Fingerprint Smart Card LED Control for Power-Saving Indication

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Solution Overview

Problem

Smart cards with visual indication functions face power insufficiency due to high current consumption during operations, which can lead to reduced processing efficiency and malfunctions.

Innovation Solution

A smart card design that includes a light-emitting element, a fingerprint sensor, and a microcontroller, where the microcontroller controls the current supplied to the light-emitting element, implementing power-saving periods by generating a light source control signal to decrease or stop current supply during high power consumption operations.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If the light-emitting element is continuously operated to provide visual indication, then the user can know the operation status of the smart card, but the smart card experiences power insufficiency during high current operations

Engineering Contradiction:
Improvevisual indication reliabilityVSAvoidpower consumption
Core Design Contradiction:
ReliabilityVSUse of energy by moving object

Solution Approach 1:

The patent implements periodic action by dividing the operation indication into multiple indication periods with different brightness levels. The light-emitting element operates at full brightness during low-power periods and reduces brightness or turns off during high-power consumption periods, creating a periodic on/off or dim/bright cycle that maintains visual indication while managing power consumption.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent applies dynamics by making the brightness of the light-emitting element adjustable and variable. The microcontroller dynamically controls the current supplied to the light-emitting element based on the operational state of the smart card, switching between different brightness levels or states (on/off) depending on power availability and operational requirements.

Inventive Principle:
Principle #15Dynamics

2Illumination intensity

If the light-emitting element operates at full current to ensure visible indication, then the indication is clear and visible, but the processing efficiency of the smart card decreases due to power insufficiency

Engineering Contradiction:
Improvelight brightnessVSAvoidprocessing efficiency
Core Design Contradiction:
Illumination intensityVSProductivity

Solution Approach 1:

The system uses periodic action to alternate between high brightness periods (when processing is complete or low power is needed) and low brightness or off periods (when high power consumption operations are occurring). This timing strategy ensures that visual indication is maintained when it matters most while freeing up power for processing operations.

Inventive Principle:
Principle #19Periodic action

Solution Approach 2:

The patent changes the electrical parameters (current, brightness level) of the light-emitting element based on operational conditions. The microcontroller adjusts the current parameter dynamically, switching between different current levels to match the processing requirements of the smart card, thereby optimizing both visibility and processing efficiency.

Inventive Principle:
Principle #35Parameter changes

3Use of energy by moving object

If the light-emitting element is controlled to save power during high current operations, then power insufficiency is prevented, but the visual indication may be interrupted or reduced

Engineering Contradiction:
Improvepower savingVSAvoidvisual indication continuity
Core Design Contradiction:
Use of energy by moving objectVSReliability

Solution Approach 1:

The periodic action principle is applied to create a rhythm of indication that alternates between visible and reduced/hidden states. By carefully timing the off or dim periods to coincide with high-power operations and restoring full indication during low-power periods, the system maintains overall reliability of information communication while enabling power savings during critical operations.

Inventive Principle:
Principle #19Periodic action

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

Prevents power insufficiency by managing current supply to the light-emitting element, ensuring the smart card operates efficiently and reliably while maintaining visual indication functionality.

Implementation Method 1

light-emitting elements are arranged on the smart card for visual indication. Normally, light-emitting diodes (LED) are used as the light-emitting elements

Methodology Applied
Scientific EffectLight-emitting diode: Light Emitting Diode

Data Source

PatentEP3839825B1Smart card and control method thereof
Publication Date: 2023.03.01 ELAN MICROELECTRONICS CORPORATION
  • EP3839825B1 patent drawingFigure 1
  • EP3839825B1 patent drawingFigure 2
  • EP3839825B1 patent drawingFigure 3

AI summary

A smart card has a light-emitting element, a fingerprint sensor and a microcontroller. An operation of the smart card has a plurality of indication periods to indicate operation statuses of the smart card by the light-emitting element. The control method of the smart card includes generating a light source control signal, controlling a current supplied to the light-emitting element by the microcontroller according to the light source control signal, and decreasing the current supplied to the light-emitting element or stop the current supplied to the light-emitting elementduring at least one power-saving period in a first indication period of the plurality of indication periods.