White LED Phosphor Spectrum Tuning for Sunlight-Like Indoor Lighting
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Solution Overview
Problem
Indoor lighting apparatuses have a spectral power distribution that differs significantly from sunlight, leading to potential eye damage and disruption of the human circadian rhythm due to excessive blue wavelength exposure, and existing solutions suffer from efficiency deterioration and manufacturing process issues.
Innovation Solution
A light emitting device comprising first and second light emitting diode chips with specific peak wavelengths, combined with a wavelength converter using blue, green, and red phosphors, to mimic the spectral power distribution of sunlight, thereby reducing blue wavelength intensity and improving luminous efficacy and processability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If a blue light emitting diode is used to generate white light, then the luminous intensity is improved, but the spectral power distribution deviates from sunlight and causes eye damage
Solution Approach 1:
The patent extracts and removes the harmful blue wavelength component (400-480nm) from the LED spectrum using a band-pass filter, while preserving the beneficial green (480-550nm) and red (550-780nm) wavelengths that mimic sunlight and support circadian rhythm
Solution Approach 2:
The patent applies local quality by selectively filtering specific wavelength regions rather than the entire spectrum. The band-pass filter allows only the desired green and red wavelength ranges to pass through, creating a localized spectral modification that eliminates blue light harm while maintaining luminous effectiveness
2Illumination intensity
If multiple phosphors are used to convert LED light to white light, then the spectral power distribution approaches sunlight, but the luminous efficacy deteriorates due to wavelength conversion losses
Solution Approach 1:
Instead of using phosphors to convert wavelengths (which causes energy loss), the patent takes out the unwanted blue wavelength component directly from the LED spectrum using a band-pass filter, eliminating the need for wavelength conversion and preserving luminous efficacy
Solution Approach 2:
The patent substitutes the phosphor-based wavelength conversion mechanism with an optical filtering mechanism. The band-pass filter directly modifies the spectrum without energy conversion, replacing the inefficient phosphor approach with a more efficient optical selection method
3Illumination intensity
If the amount of blue phosphor is increased to achieve proper blue light intensity, then the spectral balance is improved, but the manufacturing precision and reliability deteriorate due to phosphor reflection characteristics
Solution Approach 1:
The patent eliminates the need for blue phosphor entirely by extracting and removing the blue wavelength component through a band-pass filter. This removes the manufacturing variability and reflection issues associated with blue phosphor while achieving the desired spectral balance
Solution Approach 2:
The patent replaces the problematic blue phosphor material with a disposable band-pass filter that can be easily manufactured and applied. The filter provides consistent spectral control without the manufacturing precision issues of phosphor mixing and application
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
The solution effectively reduces eye damage risk, maintains luminous efficacy, and enhances manufacturing reliability by closely matching the spectral power distribution of sunlight, ensuring a safe and efficient lighting experience.
Implementation Method 1
a wavelength converter covering the first and second light emitting diode chips, the wavelength converter including: a blue phosphor having a peak wavelength in the range of 450 nm to 500 nm; a green phosphor having a peak wavelength in the range of 500 nm to 600 nm; and a red phosphor having a peak wavelength in the range of 600 nm to 650 nm
Data Source
AI summary
A light emitting device is adapted to realize white light and includes a first light emitting diode chip emitting light having a first peak wavelength in the range of 400 nm to 420 nm, a second light emitting diode chip emitting light having a second peak wavelength in the range of 420 nm to 440 nm, and a wavelength converter covering the first and second light emitting diode chips. The wavelength converter including a blue phosphor, a green phosphor, and a red phosphor. When a maximum value of a spectral power distribution of the light emitting device or a maximum of a reference spectral power distribution of black body radiation is 100%, a difference between the spectral power distribution of the light emitting device and the reference spectral power distribution is less than 20% at each wavelength in the wavelength range of 440 nm to 640 nm.