Liquid crystal display device

• US 9,082,367 B2
• Filed: 03/27/2013
• Issued: 07/14/2015
• 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): Lao, Lun-Yi
• Assistant Examiner(s): KHAN, IBRAHIM A
• Application Number:
  US13/851,229
• Publication Number:
  US 20130321382A1
• Time in Patent Office: 839 Days
• Field of Search: 345204-212, 345/89, 345/100, 345/104, 345/96, 345/173, 345/174, 349/12, 713/320, 713/330, 713/340
• US Class Current: 1/1
• 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, in which there is provided a display section formed of a plurality of pixels arranged in matrix,

wherein the second substrate has detection electrodes of a touch panel,

wherein each pixel has a pixel electrode and a counter electrode,

wherein the display section is divided into a plurality of blocks each of which is formed of the pixels disposed on a plurality of display lines adjacent to one another,

wherein the counter electrode is an electrode common to the pixels in each block,

wherein the counter electrode of each block also functions as a scanning electrode of the touch panel,

wherein the liquid crystal display device has a driving circuit which supplies a counter voltage and a touch panel scanning voltage to the counter electrodes of the respective blocks,

wherein the driving circuit has a gradation voltage generation circuit which generates a plurality of gradation voltages,

wherein the gradation voltage generation circuit has a plurality of amplifier circuits which output the plurality of gradation voltages,

wherein each amplifier circuit has a current adjustment circuit capable of adjusting current flowing in the amplifier circuit itself, and

wherein the driving circuit

causes the current adjustment circuit of a middle amplifier circuit other than a top amplifier circuit, which outputs a highest gradation voltage, and a bottom amplifier circuit, which outputs a lowest gradation voltage, among the plurality of amplifier circuits, to stop an operation of the corresponding middle amplifier circuit, in a first low power consumption mode for achieving lower power consumption than a normal operation,

causes the current adjustment circuit of the middle amplifier circuit to stop the operation of the corresponding middle amplifier circuit and causes the current adjustment circuits of the top amplifier circuit and the bottom amplifier circuit to reduce current, which flows in the top amplifier circuit and the bottom amplifier circuit, such that the current is lower than current, which flows in the amplifier circuit at the time of the normal operation, in a second low power consumption mode for achieving lower power consumption than the first low power consumption mode, and

causes the current adjustment circuits of the respective amplifier circuits, which output the plurality of gradation voltages, to stop operations of the respective amplifier circuits and supply a GND voltage as the lowest gradation voltage, in a third low power consumption mode for achieving lower power consumption than the second low power consumption mode.

2. The liquid crystal display device according to claim 1, further comprising a first counter electrode selection circuit and a second counter electrode selection circuit that are disposed on both sides of the display section and select the counter electrodes of the respective blocks,

wherein the first counter electrode selection circuit and the second counter electrode selection circuit are circuits formed inside the liquid crystal display panel, and

wherein the driving circuit supplies an address signal to the first counter electrode selection circuit and the second counter electrode selection circuit.

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

wherein each of the first counter electrode selection circuit and the second counter electrode selection circuit has

an address decoder circuit that selects the counter electrode of arbitrary one block among the plurality of blocks, and

a selection circuit that supplies the touch panel scanning voltage to the counter electrode of the block, which is selected by the address decoder circuit, and supplies the counter voltage to the counter electrode of the block which is not selected by the address decoder circuit.

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

wherein the driving circuit supplies the touch panel scanning voltage to the counter electrode and detects the touch position on the touch panel in the third low power consumption mode.

5. 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, in which there is provided a display section formed of a plurality of pixels arranged in matrix,

wherein the second substrate has detection electrodes of a touch panel,

wherein the first substrate has a plurality of scanning lines which supply a selection scanning voltage VGH and a non-selection scanning voltage VGL to the respective pixels,

wherein each pixel has a pixel electrode and a counter electrode,

wherein the display section is divided into a plurality of blocks each of which is formed of the pixels disposed on a plurality of display lines adjacent to one another,

wherein the counter electrode is an electrode common to the pixels in each block,

wherein the counter electrode of each block also functions as a scanning electrode of the touch panel,

wherein the corresponding liquid crystal display device has a driving circuit which outputs the VGH and the VGL and supplies a counter voltage and a touch panel scanning voltage to the counter electrodes of the respective blocks, and

wherein the driving circuit

has a charge-pump VGH/VGL generation circuit which generates the VGH and the VGL, and

sets an ON/OFF period of a switching circuit in the VGH/VGL generation circuit such that the ON/OFF period is longer than an ON/OFF period at the time of a normal operation, in a low power consumption mode for achieving lower power consumption than the normal operation.

