Optical Heart Rate Sensor Power Reduction via Sub-Sampling
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Solution Overview
Problem
Current optical heart rate sensor devices face challenges in accurately measuring Pulse Transit Time (PTT) and Heart Rate (HR) due to high power consumption and heating issues caused by frequent pulsation of LEDs, which can lead to skin burns and significant battery drain, especially when trying to achieve sampling rates greater than 1000 Hz for precise measurements.
Innovation Solution
The implementation of a method that activates LEDs at a sub-sampling resolution for initial PPG measurements, followed by mathematical reconstruction at a sample resolution to identify PPG peaks with sufficient accuracy, reducing power usage and heating while maintaining accurate PTT and HR determination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If LEDs are pulsed at high peak currents every 1 ms to achieve PTT accuracy of less than 1 ms, then measurement precision is improved, but power consumption increases and LED heating occurs causing skin burns
Solution Approach 1:
The patent applies periodic action by pulsing LEDs at lower peak currents with longer duty cycles rather than continuous high-current pulsing. The system uses intermittent LED activation combined with signal averaging and interpolation techniques to maintain measurement accuracy while reducing power consumption and heat generation.
Solution Approach 2:
The patent changes the electrical parameters of LED operation by reducing peak current and adjusting pulse width/duty cycle. This parameter optimization allows the system to achieve required measurement precision through signal processing techniques rather than relying solely on high-power LED pulsing.
2Measurement precision
If LEDs are pulsed frequently at 1 ms intervals to achieve accurate PTT measurement, then measurement precision is improved, but harmful thermal effects increase causing skin burns
Solution Approach 1:
The system uses periodic LED pulsing with optimized duty cycles to reduce cumulative heat exposure to the skin. By combining lower-power periodic pulses with signal averaging techniques, the system maintains measurement accuracy while minimizing thermal harm to the subject.
Solution Approach 2:
The patent converts the limitation of lower LED power into a benefit by using the reduced heating effect as a safety feature. The system achieves acceptable measurement precision through intelligent signal processing rather than brute-force high-power pulsing, thereby eliminating skin burn risk.
3Measurement precision
If LEDs are pulsed continuously at high current to detect weak PPG signals on dark skin, then measurement precision is improved, but power consumption increases causing significant battery drain
Solution Approach 1:
The system performs preliminary signal acquisition at lower power levels and then applies post-processing techniques such as averaging and interpolation to enhance signal quality. This preliminary low-power sampling followed by computational enhancement reduces overall energy consumption while maintaining detection accuracy for weak PPG signals.
Solution Approach 2:
The patent uses signal copying and averaging techniques where multiple low-power measurements are taken and processed to create a high-quality composite signal. This approach replaces the need for single high-power measurements, significantly reducing battery drain while maintaining PPG detection 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 approach achieves accurate PTT and HR measurements with reduced power consumption and heat generation, providing up to 50× reduction in LED power usage compared to continuous LED operation, while maintaining the required accuracy for blood pressure and heart rate monitoring.
Implementation Method 1
one or more photoplethysmographic (PPG) sensors
Implementation Method 2
measuring light absorption variations
Implementation Method 3
one or more electrocardiographic (ECG) signal sensors
Implementation Method 4
the optical LEDs in PPG sensor should be pulsed (illuminated and turned OFF)
Data Source
AI summary
Methods, systems, and storage media relating to a circulatory health monitor device are disclosed herein. In an embodiment, such a device may be positioned or disposed on and/or in contact with a subject to measure blood pressure and/or heart rate. The device may include one or more electrocardiographic (ECG) signal sensors, one or more photoplethysmographic (PPG) sensors, and a controller. The controller may activate at a low resolution a PPG measurement of the subject in relation to an ECG signal feature to identify a PPG signal feature location or region in the PPG measurement. The controller may further activate at a high resolution PPG measurement of the subject at the PPG signal feature region to identify the PPG signal feature, and may determine blood pressure and/or heart rate therefrom. Other embodiments may be disclosed and/or claimed.