KR101343495B1 - Circuit for controlling a backlight in a liquid crystal display - Google Patents

Abstract

The present invention relates to a technology for detecting a luminance and color of a backlight irradiated onto a liquid crystal panel of a liquid crystal display device using an image pickup device so that a target luminance and color coordinate are implemented. The present invention, the LED backlight unit for emitting a white backlight on the front of the liquid crystal panel having red, green, blue LED; A sensor unit which detects the luminance and color of the light projected on the liquid crystal panel with an image pickup device and outputs a signal according to the image pickup device; A controller for outputting a control signal for realizing the luminance and color on the liquid crystal panel with the luminance and color required by the user based on the signal input from the sensor unit; It is achieved by the LED driver for controlling the driving of the LED backlight unit in accordance with the control signal input from the controller to reproduce the brightness and color of the degree required by the user.

Description

CIRCUIT FOR CONTROLLING A BACKLIGHT IN A LIQUID CRYSTAL DISPLAY}

1,

DESCRIPTION OF THE REFERENCE SYMBOLS

1: Liquid crystal panel 2A, 2B:: LED backlight

3A, 3B: Image pickup device 4: luminance and color sensor

5 controller 6 LED driver

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a technology for controlling backlight driving of a liquid crystal display device. In particular, a liquid crystal capable of controlling the driving of a backlight to detect a luminance and a color of a backlight irradiated to the liquid crystal panel to realize a target luminance and color coordinate. A backlight control circuit of a display device.

Recently, with the development of information technology (IT), the importance of the display as a visual information transmission medium is further emphasized, and in order to occupy a major position in the future, such as low power consumption, thinness, light weight, high quality, etc. The requirements must be met.

Liquid Crystal Display (LCD) is a representative flat panel display device that displays images by using optical anisotropy of liquid crystal. Cathode ray tube (CRT) is advantageous due to its thin, small size, low power consumption and high image quality. It is being developed as a major product of the flat panel display that can replace the.

In general, a liquid crystal display device is a display device in which image information is individually supplied to pixels arranged in a matrix, and a desired image is displayed by adjusting light transmittance of the pixels. Accordingly, the liquid crystal display includes a liquid crystal panel in which pixels, which are the smallest unit for implementing an image, are arranged in an active matrix form, and a driving unit for driving the liquid crystal panel. Since the LCD does not emit light by itself, a backlight unit is provided to supply light to the LCD.

The backlight unit of the liquid crystal display device has a trend of miniaturization, thinness, and light weight, and according to this trend, a light emitting diode (LED), which is advantageous in power consumption, weight, and brightness, has been proposed instead of the CCFL used in the backlight unit. .

However, the LED backlight unit employing the white LED has a complex structure because it uses a color filter, and three red, green, and blue LEDs must be spatially arranged in order to express one color. Has the disadvantage of falling.

In response to this, an LED backlight unit of a field sequential color (FSC) driving method having excellent transmittance, resolution, and power has been proposed. In the FSC driving method, by sequentially driving light sources of three primary colors (red, green, and blue) without using color filters of red, green, and blue in displaying colors, A driving method capable of displaying color by using an afterimage effect of a human eye is used.

However, in the LED backlight unit of the conventional liquid crystal display device, since the color and luminance irradiated to the liquid crystal display module (LCM) is not directly detected to control the driving of the LED driver, the color and luminance of each part of the LCM are uniform. There was a difficulty in controlling.

Even though the color and brightness of the LED backlight can be corrected by the tuning of the circuit part, it is difficult to control the target color and brightness to be realized because the characteristics of the LEDs are different, and the tuning process is difficult, so that the production process of the actual product is difficult. There was a difficulty applying the tuning technique.

Accordingly, an object of the present invention is to provide a backlight control circuit that detects the luminance and color of a backlight irradiated onto a liquid crystal panel using an image pickup device, and controls the driving of the backlight so that a target luminance and color coordinates are implemented based on the image pickup device. Is in.

The present invention for achieving the above object, the LED backlight unit for irradiating a white backlight on the front of the liquid crystal panel with red, green, blue LED; A sensor unit which detects luminance and color of light projected on the liquid crystal panel by using at least one image pickup device disposed around the liquid crystal panel, and outputs a signal according to a detection result; The current luminance and color of the liquid crystal panel according to the signal output from the sensor unit is compared with the target luminance and color requested by the user, and based on the comparison result, the difference between the current luminance and color and the target luminance and color. A controller for outputting a corresponding control signal; The red, green, and blue LEDs output a brighter or darker white backlight according to the control signal output from the controller, or one of the red, green, and blue LEDs is applied to the remaining LEDs according to the control signal. Compared to the LED driving unit to control the driving of the LED backlight to output a brighter light.

