Liquid crystal display device and method for driving same

Patent metadata

Field	Value
Publication number	US-2016196781-A1
Application number	US-201314655812-A
Country	US
Kind code	A1
Filing date	Dec 20, 2013
Priority date	Dec 28, 2012
Publication date	Jul 7, 2016
Grant date	—

Abstract

Provided is a liquid crystal display device capable of reliably reducing power consumption during pause drive by controlling the timing of performing refresh.
When there is an image change in externally inputted RGB data, or when the number of consecutive pause frames reaches a predetermined value, if the number of immediately preceding pause frames is less than a threshold BCTH, image signal refresh is performed once, or if the number of pause frames is greater than or equal to the threshold BCTH, boost charge refresh is performed first, and then, the image signal refresh is performed. As a result, it is rendered possible to reduce flicker due to luminance reduction, and it is also rendered possible to eliminate the need to perform refresh consecutively even if the frequency of RGB data is high (e.g., 30 Hz) during pause drive.

First claim

1 . A liquid crystal display device performing pause drive with a pause frame for pausing screen refresh being set between two refresh frames in which screen refresh is performed, the device comprising:
a display portion including a plurality of scanning signal lines formed on an insulating substrate, a plurality of data signal lines crossing each of the scanning signal lines, and a plurality of pixel forming portions arranged in a matrix corresponding to respective intersections of the scanning signal lines and the data signal lines; a scanning signal line driver circuit configured sequentially to select the scanning signal lines; a data signal line driver circuit configured to write image signal voltages to the data signal lines, the image signal voltages being generated on the basis of externally inputted image data; and a display control circuit configured to control the operation of the scanning signal line driver circuit and the data signal line driver circuit, wherein, the display control circuit includes: a correction circuit configured either to output correction image data obtained by subjecting image data for a current frame to a tone emphasizing process for emphasizing a temporal change or to output the image data for the current frame without performing the tone emphasizing process; and a first register configured to store a preset threshold, the display control circuit determines whether the number of pause frames preceding the current frame is greater than the threshold, and when the number of pause frames is determined to be greater than the threshold, the data signal line driver circuit applies a boost charge voltage and an image signal voltage successively to the data signal lines, the boost charge voltage being different in polarity from image data for the pause frame and being based on the correction image data outputted by the correction circuit, the image signal voltage having the same polarity as the correction image data and being based on the image data for the current frame, whereas when the number of pause frames is determined to be less than the threshold, the data signal line driver circuit applies the image signal voltage to the data signal lines, the image signal voltage being different in polarity from the image data for the pause frame.

2 . The liquid crystal display device according to claim 1 , wherein the display control circuit further includes an image change detection circuit configured to detect a state change of the image data for the current frame.

3 . The liquid crystal display device according to claim 2 , wherein,
the externally inputted image data is data that is inputted successively on a frame-by-frame basis, the image change detection circuit detects a change in an image represented by the image data on a frame-by-frame basis, and when there is any change detected in the image, the display control circuit starts providing both the correction image data and the image data or only the image data to the data signal line driver circuit from the next frame after the frame with the detected image change.

4 . The liquid crystal display device according to claim 3 , wherein,
the display control circuit further includes: a counter configured to count the number of consecutive pause frames preceding the frame determined to have a change in the image data; and a second register configured to store a preset specific value, and the display control circuit determines whether the number of counted pause frames is greater than the specific value regardless of the presence or absence of a change in the image, and provides both the correction image data outputted by the correction circuit and the image data successively to the data signal line driver circuit when the number is determined to be greater than the specific value, or provides only the image data to the data signal line driver circuit when the number is determined to be less than the specific value.

5 . The liquid crystal display device according to claim 1 , wherein,
the externally inputted image data is data that is inputted intermittently or in response to a transmission request made by the liquid crystal display device, and upon reception of the externally inputted image data, the display control circuit starts providing both the correction image data and the image data or only the image data to the data signal line driver circuit from a frame in which the image data has been detected.

6 . The liquid crystal display device according to claim 5 , wherein,
the display control circuit further includes: a counter configured to count the number of consecutive pause frames preceding the frame in which the image data was detected as having been inputted; and a second register configured to store a preset specific value, and the display control circuit determines whether the number of counted pause frames is greater than the specific value regardless of whether the image data has been detected, and provides both the correction image data outputted by the correction circuit and the image data successively to the data signal line driver circuit when the number is determined to be greater than the specific value, or provides only the image data outputted by the correction circuit to the data signal line driver circuit when the number is determined to be less than the specific value.

7 . The liquid crystal display device according to claim 2 , wherein,
the display control circuit further includes first frame memory configured to hold at least the image data whose state change has been detected, the first frame memory being rewritable memory, and when the display portion displays the refresh frame, the display control circuit reads the image data being held in the first frame memory, and provides the image data to the data signal line driver circuit.

8 . The liquid crystal display device according to claim 1 , wherein,
the display control circuit further includes an interface portion configured to obtain the image data and a timing signal from externally inputted data, the timing signal being required for activating the display control circuit, and in accordance with a control signal generated from the timing signal, the display control circuit controls the timing of providing the image data or the correction image data to the data signal line driver circuit.

9 . The liquid crystal display device according to claim 1 , wherein the display control circuit further includes a command register configured to output the image data as RAM write data in accordance with an externally inputted command, and internally generates a timing control signal for operation control.

10 . The liquid crystal display device according to claim 2 , wherein the image change detection circuit detects the presence or absence of an image change by comparing a value obtained by an arithmetic operation using image data for a preceding frame and a value obtained by an arithmetic operation using image data for a current frame.

11 . The liquid crystal display device according to claim 2 , wherein the image change detection circuit detects the presence or absence of an image change by comparing image data for a preceding frame and image data for a current frame.

12 . The liquid crystal display device according to claim 2 , wherein the image change detection circuit detects the presence or absence of an image change on the basis of a predetermined signal that is externally inputted.

13 . The liquid crystal display device according to claim 2 , wherein the image change detection circuit includes a third register in which a value that specifies the presence or absence of an

Assignees

• Sharp Kk

Inventors

• Tanaka Noriyuki
• Suyama Tatsuhiko
• SONE Takuya
• Ohmura Norio
• Uemura Kentaroh
• Kumada Kouji

Classifications

• G09G2320/0242

  Compensation of deficiencies in the appearance of colours · CPC title

• G09G2320/0285

  using tables for spatial correction of display data · CPC title

• G09G3/2096

  Details of the interface to the display terminal specific for a flat panel (suitable for both CRT and flat panel G09G5/006; specific for a CRT G09G1/167) · CPC title

• G09G2320/0247

  Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes · CPC title

• G09G3/3648 Primary

  using an active matrix (G09G3/367 - G09G3/3696 take precedence) · CPC title