JPH07118795B2 - Driving method for liquid crystal display device - Google Patents

Description

TECHNICAL FIELD The present invention relates to a liquid crystal display device for displaying, for example, a television image.

[Conventional technology]

For example, it has been proposed to display television images using liquid crystals.

In FIG. 3, (1) is an input terminal to which a video signal of the television is supplied, and a signal from the input terminal (1) is a switching element M ₁ composed of, for example, an N channel FET,
M ₂ ... Lines L ₁ and L _{2 in the} vertical (Y-axis) direction through Mm
..Supplied to Lm Note that m is a number corresponding to the number of pixels in the horizontal (X axis) direction. Further, an m-stage shift register (2) is provided, and clock signals Φ _1H and Φ _2H of m times the horizontal frequency are supplied to the shift register (2), and clocks from the output terminals of the shift register (2) are supplied. Pixel switch signal φ sequentially scanned by signals Φ _1H and Φ _2H
H1 , φ _H2 ... φ _Hm are supplied to the respective control terminals of the switching elements M _{1 to} Mm. The shift register (2) is supplied with a low potential (V _SS ) and a high potential (V _DD ) and drive pulses of these two potentials are formed.

Further, for example, N-channel FETs are provided on the respective lines L _{1 to} Lm.
Switching elements M ₁₁ , M ₂₁ ... M _n1 , M ₁₂ , M ₂₂
.. One end of M _n2 , ... M _1m , M _2m, ... M _nm is connected.
Note that n is a number corresponding to the number of horizontal scanning lines. The other ends of the switching elements M _{11 to} M _nm are respectively connected to the liquid crystal cells C ₁₁ and C _21.
... Connected to the target terminal (3) through C _nm .

Further, an n-stage shift register (4) is provided, and a horizontal frequency clock signal Φ _1V ,
Φ _2V is supplied, and scanning line switch signals Φ _V1 , Φ _V2 ... Φ _{Vn, which} are sequentially scanned by the clock signals Φ _1V and Φ _2V from the output terminals of the shift register (4), are ) Direction gate lines G ₁ , G ₂ ... G _n through each row of switching elements M _{11 to} M _{nm in} the X-axis direction (M _{11 to} M _1m ),
(M _{21 to} M _2m ) ... (M _{n1 to} M _nm ) is supplied to each control terminal. Note that V _SS and V _DD are supplied to the shift register (4) as well as the shift register (2).

That is, in this circuit, the shift register (2),
In (4), the clock signals Φ _1H , Φ as shown in FIGS.
_2H , Φ _1V and Φ _2V are supplied. Then, from the shift register (2), as shown in FIG.
_{H1 to} φ _Hm are output, and the fourth from the shift register (4)
As shown in FIG. D, φ _V1 to φ _Vn are output every horizontal period. Further, a signal as shown in FIG. 4E is supplied to the input terminal (1).

When φ _V1 and φ _H1 are output, the switching elements M ₁ and M _{11 to} M _1m are turned on, and the input terminal (1) → M ₁ →
A current path of L ₁ → M ₁₁ → C ₁₁ → target terminal (3) is formed, and the potential difference between the signal supplied to the input terminal (1) and the target terminal (3) is supplied to the liquid crystal cell C ₁₁ . Therefore, the charge corresponding to the potential difference due to the signal of the first pixel is sampled and _{held in} the capacity of the cell C ₁₁ . The light transmittance of the liquid crystal is changed according to this charge amount. The same operation is sequentially performed on the cells C _{12 to} C _nm , and at the time when the signal of the next field is supplied, each cell C _{11 to} C _nm is further supplied.
The charge amount of _nm is rewritten.

In this way, the liquid crystal cell corresponding to each pixel of the video signal
The light transmittance of C _{11 to} C _nm is changed, and this is repeated in sequence to display a television pixel.

By the way, when displaying with a liquid crystal, an AC drive is generally used in order to improve its reliability and life. For example, in displaying a television image, a signal obtained by inverting the video signal for each field or frame is supplied to the input terminal (1). That is, as shown in FIG. 4E, the input terminal (1) is supplied with an inverted signal for each field or frame.

By the way, in the above apparatus, the signal supplied to the input terminal (1) is as shown in FIG. 4E. Therefore, the external circuit that supplies the signal to the input terminal (1) must have a sufficient dynamic range to pass the entire amplitude of the polarity-inverted signal. For example, an extremely large dynamic range of 10 V _PP. Has been a problem in circuit design.

[Problems to be solved by the invention]

The conventional device is configured as described above. Therefore, the conventional device has a problem that a large dynamic range is required for the circuit, the configuration is complicated, and the design is not easy.

