Capacitive Measurement IC with Floating Bridge and Guard
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Solution Overview
Problem
Existing capacitive measurement systems face integration challenges due to the need for separate electronics with distinct reference potentials, leading to interference issues and difficulties in integrating decoupling components, which limits their ability to be produced in the form of a single integrated circuit suitable for portable devices.
Innovation Solution
A capacitive measurement device comprising a first electronic system referenced to a guard potential and a second system referenced to ground potential, connected via excitation means that impose an AC voltage difference, integrated into a single circuit with shielding to protect sensitive components from parasitic capacitances, using technologies like CMOS and silicon on insulator to facilitate electrical isolation and integration.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If separate electronics with distinct reference potentials are used, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The patent merges the floating bridge measurement circuit and the oscillating guard potential generator into a single integrated circuit. The floating bridge circuit includes capacitive electrodes, voltage followers, and operational amplifiers that operate at a floating guard potential, while the oscillating guard potential is generated by an oscillator connected to ground. This integration eliminates the need for separate discrete components and external printing circuits, reducing device complexity while maintaining measurement precision through the floating reference architecture.
2Measurement precision
If floating electronics are used to eliminate parasitic capacitances, then measurement precision is improved, but ease of manufacture deteriorates
Solution Approach 1:
The patent combines multiple floating and grounded components into a single integrated circuit, eliminating the need for external printing circuits and discrete components. The integrated circuit includes the floating bridge circuit with operational amplifiers and voltage followers, along with the oscillating guard potential generator. This integration simplifies manufacturing by replacing complex external assembly with a single semiconductor device that can be manufactured using standard IC fabrication processes.
Solution Approach 2:
The patent introduces an oscillating guard potential as an intermediary reference that mediates between the floating measurement circuit and the grounded oscillator. This oscillating guard potential eliminates parasitic capacitances by providing a dynamic reference that prevents capacitive coupling between the floating electronics and ground, while the oscillator serves as the intermediary that generates this reference from the grounded domain.
3Reliability
If decoupling components are added to isolate floating and grounded parts, then reliability is improved, but device complexity increases
Solution Approach 1:
The patent integrates the decoupling function directly into the integrated circuit architecture rather than using external components. The floating bridge circuit and oscillating guard potential generator are designed as integrated blocks within a single IC, where the decoupling between floating and grounded sections is achieved through the internal circuit design and the oscillating guard potential mechanism, eliminating the need for separate decoupling components like choke coils or optical couplers.
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 configuration allows for the production of a compact, low-power capacitive measurement system that minimizes interference and facilitates integration, enhancing sensitivity and accuracy by isolating sensitive components from parasitic capacitances while maintaining efficient signal transfer and power supply within the integrated circuit.
Implementation Method 1
an oscillator which connects the ground and the guard. Thus, no part of the electronics of the sensitive stages is at the ground and it cannot create parasitic capacitances with the ground
Implementation Method 2
When an object such as a finger comes close to these electrodes, an electrical coupling of capacitive type is created between this object which represents an electrical ground, and the electrodes
Data Source
AI summary
A capacitive measurement device is provided, including: (i) a first electronic system electrically referenced to a guard potential and connectable to capacitive electrodes; (ii) a second electronic system electrically referenced to a ground potential; and (iii) an energizing component connected to the guard and ground potentials, respectively, to impart an AC voltage differential between the potentials. The device also includes an integrated circuit that is referenced to the ground and includes a first installation area in which the first electronic system is implemented, and a second installation area in which the second electronic system is implemented. Also included are systems using the device and uses of the device.