 111 ... correction circuit, 111A ... Vcs correction system, 113 ... Vsig correction .

Claims (11)

A display device having a multi-color display mode and a low-color display mode, and performing AC inversion driving by applying a common voltage signal whose level is switched at a predetermined cycle to the pixel electrode,
An effective pixel portion in which a plurality of pixel circuits for writing image pixel data through a switching element are arranged in a matrix;
A plurality of scanning lines arranged to correspond to the row arrangement of the pixel circuits of the effective pixel portion, and for controlling the conduction of the switching elements;
A plurality of capacitor wirings arranged to correspond to the row arrangement of the pixel circuits;
A plurality of signal lines arranged to correspond to the column arrangement of the pixel circuits and propagating the pixel data;
A first drive circuit for selectively driving the plurality of scan lines and the plurality of capacitance lines;
A second drive circuit for driving the signal line,
The second drive circuit includes:
A display device that sets a signal line applied voltage in a low color display mode to be lower than a signal line applied voltage in a multicolor display mode. The display device according to claim 1, wherein, when the low color display mode is shifted to the multicolor display mode, no voltage is applied to the pixels during a period in which the center voltage of AC inversion driving is changing. 2. The display device according to claim 1, wherein black or white is displayed during a period in which the center voltage of AC inversion driving is changed when shifting from the low color display mode to the multicolor display mode. The display device according to claim 1, wherein when shifting from the low color display mode to the multicolor display mode, the low color drive is performed while the multicolor display drive is performed during a period in which the center voltage of the AC inversion drive is changing. The display device according to claim 1, wherein the driving frequency during low color display is lower than the driving frequency during the multicolor display mode. The display device according to claim 5, wherein, when shifting from the low color display mode to the multicolor display mode, no voltage is applied to the pixels during a period in which the center voltage of AC inversion driving is changing. When shifting from the low color display mode to the multicolor display mode, black or white is displayed during the period when the center voltage of AC inversion drive is changing, and the drive frequency is the same as the multicolor display mode. The display device according to claim 5, wherein when shifting to the low-color display mode, the drive frequency during a period in which the center voltage of AC drive is changing is the same as that in the multi-color display mode while being in the low-color display mode. When shifting from the low color display mode to the multicolor display mode, the low color drive is performed while the center voltage of the AC inversion drive is changing while the multicolor display drive is being performed, and the drive frequency is equal to the multicolor display mode. 6. When shifting from the multicolor display mode to the low color display mode, the drive frequency during the period in which the center voltage of the AC drive is changed is equal to that of the multicolor display mode while being in the low color display mode on display. The display device described. A monitor circuit capable of correcting a center value of a common voltage signal whose level is switched at a predetermined cycle by detecting a potential obtained by averaging detection potentials of positive and negative monitor pixels formed separately from the effective pixel portion; Have
Each pixel circuit arranged in the effective pixel portion is
A display element having a first pixel electrode and a second pixel electrode;
A storage capacitor having a first electrode and a second electrode,
The first pixel electrode of the display element, the first electrode of the storage capacitor, and one terminal of the switching element are connected,
A second electrode of the storage capacitor is connected to the capacitor wiring arranged in a corresponding row;
The display device according to claim 1, wherein a common voltage signal whose level is switched at a predetermined cycle is applied to the second pixel electrode of the display element. An effective pixel portion in which a plurality of pixel circuits for writing image pixel data through a switching element are arranged in a matrix;
A plurality of scanning lines arranged to correspond to the row arrangement of the pixel circuits of the effective pixel unit, and for controlling conduction of the switching elements;
A plurality of capacitor wirings arranged to correspond to the row arrangement of the pixel circuits;
A plurality of signal lines arranged to correspond to the column arrangement of the pixel circuits and propagating the pixel data;
A first drive circuit that selectively drives the plurality of scan lines and the plurality of capacitance lines;
A second drive circuit for driving the signal line,
A driving method of a display device that has a multi-color display mode and a low-color display mode, and performs AC inversion driving by applying a common voltage signal whose level is switched at a predetermined cycle to a pixel electrode.
A driving method of a display device, wherein a signal line applied voltage in a low color display mode is set lower than a signal line applied voltage in a multicolor display mode. An electronic device provided with a display device,
The display device is a display device that has a multicolor display mode and a low color display mode, and performs AC inversion driving by applying a common voltage signal whose level is switched at a predetermined cycle to the pixel electrode.
An effective pixel portion in which a plurality of pixel circuits for writing image pixel data through a switching element are arranged in a matrix;
A plurality of scanning lines arranged to correspond to the row arrangement of the pixel circuits of the effective pixel portion, and for controlling conduction of the switching elements;
A plurality of capacitor wirings arranged to correspond to the row arrangement of the pixel circuits;
A plurality of signal lines arranged to correspond to the column arrangement of the pixel circuits and propagating the pixel data;
A first drive circuit that selectively drives the plurality of scan lines and the plurality of capacitance lines;
A second drive circuit for driving the signal line,
The second drive circuit includes:
Electronic equipment that sets the signal line applied voltage in the low color display mode to be lower than the signal line applied voltage in the multicolor display mode.

Images