# US 10,121,426 B2 · Polarity inversion control device for liquid crystal display, liquid crystal display device, and driving method thereof > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 10,121,426 B2 - Document ID: US10121426B2 - Status: Granted - Kind: B2 - Application number: 15/000,787 - Filed: 2016-01-19 - Published: 2016-07-21 - Granted: 2018-11-06 - Earliest claimed: 2015-01-20 - Assignees: NLT Technologies, Ltd. - Applicants: Nlt Technologies, Ltd. - Inventors: Hiroki Ishikawa - Web page: https://patentgrep.com/patent/US10121426B2 ## CPC - G09G 3/3614: {Control of polarity reversal in general} - G09G 2340/16: Determination of a pixel data signal depending on the signal applied in the previous frame - G09G 2360/16: Calculation or use of calculated indices related to luminance levels in display data - 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 To provide a liquid crystal display device and the like capable of achieving a function with which the charging polarity for the liquid crystal panel is not deviated even when the frame rate for writing to the liquid crystal panel changes dynamically only with simple structures and low power consumption. A polarity inversion control circuit is for supplying polarity inversion signals to the liquid crystal panel, and it is characterized to switch the levels of the polarity inversion signals in such a manner that a difference between an integrated value of frame periods when the polarity inversion signal is in a first level and an integrated value of the frame periods when the polarity inversion signal is in a second level becomes small. ## Claims ### Claim 1 A polarity inversion control device for a liquid crystal display panel having a plurality of pixels writeable with pixel voltages, comprising: an output configured to couple a polarity inversion signal to the liquid crystal display panel, wherein the polarity inversion signal is based on frame periods of data representing the pixel voltages, and causes inversion of polarities of the pixel voltages; a frame period detection unit which detects the frame period; and a write integrated value calculation unit configured to switch a level of the polarity inversion signal in such a manner that a difference between an integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in a first level and an integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in a second level becomes small, wherein the write integrated value calculation unit, regarding the frame period detected by the frame period detection unit, calculates the difference between the integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in the first level and the integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in the second level. ### Claim 2 (depends on 1) The polarity inversion control device as claimed in claim 1, wherein the write integrated value calculation unit switches the level of the polarity inversion signal when the write integrated value reaches an integrated threshold value. ### Claim 3 (depends on 2) The polarity inversion control device as claimed in claim 2, wherein: the integrated threshold value is a value of zero; and the write integrated value calculation unit calculates the write integrated value by taking the frame period when the polarity inversion signal is in the first level as a positive value and the frame period when the polarity inversion signal is in the second level as a negative value, and switches the level of the polarity inversion signal when the write integrated value reaches the value of zero from a positive side or a negative side. ### Claim 4 (depends on 3) The polarity inversion control device as claimed in claim 3, wherein the write integrated value calculation unit delays timing for switching the level of the polarity inversion signal. ### Claim 5 (depends on 2) The polarity inversion control device as claimed in claim 2, wherein: the integrated threshold value is constituted with a positive-side threshold value and a negative-side threshold value; and the write integrated value calculation unit calculates the write integrated value by taking the frame period when the polarity inversion signal is in the first level as a positive value and the frame period when the polarity inversion signal is in the second level as a negative value, and switches the level of the polarity inversion signal only when the write integrated value reaches the negative-side threshold value from the positive side or when the write integrated value reaches the positive-side threshold value from the negative side. ### Claim 6 (depends on 5) The polarity inversion control device as claimed in claim 5, wherein the write integrated value calculation unit delays timing for switching the level of the polarity inversion signal. ### Claim 7 (depends on 1) The polarity inversion control device as claimed in claim 1, wherein the frame period detection unit inputs a vertical synchronizing signal and a clock signal, specifies the frame period by the two continuous vertical synchronizing signals, and count counts the clock signals in the specified frame period to detect the frame period. ### Claim 8 (depends on 7) The polarity inversion control device as claimed in claim 7, further comprising a clock signal generation unit which generates the clock signal. ### Claim 9 (depends on 1) A liquid crystal display device, comprising the polarity inversion control device claimed in claim 1 and the liquid crystal panel. ### Claim 10 A driving method of a liquid crystal display device comprising a liquid crystal panel which includes a plurality of pixels, applies pixel voltages of different frame periods to the pixels, and inverts polarities of the pixel voltages according to a polarity inversion signal that is configured to employ either a first level or a second level for each of the frame periods when applying the pixel voltages to the pixels, the method comprising: detecting, by a frame period detection unit, the frame period; regarding the detected frame period, switching the level of the polarity inversion signal in such a manner that a difference between an integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in the first level and an integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in the second level becomes small, wherein a write integrated value calculation unit calculates the difference between the integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in the first level and the integrated value generated by continuously integrating multiple different frame periods when the polarity inversion signal is in the second level; and supplying the switched polarity inversion signal to the liquid crystal panel.