CN1527261A - Drive circuit of single pixel of transmission reflection type liquid crystal display - Google Patents

Abstract

A driving circuit for a single pixel of a transmissive reflective liquid crystal display is used to control the gamma correction signals of a transmissive liquid crystal capacitor and a reflective liquid crystal capacitor respectively through different analog-to-digital signal converters, so as to improve the display quality of the transmissive reflective liquid crystal display. The driving circuit includes a first transistor and a second transistor, whose gate terminals are commonly coupled to a scanning line; a first signal converter, coupled to the source terminal of the first transistor through a first data line; and a second signal converter, coupled to the source terminal of the second transistor through a second data line, the drain terminal of the first transistor is coupled to the transmissive liquid crystal capacitor, and the drain terminal of the second transistor is coupled to the reflective liquid crystal capacitor.

Description

Driving circuit for a single pixel of a transflective liquid crystal display

technical field

The invention relates to a driving circuit of a liquid crystal display, in particular to a driving circuit of a transflective liquid crystal display.

Background technique

Lightness, thinness, shortness, and smallness have become the primary considerations of flat panel display technology, and liquid crystal panels have become the mainstream of current displays. LCD panels can be divided into active and passive. The response speed, resolution, image quality and dynamic images of active matrix LCD are better than those of passive type. With the demand of users for high image quality, the display panel has already changed from monochrome Switching to full-color, and paying more and more attention to the power consumption, number of colors, and resolution of liquid crystal displays, it is necessary to adopt active matrix panels that respond faster and are more suitable for dynamic image applications. Therefore, the use of active matrix panels has become the current technology. trend.

At present, a popular display technology is low-temperature polysilicon thin-film transistor liquid crystal display panel (LTPS TFT-LCD), which has the advantages of high brightness, low power consumption, ultra-high resolution, high image quality and fast response speed. The most advanced and competitive technology in the industry.

In order to reduce the power consumption of the panel, most of the current technical trends are towards the development of reflective type or transflective type LCD panel. Both the transmissive mode and the reflective mode of the current transflective LCD panel use the same gamma curve to correct the brightness of each pixel. However, transmissive liquid crystals and reflective liquid crystals have different characteristics, so the corrected gamma curves are also different. Using the same gamma curve will affect its image quality. Therefore, a transflective liquid crystal display can improve the image quality. High-quality drive circuits are necessary.

Contents of the invention

In view of the above problems, the main purpose of the present invention is to provide a driving method for a transflective liquid crystal display, so as to improve the image quality of the transflective liquid crystal display.

Therefore, in order to achieve the above object, the transflective liquid crystal display disclosed in the present invention includes a first transistor and a second transistor, the gate terminals of which are commonly coupled to a scanning line; a first signal converter, through a first A data line is coupled to the source terminal of the first transistor; and a second signal converter is coupled to the source terminal of the second transistor through a second data line.

Wherein, the drain terminal of the first transistor is coupled to the transmissive liquid crystal capacitor, and the drain terminal of the second transistor is coupled to the reflective liquid crystal capacitor.

In order to have a further understanding of the purpose, structure, features, and functions of the present invention, combine

Examples are detailed below.

Description of drawings

Fig. 1 is the driving circuit of a single pixel of a known transflective liquid crystal display; and

FIG. 2 is a driving circuit for a single pixel of the transflective liquid crystal display of the present invention.

Explanation of reference numbers

10... Scan shift register

11...Scanning lines

20...Data shift register

21...Signal converter

22...Data cable

24...Transistors

25......Transmissive liquid crystal capacitor

26...reflective liquid crystal capacitor

27...reflective liquid crystal capacitor

28......Transmissive liquid crystal capacitor

31...the first signal converter

32...the second signal converter

41...the first data line

42...the second data line

51...the first transistor

52...second transistor

61...Storage capacitor

62...Storage capacitor

Detailed ways

The technology of the transflective liquid crystal display panel is to make full use of the ambient light source and reduce the use of the backlight source. A slightly inclined reflective surface is used as a reflector on the pixel to separate the image from the stray light reflected by the surface and make the light source Concentrating and controlling the distribution of light to a certain viewing angle and reflecting it to the direction of the observer not only effectively improves the light utilization rate, but also improves the brightness and contrast of the panel. Therefore, how to improve the light utilization rate of the reflective system becomes a urgent technical issues to be resolved.

