# US 12,223,876 B2 · Power saving in OLED displays with multiple refresh rates > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 12,223,876 B2 - Document ID: US12223876B2 - Status: Granted - Kind: B2 - Application number: 18/261,245 - Filed: 2021-02-12 - Published: 2024-03-07 - Granted: 2025-02-11 - Earliest claimed: 2021-02-11 - Assignees: Google Inc. - Applicants: Google LLC - Inventors: Sangmoo Choi; Sang Young Youn; Chang Ju Kang; Sun-Il Chang - Web page: https://patentgrep.com/patent/US12223876B2 ## CPC - G09G 3/2007: {Display of intermediate tones} - G09G 3/3233: with pixel circuitry controlling the current through the light-emitting element - G09G 2300/0417: Special arrangements specific to the use of low carrier mobility technology - G09G 2300/0819: used for counteracting undesired variations, e.g. feedback or autozeroing - G09G 2300/0842: forming a memory circuit, e.g. a dynamic memory with one capacitor - G09G 2300/0861: with additional control of the display period without amending the charge stored in a pixel memory, e.g. by means of additional select electrodes - G09G 2310/066: Waveforms comprising a gently increasing or decreasing portion, e.g. ramp - G09G 2310/08: Details of timing specific for flat panels, other than clock recovery - G09G 2320/0233: Improving the luminance or brightness uniformity across the screen - G09G 2320/0238: Improving the black level - G09G 2320/0247: Flicker reduction other than flicker reduction circuits used for single beam cathode-ray tubes - G09G 2320/0673: for control of gamma adjustment, e.g. selecting another gamma curve - G09G 2330/021: Power management, e.g. power saving - G09G 2340/0435: Change or adaptation of the frame rate of the video stream - 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 Rendering images on an active area of an OLED includes rendering images on the active area of the display panel with a plurality of different frame rates. For a plurality of the different frame rates having a frame rate that matches or is above a threshold frame rate, an image refresh operation is performed once per frame period and a self-refresh operation is not performed during the frame period. When rendering images on the active area, for at least one of the different frame rates having a frame rate that is lower than the threshold frame rate, an image refresh operation is performed once per frame period and a self-refresh operation is performed at least once during the frame period. ## Claims ### Claim 1 A display panel comprising: a plurality of pixels arranged in an array, the array including rows and columns, each pixel of the array including at least one OLED light-emitting device; a plurality of pixel circuits, each pixel circuit associated with one of the OLED light-emitting devices and configured to drive its associated OLED light-emitting device; a plurality of scan lines configured for selecting the pixel circuits associated with each row of the pixels; a plurality of column data lines configured for controlling the pixel circuits associated with each column of the pixels; a plurality of emission lines configured for supplying signals to pixel circuits associated with each row of the pixels to cause the pixel circuits to supply driving current to anodes of OLED pixels of the row; a device driver configured to supply signals to the scan lines, the column lines and the emission lines to cause the display panel to render images on an active area of the display panel with a plurality of different frame rates, including: (i) for a plurality of frame rates that match or are above a threshold frame rate, performing an image refresh operation once per frame period and not performing a self-refresh operation during the frame period; (ii) for a lower frame rate that is lower than the threshold frame rate and when a brightness of the active area of the display panel is lower than a threshold brightness, performing an image refresh operation once per frame period and performing a self-refresh operation at least once during the frame period; and (iii) for the lower frame rate that is lower than the threshold frame rate and when a brightness of the active area of the display panel is higher than the threshold brightness, performing an image refresh operation once per frame period and performing no self-refresh operation during the frame period. ### Claim 2 (depends on 1) The display panel of claim 1, wherein each of the pixel circuits includes at least two metal oxide transistors. ### Claim 3 (depends on 1) The display panel of claim 1, wherein the threshold rate is 60 Hz or lower. ### Claim 4 (depends on 1) The display panel of claim 1, wherein the first frame rate and the second frame rate have rates that are factors of the threshold frame rate. ### Claim 5 (depends on 1) The display panel of claim 1, wherein the device driver is configured to apply a first gamma correction value when rendering frames at frame rates below the threshold frame rate, and to apply a second gamma correction value, different from the first gamma correction value, when rendering frames at a frame rate that is higher than the threshold frame rate. ### Claim 6 (depends on 1) The display panel of claim 1, wherein when the threshold frame rate is N Hz, with N being a real value, the first frame rate has a frame rate that is a factor of N. ### Claim 7 (depends on 6) The display panel of claim 6, wherein a number of self-refresh operations performed during the rendering of a frame at one of the different frame rates of M Hz, is (N/M−1). ### Claim 8 (depends on 1) The display panel of claim 1, wherein the device driver is further configured to, for the lower frame rate: when the self-refresh operation is performed at least once during the frame period, apply a first gamma correction value to the rendering of images, and when no self-refresh operations is performed during the frame period, apply a second gamma correction value, different from the first gamma correction value, to the rendering of images. ### Claim 9 (depends on 1) The display panel of claim 1, comprising: identifying that the brightness of the active area of the display panel is lower than the threshold brightness by identifying that a gray level of the active area of the display panel is lower than a particular brightness; and identifying that the brightness of the active area of the display panel is higher than the threshold brightness by identifying that a gray level of the active area of the display panel is greater than the particular brightness. ### Claim 10 (depends on 9) The display panel of claim 9, wherein the gray level is based on a mean gray level of all the pixels in the active area. ### Claim 11 (depends on 9) The display panel of claim 9, wherein the gray level is based on a percentage of pixels in the active area whose gray level is above a threshold gray level. ### Claim 12 (depends on 1) The display panel of claim 1, comprising: identifying