JPH0954309A - Liquid crystal display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To make it possible to reduce the electric power consumption of a gradation voltage forming circuit forming many gradations of gradation voltages by specifying the circuitry construction of this gradation voltage forming circuit. SOLUTION: The rear stage of the gradation voltage forming circuit forming the many gradations of the gradation voltages is provided with a first switching element Sc and second switching element Sg of which the terminals at one side are connected to pixel electrodes and the terminal on the other side are inputted with power supply voltage and reference voltage. The first switching element Sc or second switching element Sg is alternately conducted in the prescribed period from the time of the voltage inversion to invert the gradation voltage to be impressed on a drain signal line in synchronization with a current alternating signal, by which the liquid crystal layer is precharged to the power supply potential when the common driving voltage Vcom to be impressed on a common electrode is at an H level and to the reference potential when the common driving voltage is at an L level. The charging and discharging currents flowing to the liquid crystal layer are decreased via the gradation reference voltage source forming the gradation reference voltage and the drain driver.

Description

Detailed Description of the Invention

[0001]

The present invention relates to a TFT (Thin F
The present invention relates to a liquid crystal display device such as a liquid crystal display module, and particularly to a technique effectively applied to a grayscale voltage generation circuit of the liquid crystal display device.

[0002]

2. Description of the Related Art FIG. 4 is a block diagram showing a schematic structure of a conventional TFT liquid crystal display module, and FIG.
The liquid crystal display panel of the conventional TFT liquid crystal display module (T
It is a figure which shows the equivalent circuit of (FT-LCD).

As is clear from the equivalent circuit of FIG. 5, a thin film transistor (TFT) has two adjacent signal lines (drain signal line (D) or gate signal line (G)) and two adjacent signals. It is arranged in the intersection region with the line (gate signal line (G) or drain signal line (D)).

The drain electrode and gate electrode of the thin film transistor (TFT) are connected to the drain signal line (D) and the gate signal line (G), respectively.

Since the source electrode of the thin film transistor (TFT) is connected to the pixel electrode and the liquid crystal layer is provided between the pixel electrode and the common electrode, the thin film transistor (TFT).
The liquid crystal capacitance CLC is equivalently connected between the source electrode and the common electrode of the.

A thin film transistor (TFT) becomes conductive when a positive bias voltage is applied to its gate electrode and becomes non-conductive when a negative bias voltage is applied to its gate electrode.

Further, a storage capacitor CADD is connected between the source electrode of the thin film transistor (TFT) and the gate signal line (G) of the previous line.

A liquid crystal display panel (TFT-LCD)
A drain driver 11 is arranged on the above, and the drain driver 11 is connected to a drain signal line (D) of a thin film transistor (TFT) to supply a voltage for driving a liquid crystal to the thin film transistor (TFT).

The gate signal line (G) of the thin film transistor (TFT) is connected to a liquid crystal display panel (TFT-LC).
Connect the gate driver 12 arranged on the side surface of D),
A voltage is supplied to the gate of the thin film transistor (TFT) for one horizontal operation time.

The display control device 10 receives the display data and the display control signal from the main computer, and drives the drain driver 11 and the gate driver 12 based on the display data and the display control signal.

FIG. 6 is a block diagram showing a schematic configuration of the drain driver 11 of the conventional TFT liquid crystal display module.

As shown in FIG. 6, the drain driver 11
Is composed of a data latch unit 111 for display data and a gradation voltage generation circuit 112.

In the drain driver 11 shown in FIG. 6, 6-bit display data and a 9-value gradation reference voltage are input from the outside to obtain a 64-level gradation voltage value.

The data latch section 111 fetches the display data by the number of outputs in synchronization with the display data latching clock signal, and the gradation voltage generating circuit 112 generates it from the 9-value gradation reference voltage input from the outside. Among the 64 gradation voltages to be generated, the gradation voltage corresponding to the display data from the data latch unit 111 is selected according to the output timing control clock signal and is output to the drain signal line (D).

FIG. 7 is a diagram showing a circuit configuration of the grayscale voltage generation circuit 112 of the drain driver 11 of the conventional TFT liquid crystal display module. The grayscale voltage generation circuits provided for the total number of drain signal lines (D). 1 shows the circuit configuration for one circuit.

