Cirrus Logic Inc.

Apple Inc.

Shatam Agarwal

Alvin Chuck Storvik

Fenghua Zheng

Hyunwoo Nho

Kingsuk Brahma

Jie Won Ryu

Daniel John Allen

Hyunsoo Kim

David S Zalatimo

Anand Ilango

Yao Shi

Li-Xuan Chuo

Shih Chang Chang

Wei Hsin Yao

Chaohao Wang

Rahul Singh

Shengkui Gao

Aniruddha Satoskar

ByoungSuk Kim

Kyung Wook Kim

Hao-Lin Chiu

Alfredo R Linz

Cory Jay Peterson

Kwang Soon Park

Myungjoon Choi

Rungrot Kitsomboonloha

Graeme M Williams

Pei-En Chang

Vehbi Calayir

Alex H Pai

Ce Zhang

Yaser Azizi

Steven N Hanna

Kan Wang

Sachiko Oda

Jiaxi Hu

Jesse R Manders

Joonggun Lee

An electronic device may include a display having an array of pixels that receive data signals from multiple column driver integrated circuits. Each column driver integrated circuit may include gamma amplifiers that are used to set gamma references for driving the data signals. Each gamma reference can be set using first and second (redundant) gamma amplifiers in an alternating fashion to perform auto-zeroing. The auto-zeroing operation can be combined with a chopping operation to minimize amplifier offset across the different column driver integrated circuits. The auto-zeroing and/or the chopping function can be spatially alternated across the different rows in the array and temporally alternated across the different display frames.

Display column driver devices with offset cancellation

This disclosure provides various techniques for providing fine-grain digital and analog pixel compensation to account for voltage error across an electronic display. By employing a two-dimensional digital compensation and a local analog compensation, a fine-grain and robust pixel compensation scheme may be provided to the electronic display.

Two-dimensional content-adaptive compensation to mitigate display voltage drop

An electronic device may include an electronic display having multiple display pixels to display an image based on analog voltage signals. The electronic device may also include optical calibration circuitry to generate digital-to-analog converter (DAC) data based on image data associated with the image and dither circuitry to reduce a bit-depth of the DAC data, generating dithered DAC data. Additionally, the electronic device may include a gamma generator having one or more DACs to generate the analog voltage signals based on the dithered DAC data, which may instruct the gamma generator to generate the analog voltage signals indicative of the image data.

Dither enhancement of display gamma DAC systems and methods

Aspects of the subject technology relate to control circuitry for displays. A display control circuitry includes a plurality of amplifiers to drive gamma signals for a pixel array having a plurality of pixels of a display and a segmented resistor string coupled to the plurality of amplifiers. The resistor string includes a plurality of resistor segments with a resistor segment being designed with a modified resistance to modify display performance parameters including at least one of a settling time of an associated gamma signal, a power supply rejection ratio (PSRR) of an amplifier of the plurality of amplifiers, or an output voltage offset of an amplifier of the plurality of amplifiers.

Display circuitry and method to utilize segmented resistors for optimizing front of screen performance

An electronic device may include a display. The display may include display driver circuitry that is configured to provide image data to columns of pixels and gate driver circuitry that is configured to provide control signals to rows of pixels. The display may be operable at a native refresh rate that is equal to the highest refresh rate at which the display has full resolution. The display may also be operable in a high refresh rate mode with a high refresh rate that is twice (or some other scaling factor greater than) the native refresh rate. To enable operation at the high refresh rate mode, vertical resolution of the display may be sacrificed. In other words, rows of pixels may be grouped together into effective rows that are then scanned in sequence. The gate driver circuitry may be formed as thin-film transistor circuitry or from gate driver integrated circuits.

Displays with multiple refresh rate modes

An electronic device may be configured to identify a load coupled to the device. The device may measure direct current (DC) and/or alternating current (AC) impedances of the load to identify the load. The device may then take action based on the identification of the load. For example, a specific transducer may be identified as coupled to the electronic device and an appropriate equalization curve applied to an audio output of the device. The measurement of load impedance may include controlling a reference generator according to a search algorithm to identify the load, including compensating the measured impedance for temperature changes. An analog-to-digital converter (ADC) may operate through the search algorithm to provide feedback to digital circuitry regarding how to proceed through the search algorithm to identify the load.

Temperature compensation for load identification

A portable audio device may be configured to measure load characteristics of headphones. The device may measure direct current (DC) and/or alternating current (AC) characteristics of the load. These characteristics may be measured by an audio component, such as an audio codec chip or integrated circuit (IC) controller, and reported to software or firmware executing on a processor coupled to the audio component. The software or firmware may then take action based on the measured load characteristics. For example, the load characteristics may be compared to a database of headphones and their known load characteristics to determine a particular headphone model or type of headphone attached to the audio output. The processor may then apply an appropriate equalization curve.

Direct current (DC) and/or alternating current (AC) load detection for audio codec

An electronic device may be configured to identify a load coupled to the device. The device may measure direct current (DC) and/or alternating current (AC) characteristics of the load to identify the load. The device may then take action based on the identification of the load. For example, a specific transducer may be identified as coupled to the electronic device and an appropriate equalization curve applied to an audio output of the device. The measurement of characteristics of the load may include controlling a reference generator according to a search algorithm, such as a step ramp or binary search, to identify the load. An analog-to-digital converter (ADC) may operate through the search algorithm to provide feedback to digital circuitry regarding how to proceed through the search algorithm to identify the load.

Identification of a load with a search algorithm that controls application of signals to the load and a reference generator

Alternating current (AC) load identification technique using a search algorithm

A bipolar junction transistor (BJT) may be used in a power stage DC-to-DC converter, such as a converter in LED-based light bulbs. The power stage may be operated by a controller to maintain a desired current output to the LED load. A resistor may be coupled to the BJT through a switch at the emitter of the BJT. The switch may regulate operation of the BJT by allowing current flow to ground through the resistor. The controller may perform measurements of the resistor to allow higher accuracy determinations of the current through the BJT and thus improve regulation of current to the LED load.

Resistance measurement of a resistor in a bipolar junction transistor (BJT)-based power stage

A feedback path may be provided within the voltage regulator to reduce the effect of a current step or load transient on the output of a voltage regulator. The feedback path may provide a fast path for stabilizing the voltage regulator after the load transient. The feedback path may be configurable to be activated or de-activated during operation of the voltage regulator. The feedback path may be activated when the voltage regulator takes over generation of an output voltage from another voltage regulator. The feedback path may then be de-activated to allow normal operation of the voltage regulator after a steady-state condition is reached.

Feedback path for fast response to transients in voltage regulators

A variable resistance device may be used in a dimmer compatibility circuit to reduce power dissipation in an integrated circuit of the dimmer compatibility circuit. For example, the integrated circuit may include switches coupled to resistors external to the integrated circuit. The integrated circuit may operate the switches to commutate among the external resistors and select a voltage drop that reduces a voltage at a drain voltage of the switches. The reduced drain voltage reduces power dissipation in the switches and instead dissipates the power in the external resistors.

Variable resistance device for reduced power dissipation in dimmer compatibility circuits

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Austin, TX, United States of America

Shatam Agarwal