Wearable PPG Sensor Current Control for Ambient Light Adaptation
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Solution Overview
Problem
Wearable computing devices face a trade-off between power consumption and PPG sensor accuracy due to continuous heart rate monitoring, with LED brightness being dimmed to conserve power, affecting measurement quality and availability.
Innovation Solution
A wearable computing device adjusts current supplied to light sources based on ambient light and motion detection using pre-existing sensors, increasing brightness in bright environments or high motion to enhance accuracy and reducing power consumption when conditions allow.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the LED of the PPG sensor is driven at a high level to improve measurement accuracy, then PPG sensor accuracy is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the LED brightness adjustable rather than fixed. The system dynamically changes the LED drive level based on ambient light conditions detected by the ambient light sensor. In bright environments, the LED is driven at lower levels to save power, while in dark environments, it is driven at higher levels to maintain measurement accuracy, thus resolving the contradiction between power consumption and measurement accuracy
Solution Approach 2:
The patent changes the operating parameter (LED brightness/current) based on environmental conditions. The processor adjusts the LED drive current as a variable parameter rather than a constant, allowing the system to optimize between power consumption and measurement accuracy by adapting the parameter to match ambient light levels
2Use of energy by moving object
If the LED brightness is dimmed to reduce power consumption, then power consumption is reduced, but PPG sensor accuracy deteriorates
Solution Approach 1:
The system changes the LED brightness parameter dynamically based on ambient light conditions. In bright environments where ambient light provides sufficient illumination, the LED is dimmed to reduce power consumption. In dark environments, the LED brightness is increased to maintain measurement accuracy, thus resolving the contradiction between power consumption and measurement accuracy
3Adaptability or versatility
If continuous heart rate monitoring is implemented to improve availability, then PPG sensor availability is improved, but power consumption increases
Solution Approach 1:
The patent applies dynamics by making the PPG monitoring mode adjustable rather than fixed. The system dynamically switches between continuous and periodic monitoring based on ambient light conditions. In bright environments, continuous monitoring is enabled to maintain high availability, while in dark environments, periodic monitoring is used to reduce power consumption, thus resolving the contradiction between availability and power consumption
Solution Approach 2:
The monitoring frequency parameter is changed based on environmental conditions. The system varies the monitoring mode (continuous vs. periodic) as a controllable parameter, allowing optimization between availability and power consumption by adapting the parameter to match ambient light levels
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 extends battery life and maintains or enhances PPG sensor accuracy by optimizing LED brightness based on ambient light and motion, balancing power usage and measurement quality.
Implementation Method 1
the one or more detectors is configured to receive a reflection of the light emitted toward the body part to generate a signal indicating a biometric of the user
Implementation Method 2
the one or more detectors is configured to receive a reflection of the light emitted toward the body part to generate a signal
Implementation Method 3
The first sensor is configured to detect ambient light in a surrounding environment of the wearable computing device
Data Source
AI summary
A wearable computing device includes a body, a first sensor disposed at an upper part of the body, and a second sensor disposed at a lower part of the body. The first sensor detects ambient light in a surrounding environment of the wearable computing device and the second sensor includes one or more light sources and one or more detectors, the one or more light sources emitting light toward a body part of a user when the wearable computing device is worn by the user, and the one or more detectors receiving a reflection of the light emitted toward the body part to generate a signal indicating a biometric of the user. The wearable computing device further includes one or more processors which adjust a current supplied to the one or more light sources based on an amount of ambient light detected by the first sensor.