Ferroelectric Variable Capacitance Element for Contactless Receiver Overvoltage Protection

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Solution Overview

Problem

Contactless receivers, such as contactless IC cards, face damage from excessively high received voltages when brought close to a reader/writer, and existing protection circuits using variable capacitance elements have limitations including the need for additional circuits and low voltage endurance due to semiconductor components.

Innovation Solution

A contactless receiver design incorporating a resonant circuit with a ferroelectric variable capacitance element whose capacitance changes with received alternating current voltage, eliminating the need for control signals and bias removal capacitors, and utilizing a ferroelectric material for higher voltage resistance.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If a variable capacitance element with semiconductor components is used for protection, then the protection function is provided, but the voltage endurance is limited

Engineering Contradiction:

Improveprotection functionVSAvoidvoltage endurance

Core Design Contradiction:

ReliabilityVSStrength

Solution Approach 1:

The patent changes the material parameter of the variable capacitance element from semiconductor to ferroelectric material. This material substitution fundamentally alters the voltage endurance characteristic while maintaining the protection function, allowing the element to withstand excessively high received voltages without damage.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If a variable capacitance element with control terminals is used, then the capacitance control function is provided, but additional circuits and bias removal capacitors are required

Engineering Contradiction:

Improvecapacitance control functionVSAvoidcircuit structure

Core Design Contradiction:

Adaptability or versatilityVSDevice complexity

Solution Approach 1:

The ferroelectric variable capacitance element automatically changes its capacitance in response to the received voltage without requiring external control signals or bias removal capacitors. The element serves itself by directly utilizing the received alternating current voltage to modulate its capacitance, thereby eliminating the need for additional control circuits and simplifying the overall device structure.

Inventive Principle:

Principle #25Self-service

Solution Approach 2:

The ferroelectric variable capacitance element performs multiple functions simultaneously: it provides protection against overvoltage, automatically adjusts capacitance based on received signal strength, and eliminates the need for separate bias removal capacitors. This multi-functionality reduces device complexity while maintaining adaptability.

Inventive Principle:

Principle #6Universality (Multi-functionality)

3Reliability

If protection circuits with additional components are used, then the protection capability is enhanced, but the element size and production cost increase

Engineering Contradiction:

Improveprotection capabilityVSAvoidelement size

Core Design Contradiction:

ReliabilityVSWeight of moving object

Solution Approach 1:

The patent extracts and eliminates unnecessary components such as bias removal capacitors and control circuitry from the protection circuit. By using a ferroelectric variable capacitance element that inherently provides protection without these additional components, the element size is reduced while maintaining protection capability.

Inventive Principle:

Principle #2Taking out (Extraction)

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 design provides a simpler structure with enhanced resistance to received voltages, reducing the risk of damage to semiconductor devices and lowering production costs by eliminating the need for additional circuits and larger element sizes.

Implementation Method 1

a ferroelectric layer (51) formed with a ferroelectric material and two electrodes (52, 53) sandwiching the ferroelectric layer (51). The ferroelectric layer (51) has characteristics in which the capacitance changes according to an input alternating current voltage

Methodology Applied

Scientific EffectFerroelectric effect:

Implementation Method 2

a resonant circuit including a resonant capacitor (5) including a variable capacitance element and a resonance coil (4) connected to the resonant capacitor (5)

Methodology Applied

Scientific EffectResonance: Resonance

Data Source

PatentUS8781396B2Contactless receiver, resonant circuit, and variable capacitance element

Publication Date: 2014.07.15 DEXERIALS CORP

AI summary

A contactless receiver is provided with a receiving section and a rectification section. The receiving section has a resonant circuit including a resonant capacitor having a variable capacitance element formed with a ferroelectric material, a capacitance of the variable capacitance element changing according to a received voltage at a predetermined frequency, and a resonance coil connected to the resonant capacitor. The rectification section converts an alternating current voltage output from the receiving section into a direct current voltage.