# US 11,112,628 B2 · Liquid crystal display device including common electrode control circuit > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 11,112,628 B2 - Document ID: US11112628B2 - Status: Granted - Kind: B2 - Application number: 16/609,586 - Filed: 2018-06-08 - Published: 2020-05-14 - Granted: 2021-09-07 - Earliest claimed: 2017-06-16 - Assignees: Sharp Kabushiki Kaisha - Applicants: Sharp Kabushiki Kaisha - Inventors: Yuta Ueyama; Masami Ozaki; Hideki Morii - Web page: https://patentgrep.com/patent/US11112628B2 ## CPC - G02F 1/13306: {Circuit arrangements or driving methods for the control of single liquid crystal cells (G02F1/132, G02F1/133382 take precedence)} - G09G 3/3655: {Details of drivers for counter electrodes, e.g. common electrodes for pixel capacitors or supplementary storage capacitors} - G02F 1/13439: {characterised by their electrical, optical, physical properties; materials therefor; method of making} - G09G 3/20: for presentation of an assembly of a number of characters, e.g. a page, by composing the assembly by combination of individual elements arranged in a matrix {no fixed position being assigned to or needed to be assigned to the individual characters or partial characters} - G09G 3/36: using liquid crystals - G09G 3/3648: {using an active matrix (G09G3/367 - G09G3/3696 take precedence)} - G02F 1/13454: {Drivers integrated on the active matrix substrate (G02F1/136277 takes precedence)} - G02F 2201/121: common or background - G02F 2202/10: semiconductor - G09G 2310/0245: Clearing or presetting the whole screen independently of waveforms, e.g. on power-on (G09G2310/063 takes precedence) - G09G 2320/046: Dealing with screen burn-in prevention or compensation of the effects thereof - G09G 2330/027: Arrangements or methods related to powering off a display - G02F: OPTICAL DEVICES OR ARRANGEMENTS FOR THE CONTROL OF LIGHT BY MODIFICATION OF THE OPTICAL PROPERTIES OF THE MEDIA OF THE ELEMENTS INVOLVED THEREIN; NON-LINEAR OPTICS; FREQUENCY-CHANGING OF LIGHT; OPTICAL LOGIC ELEMENTS; OPTICAL ANALOGUE/DIGITAL CONVERTERS - G09G: ARRANGEMENTS OR CIRCUITS FOR CONTROL OF INDICATING DEVICES USING STATIC MEANS TO PRESENT VARIABLE INFORMATION (arrangements for transferring data between digital computers and displays G06F3/14; static indicating arrangements comprising an association of a number of separate sources or light control cells G09F9/00; static indicating arrangements comprising integral associations of a number of light sources H01J, H01K, H10H, H05B33/12; scanning, transmission or reproduction of documents or the like, e.g. facsimile transmission, details thereof H04N1/00) ## Abstract A charge pull-out period is set after power off, and an all-on control signal is set to a high level in the charge pull-out period. A high-level voltage which is output to a scanning line drive circuit formed on a liquid crystal panel is kept at a high level even after power off until a middle of the charge pull-out period. A common electrode control circuit for connecting a common electrode to a ground when the all-on control signal is at the high level and the high-level voltage is at an operation level is configured using two resistors, a NOT circuit, and two FETs, and is provided to a liquid crystal display device. With this, a liquid crystal display device which can lower a common electrode voltage to a ground level when power off and can prevent burn-in after power on is provided. ## Claims ### Claim 1 A liquid crystal display device comprising: a liquid crystal panel having a common electrode and formed using oxide semiconductor; a power supply control circuit configured to output a control signal which becomes an active level in a period set after power off, and a power supply voltage which is kept at an operation level even after power off until a middle of the period; and a common electrode control circuit configured to connect the common electrode to a ground when the control signal is at the active level and the power supply voltage is at the operation level, wherein the common electrode control circuit includes: a first resistor having one end to which the power supply voltage is supplied and another end connected to a first node; a second resister having one end connected to the first node and another end connected to the ground; a NOT circuit configured to output an inverted signal of the control signal; a first transistor having a first conduction terminal connected to the first node, a second conduction terminal connected to the ground, and a control terminal to which the inverted signal is supplied; and a second transistor having a first conduction terminal connected to the common electrode, a second conduction terminal connected to the ground, and a control terminal connected to the first node. ### Claim 2 (depends on 1) The liquid crystal display device according to claim 1, wherein the liquid crystal panel has scanning lines, and the control signal is an all-on control signal for selecting all of the scanning lines. ### Claim 3 (depends on 2) The liquid crystal display device according to claim 2, wherein a scanning line drive circuit configured to drive the scanning lines is formed on the liquid crystal panel, and the power supply voltage is a high-level voltage which is output to the scanning line drive circuit. ### Claim 4 (depends on 2) The liquid crystal display device according to claim 2, wherein the power supply voltage is equal to or more than 5 V. ### Claim 5 (depends on 2) The liquid crystal display device according to claim 2, wherein the period is a charge pull-out period, and the all-on control signal becomes a high level in the charge pull-out period.