KR20010028535A - Apparatus for Driving Liquid Crystal Display Panel - Google Patents

Abstract

PURPOSE: A liquid crystal display(LCD) panel driving apparatus is provided to be capable of performing a sleep mode by itself without software control of an operating system. CONSTITUTION: A system block(52) supplies a drive power and a video data signal to an LCD module(50), and a back light power part(54) converts a direct current voltage supplied from the system block(52) into an alternating current voltage suitable for driving a back light. An LCD power part(56) converts a level of the direct current voltage from the system block(52) into a voltage level suitable for driving a liquid crystal panel and a drive circuit thereof. A display timing control part(58) supplies video data supplied from the system block(52) to a driver integrated circuit of the LCD. A power control part(60) senses whether the video data is changed or not and controls outputs of the LCD power part(56) and the back light power part(54).

Description

Apparatus for Driving Liquid Crystal Display Panel

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving device of a liquid crystal display panel, and more particularly to a driving device of a liquid crystal display panel capable of performing a sleep mode function by itself without resorting to software control of a system operating system.

The life of a back light used in a liquid crystal display panel (hereinafter referred to as "LCD") is about 10,000 hours. This is a relatively short time compared to the lifetime of other display devices, such as cathode ray tubes (CRTs). Notebook computers, which mainly use LCD as a display means, use various methods to efficiently drive LCD modules including backlights, driving circuits, etc. to extend the service life of the device and to reduce power consumption. One of these methods is the sleep mode function. The sleep mode function is a function to limit the operation of the LCD by cutting off the power applied to the backlight or the LCD driving circuit part for a certain period of time when there is no change in the data displayed on the screen. This sleep mode function allows for a longer period of use by reducing the amount of time the backlight needs to run unnecessarily. The sleep mode function of a notebook computer is mostly accomplished by software control of the system.

1 is a block diagram schematically showing an LCD driver in a notebook computer. Referring to FIG. 1, the LCD driver drives the system power supply unit 24 for supplying a DC driving voltage to the LCD module 20 and the backlight power supply unit 22, and drives the backlight of the DC voltage supplied from the system power supply unit 24. A backlight power supply unit 22 for converting into an AC voltage suitable for the display, an LCD power supply unit 26 for converting a level of the DC driving voltage supplied from the system power supply unit 24 into a level suitable for driving LCDs and LCD driving circuits; The display timing controller 30 receives the video data from the chipset 28 and supplies the video data to a driver integrated circuit (IC) of the liquid crystal panel. The system power supply 24 and the video chipset 28 are included in the system block 32 of the notebook computer and controlled in software by the operating system of the system. These system operating systems include Windows 95/98, MAC, and OS2. The LCD power supply 26 and the display timing controller 30 are included in the LCD module 20. In general, the system power supply unit 24 and the LCD power supply unit 26 are implemented as a DC-DC converter for converting a level of an input DC voltage.

The following describes the sleep mode operation process in a notebook computer. When a user's input is not applied by an input device such as a keyboard or a mouse in a notebook computer, there is no change in the video data displayed on the LCD. When there is no change in the video data as described above, the automatic power manager (hereinafter referred to as "APM") program included in the system operating system detects this. If the invariant state of the video data continues for a certain period of time and exceeds a predetermined reference time (user adjustable), the APM causes the system power supply 24 to instruct the central processing unit (not shown) of the system to stop supplying power. do. Then, a disable signal is applied to the control input terminal of the system power supply unit 24 so that the power supply to the LCD module 20 is cut off and the power supply to the backlight power supply 22 is also cut off, thereby stopping the LCD screen output. Will be. If there is a separate on / off output terminal in the backlight power supply unit 22, the output terminal of the backlight power supply unit 22 is turned off while maintaining the power supply to the backlight power supply unit 22. Thereafter, when a user's input is received, the APM detects this and instructs an enable signal to be applied to the system power supply 24 and the video chipset 28 to switch the LCD to the normal screen output mode.

In addition to notebook computers, various systems that use LCD as a display means require this sleep mode function to extend the service life of the system and reduce power consumption by reducing unnecessary driving time of the backlight having a limited lifetime. Doing. However, the implementation of the sleep mode function in a system using a conventional LCD driver is limited to a software method that depends entirely on the operating system of the system as in the case of the notebook computer. Most of the systems that use LCDs, except for notebook computers, cannot install system operating systems such as Windows 95/98 and MAC that support sleep mode. In preparation for such a situation, an LCD driver capable of performing a sleep mode function on its own has not yet been developed. Accordingly, there is a problem in that the sleep mode function cannot be implemented when the conventional LCD and its driving apparatus are used in systems where the system operating system supporting the sleep mode function is not installed.