As shown in FIG. 7, the gradation voltage generating circuit 11
2 is a plurality of first input side switching elements 1 and a plurality of second input side switching elements 1.
The input side switch element 2, the series-divided resistor circuit 3, the plurality of output side switch elements 4, and the control circuit 113 are included.

The control circuit 113 controls the plurality of first input-side switching elements 1 and the plurality of second input-side switching elements 2 so as to externally input a nine-value gradation reference voltage (VI0 to VI8). 2), the gray scale reference voltages on both sides are selected and applied to the series division resistor circuit 3.

Further, the series-divided resistor circuit 3 outputs a grayscale voltage obtained by equally dividing the adjacent grayscale reference voltages applied to both ends thereof into eight.

The control circuit 113 controls the plurality of output side switching elements 4 to select one from the voltage values divided into eight equal parts by the series-divided resistance circuit 3 to select the drain signal line (D). Output.

As a result, the gradation reference voltages (VI0 to VI
8) The voltage values (VO0 to VO64) obtained by equally dividing the intervals 8) are generated and output to the drain signal line (D).

Further, in the liquid crystal display device, an AC driving method is adopted in order to prevent a DC voltage from being applied to the liquid crystal, and also in the TFT liquid crystal display module, a common driving voltage applied to the common electrode ( The grayscale voltage applied to the drain signal line (D) is made alternating according to Vcom).

Therefore, when displaying black on the screen, the gradation reference voltages (VI0 to VI8) are inverted according to the common drive voltage (Vcom) applied to the common electrode, and the drain signal line (D) is displayed. For example, a voltage of 5V or 0V is alternately applied.

FIG. 8 is a circuit diagram showing a circuit configuration of a grayscale voltage generation circuit and a precharge circuit of a conventional TFT liquid crystal display module which precharges a liquid crystal layer.

In FIG. 8, the input side switching element (Si
n) and the input side switching element (Sin-1),
A plurality of first input side switching elements 1 shown in FIG. 7, and
It corresponds to the plurality of second input side switching elements 2 and includes the plurality of first input side switching elements 1 and the plurality of second input side switching elements 1 shown in FIG.
One of the input side switching elements 2 is shown, and the gray scale reference voltage applied to the input terminals (Vin, Vin-1) is the same as the gray scale reference voltages (VI0 to VI8) shown in FIG. It is a gradation reference voltage.

Further, output side switching elements (S1, S2,
.. Sn) corresponds to the output side switching element 4 shown in FIG. 7, P1 is a gate synchronization signal having a cycle of T1, and P2 is a switching element control signal.

Further, the output terminal to the drain signal line (D) is connected to the power source via the switch element (Sc).

Here, the switch element (Sc) and the control circuit 113 form a precharge circuit.

In FIG. 8, the gray scale voltage of the drain signal line (D) applied to a certain pixel electrode by the AC driving method is either the potential (Va) or the potential (Vb) depending on the AC signal. ) Is shown.

In the conventional driving method, the switch element (Sc) is turned on and all the input side switch elements and the output side switch elements are turned off during the "High level (Tw)" of the switch element control signal (P2). , The liquid crystal layer is precharged to the power supply potential (Vc).

The switch element control signal (P
During the "Low level" period of 2), the switch element (S
c) is turned off, the input side switching element (Sin, Sin-
1) and the output side switching element (Sa) (or the output side switching element (Sb)) are turned on.

[0031]

FIG. 9 is a diagram showing an example of a voltage waveform and a current waveform of each part in the conventional driving method.

FIG. 9A shows a drive voltage waveform applied to the common electrode and the drain signal line (D).
21 is a common drive voltage (Vco
m), and 22 and 23 are voltage waveforms of the gradation voltage (Vsig) applied to the drain signal line (D).

Here, 22 is a gradation voltage (V) when the potential difference between the pixel electrode and the common electrode, that is, the voltage applied to the liquid crystal layer is the largest (for example, when displaying black).
sig) of the voltage waveform, and 23 is the potential difference between the pixel electrode and the common electrode, the gradation voltage (V when the voltage applied to the liquid crystal layer is the smallest (for example, when displaying white)).
The waveform of the voltage waveform of sig) is shown.

