Multi-String LED Color Tuning via Independent Current Control
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Solution Overview
Problem
Existing semiconductor light emitting devices face challenges in achieving high efficiency, high luminous flux, and good color reproduction while maintaining color stability, particularly in producing white light that meets desired color temperature and color rendering index (CRI) requirements.
Innovation Solution
The use of multiple LED strings with associated recipient luminophoric mediums, along with adjustable current control circuits, allows for precise tuning of the color point of the emitted light to achieve desired color temperatures and high CRI values by adjusting the drive currents to the LEDs, ensuring the light output falls within specific color ranges on the 1931 CIE Chromaticity Diagram.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If multiple LED types with different spectral power distributions are combined to achieve desired color temperature and CRI, then color reproduction quality improves, but device complexity increases
Solution Approach 1:
The invention divides the lighting system into multiple independent LED strings, each containing LEDs of a specific type with defined spectral characteristics. This segmentation allows precise control over the spectral power distribution by independently adjusting the drive current to each string, thereby achieving desired color temperature and CRI while maintaining manageable system complexity through modular architecture.
Solution Approach 2:
The patent creates a multi-functional LED lighting system where different LED strings serve distinct spectral functions (e.g., some strings provide blue light for high CRI, others provide fill light for color temperature control). This multi-functionality enables a single device to simultaneously achieve multiple optical performance targets—high CRI, specific color temperature, and good color stability—without requiring separate lighting systems for each function.
2Manufacturing precision
If drive currents to multiple LED strings are adjusted to tune color point, then color temperature control improves, but ease of operation deteriorates
Solution Approach 1:
The system implements dynamic color temperature control by enabling independent adjustment of drive currents to multiple LED strings. This dynamic capability allows the lighting system to adapt its spectral output in real-time, tuning the color point along the blackbody locus to achieve precise color temperature control while maintaining ease of operation through programmable control.
Solution Approach 2:
The patent utilizes parameter changes in the drive currents supplied to different LED strings as the primary control mechanism. By varying these electrical parameters, the system achieves precise control over the combined spectral power distribution, enabling accurate color temperature tuning and color point adjustment along the blackbody locus without complex mechanical or optical adjustments.
3Manufacturing precision
If multiple LED strings with different spectral characteristics are used to achieve high CRI, then color rendering index improves, but luminous flux is reduced
Solution Approach 1:
The system optimizes the balance between CRI and luminous flux by dynamically adjusting the drive current parameters to each LED string based on operational requirements. During periods when high color rendering is prioritized, the control system increases current to LED strings configured for high CRI output. When luminous flux becomes the priority, the system redistributes power to maximize total light output while maintaining acceptable color rendering, thereby resolving the trade-off between these two performance metrics.
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 production of warm white light with high CRI values exceeding 90, maintaining high luminous power output and efficacy, while allowing for adjustment of color temperature to various settings, thereby addressing the limitations of traditional LED technologies.
Implementation Method 1
one or more luminescent materials that convert light having a first wavelength to light having a second wavelength that is different from the first wavelength
Implementation Method 2
other of the blue light emitted by the LED is absorbed by the YAG:Ce phosphor, which becomes excited and emits yellow fluorescence with a peak wavelength of about 550 nm (i.e., the blue light is down-converted to yellow light)
Implementation Method 3
As the electrons and holes flow toward each other, some of the electrons will 'collide' with corresponding holes and recombine. Each time this occurs, a photon of light is emitted, which is how LEDs generate light.
Data Source
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AI summary
Semiconductor light emitting devices include a first string of at least one blue-shifted-yellow LED, a second string of at least one blue-shifted-green LED, and a third string of at least one LED that emits light in the red color range. These devices include at least a first circuit that is configured to provide an operating current to at least one of the first LED or the second LED and a second circuit that is configured to provide an operating current to the third light source. The drive currents supplied by the first and second circuits may be independently controlled to set a color point of the light emitting device at a desired color point.