# US 2022/0044643 A1 · Display backlighting systems and methods having current mirror based display drivers to improve pulse width modulation resolution > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 2022/0044643 A1 - Document ID: US20220044643A1 - Status: Published application - Kind: A1 - Application number: 17/223,929 - Filed: 2021-04-06 - Published: 2022-02-10 - Earliest claimed: 2020-08-04 - Assignees: Apple Inc. - Applicants: Apple Inc. - Inventors: Ming Gu; Asif Hussain; Zhiyuan Hu; Marc Albrecht; Jingdong Chen; Yanhui Xie; Mohammad Jafar Navabi-Shirazi; Behzad Mohtashemi - Web page: https://patentgrep.com/patent/US20220044643A1 ## CPC - G09G 3/342: {using several illumination sources separately controlled corresponding to different display panel areas, e.g. along one dimension such as lines} - G09G 3/3611: {Control of matrices with row and column drivers} - G09G 3/2092: {Details of a display terminals using a flat panel, the details relating to the control arrangement of the display terminal and to the interfaces thereto (suitable for both CRT and flat panel G09G5/003; specific for a CRT G09G1/165)} - G09G 3/32: semiconductive, e.g. using light-emitting diodes [LED] - G09G 3/3426: {the different display panel areas being distributed in two dimensions, e.g. matrix} - G09G 5/10: Intensity circuits - G09G 2310/0291: Details of output amplifiers or buffers arranged for use in a driving circuit - G09G 2310/08: Details of timing specific for flat panels, other than clock recovery - G09G 2320/064: by time modulation of the brightness of the illumination source - 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 an electronic device with a display. The display includes a plurality of light-emitting diodes and first and second driver circuits coupled to the plurality of light-emitting diodes. The first driver circuit is configured to receive a first pulse-width modulated (PWM) signal to control a first current mirror branch and the second driver circuit to receive a second PWM signal to control a second current mirror branch to provide an extra N bits of resolution for controlling the plurality of the light-emitting diodes. ## Claims ### Claim 1 An electronic device with a display, the display comprising: a plurality of light-emitting diodes; and first and second driver circuits coupled to the plurality of light-emitting diodes, wherein the first driver circuit is configured to receive a first pulse-width modulated (PWM) signal to control a first current mirror branch and the second driver circuit to receive a second PWM signal to control a second current mirror branch to provide an extra N bits of resolution for controlling the plurality of the light-emitting diodes. ### Claim 2 (depends on 1) The electronic device of claim 1, wherein the first current mirror branch to second current mirror branch ratio is 1:½N. ### Claim 3 (depends on 1) The electronic device of claim 1, wherein the second current mirror branch to provide extra N bits of resolution during a single PWM period. ### Claim 4 (depends on 1) The electronic device of claim 1, wherein the second current mirror branch to provide extra N bits of resolution without increasing a clock frequency for the first PWM signal. ### Claim 5 (depends on 1) The electronic device of claim 1, wherein the first and second PWM signals control a brightness level of the plurality of light-emitting diodes, which is coupled to a voltage supply circuitry. ### Claim 6 (depends on 1) The electronic device of claim 1, wherein the display comprises a current source to set a current level of the first and second current mirror branches. ### Claim 7 (depends on 1) The electronic device of claim 1, wherein the display comprises a first reference current to set an accurate reference with trim for the first current mirror branch and a second reference current to set an accurate reference with trim for the second current mirror branch. ### Claim 8 (depends on 1) The electronic device of claim 1, wherein the display comprises: a first PWM controller to receive a counter clock signal and brightness level information and to generate the first PWM signal for controlling the first current mirror branch to provide M bits of resolution; and a second PWM controller to receive the counter clock signal and brightness level information and to generate the second PWM signal for controlling the second current mirror branch to provide N bits of resolution. ### Claim 9 (depends on 1) The electronic device of claim 1, wherein a counter clock signal is designed for M bits of resolution with the resolution being based on the counter clock signal and a PWM clock signal. ### Claim 10 A computer implemented method for operating a display of an electronic device, comprising: generating, with a light-emitting diode (LED) circuit of the display, a first pulse-width modulated (PWM) signal to control a first current mirror branch of a first driver stage; and generating a second PWM signal to control a second current mirror branch of a second driver stage to provide an extra N bits of resolution for controlling a plurality of light-emitting diodes of the LED circuit. ### Claim 11 (depends on 10) The computer implemented method of claim 10, wherein the first current mirror branch to second current mirror branch ratio is 1:½N. ### Claim 12 (depends on 10) The computer implemented method of claim 10, wherein the second current mirror branch to provide extra N bits of resolution during a single PWM period. ### Claim 13 (depends on 10) The computer implemented method of claim 10, wherein the LED circuit does not have a digital to analog converter (DAC) to minimize area. ### Claim 14 (depends on 10) The computer implemented method of claim 10, wherein the first and second PWM signals control a brightness level of the plurality of light-emitting diodes, which is coupled to a voltage supply circuitry. ### Claim 15 (depends on 10) The computer implemented method of claim 10, further comprising: generating a third PWM signal to control a third current mirror branch of a third driver stage for controlling the plurality of light-emitting diodes of the LED circuit. ### Claim 16 (depends on 15) The computer implemented method of claim 15, wherein the first PWM signal has pulses with a first step size, the second PWM signal has pulses with a second step size, and the third PWM signal has pulses with a third step size. ### Claim 17 Backlight circuitry, comprising: a plurality of light-emitting diodes to generate backlight for a display; and first and second driver circuits coupled to the plurality of light-emitting diodes, wherein the first driver circuit is configured to receive a first pulse-width modulated (PWM) signal to control a first current mirror branch and the second driver circuit to receive a second PWM signal to control a second current mirror branch to provide an extra N bits of resolution for controlling the plurality of the light-emitting diodes. ### Claim 18 (depends on 17) The backlight circuitry of claim 17, wherein the first current mirror branch to second current mirror branch ratio is 1:½N. ### Claim 19 (depends on 17) The backlight circuitry of claim 17, wherein the second current mirror branch to provide extra N bits of resolution during a single PWM period. ### Claim 20 An electronic device with a display, the display comprising: a channel of light-emitting diodes; and current mirror circuitry coupled to the channel of light-emitting diodes, wherein the current mirror circuitry has N branches and the current mirror circuitry is configured to receive a first pulse-width modulated (PWM) signal to control a first current mirror branch and to receive a second PWM signal to control a second current mirror branch for controlling the channel of the light-emitting diodes. ### Claim 21 (depends on 20) The electronic device of claim 20, further comprising: a current source to provide a reference current to the current mirror circuitry. ### Claim 22 (depends on 21) The electronic device of claim 21, wherein each of the N branches has a same targeted current ratio relative to the reference current. ### Claim 23 (depends on 20) The electronic device of claim 20, wherein the first current mirror branch has a current level to cause a brightness that is less than a first brightness level while being in a PWM mode. ### Claim 24 (depends on 23) The electronic device of claim 23, wherein the first current mirror branch remains ON at a maximum current level after being in the PWM mode while the second current mirror has a current level to cause a brightness that is greater than a first brightness level and less than a second brightness level while being in a PWM mode. ### Claim 25 (depends on 24) The electronic device of claim 24, wherein the first and second current mirror branches remain ON at a maximum current level after being in the PWM mode while a third current mirror has a current level to cause a brightness that is greater than the second brightness level and less than a third brightness level while being in a PWM mode. ### Claim 26 (depends on 20) The electronic device of claim 20, wherein N equals 8 branches with a bit for dither control, 8 bits for PWM control of the 8 branches and 3 bits for control code to allocate branch control.