CN101593501B - Method for driving liquid crystal display and drive device thereof - Google Patents
Method for driving liquid crystal display and drive device thereof Download PDFInfo
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- CN101593501B CN101593501B CN2009103037454A CN200910303745A CN101593501B CN 101593501 B CN101593501 B CN 101593501B CN 2009103037454 A CN2009103037454 A CN 2009103037454A CN 200910303745 A CN200910303745 A CN 200910303745A CN 101593501 B CN101593501 B CN 101593501B
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- 239000004973 liquid crystal related substance Substances 0.000 title claims abstract description 19
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Abstract
The invention provides a method for driving a liquid crystal display and a drive device thereof. The drive device comprises a difference value circuit, wherein the difference value circuit determines whether to enable an overdrive circuit and a memory controller by the grey scale variation degrees of images preceding and following; and when variations of the images preceding and following are smaller than a default value, the overdrive circuit and the memory controller are disabled to reduce power consumption.
Description
Technical Field
The present invention relates to a driving method and a driving apparatus for a liquid crystal display, and more particularly, to a driving method and a driving apparatus for a liquid crystal display with energy saving effect.
Background
Liquid Crystal Displays (LCDs) have been widely used recently, and have advantages of low power consumption, light weight, and low voltage driving with the improvement of driving technology, and are widely used in video recorders, notebook computers, desktop displays, and various projection devices. In terms of Display devices, Thin Film Transistor Liquid Crystal displays (TFT-LCDs) having excellent characteristics such as high space utilization efficiency, low power consumption, and no radiation have gradually become the mainstream of the market.
However, in order to improve the response time of the lcd, the driving device usually utilizes an overdrive circuit to drive the liquid crystal to accelerate the transition of the liquid crystal. Referring to fig. 1, fig. 1 is a driving circuit according to the prior art, which includes a memory 110, a memory controller 120, and an overdrive circuit 130. The memory controller 120 stores the previous frame data in the memory 110, and the overdrive circuit 130 reads the previous frame data in the memory 110 and compares the previous frame data with the current frame data to output the overdrive frame data. The overdrive circuit 130 adjusts the driving signal according to the change of the frame to accelerate the response time of the pixel. However, the prior art writes each frame into the memory and reads the previously written frame repeatedly, which does not help the frame quality and causes power consumption when the gray level is not changed.
Disclosure of Invention
The invention provides a driving method and a driving device of a liquid crystal display, which selectively enable an overdrive circuit and a memory controller according to the gray scale change degree of a picture. When the frame variation is small, the overdrive circuit and the memory controller are disabled to reduce the power consumption.
In view of the above, the present invention provides a driving method suitable for a driving apparatus of a liquid crystal display, the driving apparatus includes a memory, a memory controller and an overdrive circuit, the driving method includes the following steps: firstly, dividing a picture into a plurality of pixel blocks; then, receiving a first picture data and a second picture data in sequence; respectively obtaining a plurality of first gray scale differences corresponding to the first image data and a plurality of second gray scale differences corresponding to the second image data according to the pixel gray scale value corresponding to each pixel block; and comparing the first gray scale difference value with the second gray scale difference value, and determining whether to enable the memory controller and the overdrive circuit according to the comparison result of the first gray scale difference value and the second gray scale difference value.
In an embodiment of the present invention, the pixel block is an M × N matrix block, and the formula for calculating the gray-scale difference is as follows:
wherein,
representing a gray scale difference, (R, C) is a pixel coordinate at the upper left of the pixel block, (m, n) represents a pixel coordinate value, P (m, n) represents a pixel gray scale value of the first frame data, Q represents a height of the pixel block, and Y represents a width of the pixel block, wherein when n =1, P (m, 0) =0, wherein R, C, m, Q, and Y are positive integers.
In an embodiment of the invention, the step of comparing the first gray scale difference value and the second gray scale difference value includes the following steps: comparing the first gray scale difference value and the second gray scale difference value in the same pixel block, and determining an effective difference number according to whether the difference value between the first gray scale difference value and the second gray scale difference value is greater than a first threshold value; and enabling the memory controller and the overdrive circuit when the effective difference is greater than a second threshold, and disabling the memory controller and the overdrive circuit when the effective difference is less than the second threshold.
