# US 2019/0244572 A1 · Pulsed backlight systems and methods > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2019/0244572 A1 - Document ID: US20190244572A1 - Status: Published application - Kind: A1 - Application number: 16/265,902 - Filed: 2019-02-01 - Published: 2019-08-08 - Earliest claimed: 2018-02-02 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Chengrui LE; Chaohao Wang; Li Tao; Lingyu Hong; Paolo Sacchetto; Sheng Zhang; Xiaokai Li; Yingying Tang; Yunhui Hou; Johan L. Piper - Web page: https://patentgrep.com/patent/US20190244572A1 ## CPC - G09G 3/3406: {Control of illumination source (illumination devices structurally associated with liquid crystal cells G02F1/1336)} - G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines} - G09G 3/36: using liquid crystals - G09G 2320/0247: Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes - G09G 2320/0261: in the context of movement of objects on the screen or movement of the observer relative to the screen - G09G 2320/041: Temperature compensation - G09G 2320/0606: Manual adjustment - G09G 2320/062: Adjustment of illumination source parameters - G09G 2320/0633: by amplitude modulation of the brightness of the illumination source - G09G 2320/064: by time modulation of the brightness of the illumination source - G09G 2320/0646: Modulation of illumination source brightness and image signal correlated to each other - G09G 2320/103: Detection of image changes, e.g. determination of an index representative of the image change - G09G 2340/0435: Change or adaptation of the frame rate of the video stream - G09G 2354/00: Aspects of interface with display user - 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 Aspects of the subject technology relate to pulsed backlight operation for a display backlight. Backlight pulse patterns are provided that include steady state pulse patterns to be applied during operation of a liquid crystal display unit of the display at a corresponding frame rate. The backlight pulse patterns can be arranged to prevent visible artifacts such as flicker or strobing, particularly at or near a transition between LCD frame rates. In some scenarios, transition pulse patterns are provided, ## Claims ### Claim 1 A method of operating an electronic device having a display with a backlight unit and a liquid crystal display (LCD) unit, the method comprising: displaying first display content with the LCD unit at a first LCD frame rate; while providing the first display content at the first LCD frame rate, providing backlight pulses with a first backlight pulse pattern within each LCD frame; displaying second display content with the LCD unit at a second LCD frame rate; and while providing the second display content at the second LCD frame rate, providing backlight pulses with a second backlight pulse pattern within each LCD frame, wherein the first backlight pulse pattern and the second backlight pulse pattern are each arranged to prevent flicker on the display related to the change from the first backlight pulse pattern to the second backlight pulse pattern. ### Claim 2 (depends on 1) The method of claim 1, wherein providing the backlight pulses with the second backlight pulse pattern comprises providing the backlight pulses with the second backlight pulse pattern during a first LCD frame at the second LCD frame rate. ### Claim 3 (depends on 2) The method of claim 2, wherein providing the backlight pulses with the second backlight pulse pattern comprises providing the backlight pulses with the second backlight pulse pattern during all display frames at the second LCD frame rate. ### Claim 4 (depends on 3) The method of claim 3, wherein providing the backlight pulses with the first backlight pulse pattern comprises providing the backlight pulses with the first ‘backlight pulse pattern during all LCD frames at the first LCD frame rate. ### Claim 5 The method of claim I, further comprising providing backlight pulses with a third backlight pulse pattern within each LCD frame at a third LCD frame rate. ### Claim 6 A method of operating an electronic device having a display with a backlight unit and a liquid crystal display unit, the method comprising: displaying first display content with an LCD unit at a first LCD frame rate; while providing the first display content at the first LCD frame rate, providing backlight pulses with a first backlight pulse pattern; displaying second display content with the LCD unit at a second LCD frame rate; while providing the second display content at the second LCD frame rate, providing backlight pulses with a second backlight pulse pattern; and providing backlight pulses with a transition pulse pattern between providing the backlight pulses with the first backlight pulse pattern and the second backlight pulse pattern. ### Claim 7 (depends on 6) The method of claim 6, wherein providing the backlight pulses with the transition pulse pattern comprises applying the transition pulse pattern during a transition time period, wherein the transition pulse pattern changes over time, during the transition time period, from a pattern