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

1 is a block diagram showing an embodiment of a backlight control circuit of a liquid crystal display according to the present invention. As shown in FIG. 1, pixels having a matrix disposed at an intersection of a plurality of data lines and a gate line are provided. A liquid crystal panel (1) for displaying a desired image in such a manner as to supply image information to them individually and to adjust light transmittance of the pixels; LED backlight units (2A) and (2B) having red, green, and blue LEDs for illuminating a white backlight on the front surface of the liquid crystal panel (1); Imaging elements 3A and 3B for detecting the brightness and color of light projected from the LED backlights 2A and 2B onto the liquid crystal panel 1; A brightness and color sensor unit 4 for outputting signals corresponding to the brightness and color detected through the imaging devices 3A and 3B; On the basis of the signal input from the brightness and color sensor unit 4, the current brightness and color on the liquid crystal panel 1 are recognized and compared with the brightness and color requested by the user. A controller 5 for outputting a control signal for implementing color; In accordance with the control signal input from the controller (5) is configured to control the driving of the LED backlight (2A), (2B) by the LED driver (6) to reproduce the brightness and color of the degree requested by the user, Referring to the operation of the present invention configured in this way in detail as follows.

The liquid crystal panel 1 includes pixels arranged in a matrix at an intersection of a plurality of data lines and a gate line, and individually supplies image information to them through a gate driver and a data driver to adjust light transmittance of the pixels. The desired image is displayed.

Since the liquid crystal panel 1 does not emit light by itself, it requires a backlight unit for supplying light, wherein LED backlight units 2A and 2B are used as the backlight unit. The LED backlights 2A and 2B are provided with three red, green, and blue LEDs to irradiate a white backlight on the front surface of the liquid crystal panel 1.

In such a backlight structure, imaging elements 3A and 3B are provided around the liquid crystal panel 1 and projected to the liquid crystal panel 1 from the LED backlight units 2A and 2B through them. Detects the brightness and color of the light.

The luminance and color sensor unit 4 generates a signal corresponding to the luminance and color detected through the image pickup devices 3A and 3B and supplies it to the controller 5.

Accordingly, the controller 5 recognizes the current luminance and color on the liquid crystal panel 1 based on the signal input from the luminance and color sensor unit 4, and then the recognized luminance and color and the user Compare with the requested brightness and color. The controller 5 generates a control signal corresponding to the difference value according to the comparison result and outputs the control signal to the LED driver 6.

Accordingly, the LED driver 6 controls the driving of the LED backlights 2A and 2B according to the control signal input from the controller 5, and as a result, the LED backlight 2A, ( The brightness and color of the light irradiated to the liquid crystal panel 1 from 2B) are at a level required by the user.

For example, if the comparison result in the controller 5 indicates that the current luminance value is slightly lower than the target value, the controller 5 passes through the LED driver 6 to the LED backlight 2A, 2B. The driving of is controlled so that a slightly brighter backlight is irradiated from them.

As another example, if the comparison in the controller 5 turns out that a slightly greener backlight is required than the present, the controller 5 passes through the LED driver 6 to the LED backlight 2A, ( The driving of 2B) is controlled so that the greenish backlight is illuminated.

In the above description, the brightness and the color of the backlight irradiated to the liquid crystal panel 1 are detected using two imaging devices 3A and 3B as an example. When the number is further increased, the luminance and color of each part of the liquid crystal panel 1 can be measured more accurately, thereby enabling more precise backlight control.

As described in detail above, the present invention detects the brightness and color of the backlight irradiated from the LED backlight unit to the liquid crystal panel by using an image pickup device, and based on this, driving the backlight to implement the brightness and color coordinates required by the user. By controlling, there is an effect that the problem of unevenness in color and luminance of each part of the liquid crystal panel can be solved.

Claims (5)

An LED backlight unit having red, green, and blue LEDs to irradiate a white backlight on the front surface of the liquid crystal panel; A sensor unit which detects luminance and color of light projected on the liquid crystal panel by using at least one image pickup device disposed around the liquid crystal panel, and outputs a signal according to a detection result; The current luminance and color of the liquid crystal panel according to the signal output from the sensor unit is compared with the target luminance and color requested by the user, and based on the comparison result, the difference between the current luminance and color and the target luminance and color. A controller for outputting a corresponding control signal; The red, green, and blue LEDs output a brighter or darker white backlight according to the control signal output from the controller, or one of the red, green, and blue LEDs is applied to the remaining LEDs according to the control signal. And a LED driver for controlling driving of the LED backlight to output brighter light than the backlight control circuit of the liquid crystal display device. The backlight control circuit of claim 1, wherein a plurality of the LED backlight units are provided. delete delete The method of claim 1, The sensor unit further comprises a brightness and color sensor unit for outputting a signal corresponding to the brightness and color of the light detected through the at least one image pickup device.

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