In this case, in the conventional driving method, the potential of the pixel electrode changes as shown in FIG. 9 (b), and the potential of the liquid crystal layer on the pixel electrode side changes as shown in FIG. 9 (c). To do.

34 shown in FIGS. 9 (b) and 9 (c),
Reference numeral 36 denotes a potential (Va) when the grayscale voltage (Vsig) of the drain signal line (D) applied to a certain pixel electrode is “High level” when the common drive voltage (Vcom) applied to the common electrode is “High level”. ), The potential of the pixel electrode when the common drive voltage (Vcom) applied to the common electrode is the potential (Vb) when it is at the “Low level”, and
The potential on the pixel electrode side of the liquid crystal layer is shown.

As can be seen from FIGS. 9B and 9C, the potential 34 of the pixel electrode and the potential 36 of the liquid crystal layer on the pixel electrode side are the power source potential (Vc) during the precharge period (Tpc). Pre-charged to the potential (Va),
Alternatively, it changes to the potential (Vb).

At this time, the series-divided resistor circuit 3 has the configuration shown in FIG.
A current (I in FIG. 8) indicated by 38 in (d) flows.

Further, in reference numerals 35 and 37 shown in FIGS. 9B and 9C, the gradation voltage (Vsig) of the drain signal line (D) applied to a certain pixel electrode is applied to the common electrode. The common drive voltage (Vcom) applied is "High".
The potential of the pixel electrode when the power supply potential (Vc) is "level" and the common drive voltage (Vcom) applied to the common electrode is the ground potential (Vg) when "low level", and the liquid crystal layer Shows the potential on the pixel electrode side.

As can be seen from FIGS. 9B and 9C, the pixel electrode potential 35 and the liquid crystal layer pixel electrode side potential 37 are the common drive voltage (Vcom) applied to the common electrode. Does not change when is at "High level" and the common drive voltage (Vco
m) is "Low level", it is precharged to the power supply potential (Vc) in the precharge period (Tpc) and then changes to the ground potential (Vg).

At this time, the series division resistor circuit 3 is connected to the circuit shown in FIG.
A current (I in FIG. 8) indicated by 39 in (d) flows.

As is apparent from FIG. 9 (d), in addition to the direct current (shaded portions 38 and 39 in FIG. 9 (d)) for generating the gradation voltage, the series division resistor circuit 3 has
A charging / discharging current for charging / discharging the liquid crystal layer flows.

In particular, when the precharge direction is different from the potential of the pixel electrode and the potential of the liquid crystal layer on the pixel electrode side, this charge / discharge current becomes large, and therefore the series division resistor circuit 3 has a cycle. A large charging / discharging current flows.

Further, the charge / discharge current is the gradation voltage (V) of the drain signal line (D) applied to a certain pixel electrode.
sig) changes from the power supply potential (Vc) to the ground potential (Vg) or from the ground potential (Vg) to the power supply potential (Vc) according to the common drive voltage (Vcom) applied to the common electrode. Therefore, when the display screen is almost white, a large charging / discharging current flows.

In general, the display screen of a liquid crystal display device is almost white in many cases, so that according to the conventional driving method, a large charge / discharge current flows in the liquid crystal layer.

Since the serial divided resistance circuits 3 are provided for the total number of the drain signal lines (d), the charging current flowing from the gradation reference voltage source (not shown) for generating the gradation reference voltage to the drain driver 11 is provided. The discharge current becomes so large that it cannot be ignored, power consumption increases, and it is necessary that the gradation reference voltage source and drain driver 11 have a large current capacity.

As described by taking the TFT liquid crystal display module as an example, in the liquid crystal display device in which the grayscale voltage is generated by using the series divided resistance circuit, the power consumption of the grayscale reference voltage source and the drain driver is increased. There was a problem that

The present invention has been made in order to solve the problems of the conventional liquid crystal display device, and an object of the present invention is a technique capable of reducing the power consumption of the gradation voltage generating circuit in the liquid crystal display device. To provide.

The above and other objects and novel constitution of the present invention will become apparent from the description of this specification and the accompanying drawings.

[0049]

Among the inventions disclosed in the present application, the outline of typical ones will be briefly described as follows.