Accordingly, an object of the present invention is to provide a driving apparatus for a liquid crystal display panel which can perform a sleep mode function by itself without resorting to software control of a system operating system.

1 is a block diagram schematically showing a liquid crystal display panel driver in a notebook computer.

2 is a block diagram illustrating a driving device of a liquid crystal display panel according to an exemplary embodiment of the present invention.

3 is a detailed block diagram of the power control unit shown in FIG. 2;

4 is a detailed circuit diagram of the video data comparator shown in FIG.

<Description of the code | symbol about the principal part of drawing>

20,50: LCD module 22,54: backlight power unit

24: system power supply 26,56: LCD power supply

28: video chipset 30, 58: display timing control

32,52: system block 60: power control unit

70: Counter 72: Video Data Comparator

74: Register 76: Time Data Comparator

80: XOR gate 82: OR gate

In order to achieve the above object, a driving device of a liquid crystal display panel according to the present invention detects a change in image data supplied to a liquid crystal display panel and supplies power to the liquid crystal display panel, the driving circuit and the backlight according to the result. Power control means for controlling the apparatus.

Other objects and features of the present invention in addition to the above object will be apparent from the description of the embodiments with reference to the accompanying drawings.

Hereinafter, exemplary embodiments of the present invention will be described with reference to FIGS. 2 to 4.

2 is a block diagram illustrating an LCD driving apparatus according to an exemplary embodiment of the present invention. 2, the LCD driving apparatus according to the present invention is a system block 52 for supplying a data signal such as driving power and video data to the LCD module 50, and the DC voltage supplied from the system block 52 Backlight power supply 54 for converting to an AC voltage suitable for backlight driving, and LCD power supply 56 for converting the level of the DC voltage supplied from the system block 52 to a level suitable for driving the liquid crystal panel and its driving circuit. And a display timing controller 58 for supplying the video data supplied from the system block 52 to the driver integrated circuit of the LCD, and detecting whether there is a change in the video data so that the LCD power supply 56 and the backlight power supply 54 are connected. And a power supply controller 60 for controlling the output.

In the LCD driving apparatus according to the present invention, the system block 52 is not provided with a system operating system supporting the sleep mode function. Instead, the sleep mode function is implemented by itself by the power controller 60 embedded in the LCD module 50. The video data supplied from the system block 52 is applied not only to the display timing controller 58 but also to the power supply controller 60. In addition, the system block 52 supplies reference time data for controlling the operation time of the sleep mode function to the power supply controller 60. The power supply controller 60 receives video data in frame units and compares data of two consecutive frames with each other to determine whether data has changed. When there is a change in the video data, it corresponds to the case where the user is using the system. The power controller 60 applies an enable signal to the backlight power supply 54 and the LCD power supply 56 to perform a normal display operation. Let's do it. However, if there is no change in the video data for a certain period of time, that is, if the output of the same image on the LCD screen lasts for a certain period of time, since the use of the system is stopped, the power control unit 60 detects this. The disable signal is supplied to the backlight power supply 54 and the LCD power supply 56. At this time, the output of the backlight power supply 54 and the LCD power supply 56 is cut off, and the image output of the LCD is stopped. The operation time of the sleep mode function can be adjusted by the user arbitrarily adjusting the reference time data supplied from the system block 52 to the power control unit 60. The power supply controller 60 checks the duration of the same video data and compares it with the reference time of the reference time data. The sleep mode function is activated when the invariable period of video data is reached and the reference time is reached. Even when the LCD operation is stopped by the sleep mode function, the power supply control unit 60 continuously checks the change of the video data. At this time, if there is a change in the video data, the power supply controller 60 supplies the enable signal back to the backlight power supply 54 and the LCD power supply 56 to switch the LCD to the normal display mode.

3 is a detailed block diagram of the power control unit shown in FIG. 2. 3, a method of controlling power supply to the backlight and the LCD in the present invention will be described. The power control unit 60 counts the vertical sync signal V _sync that is input and counts the number of data frames that are output to the LCD as an image. A video data comparator 72 for resetting the counter 70 when there is a change, a register 74 for converting and storing reference time data related to the operation time of the sleep mode function into corresponding frame number data, and a counter ( A time data comparator 76 which compares the value output from 70 and the value output from the register 74 and supplies a disable signal to the backlight power supply 54 and the LCD power supply 56 if the two values match. do.

