Pulse Wave Measurement Circuit Using Integrated Photocurrent Pulses
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Solution Overview
Problem
Conventional pulse wave measurement technologies experience high power consumption due to prolonged lighting times of LEDs and continuous operation of amplifiers, leading to reduced operation time of wearable devices and decreased commodity value.
Innovation Solution
A measurement circuit that integrates current generated by a light receiving unit during light emission periods and generates a pulse signal based on the received light, allowing for reduced light emission time and power consumption by integrating the current and converting it into voltage after light emission.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the LED lighting time is extended to ensure accurate pulse wave measurement, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The patent applies preliminary action by performing current integration during the LED light emission period itself, rather than after. The integrating unit accumulates the photoelectric current generated by the PD during the illumination period, converting it to voltage that represents the total light reception amount. This allows the measurement to be completed within the brief LED on-time, eliminating the need for prolonged LED illumination while maintaining measurement accuracy.
2Measurement precision
If the amplifier operates continuously to process signals, then the measurement precision is improved, but the power consumption increases
Solution Approach 1:
The patent extracts the signal processing function from the traditional amplifier and relocates it to the integrating unit. Instead of using an amplifier to continuously process and amplify the weak photoelectric current, the integrating unit directly accumulates the current during the LED emission period and outputs a voltage signal that already represents the integrated light reception amount. This eliminates the need for continuous amplifier operation and subsequent ADC conversion, significantly reducing power consumption while preserving measurement accuracy.
3Measurement precision
If the LED emits light for a longer duration to capture sufficient reflected light, then the measurement precision is improved, but the duty cycle increases and power consumption increases
Solution Approach 1:
The patent applies parameter changes by fundamentally altering the measurement approach from continuous amplification to temporal integration. The integrating unit accumulates the photoelectric current over the entire LED emission period, converting the time-domain signal into a voltage that represents the integrated light amount. This parameter transformation allows the system to achieve accurate measurement with shorter LED emission durations, reducing both the duty cycle and power consumption while maintaining measurement precision.
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 significantly reduces power consumption by minimizing LED light emission time and overall current consumption, enabling longer operation of wearable devices while maintaining accurate pulse wave measurement.
Implementation Method 1
a light receiving unit that receives light from an object; an integrating unit that performs integration of a current generated in accordance with the reception of light by the light receiving unit
Data Source
AI summary
The present technology relates to a measurement circuit, a driving method, and an electronic instrument capable of reducing power consumption. In the measurement circuit, irradiation light is emitted from the light emitting unit toward the object, and light from the object is received to measure pulse waves or the like. The measurement circuit includes: a light receiving unit that receives light from an object; an integrating unit that performs integration of a current generated in accordance with the reception of the light by the light receiving unit and generates a voltage according to the amount of reception of the light; and a pulse generating unit that generates a pulse signal having a pulse width corresponding to the amount of reception of the light on the basis of the voltage. The present technology can be applied to electronic instruments such as wearable devices, for example.