(1) A liquid crystal layer, a pixel electrode and a common electrode that face each other with the liquid crystal layer in between, a plurality of gray scale reference voltages and display data are input, and they are adjacent to each other in the plurality of gray scale reference voltages. In the liquid crystal display device, the grayscale voltage generation circuit generates a grayscale voltage of multiple grayscales to be applied to the pixel electrodes by dividing the grayscale voltage between matching grayscale reference voltages with a series voltage dividing resistor circuit. In the latter stage of the circuit, one terminal is connected to the pixel electrode, the other terminal is applied with a power supply voltage, and the first switch element is connected to the pixel electrode, and the other terminal is connected to the reference voltage. Is applied to the second switch element and the first switch element or the second switch within a predetermined period from the time of voltage inversion in which the grayscale voltage applied to the pixel electrode is inverted in synchronization with the alternating signal. Conducting elements alternately Then, when the common drive voltage applied to the common electrode is "High level", it is the power supply potential, and when the common drive voltage applied to the common electrode is "Low level", it is the reference potential. And a precharging means for precharging.

(2) A liquid crystal layer, a pixel electrode and a common electrode facing each other with the liquid crystal layer interposed therebetween, a plurality of gray scale reference voltages and display data are input, and adjacent to the plurality of gray scale reference voltages. A gradation voltage generating circuit for generating a multi-gradation gradation voltage to be applied to a pixel electrode by dividing a matching gradation reference voltage by a series voltage dividing resistor circuit. The voltage generating circuit applies a predetermined adjacent grayscale reference voltage among the plurality of grayscale reference voltages to both ends of the series voltage dividing resistor circuit, and a plurality of voltage generating circuits generated by the series voltage dividing resistor circuit. A liquid crystal display device comprising a selection means for selecting one of grayscale voltages and outputting it to the pixel electrode, and a control circuit for controlling the application means and the selection means based on the display data. In the gradation voltage generating circuit In a subsequent stage, one terminal is connected to the pixel electrode and a power supply voltage is applied to the other terminal, and a first switch element is connected to the pixel electrode and a reference voltage is applied to the other terminal. And a second switch element for controlling the gray scale voltage applied to the pixel electrode in synchronism with the alternating signal within a predetermined period from the time of voltage reversal, based on the control signal from the control circuit. When the common drive voltage applied to the common electrode is "High level" by alternately conducting the first switch element or the second switch element, the common drive voltage applied to the common electrode is applied. When the voltage is "Low level", the liquid crystal layer is precharged to the reference potential.

[0052]

According to each of the above means, in the liquid crystal display device,
A first switch, one terminal of which is connected to the pixel electrode and the other terminal of which is supplied with a power supply voltage and a reference voltage, respectively, at a subsequent stage of a gradation voltage generation circuit for generating a gradation voltage of multiple gradations. An element and a second switch element, and within a predetermined period from the time of voltage inversion in which the grayscale voltage applied to the drain signal line is inverted in synchronization with the alternating signal, the first
The switching element or the second switching element is alternately turned on so that the common drive voltage applied to the common electrode is "
Since the liquid crystal layer is precharged to the power supply potential at the “High level” and to the reference potential when the common drive voltage applied to the common electrode is at the “Low level”, the gradation reference voltage is generated. The charge / discharge current flowing in the liquid crystal layer can be reduced through the adjustment reference voltage source and the drain driver, and the power consumption in the grayscale voltage generation circuit can be reduced.

As a result, the power consumption of the gradation reference voltage source and the drain driver for generating the gradation reference voltage can be reduced, and the gradation reference voltage source and the drain driver for generating the gradation reference voltage are of low current capacity. Can be used.

[0054]

Embodiments of the present invention applied to a TFT liquid crystal display module will be described below in detail with reference to the drawings.

In all the drawings for explaining the embodiments, those having the same function are designated by the same reference numerals, and the repeated description thereof will be omitted.

The structure of the TFT liquid crystal display module to which the present invention is applied will be described below with reference to the conventional TF shown in FIGS.
The description is omitted because it is the same as the T liquid crystal display module.

FIG. 1 is a circuit diagram showing a circuit configuration of a grayscale voltage generation circuit and a precharge circuit of a liquid crystal display device which is an embodiment of the present invention.

