Tunable LED Lighting with Phosphor Mixing for Wide-CCT Color Rendering
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Solution Overview
Problem
Current light emitting diode (LED) devices struggle to achieve high color fidelity across a wide correlated color temperature (CCT) range while maintaining high subjective preference, particularly in lighting applications where red saturation is prioritized over general color fidelity.
Innovation Solution
The use of a combination of LEDs and phosphors configured to emit red, blue, and green spectral components, with the green spectral component having at least 30% radiant flux in the 630 nm to 780 nm range, and a controller to independently control input power, allowing for precise tuning of color profiles and improved color rendering indices.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a single LED with phosphor is used to produce white light, then the device complexity is low, but the color rendering index and color fidelity cannot be optimized across a wide CCT range
Solution Approach 1:
The white light source is segmented into multiple independent LED chips (first LED, second LED, third LED) each emitting different spectral components (red, blue, green). This segmentation allows independent optimization of each LED's phosphor conversion to achieve precise control over the overall spectral power distribution, enabling high color rendering index (Ra≥90, R9≥50) across a wide correlated color temperature range (2700K-6500K) while maintaining manageable device complexity through modular integration.
2Manufacturing precision
If phosphor concentration is increased to enhance color saturation, then the color fidelity improves, but the luminous efficacy decreases due to increased light absorption
Solution Approach 1:
Different phosphor materials and concentrations are applied locally to each LED chip based on its specific spectral requirements. The first LED uses phosphor for red spectral component, the second LED uses phosphor for blue spectral component, and the third LED uses phosphor for green spectral component. This localized optimization allows each phosphor layer to operate at its most efficient concentration for the specific wavelength range it targets, maximizing color fidelity (excitation purity <0.95 for all components) while minimizing energy loss through optimized phosphor absorption characteristics.
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 achieves a color rendering index (CRI) of Ra ≥ 90, R9 ≥ 50, and a TM-30-18 gamut index ≥ 100 over a CCT range of 2700 K to 6500 K, with minimal chroma shift, enhancing color fidelity and subjective preference.
Implementation Method 1
An LED can be combined with a 'phosphor' to produce light with increased longer wavelength components. A phosphor, as used herein, refers to a material that converts or modifies the spectral power distribution of the LED. When the excited state electrons relax to the ground state, energy in the form of light is emitted. The emitted light has a lower energy (longer wavelength) than the light initially absorbed by the phosphor.
Data Source
AI summary
Light emitting devices having a first LED with a first phosphor, a second LED with a second phosphor and a third LED with a third phosphor to emit a composite white light are described. The first LED and first phosphor emit the red spectral component, the second LED and the second phosphor emit the blue spectral component and the third LED and third phosphor emit the green spectral component of the composite white light. The green spectral component has at least 30% radiant flux in a deep red spectral wavelength region.