Color Ambient Light Sensor Circuitry for Accurate Display Adjustment
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Solution Overview
Problem
Existing ambient light sensors in electronic devices face challenges in accurately converting light into digital measurements due to variations in performance between analog-to-digital converter circuitry, leading to inconsistent light measurement and display adjustments.
Innovation Solution
A color ambient light sensor with photodiodes of different spectral sensitivities and a dark current photodiode is used, coupled with a switch array to distribute signals across multiple analog-to-digital converters, allowing for signal averaging and minimizing the impact of converter variations, and a dark current signal is subtracted to improve accuracy.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a single analog-to-digital converter is used to digitize photodiode signals, then the device complexity is reduced, but the measurement precision deteriorates due to converter performance variations
Solution Approach 1:
The patent divides the single analog-to-digital conversion function into multiple parallel converters (e.g., ADC0, ADC1, ADC2). Each photodiode signal is distributed to multiple converters simultaneously, and the results are averaged to produce the final digital output. This segmentation allows the system to overcome variations in individual converter performance while maintaining reasonable device complexity through systematic distribution and averaging.
Solution Approach 2:
The patent combines the outputs of multiple analog-to-digital converters through averaging to produce a single, more accurate digital representation of the photodiode signal. By merging the results from multiple converters that each have different performance characteristics, the system achieves improved measurement precision that compensates for individual converter variations.
2Measurement precision
If photodiode signals are directly converted without dark current compensation, then the conversion process is simpler, but the measurement precision deteriorates due to dark current interference
Solution Approach 1:
The patent extracts and separates the dark current component from the total photodiode signal by using a dedicated dark current photodiode that is insensitive to light. This dark current photodiode measures only the dark current component, which is then subtracted from the signals of the light-sensitive photodiodes. This extraction approach isolates the interference element for separate processing, improving measurement precision without significantly increasing overall device complexity.
Solution Approach 2:
The patent applies preliminary anti-action by measuring the dark current component separately using a dedicated photodiode and then subtracting it from the light-sensitive photodiode signals before digital conversion. This preliminary compensation for the harmful dark current effect occurs in the analog domain, preventing it from degrading the final measurement accuracy.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This configuration ensures accurate digitization of light measurements, enabling precise adjustments to display brightness and color based on ambient light intensity and color information, thereby enhancing the reliability of ambient light sensing in electronic devices.
Implementation Method 1
Ambient light sensors may contain photodiodes that convert incoming light to analog signals
Data Source
AI summary
An electronic device may be provided with a display mounted in a housing. The display may have an array of pixels that form an active area and may have an inactive area that runs along an edge of the active area. A color ambient light sensor may gather ambient light measurements through a window in an opaque masking layer in the inactive area. The color ambient light sensor may have photodiodes with different spectral sensitivities and may have a dark current photodiode that is insensitive to light. A set of analog-to-digital converters may be used to digitize photodiode signals from the photodiodes. A switch array may be used to distribute signals from the photodiodes to each of the analog-to-digital converters. This allows the output of each photodiode to be averaged over multiple analog-to-digital converters to remove any impact of variations in performance between converters.