In FIG. 1, the input side switching element (Sin) and the input side switching element (S
in-1) corresponds to the plurality of first input side switching elements 1 and the plurality of second input side switching elements 2 shown in FIG. 7, and the plurality of first input side switching elements 1 shown in FIG. , One of the plurality of second input side switching elements 2 is shown, and the gradation reference voltage applied to the input terminals (Vin, Vin−1) is the gradation reference voltage (VI0 to VI0 shown in FIG. V
It is the gradation reference voltage on both sides of I8).

Further, output side switching elements (S1, S2,
.. Sn) corresponds to the output side switching element 4 shown in FIG. 7, P1 is a gate synchronization signal having a cycle of T1, and P2 is a switching element control signal.

In this embodiment, the common drive voltage (Vcom) applied to the common electrode is inverted every line.

Further, in this embodiment, the output terminal to the drain signal line (D) is connected to the power source via the switch element (Sc) and to the ground (earth) via the switch element (Sg).

Here, the switch element (Sc), the switch element (Sg), and the control circuit 113 form a precharge circuit.

In FIG. 1, the gray scale voltage of the drain signal line (D) applied to one pixel electrode is "High" when the common drive voltage (Vcom) applied to the common electrode is "High".
The figure shows a case where the potential is Va at the “level” and the potential is Vb when the common drive voltage (Vcom) applied to the common electrode is at the “Low level”.

As described above, in the TFT liquid crystal display module, the gradation reference voltages (VI0 to VI8) are inverted in synchronization with the alternating signal, that is, in accordance with the common drive voltage (Vcom) applied to the common electrode. When displaying black on the screen, the drain signal line (D) is, for example, 5V.
Alternatively, a voltage of 0V is applied alternately.

In the conventional driving method, when the grayscale voltage applied to the drain signal line (D) is inverted according to the common drive voltage (Vcom) applied to the common electrode, the switch element control signal (P2). During the period of "High level (Tw)"
All the input side switching elements and the output side switching elements are turned off, and the liquid crystal layer is precharged to the power supply potential (Vc).

In the driving method of this embodiment, when the grayscale voltage applied to the drain signal line (D) is inverted in accordance with the common drive voltage (Vcom) applied to the common electrode, the switch element control signal ( P2) "High
During the period of “h level (Tw)”, the switching elements (Sc, S
g) is alternately turned on, and all input-side switching elements and output-side switching elements are turned off.

In this case, when the common drive voltage (Vcom) applied to the common electrode is "Low level", the switch element (Sg) is turned on and the common drive voltage (Vcom) applied to the common electrode. ) Is "High level", the switch element (Sc) is turned on.

FIG. 2 is a diagram showing an example of voltage waveforms and current waveforms of various parts in the driving method of this embodiment.

Next, the driving method of this embodiment will be described in more detail with reference to FIG.

Similar to FIG. 9A, FIG. 2A shows a drive voltage waveform applied to the common electrode and the drain signal line (D), and 21 is a common drive voltage applied to the common electrode. The voltage waveform 21 of (Vcom), and 22 and 23 show the voltage waveform of the gradation voltage (Vsig) applied to the drain signal line (D).

Similarly, 22 is a gradation voltage (V) when the potential difference between the pixel electrode and the common electrode, that is, the voltage applied to the liquid crystal layer is the largest (for example, when displaying black).
sig) of the voltage waveform, and 23 is the potential difference between the pixel electrode and the common electrode, the gradation voltage (V when the voltage applied to the liquid crystal layer is the smallest (for example, when displaying white)).
The waveform of the voltage waveform of sig) is shown.

In this case, in the driving method of the present embodiment, the potential of the pixel electrode changes as shown in FIG. 2B, and the potential of the liquid crystal layer on the pixel electrode side is as shown in FIG. 2C. Changes to.

24 shown in FIGS. 2 (b) and 2 (c),
Reference numeral 26 denotes a potential (Va) when the grayscale voltage (Vsig) of the drain signal line (D) applied to a certain pixel electrode is “High level” when the common drive voltage (Vcom) applied to the common electrode is “High level”. ), The potential of the pixel electrode when the common drive voltage (Vcom) applied to the common electrode is the potential (Vb) when it is at the “Low level”, and
The potential on the pixel electrode side of the liquid crystal layer is shown.