6. The liquid crystal display device according to claim 5, further comprising a first counter electrode selection circuit and a second counter electrode selection circuit that are disposed on both sides of the display section and select the counter electrodes of the respective blocks,

wherein the first counter electrode selection circuit and the second counter electrode selection circuit are circuits formed inside the liquid crystal display panel, and

wherein the driving circuit supplies an address signal to the first counter electrode selection circuit and the second counter electrode selection circuit.

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

wherein each of the first counter electrode selection circuit and the second counter electrode selection circuit has

an address decoder circuit that selects the counter electrode of arbitrary one block among the plurality of blocks, and

a selection circuit that supplies the touch panel scanning voltage to the counter electrode of the block, which is selected by the address decoder circuit, and supplies the counter voltage to the counter electrode of the block which is not selected by the address decoder circuit.

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

wherein the driving circuit supplies the touch panel scanning voltage to the counter electrode and detects the touch position on the touch panel in the low power consumption mode.

9. 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, in which there is provided a display section formed of a plurality of pixels arranged in matrix,

wherein the second substrate has detection electrodes of a touch panel,

wherein the first substrate has a plurality of video lines which supply video voltages to the respective pixels,

wherein each pixel has a pixel electrode and a counter electrode,

wherein the display section is divided into a plurality of blocks each of which is formed of the pixels disposed on a plurality of display lines adjacent to one another,

wherein the counter electrode is an electrode common to the pixels in each block,

wherein the counter electrode of each block also functions as a scanning electrode of the touch panel,

wherein the liquid crystal display device has a driving circuit which supplies the video voltages to the respective video lines and supplies a counter voltage and a touch panel scanning voltage to the counter electrodes of the respective blocks,

wherein the driving circuit has

a source amplifier circuit which supplies the video voltages to the video lines, and

a VSP generation circuit, which supplies a high potential voltage VSP to the source amplifier circuit, and a VSN generation circuit which supplies a low potential voltage VSN to the source amplifier circuit,

wherein the VSP generation circuit and the VSN generation circuit are switching-regulator-type step-up circuits, and

wherein the driving circuit

reduces switching frequencies of the VSP generation circuit and the VSN generation circuit, in a first low power consumption mode for achieving lower power consumption than the normal operation, and

reduces the switching frequency of the VSP generation circuit and stops an operation of the VSN generation circuit, in a second low power consumption mode for achieving lower power consumption than the first low power consumption mode.

10. The liquid crystal display device according to claim 9, further comprising a first counter electrode selection circuit and a second counter electrode selection circuit that are disposed on both sides of the display section and select the counter electrodes of the respective blocks,

wherein the first counter electrode selection circuit and the second counter electrode selection circuit are circuits formed inside the liquid crystal display panel, and

wherein the driving circuit supplies an address signal to the first counter electrode selection circuit and the second counter electrode selection circuit.

11. The liquid crystal display device according to claim 10,

wherein each of the first counter electrode selection circuit and the second counter electrode selection circuit has

an address decoder circuit that selects the counter electrode of arbitrary one block among the plurality of blocks, and

a selection circuit that supplies the touch panel scanning voltage to the counter electrode of the block, which is selected by the address decoder circuit, and supplies the counter voltage to the counter electrode of the block which is not selected by the address decoder circuit.

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

wherein the driving circuit supplies the touch panel scanning voltage to the counter electrode and detects the touch position on the touch panel in the second low power consumption mode.

13. 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, in which there is provided a display section formed of a plurality of pixels arranged in matrix,

wherein the second substrate has detection electrodes of a touch panel,

wherein each pixel has a pixel electrode and a counter electrode,

wherein the display section is divided into a plurality of blocks each of which is formed of the pixels disposed on a plurality of display lines adjacent to one another,

wherein the counter electrode is an electrode common to the pixels in each block,

wherein the counter electrode of each block also functions as a scanning electrode of the touch panel,

wherein the liquid crystal display device has a driving circuit which supplies a counter voltage and a touch panel scanning voltage to the counter electrodes of the respective blocks,

wherein the driving circuit has a gradation voltage generation circuit which generates a plurality of gradation voltages,

wherein the gradation voltage generation circuit has a plurality of amplifier circuits which output the plurality of gradation voltages,

wherein each amplifier circuit has a current adjustment circuit capable of adjusting current flowing in the amplifier circuit itself, and

wherein the driving circuit

performs, in a standby state, a scanning operation for touch position detection in a plurality of frames once;

in a first low power consumption mode, in the standby state, adopts a column inversion driving method as the AC driving method of the corresponding liquid crystal display device,

performs a gate scanning operation for writing the video voltages into the respective pixels for each frame, and

causes the current adjustment circuit of a middle amplifier circuit other than a top amplifier circuit, which outputs a highest gradation voltage, and a bottom amplifier circuit, which outputs a lowest gradation voltage, among the plurality of amplifier circuits of the gradation voltage generation circuit, to stop an operation of the corresponding middle amplifier circuit.

