PPG Sensor Switching Circuit for Pulse Wave Noise Removal
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing photoplethysmography (PPG) sensors face challenges in efficiently removing noise such as external light interference, sound, vibration, or motion, which deteriorate measurement sensitivity when measuring pulse wave signals.
Innovation Solution
A photoplethysmography sensor design that includes a photoelectric conversion element, current-to-voltage converter, and a switch to control the connection between them, along with a semiconductor device that modulates light output and uses storage units to separate signal and noise components, effectively removing noise through controlled switching and modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional PPG sensors are used to measure pulse wave signals, then the measurement can be performed, but noise such as external light interference, sound, vibration, or motion deteriorates measurement sensitivity
Solution Approach 1:
The patent applies periodic action by modulating the light source at a specific frequency and using synchronous detection to distinguish the pulse wave signal from noise. The light source is turned on and off periodically, and the detector synchronously processes the reflected light signals to extract the pulse wave information while rejecting noise components that do not follow the same periodic pattern.
Solution Approach 2:
The patent implements feedback through a control circuit that generates control signals based on the detected pulse wave signal. The control signal adjusts the light source modulation and the switch timing to optimize signal detection. This closed-loop feedback mechanism enhances measurement sensitivity by dynamically adapting to the detected physiological signals and maintaining optimal detection conditions.
2Measurement precision
If additional sampling circuits are added to remove noise, then noise removal capability improves, but device complexity increases
Solution Approach 1:
The patent merges multiple functions into a single integrated circuit structure. The switch, current-to-voltage converter, and storage unit are combined in one detector circuit, eliminating the need for separate sampling circuits. This integration achieves noise removal functionality while maintaining simple device architecture and facilitating miniaturization.
Solution Approach 2:
The detector circuit is designed with multi-functionality, where the same circuit components serve multiple purposes: the photoelectric conversion element converts light to current, the switch controls signal routing based on light source state, the current-to-voltage converter transforms current signals to voltage signals, and the storage unit simultaneously acts as both signal storage and noise filtering mechanism. This universal design reduces overall device complexity.
3Measurement precision
If light source is continuously on to improve signal detection, then signal detection capability improves, but noise from external light and interference increases
Solution Approach 1:
The light source operates periodically rather than continuously, being turned on and off at controlled intervals. During the off period, external light interference is minimized. The periodic modulation creates a distinctive signal pattern that can be easily distinguished from continuous background noise, improving signal detection capability while reducing susceptibility to external light interference.
Solution Approach 2:
The system takes preliminary anti-action by using the switch to block or route signals based on the light source state before noise can affect the measurement. The control circuit anticipates the light source modulation and pre-configures the signal path to accept only the modulated light signals during the on-period, rejecting external light interference that does not follow the predetermined modulation pattern.
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
The solution enables efficient noise removal from pulse wave signals, enhancing measurement sensitivity and allowing for accurate extraction of physiological parameters without the need for additional sampling circuits, facilitating miniaturization and direct digital conversion of pulse wave signals.
Implementation Method 1
a photoelectric conversion element configured to generate electric charges corresponding to the received light
Data Source
AI summary
A photoplethysmography sensor that includes a photoelectric conversion element including a first terminal and a second terminal, and that receives light reflected from a blood vessel and generates a current corresponding to the received light, a current-to-voltage converter that receives the generated current through a first input terminal and a second input terminal, and generates an output voltage corresponding to the received current, and a switch that, in response to a control signal of a first level, connects the first and second terminals of the photoelectric conversion element respectively to the first and second input terminals of the current-to-voltage converter and in response to the control signal of a second level different from the first level, connects the first and second terminals of the photoelectric conversion element respectively to the second and first input terminals of the current-to-voltage converter.