that the brightness of the active area of the display panel is lower than the threshold brightness, based on a value of a function of a brightness level of the active area of the display panel and a gray level of the frames being rendered satisfying criteria; and identifying that the brightness of the active area of the display panel is higher than the threshold brightness, based on the value of the function of the brightness level of the active area of the display panel and the gray level of the frames being rendered failing to satisfy the criteria. ### Claim 13 (depends on 12) The display panel of claim 12, wherein a first partial derivative of the function with respect to the gray level value is negative and a second partial derivative of the function with respect to the panel brightness value is positive. ### Claim 14 (depends on 1) The display panel of claim 1, wherein the device driver is configured to apply a single gamma correction value when rendering frames at the lower frame rate that is below the threshold frame rate and when rendering frames at a frame rate that is higher than the threshold frame rate. ### Claim 15 A method of rendering images on an active area of a display panel, the display panel including a plurality of pixels arranged in an array of OLED pixels with each pixel of the array including at least one OLED light-emitting device, a plurality of pixel circuits with each pixel circuit being associated with one of the OLED light-emitting devices and being configured to drive its associated OLED light-emitting device, the method comprising: rendering images on the active area of the display panel with a plurality of different frame rates, including: (i) for a plurality of frame rates that match or are above a threshold frame rate, performing an image refresh operation once per frame period and not performing a self-refresh operation during the frame period; (ii) for a lower frame rate that is lower than the threshold frame rate and when a brightness of an active area of the display panel is lower than a threshold brightness, performing an image refresh operation once per frame period and performing a self-refresh operation at least once during the frame period; and (iii) for the lower frame rate that is lower than the threshold frame rate and when a brightness of the active area of the display panel is higher than the threshold brightness, performing an image refresh operation once per frame period and performing no self-refresh operation during the frame period. ### Claim 16 (depends on 15) The method of claim 15, wherein the threshold rate is 60 Hz or lower. ### Claim 17 (depends on 15) The method of claim 15, wherein the different frame rates having a frame rate lower than the threshold frame rate have rates that are factors of the threshold frame rate. ### Claim 18 (depends on 15) The method of claim 15, further comprising: applying a first gamma correction value when rendering frames at frame rates below the threshold frame rate; and applying a second gamma correction value, different from the first gamma correction value, when rendering frames at a frame rate that is higher than the threshold frame rate. ### Claim 19 (depends on 15) The method of claim 15, wherein when the threshold frame rate is N Hz, with N being a real value, the first frame rate has a frame rate that is a factor of N. ### Claim 20 (depends on 19) The method of claim 19, wherein a number of self-refresh operations performed during the rendering of a frame at one of the different frame rates of M Hz, is (N/M−1). ### Claim 21 (depends on 15) The method of claim 15, further comprising, for the lower frame rate, when rendering images on the active area: when the self-refresh operation is performed at least once during the frame period, applying a first gamma correction value to the rendering of images, and when no self-refresh operation is performed during the frame period, applying a second gamma correction value, different from the first gamma correction value, to the rendering of images. ### Claim 22 (depends on 15) The method of claim 15, further comprising: identifying that the brightness of the active area of the display panel is lower than the threshold brightness by identifying that when a gray level of the active area of the display panel is lower than a particular brightness; and identifying that the brightness of the active area of the display panel is higher than the threshold brightness by identifying that a gray level of the active area of the display panel is greater than the particular brightness. ### Claim 23 (depends on 22) The method of claim 22, wherein the gray level is based on a mean gray level of all the pixels in the active area. ### Claim 24 (depends on 22) The method of claim 22, wherein the gray level is based on a percentage of pixels in the active area whose gray level is above a threshold gray level. ### Claim 25 (depends on 22) The method of claim 22, further comprising, when rendering images on the active area: when self-refresh operations are performed at least once during the frame period, applying a first gamma correction value to the rendering of images; and when no self-refresh operations are performed during the frame period, applying a second gamma correction value, different from the first gamma correction value, to the rendering of images. ### Claim 26 (depends on 15) The method of claim 15, further comprising: identifying that the brightness of the active area of the display panel is lower than the threshold brightness, based on a value of a function of a brightness level of the active area of the display panel and a gray level of the frames being rendered satisfying criteria; and identifying that the brightness of the active area of the display panel is higher than the threshold brightness, based on the value of the function of the brightness level of the active area of the display panel and the gray level of the frames being rendered failing to satisfy the criteria. ### Claim 27 (depends on 26) The method of claim 26, wherein a first partial derivative of the function with respect to the gray level value is negative and a second partial derivative of the function with respect to the panel brightness value is positive. ### Claim 28 (depends on 26) The method of claim 26, further comprising: when self-refresh operations are performed at least once during the frame period, applying a first gamma correction value to the rendering of images; and when no self-refresh operations are performed during the frame period, applying a second gamma correction value, different from the first gamma correction value, to the rendering of frames. ### Claim 29 (depends on 15) The method of claim 15, comprising: applying a single gamma correction value when rendering frames at the lower frame rate that is below the threshold frame rate and when rendering frames at a frame rate that is higher than the threshold frame rate.