LED Color Accuracy Control via Phosphor Selection
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Solution Overview
Problem
High power light-emitting diodes (LEDs) face challenges in maintaining color accuracy across varying operating conditions, such as temperature changes, due to shifts in dominant wavelength and luminous flux, which affect the luminous efficacy of white light emission.
Innovation Solution
A method and apparatus that combines specific LED color sources and phosphors to compensate for changes in light characteristics by selecting color sources with reproducible changes, ensuring the emitted color remains within desired accuracy in the CIE chromaticity diagram across different operating conditions, potentially using additional red LED dice to enhance luminous efficacy and omitting red phosphors for improved spectral efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If high power LED is used to increase luminous flux, then brightness is improved, but color accuracy deteriorates due to wavelength shifts
Solution Approach 1:
The patent applies parameter changes by selecting LED dice and phosphors with specific characteristics that account for temperature-dependent wavelength shifts. The method involves choosing components whose combined spectral properties maintain color accuracy across operating temperature ranges, transforming the static component selection into a dynamic parameter-matching process that compensates for thermal effects.
Solution Approach 2:
The patent uses composite materials by combining specific LED dice materials with specific phosphor materials to create a hybrid light-emitting system. This composite approach allows the LED-phosphor combination to compensate for individual component deficiencies, where the LED provides high luminous flux and the phosphor converts wavelengths to maintain color accuracy despite temperature-induced shifts.
2Power
If operating temperature increases, then luminous flux increases, but dominant wavelength shifts causing color inaccuracy
Solution Approach 1:
The patent applies preliminary anti-action by pre-selecting LED and phosphor combinations whose spectral characteristics are designed to counteract expected temperature-induced wavelength shifts. The component selection process anticipates thermal effects and chooses materials whose combined response compensates for the dominant wavelength shifts that would otherwise occur during high-power operation.
Solution Approach 2:
The patent implements feedback by measuring the actual color output of the LED-phosphor combination under operating conditions and using this information to refine component selection. The method involves characterizing the spectral behavior of candidate components and selecting combinations that demonstrate stable color output across the expected operating temperature range, effectively using performance data to guide component matching.
3Manufacturing precision
If red phosphor is added to improve color rendering, then color accuracy is improved, but luminous efficacy decreases
Solution Approach 1:
The patent applies the taking out principle by selectively removing red phosphor from the phosphor combination, recognizing that its contribution to color accuracy is outweighed by its negative impact on luminous efficacy. The method extracts the problematic component (red phosphor) while retaining beneficial phosphors, achieving color accuracy through alternative means such as precise LED dice selection and combination with phosphors that do not significantly reduce overall efficiency.
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 approach maintains color accuracy and luminous efficacy by selecting LED and phosphor combinations that minimize changes in light characteristics over operating conditions, ensuring the emitted light meets design specifications within a predetermined range, even under varying temperatures or other environmental changes.
Implementation Method 1
A method and apparatus that combines specific LED color sources and phosphors to compensate for changes in light characteristics
Implementation Method 2
High power light-emitting diodes (LEDs) face challenges in maintaining color accuracy across varying operating conditions
Data Source
AI summary
A method for controlling color accuracy of a light-emitting semiconductor-based device, and a process for producing a light-emitting semiconductor-based device with desired color accuracy is disclosed. The color accuracy is controlled by defining a desired color accuracy of a light produced by mixing colors emitted by at least two light sources over a first range of operating conditions; determining characteristics of the light as a function of operating conditions; and establishing desired light characteristics of the at least two light sources over a second range of operating condition in accordance with the step of defining and the step of determining.