As can be seen from FIGS. 2B and 2C, the potential 24 of the pixel electrode and the potential 26 of the liquid crystal layer on the pixel electrode side are the power supply potential (Va) during the precharge period (Tpc). , Or precharged to the ground potential (Vg), and then the potential (Va) or the potential (Vb)
Changes to

At this time, the series-divided resistor circuit 3 has the configuration shown in FIG.
A current (I in FIG. 1) indicated by 28 in (d) flows.

25 shown in FIGS. 2B and 2C,
Reference numeral 27 indicates a power supply potential (when the grayscale voltage (Vsig) of the drain signal line (D) applied to a certain pixel electrode is “High level” when the common drive voltage (Vcom) applied to the common electrode is “High level”. Vc), the potential of the pixel electrode when the common drive voltage (Vcom) applied to the common electrode is at the “Low level” and is the ground potential (Vg),
It also shows the potential on the pixel electrode side of the liquid crystal layer.

As can be seen from FIGS. 2B and 2C, the potential 25 of the pixel electrode and the potential 27 of the liquid crystal layer on the pixel electrode side are the common drive voltage (Vcom) applied to the common electrode. Depending on "High level" or "
It changes to "Low level", but the gate synchronization signal (P1)
It does not change during one cycle (T1).

At this time, the series-divided resistor circuit 3 has the configuration shown in FIG.
A current (I in FIG. 8) indicated by 29 in (d) flows.

As shown in FIG. 2D, also in the present embodiment, the DC current for generating the gradation voltage is generated in the series-divided resistor circuit 3 (the shaded portions 28 and 29 in FIG. 2D). In addition, a charging / discharging current for charging / discharging the liquid crystal layer flows.

However, as is apparent from FIG. 2D, in this embodiment, the charge / discharge current for charging / discharging the liquid crystal layer flowing in the series-divided resistor circuit 3 can be reduced, and the conventional driving method can be used. Compared to the method, the time for charging and discharging the liquid crystal layer becomes faster.

As is apparent from FIG. 2D, the gradation voltage (Vsig) applied to the drain signal line (D).
Is the common drive voltage (Vco
Power supply potential (Vc) when m) is "High level"
At the common drive voltage (Vco
When m) is at the “Low level” and is at the ground potential (Vg), no current other than the DC current for generating the gradation voltage flows in the series-divided resistor circuit 3.

Therefore, when the display screen is almost white, the series divided resistance circuit 3 does not flow.

As described above, since the display screen of the liquid crystal display device is almost white in many cases, according to this embodiment, the charge / discharge current flowing in the liquid crystal layer can be greatly reduced.

As described above, according to this embodiment,
During the "High level (Tw)" period of the switch element control signal (P2), the switch elements (Sc, Sg)
Are alternately turned on to set the liquid crystal layer to the power supply voltage (Vc) when the common drive voltage (Vcom) applied to the common electrode is at “High level”, and the common drive voltage applied to the common electrode. (Vcom) is "L
Since it is precharged to the ground potential (Vg) when it is at "ow level", the drain signal line (D) is changed according to the common drive voltage (Vcom) applied to the common electrode.
The drain driver 511 generates a grayscale reference voltage when the grayscale voltage applied to the
Alternatively, the charge / discharge current flowing in the liquid crystal layer can be reduced through the gray scale reference voltage source that generates the gray scale reference voltage from the drain driver 511.

As a result, it is possible to use a gray scale reference voltage source for generating a gray scale reference voltage and a drain driver 11 having a low current capacity.

Further, since the heat generation amount of the gradation reference voltage source and the drain driver 11 for generating the gradation reference voltage can be reduced, the reliability of the gradation reference voltage source and the drain driver 11 for generating the gradation reference voltage can be reduced. It is possible to improve the property.

As a result, the power consumption of the TFT liquid crystal display module can be reduced.

In this embodiment, the case where the present invention is applied to the liquid crystal display device which inverts the common drive voltage (Vcom) applied to the common electrode for each line is explained, but the present invention is not limited to this. Of course, it goes without saying that by applying an alternating signal to the controller circuit 113, for example, it can be applied to a liquid crystal display device in which the common drive voltage (Vcom) applied to the common electrode is inverted every one field.

FIG. 3 is a circuit diagram showing a circuit configuration of a gradation voltage generating circuit of a liquid crystal display device which is another embodiment of the present invention.

