LED Light Source Thermal Management via Series Resistor Calibration

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Solution Overview

Problem

Existing semiconductor radiation sources for light curing devices face challenges in achieving uniform and stable light emission due to unequal power distribution among LED chips and inadequate cooling, which affects the quality and efficiency of through-curing processes.

Innovation Solution

The arrangement of series resistors on a printed circuit board allows for improved calibration and alignment of LED chips, enabling more compact and efficient light emission while providing thermal stability, reducing the risk of lens deformation, and simplifying the adjustment process through laser trimming.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If LED chips are arranged in close proximity and bundled using a converging lens, then light emission intensity is improved, but heat dissipation becomes inadequate and lens deformation risk increases

Engineering Contradiction:
Improvelight emission intensityVSAvoidheat dissipation
Core Design Contradiction:
Illumination intensityVSTemperature

Solution Approach 1:

The patent introduces a heat dissipation plate as an intermediary component between the LED chips and the surrounding environment. This plate serves as a thermal mediator that conducts heat away from the LED chips without interfering with the optical bundling function of the converging lens, thus resolving the contradiction between intense light emission and adequate heat dissipation

Inventive Principle:
Principle #24Intermediary (Mediator)

Solution Approach 2:

The patent segments the functional areas by positioning LED chips in a central region while placing series resistors in peripheral regions on the circuit board. This spatial segmentation allows the central area to focus on light emission with proper cooling, while peripheral areas handle electrical control functions, preventing heat interference with the optical system

Inventive Principle:
Principle #1Segmentation

2Illumination intensity

If LED chips are arranged densely in a central area, then light output is improved, but power distribution uniformity deteriorates

Engineering Contradiction:
Improvelight outputVSAvoidpower distribution uniformity
Core Design Contradiction:
Illumination intensityVSStability of the object's composition

Solution Approach 1:

The patent applies local quality by assigning individual series resistors to specific LED chip groups or individual chips in the dense central arrangement. This allows each LED element to have its current independently controlled and calibrated, ensuring uniform power distribution even in a densely packed configuration where thermal and electrical conditions vary locally

Inventive Principle:
Principle #3Local quality

Solution Approach 2:

The patent utilizes laser trimming to adjust the resistance values of series resistors, changing the electrical parameters to compensate for variations in LED chip characteristics. This parameter adjustment enables precise control of current distribution across densely packed LED chips, maintaining power distribution uniformity while achieving high light output

Inventive Principle:
Principle #35Parameter changes

3Measurement precision

If series resistors are placed close to LED chips for calibration, then adjustment precision is improved, but heat interference with resistors increases

Engineering Contradiction:
Improvecalibration precisionVSAvoidheat interference
Core Design Contradiction:
Measurement precisionVSTemperature

Solution Approach 1:

The patent resolves the heat interference problem by utilizing the planar dimension of the circuit board. Series resistors are positioned in peripheral regions on the same circuit board as the LED chips, using the available two-dimensional space to separate hot and cold zones while maintaining electrical connection functionality for calibration purposes

Inventive Principle:
Principle #17Another dimension (Dimensionality change)

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 results in enhanced light output and improved through-curing results with long-term stability, ensuring uniform light yield and efficient heat management without compromising the lens integrity.

Implementation Method 1

The LED chips are firmly attached to a base body in a thermally conductive connection

Methodology Applied
Scientific EffectThermal conduction: Conduction (thermal)

Implementation Method 2

The support member is supported on the printed circuit board... it is better thermally insulated from the base body heated by the LED chips

Methodology Applied
Scientific EffectThermal insulation: Thermal Insulation

Implementation Method 3

the assigned series resistors can be adjusted by laser trimming

Methodology Applied
Scientific EffectLaser trimming: Laser Ablation

Data Source

PatentEP1843394B1Semiconductor light source and light curing apparatus with the same
Publication Date: 2019.03.27 IVOCLAR VIVADENT AG
  • EP1843394B1 patent drawingFigure 1~2
  • EP1843394B1 patent drawingFigure 3~4
  • EP1843394B1 patent drawingFigure 5

AI summary

The source (10) has a pair of centrally arranged LED chips (12,14) directly mounted to a base (24) using a thermally conductive connection. A printed circuit board (PCB) (30) mounted on the base extends from the LED chips to a peripheral region of the base. Series resistors (40,42) are extended from the LED chips to the PCB.