JPH08171370A - Liquid crystal display driving method - Google Patents

Abstract

PURPOSE: To display a video image on a liquid crystal display with a simple circuit. CONSTITUTION: The digital image data are read out from an image memory 25 in serial to be inputted to an inversion digital circuit 26. After the image data are inverted at every one field, they are converted into an analog drive signal by a D/A converter 31. Although the drive signal is impressed to a TFT- LCD 9, at this time, two scanning lines are driven by the same drive signal, and impression of a non-interlacement system is performed. Since the image data are inverted at every one field as it is in a digital signal, the inversion circuit becomes simple.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a liquid crystal display driving method for displaying digital images such as computer graphics (CG) and video images on a liquid crystal display.

[0002]

2. Description of the Related Art There are two known methods for driving a liquid crystal display, namely, simple matrix driving and active matrix driving. These days it's expensive,
Due to high image quality and fast response speed, the demand for active matrix driving method is increasing. The active matrix drive method uses a TFT (Thin Fil) for each pixel.
m Transistor) and other active elements are provided so that the target pixel can be reliably turned on and off.

As is well known, an NTSC video signal consists of two interlaced fields.
One picture is constructed by combining the field and the second field into one frame. Generally, in order to display a video image on an active matrix drive type liquid crystal display, first, a video signal which is a digital signal is converted into an analog signal, and this is converted into one field period (1/60 second).
After converting to a 30HZ video signal that inverts alternating current every time,
This video signal is applied to the liquid crystal by a non-interlaced method (image signals of odd and even rows are written in the same row).

[0004]

However, inversion conversion of an analog signal requires a complicated inversion circuit, so that the drive circuit of the liquid crystal display has a disadvantage of being expensive.

The present invention has been made to solve the above problems, and an object thereof is to provide a liquid crystal display driving method capable of displaying a video image on a liquid crystal display with a simple circuit. Is.

[0006]

In order to solve the above problems, in the liquid crystal display driving method of the present invention, a video signal is converted into a 30 HZ digital signal which is inverted every 1/60 seconds, and then this is DA converted. Since the voltage is applied to the liquid crystal display, a complicated inversion circuit that inverts the analog signal becomes unnecessary, and the cost can be reduced.

[0007]

EXAMPLE In FIG. 2, active matrix drive
Type liquid crystal display (hereinafter referred to as TFT-LCD)
9 is two glass substrates 10 and 11 with a space of several μm.
Then, they are opposed to each other and fixed, and the liquid crystal 12 is sealed in the space.
is there. On the lower glass substrate 11, the signal line Y₁,
Y₂, ... and scan line G₁, G₂, ... is a matrix
The TFTs 16 and transparent TFTs are arranged at their intersections.
The pixel electrode 17 is connected. Signal line Y₁, Y₂・ ・ ・
.. is the source terminal of the TFT 16 and the scanning line G ₁, G
₂, ... are connected to the gate terminal of TFT16 respectively.
Have been.

Below the upper glass substrate 10, a common electrode 18 and a color filter 19 are arranged. Also,
Polarizing plates 21 and 22 are bonded to the outer surfaces of the glass substrates 10 and 11, respectively. TFT-LCD 9 configured in this way
Becomes a transmissive liquid crystal display panel when white light is incident from below the lower polarizing plate 22. The color filter 19
Is composed of three primary colors of R (red), G (green), and B (blue), and is arranged corresponding to each pixel electrode 17.

In FIG. 3 showing a timing chart of signal waveforms for driving the TFT-LCD 9, reference numeral V _G is a signal of the scanning lines G ₁ , G ₂ , ... And reference numeral V _ID is a signal line Y ₁ , Y. ₂ , ... Signals. The signal V _ID is AC-inverted for each field, and the potential V _P of the pixel electrode 17 is
The waveform has a substantially positive-negative symmetry with the potential V _COM of the common electrode 18 as the center, and the voltage thereof is as shown by the diagonal lines. That is, the drive signal applied to the TFT-LCD 9 is AC inverted every 1 field period (1/60 seconds) 30 Hz
Is an analog signal. The symbol V _C is the center voltage of the signal lines Y ₁ , Y ₂ , ...