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

wherein the first substrate has a plurality of video lines which supply the video voltages to the respective pixels,

wherein the driving circuit has

a source amplifier circuit which amplifies the gradation voltages generated by the gradation voltage generation circuit, and supplies the gradation voltages as the video voltages to the video lines, and

a VSP generation circuit, which supplies a high potential voltage VSP to the source amplifier circuit, and a VSN generation circuit which supplies a low potential voltage VSN to the source amplifier circuit,

wherein the source amplifier circuit has a current adjustment circuit capable of adjusting current flowing in the source amplifier circuit itself,

wherein the VSP generation circuit and the VSN generation circuit are switching-regulator-type step-up circuits, and

wherein the driving circuit, in a second low power consumption mode for achieving lower power consumption than the first low power consumption mode, in the standby state,

adopts the column inversion driving method as the AC driving method of the corresponding liquid crystal display device,

performs the gate scanning operation for writing the video voltages into the respective pixels for each frame,

causes the current adjustment circuit of the source amplifier circuit to reduce the current, which flows in the source amplifier circuit, such that the current is lower than current, which flows in the source amplifier circuit at the time of a normal operation,

causes the current adjustment circuit of the middle amplifier circuit of the gradation voltage generation circuit to stop the operation of the corresponding middle amplifier circuit and causes the current adjustment circuits of the top amplifier circuit and the bottom amplifier circuit to reduce current, which flows in the top amplifier circuit and the bottom amplifier circuit, such that the current is lower than current, which flows in the amplifier circuit at the time of the normal operation, and

reduces switching frequencies of the VSP generation circuit and the VSN generation circuit.

15. The liquid crystal display device according to claim 14,

wherein the first substrate has a plurality of scanning lines which supply a selection scanning voltage VGH and a non-selection scanning voltage VGL to the respective pixels,

wherein the driving circuit has a charge-pump VGH/VGL generation circuit which generates and outputs the VGH and the VGL, and

wherein the driving circuit, in a third low power consumption mode for achieving lower power consumption than the second low power consumption mode, in the standby state,

adopts the column inversion driving method as the AC driving method of the corresponding liquid crystal display device,

performs the gate scanning operation for writing video voltages into the respective pixels in the plurality of frames once,

causes the current adjustment circuit of the source amplifier circuit to reduce the current, which flows in the source amplifier circuit, such that the current is lower than current, which flows in the source amplifier circuit at the time of a normal operation,

causes the current adjustment circuit of the middle amplifier circuit of the gradation voltage generation circuit to stop the operation of the corresponding middle amplifier circuit and causes the current adjustment circuits of the top amplifier circuit and the bottom amplifier circuit to reduce current, which flows in the top amplifier circuit and the bottom amplifier circuit, such that the current is lower than current, which flows in the amplifier circuit at the time of the normal operation,

reduces the switching frequencies of the VSP generation circuit and the VSN generation circuit, and

sets an ON/OFF period of a switching circuit in the VGH/VGL generation circuit such that the ON/OFF period is longer than an ON/OFF period at the time of the normal operation.

16. The liquid crystal display device according to claim 15,

wherein the driving circuit has a common amplifier circuit which supplies the counter voltage to the counter electrodes,

wherein the common amplifier circuit has a current adjustment circuit capable of adjusting current flowing in the common amplifier circuit itself, and

wherein the driving circuit, in a fourth low power consumption mode for achieving lower power consumption than the third low power consumption mode, in the standby state,

adopts the column inversion driving method as the AC driving method of the corresponding liquid crystal display device,

performs the gate scanning operation for writing the video voltages into the respective pixels in the plurality of frames once,

causes the current adjustment circuit of the source amplifier circuit to stop an operation of the source amplifier circuit and supply a GND voltage to the video lines,

causes the current adjustment circuits of the respective amplifier circuits, which output the plurality of gradation voltages of the gradation voltage generation circuit, to stop operations of the respective amplifier circuits and supply the GND voltage as the lowest gradation voltage,

reduces the switching frequency of the VSP generation circuit,

stops an operation of the VSN generation circuit,

sets the ON/OFF period of the switching circuit in the VGH/VGL generation circuit such that the ON/OFF period is longer than an ON/OFF period at the time of the normal operation, and

causes the current adjustment circuit of the common amplifier circuit to stop an operation of the common amplifier circuit and supply the GND voltage to the counter electrodes.

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

wherein the driving circuit supplies the touch panel scanning voltage to the counter electrode and detects the touch position on the touch panel in the first low power consumption mode.