[Means for solving problems]

The present invention relates to switching elements M _{11 to} M arranged in a matrix.
each associated with _nm A method of driving a liquid crystal display device configured to perform image display using the display panel (100) provided with the liquid crystal display cell C ₁₁ -C _nm, the polarity of the image signal Invert (12) every predetermined period,
By the clamp circuit (switching element (5) connected to the clamp capacitance (16) and the clamp voltage supply terminal (6)) provided in the signal path of the display panel (100), a predetermined period is set. It is configured so that the predetermined DC components (18) and (19) that are changed to be positive or negative with respect to the target potential and bias the voltage applied to the liquid crystal display cell are reproduced, and the block of the image signal is regenerated. A driving method of a liquid crystal display device, characterized in that the liquid crystal display cell is AC-driven by a signal having the predetermined DC component clamped in the ranking period (φ _HBLK ).

[Action]

According to this device, since the DC component of the signal supplied to the display panel (100) is removed, the amplitude of the signal whose polarity is inverted becomes 1/2 or less, and the dynamic range of the external circuit is significantly reduced. can do.

〔Example〕

In FIG. 1, the switching elements M _{1 to} M _m , M _{11 to} M _nm , the liquid crystal display cells C _{11 to} C _nm, etc. shown in FIG.
The display panel (100) is formed on the IC substrate.

An external input terminal (11) for a video signal from a tuner (not shown) or the like is provided, and the signal from this input terminal (11) is supplied to the polarity inverting circuit (12). This inverting circuit (1
The signal from 2) and the signal from the input terminal (11) are supplied to the switch (13). Further, the signal from the input terminal (11) is supplied to the sync separation circuit (14), and this separation circuit (14)
The switch (13) is switched by, for example, a signal that is inverted every one field. The signal from the switch (13) is supplied to the input terminal (1) of the display panel (100) through the amplifier (15) and the capacitor (16).

Further, a switching element (5) for clamping is provided in the signal path from the input terminal (1) in the display panel (100), and a clamp voltage supply terminal (6) is connected via this switching element (5). , DC voltage sources (18) and (19) for clamp voltages V _dc1 and V _dc2 are connected to this terminal (6) through a switch (17). This switch (17) is switched to be equivalent to the above-mentioned switch (13). Further, the gate of the switching element (5) is connected to the terminal (7), and the horizontal blanking pulse φ _HBLK from the sync separation circuit (14) is supplied to this terminal (7).

Therefore, in this device, for example, a second
When the signal as shown in FIG. A is supplied, this signal is clamped to the voltage V _dc1 or V _dc2 every horizontal period, and the signal inside the display panel (100) becomes as shown in FIG. 2B.
As a result, image display is performed by favorable AC drive.

In this case, the signal outside the display panel (100) and on the input side of the capacitor (16) may be a signal from which the DC component is removed, as shown in FIG. 2A, which reduces the dynamic range of the external circuit to 1/2. It can be significantly reduced to: Further, this can simplify the circuit configuration and facilitate the circuit design.

Note that this device can be applied to a liquid crystal display device using an active matrix using TFTs such as amorphous silicon, polysilicon, silicon on sapphire, and organic semiconductor.

Further, the shift registers (2) and (4) and the switching element (5) described above may be provided outside the IC constituting the display panel (100).

The switches (13) and (17) may be switched every horizontal period.

Further, the display can be applied to both dot sequential and line sequential.

〔The invention's effect〕

According to the present invention, since the DC component of the signal supplied to the display panel (100) is removed, the amplitude of the polarity-inverted signal becomes 1/2 or less, and the dynamic range of the external circuit is significantly reduced. I was able to do it.

[Brief description of drawings]

FIG. 1 is a block diagram of an example of the present invention, FIG. 2 is a diagram for explaining the same, and FIGS. 3 and 4 are diagrams for explaining a conventional device. C _{11 to} C _nm is a liquid crystal display cell, M _{1 to} Mm, M _{11 to} M _nm , (5) is a switching element, (11) is an external input terminal, (12) is a polarity reversing circuit, (13), (17 ) Is a switch, (16) is a capacitor, and (18) and (19) are DC voltage sources.

Claims (1)

[Claims] 1. A method of driving a liquid crystal display device, wherein a display panel provided with liquid crystal display cells in association with switch elements arranged in a matrix is used to display an image. While reversing the polarity of the signal every predetermined period, by the clamp circuit provided in the signal path of the display panel, it is changed to positive or negative with respect to the predetermined target potential every predetermined period, and the liquid crystal display cell The liquid crystal display cell is configured to perform reproduction of a predetermined DC component that biases the applied voltage, and AC-drives the liquid crystal display cell with the signal having the clamped predetermined DC component during the blanking period of the image signal. A method for driving a liquid crystal display device, comprising: