Capacitive Power Supply Circuit for Biological Signal Measurement
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Solution Overview
Problem
Conventional biological signal measurement devices face challenges in electrical insulation from external power supplies, leading to potential electric shocks and limitations in battery life and maintenance, particularly with the use of secondary batteries.
Innovation Solution
A power supply circuit utilizing a capacitance element and a circuit switch to provide electrical insulation between the measurement system and power supply, allowing for quick charging and reduced noise, with a DPDT push button switch for momentary operation and a current detection circuit for charging notification.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If an isolated transformer is used to supply electric power from an external apparatus to the measuring apparatus, then electrical insulation is achieved, but induction noise increases and cost increases
Solution Approach 1:
The patent extracts the power conversion function from the transformer and implements it using a circuit switch and capacitance element. The circuit switch connects the external power supply to the capacitance element to charge it, then disconnects to provide isolated power to the measurement circuit, eliminating the transformer and its associated induction noise while maintaining electrical insulation.
Solution Approach 2:
The capacitance element serves as an intermediary energy storage device between the external power supply and the measurement circuit. It accumulates energy when connected to the power supply and releases it when isolated, acting as a buffer that enables power transfer without direct electrical connection, thus achieving insulation without transformer-induced noise.
2Ease of operation
If a secondary battery is used as power supply, then portability is improved, but charging time increases and maintenance is required
Solution Approach 1:
The capacitance element is charged in advance from the external power supply before the measurement operation begins. This preliminary charging action stores sufficient energy to power the measurement circuit during the entire measurement period, eliminating the need for charging during operation and reducing total charging time compared to secondary batteries.
Solution Approach 2:
The system uses periodic charging cycles where the capacitance element is charged from the external power supply, then discharged to power the measurement circuit. This periodic charge-discharge operation allows for rapid recharging compared to secondary batteries, reducing maintenance intervals and charging time.
3Adaptability or versatility
If a secondary battery is used, then the apparatus can operate independently, but the number of charging cycles is limited and maintenance is required
Solution Approach 1:
The capacitance element provides self-service by being rapidly recharged from the external power supply through the circuit switch. Unlike secondary batteries with limited cycle life, the capacitance element can be charged and discharged numerous times without degradation, enabling maintenance-free operation while maintaining independent measurement capability.
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 electrical insulation, reduces charging time, and eliminates maintenance concerns by using a capacitor as a power source, providing a low-noise power supply and extended charging cycles.
Implementation Method 1
a capacitance element that accumulates the electric power
Implementation Method 2
a circuit switch that is coupled between the capacitance element and an external power supply for supplying electric power to the capacitance element, and that is configured to switch, not through a state where the external power supply and the biological signal measurement circuit are electrically coupled, a first state where the capacitance element is made to establish electrical continuity with the external power supply
Data Source
AI summary
Provided is a power supply circuit that supplies electric power to a biological signal measurement circuit configured to detect, with an electrode set in contact with a human body, a biological signal which is a weak electric signal emitted by the human body. The power supply circuit includes a capacitance element accumulating the electric power, and a circuit switch coupled between the capacitance element and an external power supply for supplying electric power to the capacitance element, and configured to switch, not through a state where the external power supply and the biological signal measurement circuit are electrically coupled, a first state where the capacitance element establishes electrical continuity with the external power supply and is enabled to be charged, and a second state where the capacitance element establishes electrical continuity with the biological signal measurement circuit and is enabled to supply power to the biological signal measurement circuit.