that matches the first backlight pulse pattern to a pattern that matches the second backlight pulse pattern. ### Claim 8 (depends on 7) The method of claim 7 wherein the transition time period occurs entirely while providing the second display content at the second LCD frame rate. ### Claim 9 (depends on 7) The method of claim 7, wherein the transition time period occurs entirely while providing the first display content at the first LCD frame rate. ### Claim 10 (depends on 7) The method of claim 7, further comprising determining that a frame rate transition from the first LCD frame rate to the second LCD frame rate will occur at a future time. ### Claim 11 (depends on 10) The method of claim 10, wherein determining that the frame rate transition from the first LCD frame rate to the second LCD frame rate will occur at the future time comprises receiving a user input that causes a change from static display content to moving display content ### Claim 12 (depends on 11) The method of claim 11, wherein the transition time period occurs partially while providing the first display content at the first LCD frame rate and partially while providing the second display content at the second LCD frame rate. ### Claim 13 A method of operating an electronic device having a display with a backlight unit and a liquid crystal display unit, the method comprising: displaying first display content with an LCD unit at a first LCD frame rate; while providing the first display content at the first LCD frame rate, providing ‘backlight pulses with a first backlight pulse pattern; displaying second display content with the LCD unit at a second LCD frame rate; while providing the second display content at the second LCD frame rate, providing backlight pulses with a second ‘backlight pulse pattern; and splitting at least a first pulse of the second backlight pulse pattern between at least one pulse of the first backlight pulse pattern and at least one other pulse of the second backlight pulse pattern. ### Claim 14 (depends on 13) The method of claim 13, wherein splitting at least the first pulse of the second backlight pulse pattern comprises preventing execution of the first pulse of the second backlight pulse pattern and adding equal portions of the first pulse of the second backlight pulse pattern to each of an immediately preceding pulse and an immediately following pulse. ### Claim 15 (depends on 13) The method of claim 13, wherein splitting at least the first pulse of the second backlight pulse pattern comprises preventing execution of the first pulse of the second backlight pulse pattern and splitting the first pulse of the second backlight pulse pattern unequally among multiple pulses of the first backlight pulse pattern and multiple pulses of the second backlight pulse pattern. ### Claim 16 (depends on 15) The method of claim 15, further comprising operating a digital filter to cause unequal splitting. ### Claim 17 (depends on 13) The method of claim 13, wherein splitting at least the first pulse of the second backlight pulse pattern comprises splitting the first pulse of the second backlight pulse pattern and at least one of another pulse of the second -backlight pulse pattern or a pulse of the first backlight pulse pattern. ### Claim 18 A method of operating an electronic device having a display with a backlight unit and a liquid crystal display unit, the method comprising: operating the liquid crystal display unit with a variable frame rate; while operating the liquid crystal display unit with the variable frame rate, providing backlight pulses with the backlight unit at a first pulse rate; with a decision engine for the display, determining whether one or more frequency transition conditions associated with the variable frame rate have been met:, and with the decision engine, obtaining a transition pulse pattern that is specific to a frame rate transition for the LCD unit if the one or more frequency transition conditions have been met; with the backlight unit, providing backlight pulses according to the obtained transition pulse pattern; and with the backlight unit, providing backlight pulses with a second pulse rate after providing the backlight pulses according to the obtained transition pulse pattern. ### Claim 19 (depends on 18) The method of claim 18, wherein the one or more frequency transition conditions comprise at least one of a display temperature condition, a low-frame rate detection condition, and a frame rate change frequency condition. ### Claim 20 (depends on 18) The method of claim 18, wherein the one or more frequency transition conditions comprise a display temperature condition and a high-frame rate detection condition. ### Claim 21 (depends on 18) The method of claim 18, further comprising determining whether an LCD frame phase shift has occurred. ### Claim 22 (depends on 21) The method of claim 21, further comprising: with the decision engine, obtaining a phase shift transition pulse pattern if the LCD frame phase shift has occurred; and applying the phase shift transition pulse pattern with the backlight unit.