Apple Inc.

Yanhui Xie

Jingdong Chen

Asif Hussain

Mohammad Jafar Navabi-Shirazi

Manisha P Pandya

Ji Yeoul Ryoo

Jun Qi

Behzad Mohtashemi

Alejandro Lara Ascorra

Zhiyuan Hu

Erhan Ozalevli

Ming Gu

Jason N Gomez

Dharmesh C Bhagatwala

Bo Xu

Jonathan D Paolucci

Kevin Ho

Jy Ryoo

Nathan Y Tang

A charge injection circuit for use in display system of an electronic device can include an injection capacitance and circuitry that receives an input signal corresponding to drive signals from a display driver of the display system; and generates an inverted output signal corresponding to the drive signals for delivery to a power input of a display panel of the display system via the injection capacitance, thereby mitigating transient disruption of one or more power rails of the display panel associated with parasitic capacitive coupling of the drive signals to the one or more power rails of the display panel. The injection capacitance can be a capacitor having a capacitance value corresponding to a total parasitic capacitance capacitively coupling data lines to the one or more power rails within the display panel.

Charge cancellation to minimize transient ripple

A battery powered electronic device can include a battery to power one or more loads, a first DC-DC converter having an input coupled to the battery and an output, and a second DC-DC converter cascaded with the first DC-DC converter and coupled to a second load subject to pulsed operation. The first and second converters may be configured so as to isolate the one or more loads from transients associated with the pulsed operation of the second load. The second converter may have an input coupled to the output of the first converter and an output coupled to the second load. Alternatively, the second converter may be a bidirectional converter having first terminals coupled to the output of the first converter and second terminals coupled to an energy storage device.

Mitigation of battery output voltage ripple under pulse load

Power converters can include a plurality of switching devices and a combination of one or more inductors and one or more flying capacitors. Both boost and buck converters may employ such topologies, and can achieve high efficiency and small size in at least some applications, including those with high conversion ratios. A control circuit can generate a first pair of complementary gate drive signals to drive a first complementary switch pairs and a second pair of complementary gate drive signals to drive a second complementary switch pair. The control circuit can vary a phase shift between the first pair of complementary gate drive signals and the second pair of complementary gate drive signals to regulate the flying capacitor voltage.

Inductive flying capacitor converters and control techniques therefor

Embodiments relate to a switching regulator having a dual mode control. The switching regulator includes an error amplifier configured to receive an output voltage of a power source, and to generate an error voltage based on a difference between the output voltage of the power source and a reference voltage. The switching regulator additionally includes a PFM controller configured to receive the error voltage from the error amplifier, and to generate a clock signal having a switching frequency based on a difference between the error voltage and a modulation voltage. Moreover, the switching regulator includes a PWM controller configured to receive the clock signal and an error signal determined based on a load current sensed at an output of the power source, and to generate a control signal to control the power source.

Pulse frequency modulation and frequency avoidance method and implementation for switching regulators

A display may have display layers that form an array of pixels. The array of pixels may be illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs). The multiple LED strings may be controlled by one or more backlight driver integrated circuits (ICs). In a multi-driver IC architecture, an enable signal may be used to set a desired phase delay between the multiple ICs. One or more of the LED strings may exhibit a short fault. Depending on the number of faulty LED strings, the backlight unit can selectively throttle the maximum brightness of the display. The LED strings may receive an output voltage from a DC/DC converter and may be driven using a current driver. The DC/DC converter may be controlled by a headroom feedforward control circuit to ensure sufficient headroom for the current driver while suppressing acoustic noise.

Methods and apparatus for controlling display backlight

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.

Split driver backlightsystems and methods

A display may have an array of pixels illuminated using a backlight unit. The backlight unit may include multiple strings of light-emitting diodes (LEDs) and a boost converter for providing an output voltage to the multiple LED strings. The boost converter may have a single-phase single-switch, single-phase multi-switch, and/or multi-phase multi-switch configuration, where the switches are turned off when the peak current is reached. When transitioning from a single phase to a dual phase operation, the second (slave) phase current may be slowly ramped up. When transition from the dual phase to the single phase operation, the output voltage may be elevated while slowing ramping down the slave phase current. The boost converter may include a current detection circuit for adjusting the peak current of each phase to balance the average current levels. The boost converter may also include an in-rush current controller configured to sense a short fault.

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.

Display backlight headroom control systems and methods

Aspects of the subject technology relate to display of an electronic device. The display includes a backlight unit having a voltage source, a string of light-emitting diodes and a bypass switch for each light-emitting diode in the string. The string of light-emitting diodes can receive, at a first end, a supply voltage from the voltage source. The bypass switch for each light-emitting diode is controllable to pulse-width-modulate that light-emitting diode. The headroom voltage feedback circuit is coupled to a second end of the string.

Local display backlighting systems and methods

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.

Load transient response control systems and methods for electronic device displays

Aspects of the subject technology relate to control circuitry for operating light-emitting diodes (LEDs). The control circuitry may include a pulse-width-modulation (PWM) driver for the LEDs and headroom voltage control circuitry. The PWM driver may adjust a rising edge or a trailing edge of the PWM cycles for various LEDs to ensure a headroom voltage detection window for the headroom voltage control circuitry to sample the headroom voltage of those LEDs without being affected by the rising edge of the PWM cycle for LED or the falling edge of the PWM cycle for another LED.

LED driver headroom voltage control systems and methods

Split driver backlight systems and methods

Aspects of the subject technology relate to control circuitry for light-emitting diodes. The control circuitry includes a two-dimensional light-emitting diode (LED) array. The control circuitry may include a single LED array operable by a common driver or multiple LED arrays each operable by a dedicated LED matrix driver. Each matrix driver may receive a synchronization signal from a common controller and may include a programmable phase lock loop (PLL) to synchronize each matrix driver to the synchronization signal. The LED array may include multiple strings of LEDs mounted in series along the string. Each LED in each string may include a bypass switch operable to modify the current through that LED by pulse-width modulation.

Aspects of the subject technology relate to display circuitry such as backlight control circuitry for operating light-emitting diodes (LEDs). The backlight control circuitry may include a pulse-width-modulation (PWM) transistor and a current regulation transistor coupled in series with at least one LED. The current regulation transistor may have a gate terminal that receives a feedback-controlled gate voltage. The backlight control circuitry may include a gate clamp circuit coupled to the gate terminal of the current regulation transistor that clamps the gate voltage during a portion of a PWM on pulse.

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Santa Clara, CA, United States of America

Yanhui Xie