In a liquid crystal display, each pixel is driven by crossing the X and Y axes, and the currently disclosed technology uses an active-matrix addressing method to achieve a high data density display effect, which has For better display effect and resolution, the method adopted is to use transistors made of thin film technology, and use scanning method to select the on and off of any display point (pixel). The grid-shaped small conductive lines are drawn on the glass as transmission lines, and the electrodes are matrix switches arranged by thin film transistors. There is a control switch at the intersection of each line. Although the driving signal is quickly scanned at each display point and However, only the selected display points in the transistor matrix on the electrode get enough voltage to drive the liquid crystal molecules, so that the liquid crystal molecular axes turn to form a contrast of "bright or dark", and the unselected display points are naturally "dark or bright". contrast.

The main purpose of the transflective liquid crystal display panel is to reduce the power loss of the liquid crystal panel, which is to use the reflection of external light to reduce the use of the backlight source, so as to reduce the power loss. Therefore, each pixel has a transparent area and a reflective area, and the image signal in the pixel is controlled by the data line.

The transflective liquid crystal display panel disclosed in the known technology can be divided into a reflective area (Reflective Area) and a penetrating area (Transparent Area) according to the characteristics of the liquid crystal. The display in the reflective area is provided by the reflective liquid crystal, and the transmissive area The display is provided by a transmissive liquid crystal. The image quality seen by the user is the result of correction by the gamma curve, and the brightness correction of the reflection area and the transmission area uses the same gamma correction curve to adjust the brightness.

The so-called gamma curve refers to the corresponding function curve between its input value and output value. When the gamma value is 1, the curve is a 45-degree straight line, that is, the input and output concentrations are the same. A gamma value lower than 1 will lighten the output, and a gamma value higher than 1 will cause the output to darken. The greater the difference between the gamma value and 1, the smaller the curvature of the curve. Due to the characteristics of the gamma curve, gamma correction will not affect the density domain of the image, but only affect the density distribution, that is, the brightening (when the gamma value is less than 1) or darkening (when the gamma value is less than 1) or darkening (when the gamma value is For images with a Ma value greater than 1), the Gamma correction is mainly applied to the mid-tone part. When the gamma value used is greater than 1, the highlights will be compressed and the shadows will be expanded. When the gamma value used is less than 1, the highlights will be expanded and the shadows will be compressed.

As shown in "Fig. 1", it is the drive circuit of a single pixel of a known liquid crystal display, and the scan shift register (Scan Shift Register) 10 is used to control a scan line 11 to determine which pixel signal in the matrix emits light, and the data is shifted The temporary register (Data Shift Register) 20 is used to control the signal converter 21, the data line 22 is used to control the switch of the transistor 24, and the transmissive liquid crystal capacitor 28 and the reflective liquid crystal capacitor 27 are driven by the transistor 24, that is to say, The liquid crystal turns to control the passage of light. Gamma curve correction signals of the transmissive liquid crystal capacitor 28 and the reflective liquid crystal capacitor 27 are provided by the signal converter 21 .

When the scanning line 11 scans to select a certain pixel to emit light, the correction signal will pass through a signal converter 21 to convert the analog signal into a digital signal, and the signal will be transmitted to the transmissive area electrode and the reflective area through the data line 22 through the transistor 24 The brightness is corrected in the electrode, that is, the transmissive liquid crystal capacitor 28 and the reflective liquid crystal capacitor 27 in the same pixel are corrected by the same gamma correction curve, but because of the inherent characteristics of the transmissive liquid crystal capacitor and the reflective liquid crystal capacitor For this reason, the result of using the same gamma curve correction is not ideal.