From another perspective, the present invention further provides a driving apparatus for a liquid crystal display, adapted to drive a liquid crystal panel, the driving apparatus including a memory, a memory controller, an overdrive circuit and a difference circuit. The difference circuit is coupled to the memory controller and the overdrive circuit for executing the following steps: dividing the picture area into a plurality of pixel blocks; receiving a first picture data and a second picture data in sequence; respectively obtaining a plurality of first gray scale differences corresponding to the first image data and a plurality of second gray scale differences corresponding to the second image data according to the pixel gray scale value corresponding to each pixel block; and comparing the first gray scale difference value with the second gray scale difference value, and determining whether to enable the memory controller and the overdrive circuit according to the comparison result of the first gray scale difference value and the second gray scale difference value. The rest of the operation details of the driving device are the same as those of the driving method, and are not described herein again.
Based on the above, the present invention utilizes the gray scale variation of the image to determine whether to enable the overdrive circuit and the memory controller, and reduces the power consumption by disabling the overdrive circuit and the memory controller while maintaining the original image quality.
In order to make the aforementioned and other features and advantages of the invention more comprehensible, embodiments accompanied with figures are described in detail below.
Drawings
Fig. 1 shows a driving circuit according to the prior art.
Fig. 2 shows a driving device according to an embodiment of the invention.
Fig. 3 is a block diagram of a pixel according to the present embodiment.
Fig. 4 shows a driving method according to an embodiment of the invention.
In the drawings, the main reference symbols indicate:
110. 210: memory body
120. 220, and (2) a step of: memory controller
130. 230: overdrive circuit
240: difference circuit
SOD (R, C): pixel block label
S410-S450: steps of the flow chart
Detailed Description
Referring to fig. 2, fig. 2 is a driving apparatus according to an embodiment of the invention, which includes a memory 210, a memory controller 220, an overdrive circuit 230 and a difference circuit 240. The overdrive circuit 230 and the difference circuit 240 are coupled to the memory controller 220, and the memory controller 220 is used for controlling the read/write operations of the memory 110. The overdrive circuit 230 is used for performing overdrive operation to output overdrive frame data.
The difference circuit 240 performs an operation on the received frame data to obtain a corresponding gray-scale difference, and then determines whether to enable the overdrive circuit 230 and the memory controller 220 by comparing the gray-scale differences of the previous and subsequent frames. When the frame variation is large, the difference circuit 240 enables the overdrive circuit 230 and the memory controller 220, and the memory controller 220 sequentially stores the received frame data for performing the overdrive operation. When the frame variation is small, the difference circuit 240 disables the overdrive circuit 230 and the memory controller 220, and the memory controller 220 does not store the received frame data and the overdrive circuit 230 does not perform the overdrive operation.
The step of calculating the gray scale difference by the difference circuit 240 is as follows: first, the frame is divided into a plurality of pixel blocks, as shown in fig. 3, and fig. 3 is a pixel block diagram according to the present embodiment. Fig. 3 is an example of a 192 × 120 resolution display panel, in which each pixel block is a 10 × 10 pixel block, represented by SOD (R, C), and the values of SOD (R, C) are the upper left pixel coordinates of the pixel block, and the gray scale difference of the pixel block is given by the following formula:
(m, n) represents pixel coordinate values, P (m, n) represents a pixel gray level value of the picture data, Q represents a height (in terms of the number of pixels) of the pixel block, and Y represents a width (in terms of the number of pixels) of the pixel block, wherein when n =1, P (m, 0) = 0. As can be seen from the above formula, the gray scale difference is formed by the sum of the differences of the gray scale values between the pixels in the respective blocks and the adjacent pixels on the left, and the most peripheral pixels (e.g., P (1,1) to P (10,1)) have no pixels on the left, so the original gray scale values are maintained. It should be noted that SOD (R, C) is only one of the ways to mark the pixel blocks, and the embodiment is not limited. The size of each pixel block can also be determined according to design requirements, and is not limited in the embodiment.
