Adaptive Light Sensor With Dynamic ADC Resolution for PPG
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Solution Overview
Problem
State-of-the-art PPG sensors face challenges due to low perfusion-index (PI) values, leading to reduced signal fidelity, complex signal processing, and high power consumption, particularly in applications like wearable devices and hearing aids where the PI varies significantly.
Innovation Solution
An adaptive light-to-digital conversion (LDC) system that dynamically adjusts its resolution and power consumption based on the AC/DC ratio, using a modular architecture with configurable light-to-digital converters and switches to optimize power usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high ADC resolution (above 15 bits) is used to cope with worst case PI, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent implements dynamic ADC resolution adjustment where the converter adapts its resolution based on the actual perfusion index conditions. The system transitions from fixed high-resolution conversion to variable resolution conversion, matching the ADC precision to the actual signal requirements rather than always operating at maximum resolution.
Solution Approach 2:
The system changes the ADC resolution parameter dynamically based on measured perfusion index values. When PI is high, lower ADC resolution suffices; when PI is low, the system increases ADC resolution. This parameter adaptation resolves the contradiction by making precision adjustable rather than fixed at maximum levels.
2Measurement precision
If high ADC resolution (above 15 bits) is used to cope with worst case PI, then measurement precision is improved, but power consumption increases
Solution Approach 1:
The patent implements dynamic ADC resolution adjustment where the converter adapts its resolution based on the actual perfusion index conditions. The system transitions from fixed high-resolution conversion to variable resolution conversion, matching the ADC precision to the actual signal requirements rather than always operating at maximum resolution.
Solution Approach 2:
The system changes the ADC resolution parameter dynamically based on measured perfusion index values. When PI is high, lower ADC resolution suffices; when PI is low, the system increases ADC resolution. This parameter adaptation resolves the contradiction by making precision adjustable rather than fixed at maximum levels.
3Measurement precision
If fixed high resolution PPG sensing is implemented, then signal fidelity is maintained across all conditions, but power consumption increases
Solution Approach 1:
The patent implements dynamic ADC resolution adjustment where the converter adapts its resolution based on the actual perfusion index conditions. The system transitions from fixed high-resolution conversion to variable resolution conversion, matching the ADC precision to the actual signal requirements rather than always operating at maximum resolution.
Solution Approach 2:
The system changes the ADC resolution parameter dynamically based on measured perfusion index values. When PI is high, lower ADC resolution suffices; when PI is low, the system increases ADC resolution. This parameter adaptation resolves the contradiction by making precision adjustable rather than fixed at maximum levels.
4Use of energy by moving object
If modular PPG sensing scheme is implemented, then power consumption is reduced, but device complexity increases
Solution Approach 1:
The patent divides the PPG sensing system into modular functional blocks including light source, photodetector, analog front-end, and adaptive ADC. Each module can be independently controlled and optimized, allowing the system to activate only necessary components based on measurement conditions, thus reducing overall power consumption while managing complexity through modular organization.
Solution Approach 2:
The patent implements dynamic ADC resolution adjustment where the converter adapts its resolution based on the actual perfusion index conditions. The system transitions from fixed high-resolution conversion to variable resolution conversion, matching the ADC precision to the actual signal requirements rather than always operating at maximum resolution.
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 approach reduces power consumption and enhances signal fidelity by adapting to varying physiological conditions, enabling continuous PPG monitoring in wearable devices and hearing aids with improved efficiency.
Implementation Method 1
The PPG sensor or photodetector detects the light transmitted through (transmissive PPG) or reflected from (reflective PPG) the tissue and transforms it into a photogenerated current
Data Source
AI summary
A sensor employs an adaptive light-to-digital conversion (LDC) system for high background signal applications. The system adapts the LDC resolution and the power consumption depending on the signal to background ratio. This scheme is of particular interest to photoplethysmography (PPG). The system can have a set of light-to-digital converters in which each of the light-to-digital converters includes an array of pixels and an analog to digital converter for digitizing the output from the array of pixels. Switches are then used to connect each of the light-to-digital converters to a power supply to selectively activate each of the light-to-digital converters.