Liquid crystal display device

• US 9,847,071 B2
• Filed: 05/07/2015
• Issued: 12/19/2017
• Est. Priority Date: 05/31/2012
• Status: Active Grant

• Current Assignee: Japan Display Incorporated
• Original Assignee: Japan Display Incorporated
• Inventors: Nagao, Shouji
• Primary Examiner(s): Khan, Ibrahim
• Application Number:
  US14/706,703
• Publication Number:
  US 20150243241A1
• Time in Patent Office: 957 Days
• CPC Class Codes: G06F 1/3262 Power saving in digitizer or tablet
• CPC Class Codes: G06F 1/3265 Power saving in display device
• CPC Class Codes: G06F 3/0412 Digitisers structurally integrated in a display
• CPC Class Codes: G06F 3/044 by capacitive means
• CPC Class Codes: G06F 3/0445 using two or more layers of sensing electrodes, e.g. using two layers of electrodes separated by a dielectric layer
• CPC Class Codes: G06F 3/0446 using a grid-like structure of electrodes in at least two directions, e.g. using row and column electrodes
• CPC Class Codes: G06F 3/047 using sets of wires, e.g. crossed wires
• CPC Class Codes: G09G 2300/0426 Layout of electrodes and connections
• CPC Class Codes: G09G 2330/021 Power management, e.g. power saving
• CPC Class Codes: G09G 3/3696 Generation of voltages supplied to electrode drivers
• CPC Class Codes: Y02D 10/00 Energy efficient computing, e.g. low power processors, power management or thermal management
• CPC Class Codes: Y02D 30/50 in wire-line communication networks, e.g. low power modes or reduced link rate

Abstract

In a liquid crystal display (LCD) device having a touch panel function, power consumption is reduced in the standby state. The display section is divided into blocks each of which is formed of a plurality of display lines. The counter electrode is disposed for each block. A driving circuit selectively supplies, to the counter electrode of each block, the voltage used for the liquid crystal display and the voltage used for the touch panel scanning. The driving circuit has a source amplifier that supplies the video voltages to the video lines. The driving circuit reduces the current in the source amplifier, such that the current is lower than current at the time of a normal operation, to lower the power consumption, and stops the operation of the source amplifier and supplies the GND voltage to the video lines to further lower the power consumption.

Claims

1. A liquid crystal display device comprising:

a liquid crystal display panel that has a first substrate, a second substrate, and a liquid crystal sandwiched between the first substrate and the second substrate;

a plurality of pixels formed in a display section of the first substrate;

a plurality of pixel electrodes respectively formed in the pixels;

a plurality of common electrodes respectively formed as facing to the pixel electrodes, formed in the first substrate, and used for detection of a conductor approaching or touching;

a common voltage circuit supplying a common voltage for displaying an image to the common electrodes;

a scanning control circuit supplying a scanning voltage for detecting the conductor to the common electrodes; and

a detection circuit detecting a detection voltage of a detection electrode,

wherein the display device has a first mode for displaying an image in the display section and a second mode that is a standby mode,

wherein the first mode has a first period for displaying an image and a second period for detecting,

wherein the second mode has a third period in which the display section is in a standby state and a fourth period for detecting,

wherein the display panel detects the conductor with using the common electrodes in the second period and the fourth period,

wherein an image signal is supplied to the pixel electrodes in the third period, and an image signal is not supplied to the pixel electrodes in the fourth period,

wherein detection accuracy in the fourth period is lower than detection accuracy in the second period, and

wherein the display section displays black in the third period.

2. The liquid crystal display device according to claim 1,

wherein the common voltage is not supplied to the common electrodes in the third period.

3. The liquid crystal display device according to claim 2,

wherein a ground voltage is supplied to the common electrodes in the third period.

4. The liquid crystal display device according to claim 2, further comprising a third mode for supplying the common voltage to the common electrodes and not displaying an image in the display section.

5. The liquid crystal display device according to claim 1,

wherein power consumed for detecting the conductor in the second mode is lower than power consumed for detecting the conductor in the first mode.

6. The liquid crystal display device according to claim 1,

wherein the liquid crystal display panel is set to a display off state in which black is displayed in the display section in the second mode.

7. The liquid crystal display device according to claim 1,

wherein scanning operations are performed for sequentially supplying the scanning voltage to the common electrodes in the second period and the fourth period, and

wherein a number of the scanning operations in the fourth period is less than a number of the scanning operations in the second period.

8. The liquid crystal display device according to claim 1, further comprising:

a VSP generation circuit that supplies a potential voltage to the common electrodes; and

a VSN generation circuit that supplies a negative voltage to the common electrodes,

wherein one of the VSP generation circuit and the VSN generation circuit is stopped in the second mode.

9. The liquid crystal display device according to claim 1,

wherein the first substrate has the common electrodes, and the second substrate has a detection electrode.

10. The liquid crystal display device according to claim 1 further comprising:

voltage generation circuits,

wherein the common voltage circuit and the scanning control circuit share the voltage generation circuits.

11. The liquid crystal display device according to claim 1 further comprising:

a transistor electrically connecting to one of the pixel electrodes,

wherein a state of the transistor is off state in the fourth period.

12. The liquid crystal device according to claim 1, wherein the first mode is normal operation mode and the second mode is in the standby mode.

13. The liquid crystal display device according to claim 1,

wherein in the standby mode, a voltage of the image signal has substantially no potential difference from the common voltage.