Transparent Substrate LED CoB for Warm White Light
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Solution Overview
Problem
Current LED Chip-On-Board architectures face challenges in achieving warm white light with high quantum conversion efficiency and low cost, due to low efficiency and high cost of red phosphors used to convert blue light.
Innovation Solution
The use of red LED dies and blue LED dies fabricated on transparent substrates, such as sapphire, with optimized designs addressing different degradation mechanisms, including varying current densities and sizes, to achieve long-term stability and reliability, and uniform color distribution.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If red phosphors are used to convert blue light into red light to achieve warm white light, then warm white light is generated, but the quantum conversion efficiency is low and the cost is high
Solution Approach 1:
The patent extracts the red light generation function from phosphor conversion and implements it through a dedicated red LED die. This eliminates the need for red phosphors and their associated low quantum conversion efficiency, while maintaining the ability to generate warm white light through direct red LED emission combined with blue LED emission
Solution Approach 2:
The patent uses a red LED die that replicates the red light emission function previously achieved through phosphor conversion. By copying the desired optical output (red light) through a different mechanism (red LED instead of red phosphor), the system achieves the same illumination goal with superior energy efficiency
2Illumination intensity
If red phosphors are used to convert blue light into red light to achieve warm white light, then warm white light is generated, but the cost is high
Solution Approach 1:
The patent replaces expensive red phosphor materials with relatively cheaper red LED dies. While LED dies have their own cost structure, they eliminate the need for costly red phosphor materials and their associated processing requirements, thereby reducing overall manufacturing cost for warm white LED packages
3Reliability
If different current densities are used for blue and red LED dies, then degradation is optimized and long-term stability is achieved, but the device complexity increases
Solution Approach 1:
The patent applies different current densities to different LED dies (blue and red) based on their specific degradation characteristics and operational requirements. This localized optimization allows each die type to operate at its optimal current density, maximizing overall package reliability while accounting for the different properties of blue and red LED materials
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 high-efficiency warm white light emission at a lower cost by optimizing the degradation of red and blue LED dies, resulting in improved quantum conversion efficiency and extended lifespan.
Implementation Method 1
red LED dies fabricated on transparent substrates are used in combination with blue LED dies also fabricated on transparent substrates to achieve high efficiency Chip-On-Board (CoB) LED dies
Data Source
AI summary
An LED CoB structure with the combination use of blue and red LED dies is used to achieve warm white light, with good quantum conversion efficiency at a reasonably low cost. Both the red and blue LED dies are fabricated on transparent substrates. The current density of the LED dies is designed to match the different degradation rate of each type of LED die. The methods used to achieve high efficiency include adjusting the power, wavelength, and/or position of the dies.