In FIG. 1, which shows a circuit for implementing the TFT-LCD driving method of the present invention, the image memory 25 has R,
It is composed of three frame memories that store digital signals of three primary colors of G and B independently one frame at a time. An inversion digital circuit 26 is connected to the image memory 25, and image data is serially read from a frame memory for R of the image memory 25, for example, according to an instruction from the controller 27, and is input to the inversion digital circuit 27. It

As shown in FIG. 3, the inverting digital circuit 27 is a combination of an inverter 28 and a switch 29 arranged in parallel for a required number of bits.
The switch 29 is switched each time image data for one field is input from the frame memory, and the image data is inverted for each field. As you know, 1
The screen is displayed with image data for one frame, and the image data for one frame consists of image data for two fields. One field period is 1/60 second, and one frame period is 1/30 second. That is, the image data is 1 /
It is inverted every 60 seconds, and one frame frequency becomes the standard video rate of 30 Hz.

The image data inverted in each field by the inversion digital circuit 27 is converted into an analog drive signal by the DA converter 31, and then the TFT-LCD.
9 is applied. Since the number of pixels of the TFT-LCD 9 is one frame, when a drive signal for one field is applied, it is driven by the same signal for every two scanning lines. In this way, drive signals for two fields (one frame) are TF
By applying to the T-LCD 9, a non-interlaced system is applied in which odd-numbered rows and even-numbered rows are driven by the same drive signal.

For example, to turn on the pixel electrode 17, the scanning line G ₁ is turned on and then the signal line Y ₁ is turned on. When the pixel electrode 17 is turned on, the liquid crystal 12 above this
Becomes transparent. As a result, the white light that has passed through the polarization number 22 and the glass substrate 11 passes through the liquid crystal 12 and the B filter above it, and further passes through the glass substrate 10 and the polarizing plate 21. As a result, the blue component of one pixel is colored.

The operation of the TFT-LCD drive circuit thus constructed will be described. In each frame memory for each color that constitutes the image memory 25, for example, a symbol display which is conventionally displayed by a reel in a slot machine is displayed.
Digital image data such as computer graphics (CG) for display on the FT-LCD and video images taken by a video camera are recorded.

First, 1 frame from the R frame memory
Image data is read serially and the
It is input to the digital circuit 27. This image data is inverted
Instead, the DA converter 31 directly drives the analog drive signal.
And is applied to the TFT-LCD 9. This and
Scan line G₁, G₂, ... are the same drive signal
Driven by the No. Image data for the next one field
After being inverted by the inverting digital circuit 27,
It is converted into a log signal and the scanning line G of the TFT-LCD 9 ₁,
G₂, 2 are driven by the same drive signal.
As a result, the position of the R filter of the TFT-LCD 9 is set.
Corresponding pixel electrode 17 is turned on / off and should be displayed
The R component of the image is displayed. Then, the other colors of G and B
Similarly, for the image data of, read, inversion, DA conversion
And each drive signal is applied to the TFT-LCD 9,
The G component and B component of the image to be displayed are displayed. This result
As a result, the image is displayed in color.

[0016]

As described in detail above, according to the liquid crystal display driving method of the present invention, the video signal is reduced to 1/6.
After converting to a 30HZ digital signal that reverses every 0 seconds,
Since this was DA converted and applied to the liquid crystal display,
A complicated inverting circuit for inverting an analog signal is not needed, and a circuit for driving a liquid crystal display can be produced at low cost.

[Brief description of drawings]

FIG. 1 is a block diagram showing a drive circuit of a TFT-LCD.

FIG. 2 is an explanatory diagram showing a structure of a TFT-LCD.

FIG. 3 is a timing chart of signal waveforms for driving a TFT-LCD.

FIG. 4 is a schematic diagram showing a circuit example of an inverting digital circuit.

[Explanation of symbols]

 9 TFT-LCD 26 Inversion digital circuit

Claims (1)

[Claims] 1. Inverting a video signal every 1/60 second 3
A method for driving a liquid crystal display, which comprises converting to a digital signal of 0HZ and then DA-converting the digital signal and applying it to a liquid crystal display.