公开(公告)号：US20180373094A1

公开(公告)日：2018-12-27

申请号：US15711932

申请日：2017-09-21

Applicant: Apple Inc.

Inventor： Ji Yeoul RYOO ,  Asif HUSSAIN ,  Jingdong CHEN ,  Mohammad J. NAVABI-SHIRAZI ,  Yanhui XIE

IPC: G02F1/1335 ,  H05B37/02 ,  H05B33/08 ,  G09G3/34

Abstract: Aspects of the subject technology relate to display circuitry such as backlight control circuitry for operating parallel strings of light-emitting diodes (LEDs). A voltage supply circuit of the backlight control circuitry provides a common supply voltage to the strings of LEDs. Headroom control circuitry samples a residual voltage at the end of each string, determines a minimum of the residual voltages, and provides feedback, based on the determined minimum voltage, to the voltage supply circuit. A headroom control feedback loop may be provided including sampling lines coupled to the second end of each string of LEDs for sampling a residual voltage of each string. Headroom control circuitry may modify the supply voltage based on the minimum residual voltage. Sample-and-hold circuitry may be provided that holds the sampled residual voltages until the voltage supply circuit is ready for an update.

公开(公告)号：US20190059136A1

公开(公告)日：2019-02-21

申请号：US15784943

申请日：2017-10-16

Applicant: Apple Inc.

Inventor： Mohammad J. NAVABI-SHIRAZI ,  Alejandro Lara ASCORRA ,  Asif HUSSAIN ,  Ji Yeoul RYOO ,  Jingdong CHEN ,  Jun QI ,  Manisha P. PANDYA ,  Yanhui XIE

IPC: H05B33/08

Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may operate a light-emitting diode using a multi-peak pulse-width-modulation signal. The control circuitry may include a multi-stage driver having a relatively larger driver stage for providing a direct current through a light-emitting diode and a relatively smaller driver stage configured to cooperate with a pulse-width-modulation controller to pulse-width-modulate a current through the light-emitting diode.

公开(公告)号：US20190053337A1

公开(公告)日：2019-02-14

申请号：US15785082

申请日：2017-10-16

Applicant: Apple Inc.

Inventor： Yanhui XIE ,  Asif HUSSAIN ,  Ji Yeoul RYOO ,  Jingdong CHEN ,  Mohammad J. NAVABI-SHIRAZI

IPC: H05B33/08 ,  G02F1/1335

CPC classification number: H05B33/083 ,  G02F1/1336 ,  G02F2001/133601 ,  H05B33/0812 ,  H05B33/0815 ,  H05B33/0827 ,  H05B33/0845

Abstract: Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry may include a feedforward loop and a feedback loop for a power supply for the light-emitting diodes. The light-emitting diodes may be arranged in strings that are individually controllable by a current control transistor on the string. The feedforward loop may determine a total upcoming load current for the power supply based on reference voltages for controlling each of the current control transistors. The output of the power supply may be modified based on a combination of a current from the feedforward loop and a current from the feedback loop.