Therefore, the present invention proposes a solution to the above-mentioned problems, as shown in "Fig. to control. As shown in Figure 2, the driving circuit of a single pixel includes a first signal converter 31, a second signal converter 32, a first transistor 51, and a second transistor 52, and the pixel consists of a transmissive liquid crystal capacitor 25 and a reflective Type liquid crystal capacitor 26 constitutes.

The gates (Gate) of the first transistor 51 and the second transistor 52 are commonly coupled to the scan line 11, the source (Source) of the first transistor 51 is coupled to the first data line 41, and the drain (Drain) is coupled to the transmissive In the liquid crystal capacitor 25 , the source of the second transistor 52 is coupled to the second data line 42 , and the drain is coupled to the reflective liquid crystal capacitor 26 .

The first signal converter 31 controls the switching of the first transistor 51 through the first data line 41 , and the second signal converter 32 controls the switching of the second transistor 52 through the second data line 42 . When the pixel is selected by the scanning line 11, the control of the first data line 41 and the second data line 42 is coordinated so that the first transistor 51 and the second transistor 52 are turned on, and the correction signal of the transmissive liquid crystal capacitor 25 is used to The brightness is corrected by the first signal converter 31 through the first transistor 51 . Similarly, the correction signal of the reflective liquid crystal capacitor 26 is used to correct the brightness of the second signal converter 32 through the second transistor 52 .

Wherein, the first signal converter 31 and the second signal converter 32 are an analog-to-digital signal converter. The first transistor 51 and the second transistor 52 are thin film transistors (Thin Film Transistor; TFT), and the transmissive liquid crystal capacitor 25 is also connected in parallel with a storage capacitor 61 for maintaining the voltage of the liquid crystal capacitor 25 . The reflective liquid crystal 26 is also connected in parallel with a storage capacitor 62 for maintaining the voltage of the liquid crystal capacitor 26 .

Different signal converters are used to process the gamma correction curves of the reflection and transmission parts, which can produce better impact quality. Moreover, there is no need to sacrifice the charging time in order to increase the refresh frequency (refresh).

Although the present invention is disclosed above with the aforementioned preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some modifications and modifications without departing from the spirit and scope of the present invention. Therefore The protection scope of the present invention is defined by the appended claims of this specification.

Claims (9)

1. A driving circuit for a single pixel of a transflective liquid crystal display, the single pixel includes a transmissive liquid crystal capacitor and a reflective liquid crystal capacitor, including: a first transistor, the first transistor has a gate terminal, a source terminal and a drain terminal; a second transistor having a gate terminal, a source terminal and a drain terminal; a first signal converter coupled to the source terminal of the first transistor through a first data line; and a second signal converter coupled to the source terminal of the second transistor through a second data line; Wherein, the drain terminal of the first transistor is coupled to the transmissive liquid crystal capacitor, and the drain terminal of the second transistor is coupled to the reflective liquid crystal capacitor. 2. The drive circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the first data line is used to control the switch of the first transistor to drive the transflective liquid crystal capacitor. 3. The driving circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the second data line is used to control the switch of the second transistor to drive the reflective liquid crystal capacitor. 4. The driving circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the first transistor is a thin film transistor. 5. The driving circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the second transistor is a thin film transistor. 6. The driving circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the first signal converter is an analog-to-digital signal converter. 7. The driving circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the second signal converter is an analog-to-digital signal converter. 8 . The drive circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1 , wherein a storage capacitor is connected in parallel with the transflective liquid crystal capacitor. 9. The driving circuit for a single pixel of a transflective liquid crystal display as claimed in claim 1, wherein the reflective liquid crystal capacitor is further connected in parallel with a storage capacitor.

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