Tunable White Light LED Strings with High Color Rendering
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Solution Overview
Problem
Current LED lamps face challenges in providing white light across a range of correlated color temperatures (CCT) while maintaining high efficiency, luminous flux, and good color rendering with acceptable color stability.
Innovation Solution
The solution involves semiconductor light emitting devices comprising multiple LED strings with different luminescent materials and a drive circuit that adjusts the relative drive currents to achieve a combination of unsaturated lights within specific color ranges, allowing for tunable white light generation with high color rendering indices across a broad range of CCT values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If multiple LEDs with different peak wavelengths are used to generate white light, then the correlated color temperature range is expanded, but the color rendering index deteriorates due to gaps in spectral power distribution
Solution Approach 1:
The patent divides the white light generation into multiple independent LED channels, each responsible for specific wavelength regions (violet 380-420nm, blue 420-500nm, cyan 460-530nm, green 500-560nm, yellow-green 540-600nm, red 600-780nm). This segmentation allows each channel to be optimized for its spectral region while collectively providing continuous coverage across the visible spectrum, resolving the contradiction between CCT range and CRI.
Solution Approach 2:
The patent employs a composite approach by combining multiple LED types with distinct spectral characteristics into a single illumination system. Each LED channel uses specific phosphor materials (e.g., BaMgAl10O17:Eu for red, Y3Al5O12:Ce for yellow-green) to create a composite spectral power distribution that maintains continuity across all visible wavelengths, thereby achieving both broad CCT tunability and high color rendering.
2Reliability
If the spectral power distribution is broadened to improve color rendering, then the power efficiency deteriorates
Solution Approach 1:
The patent applies local quality by providing enhanced spectral power in specific wavelength regions where human color perception is most sensitive (particularly 480-680nm range with emphasis on red, green, and blue regions). Rather than uniformly broadening the spectrum, each LED channel is optimized to emit strongly in its designated region while maintaining appropriate intensity relative to human visual response, thus improving CRI without excessive energy consumption across the entire spectrum.
Solution Approach 2:
The system dynamically adjusts the drive currents to each LED channel based on the desired correlated color temperature and color rendering requirements. By changing the relative intensity parameters of individual LED channels, the system optimizes the spectral power distribution to match the luminous efficiency function of the human eye, thereby maintaining high power efficiency while achieving broad color rendering across different operating conditions.
3Adaptability or versatility
If the drive currents to individual LEDs are adjusted to change CCT, then the color stability deteriorates
Solution Approach 1:
The patent incorporates feedback control by using photodetectors to monitor the actual spectral power distribution and correlated color temperature of the emitted light. The control system compares the measured values with target values and adjusts the drive currents to each LED channel accordingly, compensating for variations in LED aging, temperature drift, and manufacturing tolerances. This closed-loop control maintains both CCT tunability and color stability simultaneously.
Solution Approach 2:
The system employs dynamic current adjustment with independent control of each LED channel's drive current. The control circuit continuously optimizes the relative intensities of violet, blue, cyan, green, yellow-green, and red channels based on the desired CCT point, allowing smooth transitions across the full CCT range while maintaining stable chromaticity coordinates through real-time compensation for non-linear LED responses.
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 enables the generation of white light with high color rendering performance, achieving Ra≥90, R9≥60, and GAIBB≥95 across a range of CCT values from 1800K to 10000K, providing improved color rendering and tunability.
Implementation Method 1
utilizing one or more luminescent materials such as phosphors to convert some of the light emitted by one or more LEDs to light of one or more other colors
Data Source
AI summary
The present disclosure provides systems for generating tunable white light. The systems include a plurality of LED strings that generate light with color points that fall within blue, yellow/green, red, and cyan color ranges, with each LED string being driven with a separately controllable drive current in order to tune the generated light output.