Color Tunable LED Assembly with Reflective Layer
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Solution Overview
Problem
Conventional LED assemblies face challenges in achieving uniform color temperature and efficient heat dissipation while maintaining light output, especially during dimming operations, due to the separation of LED devices and the presence of phosphor particles generating heat.
Innovation Solution
The LED assembly incorporates a substrate with surface-mounted LED devices of different color temperatures, a Highly Reflective (HR) layer with TiO2 particles, and a warm-dimming color tuning circuit, where the HR layer is microjetted to specific thickness and a transparent layer without phosphor particles is used to cover the devices, allowing heat to dissipate through the ceramic substrate and adjusting light output proportionally with current reduction.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of manufacture
If LED devices are separated to accommodate conductor patterning, then manufacturing is easier, but color uniformity deteriorates as light appears as multiple point sources rather than a single point source
Solution Approach 1:
The patent merges the light emission function of multiple LED devices into a single apparent point source by spacing devices closely (0.2-0.6mm) and using an HR layer to reflect and blend light, making separated LEDs appear as one unified light source with consistent color temperature
Solution Approach 2:
The HR layer acts as an intermediary between the LED devices and the observer, reflecting and diffusing light to create a unified appearance while allowing conductor patterning to proceed with adequate spacing
2Adaptability or versatility
If phosphor particles are included in the transparent layer to convert wavelength, then color temperature adjustment is achieved, but heat generation increases due to wavelength-converting light
Solution Approach 1:
The patent extracts phosphor particles from the transparent layer, eliminating the wavelength-converting function in that layer and thereby removing the associated heat generation, while relying on the LED devices' inherent color temperatures and the HR layer for optical management
Solution Approach 2:
The patent changes the optical parameters of the transparent layer by removing phosphor particles, making it substantially transparent and non-heat-generating, while achieving color temperature control through circuit regulation of LED device proportions
3Illumination intensity
If HR layer thickness is increased to improve reflectivity, then light emission is enhanced, but manufacturing precision requirements increase to achieve optimal thickness range
Solution Approach 1:
The patent specifies a precise thickness range (20%-50% of LED die height) for the HR layer to optimize the balance between reflectivity and light extraction, ensuring sufficient light emission while providing clear manufacturing guidelines to control thickness within this range
Solution Approach 2:
The HR layer uses composite material (silicone with TiO2 particles) that provides high reflectivity with controlled thickness, where the particle distribution and matrix material work together to achieve optimal optical performance within the specified thickness range
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 ensures a consistent color temperature shift from 3000K to 1800K during dimming, enhances light emission by optimizing HR layer thickness and spacing, and maintains efficient heat dissipation without generating heat from the transparent layer, resulting in improved light output and thermal management.
Implementation Method 1
The HR layer includes reflective particles (for example, TiO2 particles) that render the HR layer highly reflective
Implementation Method 2
The transparent layer is substantially transparent to light emitted from the LED devices and it comprises substantially no phosphor particles
Implementation Method 3
heat from the LED devices tends to pass downward through the heat conductive ceramic portion of the substrate
Data Source
AI summary
An LED assembly includes two strings of surface mounted LED devices mounted to a central ceramic plug portion of a PCB substrate. One string has a CCT of 4000 degrees Kelvin. The other has a CCT of 1800 degrees Kelvin. For each LED device in one string there is a corresponding LED device in the other string. The LED devices of each pair are closely spaced with 0.2-0.6 mm between them. A Highly Reflective (HR) layer is disposed on the substrate between the LED devices. The HR layer has a thickness in a range of from 20 to 50 percent H, where H is the height of an LED die. A transparent silicone layer covers the LED devices. A resistor of a warm-dimming circuit is mounted over the ceramic portion of the substrate whereas an integrated circuit portion of the circuit is mounted over the PCB portion of the substrate.