The counter 70 counts the number of video data frames output as an image according to the input vertical sync signal V _sync . The video data comparator 72 continuously compares two consecutive frames and detects the change of video data. When the data is the same for each frame, the counter 70 counts the same number of data frames. On the other hand, if a change occurs in the video data, the video data comparator 72 detects this and supplies a reset signal to the counter 70. At this time, the counter 70 loses the data of the number of frames counted up to the previous time and counts the number of frames again from the next frame. If the invariant of the video data for each frame continues and the number of the same frames counted by the counter matches the number of reference frames stored in the register 74, the time data comparator 76 returns the backlight power supply 54 and the LCD power supply 56. To provide a disable signal. Accordingly, the backlight of the backlight is turned off, power supply to the liquid crystal panel and the driving circuit is stopped, and the display operation of the LCD is stopped. When the video data change occurs while the sleep mode function is operating, the video data comparator 72 supplies a reset signal to the counter 70, and the counter 70 starts a new frame count. At this time, the number of frame counts output from the counter 70 does not match the number of reference frames stored in the register 74, so that the time data comparator 76 outputs the enable signal. Then, the backlight power supply 54 resumes supplying power to the backlight, and the LCD power supply 56 resumes supplying power to the liquid crystal panel and the driving circuit so that the LCD is switched back from the sleep mode to the normal display mode. .

4 is a detailed circuit diagram of the video data comparator shown in FIG. 3. Referring to FIG. 4, a method of detecting the presence or absence of a change in video data for each frame will be described in the present invention. The video data comparator 72 includes a first frame data latch D and a second frame data latch D + for sequentially holding applied video data in units of frames, and the first and second frame data latches XOR (Exclusive OR) that compares two frame data held in D, D +) by red (R), green (G), and blue (B) data respectively and outputs a low signal when the two data are the same. ) Gates 80 and OR gates 82 having three inputs for each output of these XOR gates 80.

The first and second frame data latches D and D + hold data in frame units in synchronization with the vertical synchronization signal V _sync input thereto. The first frame data latch D holds a currently input video data frame. When the next frame data is input to the first frame data latch D, the frame data held in the first frame data latch D is transferred to the second frame data latch D +, and thus the second frame data latch D +. Is held in. The two frame data held in the first and second frame data latches (D, D +), respectively, are compared by the XOR gates 80 for data of red (R), green (G), and blue (B) colors. When the frame data held in the first frame data latch (D) and the frame data held in the second frame data latch (D +) are the same, the data of each of the red (R), green (G), and blue (B) colors The XOR gates 80 comparing all output a low signal. In this case, since all three input values of the OR gate 82 are low, the output of the OR gate 82 is low, and the counter 70 is not reset, but the vertical synchronization signal V _sync . As a result, the number of the same frame is continuously counted. Then, the sleep mode function is activated when the same frame number is equal to the reference frame number. Meanwhile, when a change occurs in the frame data, at least one of the three XOR gates 80 becomes high in output. Accordingly, the counter 70 is reset while the output of the OR gate 82 becomes high. At this time, when the sleep mode function is in operation, the sleep mode function is released, and the counter 70 starts a new frame count. In the case where video data continuously changes from frame to frame, the output of the OR gate 82 continues to be high, and the counter 70 is reset every frame. In this case, the enable signal is continuously supplied to the backlight power supply 54 and the LCD power supply 56 so that the LCD performs a normal display operation.

As described above, the driving apparatus of the liquid crystal display panel according to the present invention detects the change of video data supplied from the system by itself and controls on / off of the liquid crystal panel, the driving circuit unit, and the backlight. In contrast to the conventional implementation of the sleep mode function of the LCD by a software method depending only on the operating system of the system, using the LCD drive device of the present invention, even in systems where the system operating system is not installed or can not be installed, the LCD sleep mode You can perform the function.

Those skilled in the art will appreciate that various changes and modifications can be made without departing from the technical spirit of the present invention. Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification but should be defined by the claims.

Claims (5)

And a power supply control means for sensing a change in the image data supplied to the liquid crystal display panel and controlling the power supply device for supplying power to the liquid crystal display panel, its driving circuit and the backlight according to the result. Drive of the panel. The method of claim 1, The power supply control means includes a counter for counting the number of frames of the image data; Data change detection means for detecting a change in the image data in units of frames and supplying a reset signal to the counter when there is a change in the image data; Reference time setting means for setting a reference time which is a time point at which the output of the power supply is turned off; Reference data storage means for storing data of a reference frame number corresponding to the reference time; And a time data comparing means for disabling the power supply device if the number of frames counted by the counter and the number of reference frames stored in the reference data storage unit are equal to each other. . The method of claim 2, And the reference time can be adjusted by a user. The method of claim 2, The data change detection means includes first data storage means for storing image data of a frame currently being input; Second data storage means for storing image data of a previous frame; And an image data comparison means for comparing the image data stored in each of the first and second data storage means, and resetting the counter if they are different from each other. The method of claim 4, wherein The image data comparing means may include exclusive OR gates respectively detecting whether the image data corresponding to red, green, and blue included in the frame data stored in the first and second data storage means are the same; And an OR gate for supplying the reset signal to the counter by performing an OR operation on the data output from each of the exclusive OR gates.