As shown in FIG. 3, in the second embodiment, the switch element (Sc) and the switch element (Sg) are turned on by the precharge control circuit 114 to which the AC signal is input.
It's turned off.

Here, the switch element (Sc), the switch element (Sg), and the precharge control circuit 114.
Form a precharge circuit.

In FIG. 3, the gray scale voltage of the drain signal line (D) applied to one pixel electrode is "High" when the common drive voltage (Vcom) applied to the common electrode is "High".
The figure shows a case where the potential is Va at the “level” and the potential is Vb when the common drive voltage (Vcom) applied to the common electrode is at the “Low level”.

Also in the second embodiment, when the grayscale voltage applied to the drain signal line (D) is inverted according to the common drive voltage (Vcom) applied to the common electrode, the switch element control signal (P3). During the period of "High level (Tw)", the switch elements (Sc, Sg) are alternately turned on, and the switch element control signal (P2)
During the "High level (Tw)" period, all the input side switching elements and the output side switching elements are turned off.

Also in this case, when the common drive voltage (Vcom) applied to the common electrode is "Low level", the switch element (Sg) is turned on and the common drive voltage applied to the common electrode. (Vcom) is “Hig
If it is at "h level", the switch element (Sc) is turned on.

According to this embodiment, the switch elements (Sc, Sg) are alternately turned on during the "High level (Tw)" of the switch element control signal (P3).
In the liquid crystal layer, when the common drive voltage (Vcom) applied to the common electrode is "High level", the power supply voltage (Vc) is applied, and the common drive voltage (Vcom) applied to the common electrode is "Low". When it is "level", it is precharged to the ground potential (Vg).

Therefore, also in this embodiment, when the gray scale voltage applied to the drain signal line (D) is inverted in accordance with the common drive voltage (Vcom) applied to the common electrode, the gray scale reference voltage is used. It is possible to reduce the charge / discharge current flowing in the liquid crystal layer from the generated gray scale reference voltage source to the drain driver 511 or via the gray scale reference voltage source that generates the gray scale reference voltage from the drain driver 511. .

As a result, it becomes possible to use a low-current-capacity gray scale reference voltage source and a drain driver 11 for generating a gray scale reference voltage.

Further, since the heat generation amount of the gradation reference voltage source and the drain driver 11 for generating the gradation reference voltage can be reduced, the reliability of the gradation reference voltage source and the drain driver 11 for generating the gradation reference voltage can be reduced. It is possible to improve the property.

As a result, the power consumption of the TFT liquid crystal display module can be reduced.

Although the present invention has been specifically described based on the embodiments, the present invention is not limited to the above embodiments, and it goes without saying that various modifications can be made without departing from the scope of the invention.

[0101]

The effects obtained by typical ones of the inventions disclosed in the present application will be briefly described as follows.

(1) According to the present invention, in the liquid crystal display device, the charge / discharge current flowing in the liquid crystal layer can be reduced via the gray scale reference voltage source for generating the gray scale reference voltage and the drain driver. Further, it is possible to reduce the power consumption in the gradation voltage generating circuit.

As a result, it is possible to reduce the power consumption in the gray scale reference voltage source and the drain driver that generate the gray scale reference voltage, and use the gray scale reference voltage source and the drain driver that generate the gray scale reference voltage having a low current capacity. Can be used.

Further, since the heat generation amounts of the gradation reference voltage source and the drain driver for generating the gradation reference voltage can be reduced, the reliability of the gradation reference voltage source and the drain driver for generating the gradation reference voltage can be improved. It is possible to improve.

As a result, the power consumption of the liquid crystal display device can be reduced and the outer size of the liquid crystal display device can be reduced.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing a circuit configuration of a grayscale voltage generation circuit and a precharge circuit of a TFT liquid crystal display module which is an embodiment of the present invention.

FIG. 2 is a voltage waveform of each part in the driving method of the present embodiment,
It is a figure which shows a current waveform.

FIG. 3 is a circuit diagram showing a circuit configuration of a grayscale voltage generation circuit and a precharge circuit of a TFT liquid crystal display module which is another embodiment of the present invention.

FIG. 4 is a block diagram showing a schematic configuration of a conventional TFT liquid crystal display module.

FIG. 5 is a diagram showing an equivalent circuit of a liquid crystal display panel (TFT-LCD) of a conventional TFT liquid crystal display module.