Then, the difference circuit 240 calculates the corresponding gray scale difference according to the received frame sequence when receiving the frame data, and then compares the gray scale difference of the previous and next frames according to the position of the respective block. When the gray scale difference is larger than the threshold value, the pixel block is taken as an effective difference block, namely the pixel block with larger gray scale change is represented. Counting the number of all effective difference blocks to obtain an effective difference number, and determining the gray scale change degree of the picture according to the numerical value of the effective difference number. When the effective variance is greater than the predetermined threshold, the memory controller 120 and the overdrive circuit 130 are enabled to perform the operation of overdriving the image data. When the effective difference is smaller than the predetermined threshold, the memory controller 120 and the overdrive circuit 130 are disabled to reduce power consumption.
Since the effective difference is smaller than the predetermined threshold, it means that the gray scale variation of the whole frame is small, even if disabling the memory controller 120 and the overdrive circuit 130 will not affect the frame quality, but the power consumption of the memory controller 120 and the memory 110 can be effectively reduced. In other words, the present embodiment determines whether the overdrive circuit 230 is enabled for performing the overdrive operation according to the gray scale variation of the image, and proposes a method for determining the gray scale variation of the image, i.e. dividing the image into a plurality of pixel blocks, calculating the gray scale difference value in each block, and then determining the gray scale variation of the image by comparing the gray scale difference values of the previous and next images. It should be noted that, since the difference circuit 240 only needs to store the gray scale difference of each frame for comparison, the data of the whole frame need not be stored during the comparison of the gray scale difference, and only the data of the whole frame need to be stored when the overdrive circuit 230 is enabled.
From another perspective, a driving method according to the above embodiment can be summarized as shown in fig. 4, where fig. 4 is a driving method according to an embodiment of the invention, the driving device is suitable for a liquid crystal display, the driving device includes a memory, a memory controller and an overdrive circuit, and the driving method includes the following steps: first, a frame is divided into a plurality of pixel blocks (step S410), and then a first frame data and a second frame data are received in sequence (step S420), and then a gray scale difference corresponding to the first frame data and the second frame data is obtained in sequence (step S430). After obtaining the gray scale difference, the gray scale difference of the front and rear frames is compared (step S440), and whether the memory controller and the overdrive circuit are enabled is determined according to the comparison result (step S450). In step S450, when the difference between the gray scale differences of the front and rear frames is large, i.e., the effective difference number is greater than the threshold value, the memory controller and the overdrive circuit are enabled. When the difference of the gray scale difference values of the current and the back pictures is small, namely the effective difference number is smaller than the threshold value, the memory controller and the overdrive circuit are disabled to reduce the power consumption.
In summary, the present invention provides a method for determining the gray scale variation degree of a front and a back image by using the gray scale difference, and selectively disables the memory controller and the overdrive circuit according to the variation degree of the gray scale difference to reduce power consumption, so that the liquid crystal display can achieve the effect of saving energy and power when the image variation is small or a static image, and maintain the image quality when the image is dynamic.
Although the present invention has been described with reference to the above embodiments, it should be understood that the invention is not limited to the embodiments, and various changes and modifications can be made by one skilled in the art without departing from the spirit and scope of the invention.
Claims (2)
1. A driving method of liquid crystal display is suitable for a driving device of the liquid crystal display, the driving device comprises a memory, a memory controller and an overdrive circuit, and the driving method is characterized by comprising the following steps:
dividing the picture area into a plurality of pixel blocks;
receiving a first picture data and a second picture data in sequence;
respectively obtaining a plurality of first gray scale differences corresponding to the first picture data and a plurality of second gray scale differences corresponding to the second picture data according to the pixel gray scale value corresponding to each pixel block;
wherein the pixel blocks are M × N matrix blocks, wherein M, N is a positive integer;
the first gray scale differences correspond to the pixel blocks, and the formula for calculating the first gray scale differences is as follows:
wherein,
representing the first gray scale differences, (R, C) is the pixel coordinate of the upper left of the pixel block, (m, n) represents the pixel coordinate value, P (m, n) represents the pixel gray scale value of the first picture data, Q represents the height of the pixel block, Y represents the width of the pixel block, wherein when n =1, P (m, 0) =0, wherein R, C, m, Q, Y are all positive integers;
the second gray scale differences correspond to the pixel blocks, and the formula for calculating the second gray scale differences is as follows:
wherein,
representing the second gray scale differences, (R, C) is the pixel coordinate of the upper left of the pixel block, (m, n) represents the pixel coordinate value, P (m, n) represents the pixel gray scale value of the second frame data, Q represents the height of the pixel block, Y represents the width of the pixel block, wherein when n =1, P (m, 0) =0, wherein R, C, m, Q, Y are all positive integers;
comparing the first gray scale differences and the second gray scale differences in the same pixel block, and determining an effective difference number according to whether the difference between the first gray scale differences and the second gray scale differences is greater than a first threshold; and
enabling the memory controller and the overdrive circuit when the effective difference number is greater than a second threshold, and disabling the memory controller and the overdrive circuit when the effective difference number is less than the second threshold.
2. A driving device of a liquid crystal display, adapted to drive a liquid crystal panel, the driving device comprising:
a memory;
a memory controller coupled to the memory;
an overdrive circuit coupled to the memory controller for generating an overdrive image data; and
a difference circuit coupled to the memory controller and the overdrive circuit, wherein the difference circuit is configured to perform the following steps:
dividing the picture area into a plurality of pixel blocks;
receiving a first picture data and a second picture data in sequence;
respectively obtaining a plurality of first gray scale differences corresponding to the first picture data and a plurality of second gray scale differences corresponding to the second picture data according to the pixel gray scale value corresponding to each pixel block;
wherein the pixel blocks are M × N matrix blocks, wherein M, N is a positive integer;
the first gray scale differences correspond to the pixel blocks, and the formula for calculating the first gray scale differences is as follows:
wherein,
representing the first gray scale differences, (R, C) is the pixel coordinate of the upper left of the pixel block, (m, n) represents the pixel coordinate value, P (m, n) represents the pixel gray scale value of the first picture data, Q represents the height of the pixel block, P represents the width of the pixel block, wherein when n =1, P (m, 0) =0, wherein R, C, m, Q, Y are all positive integers;
the second gray scale differences correspond to the pixel blocks, and the formula for calculating the second gray scale differences is as follows:
wherein,
representing the second gray scale differences, (R, C) is the pixel coordinate of the upper left of the pixel block, (m, n) represents the pixel coordinate value, P (m, n) represents the pixel gray scale value of the second frame data, Q represents the height of the pixel block, P represents the width of the pixel block, wherein when n =1, P (m, 0) =0, wherein R, C, m, Q, Y are all positive integers;
comparing the first gray scale differences and the second gray scale differences in the same pixel block, and determining an effective difference number according to whether the difference between the first gray scale differences and the second gray scale differences is greater than a first threshold; and
enabling the memory controller and the overdrive circuit when the effective difference number is greater than a second threshold, and disabling the memory controller and the overdrive circuit when the effective difference number is less than the second threshold.
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| EP1748413A1 (en) * | 2005-07-27 | 2007-01-31 | Mitsubishi Electric Corporation | Image processing circuit and image processing method |
| CN101308636A (en) * | 2007-05-15 | 2008-11-19 | 奇美电子股份有限公司 | Liquid crystal display capable of improving display quality of dynamic images and driving method thereof |
| CN101364386A (en) * | 2007-08-07 | 2009-02-11 | 奇美电子股份有限公司 | Selective overdrive method and apparatus thereof |
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| Publication number | Priority date | Publication date | Assignee | Title |
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| EP1748413A1 (en) * | 2005-07-27 | 2007-01-31 | Mitsubishi Electric Corporation | Image processing circuit and image processing method |
| CN101308636A (en) * | 2007-05-15 | 2008-11-19 | 奇美电子股份有限公司 | Liquid crystal display capable of improving display quality of dynamic images and driving method thereof |
| CN101364386A (en) * | 2007-08-07 | 2009-02-11 | 奇美电子股份有限公司 | Selective overdrive method and apparatus thereof |
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