FIG. 6 is a block diagram showing a schematic configuration of a drain driver of a conventional TFT liquid crystal display module.

FIG. 7 is a diagram showing a circuit configuration of a grayscale voltage generation circuit of a drain driver of a conventional TFT liquid crystal display module,
It is a figure which shows the circuit structure for 1 circuit in the gradation voltage generation circuit provided only for the total number of drain signal lines.

FIG. 8 is a conventional T in which a liquid crystal layer is precharged.
A grayscale voltage generation circuit of an FT liquid crystal display module, and
It is a circuit diagram showing a circuit configuration of a precharge circuit.

FIG. 9 is a diagram showing an example of voltage waveforms and current waveforms of respective parts in a conventional driving method.

[Explanation of symbols]

TFT-LCD ... TFT liquid crystal display panel, D ... Drain line, G ... Gate line, Sc, Sg ... Switch element, 1, S
in ... 1st input side switch element, 2, Sin-1 ... 2nd
Input side switch element, 3 ... Series division resistance circuit, 4, S1
~ Sn ... Output side switching element, 10 ... Display control device, 1
1 ... Drain driver, 12 ... Gate driver, 111
Data latch unit 112 Grayscale voltage generation circuit 113
... control circuit, 114 ... precharge control circuit.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Hironobu Yu, 3300 Hayano, Mobara-shi, Chiba Electronic Device Division, Hitachi, Ltd. (72) Noboru Kataoka 3300 Hayano, Mobara, Chiba Hitachi, Ltd. Electronic Device Business (72) Inventor Shinji Yasukawa 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd. (72) Inventor Yukihide Ote 3681 Hayano, Mobara-shi, Chiba Hitachi Device Engineering Co., Ltd.

Claims (2)

[Claims] 1. A liquid crystal layer, a pixel electrode and a common electrode facing each other with the liquid crystal layer interposed therebetween, a plurality of gray scale reference voltages and display data are input, and adjacent to each other in the plurality of gray scale reference voltages. A gray scale voltage generation circuit that divides a gray scale reference voltage by a series voltage dividing resistor circuit to generate a multi-gray scale gray scale voltage applied to a pixel electrode. In the subsequent stage, one terminal is connected to the pixel electrode, the other terminal is applied with a power supply voltage, and the first switch element is connected to the pixel electrode, and the other terminal is connected to the reference voltage. A second switch element to be applied, and within a predetermined period from the time of voltage inversion in which the grayscale voltage applied to the pixel electrode is inverted in synchronization with the alternating signal.
When the common drive voltage applied to the common electrode is "High level", the first switch element or the second switch element is alternately conducted, and the power supply potential is
Also, the common drive voltage applied to the common electrode is "
A liquid crystal display device comprising: precharge means for precharging the liquid crystal layer to a reference potential when it is at "Low level". 2. A liquid crystal layer, a pixel electrode and a common electrode that face each other with the liquid crystal layer in between, a plurality of gray scale reference voltages and display data are input, and the plurality of gray scale reference voltages are adjacent to each other. A liquid crystal display device comprising: a gray scale voltage generation circuit that divides a gray scale reference voltage by a series voltage dividing resistor circuit to generate a multi-gray scale gray scale voltage applied to a pixel electrode. The generating circuit applies a predetermined adjacent grayscale reference voltage among the plurality of grayscale reference voltages to both ends of the series voltage dividing resistor circuit, and a plurality of floors generated by the series voltage dividing resistor circuit. A liquid crystal display device comprising: a selection unit that selects one of the adjusted voltages and outputs the selected voltage to the pixel electrode; and a control circuit that controls the application unit and the selection unit based on the display data. After the gradation voltage generation circuit A first switch element having one terminal connected to the pixel electrode and a power supply voltage applied to the other terminal; and one terminal connected to the pixel electrode and a reference voltage applied to the other terminal. And a second switch element for switching the grayscale voltage applied to the pixel electrode in synchronism with the alternating signal, and based on the control signal from the control circuit within a predetermined period from the time of voltage inversion. When the common drive voltage applied to the common electrode is "High level" by alternately connecting the first switch element or the second switch element, the common drive voltage applied to the common electrode is applied. Is a "Low level", the liquid crystal layer is precharged to a reference potential.