Bulbous Light Guide for SSL Thermal and Optical Trade-offs
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Solution Overview
Problem
Solid state lighting (SSL) devices struggle to produce a uniform luminous distribution similar to incandescent light bulbs, leading to spotty and restricted output, which affects market penetration and thermal management due to the intimate coupling with light guide bodies and the need for thicker light guide structures.
Innovation Solution
A lighting device featuring a heat sink with an annular surface portion carrying SSL elements and a bulbous member that acts as a light guide, allowing for a thin bulbous member design, improved thermal management, and increased angular luminous distribution, with a reflective coating on the inner surface to enhance homogeneity and meet Energy Star requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If a thick light guide body is used to envelop the LEDs, then the structural integrity and light guiding capability are improved, but the luminous efficiency is compromised and thermal management becomes difficult
Solution Approach 1:
The invention extracts the light guiding function from a thick light guide body and implements it through a thin bulbous member with a specific geometric configuration. The bulbous member extends axially beyond the LED array, creating a light-guiding structure that requires minimal thickness while maintaining structural integrity and optical performance.
Solution Approach 2:
The invention transitions from a conventional planar light guide configuration to a three-dimensional bulbous structure that extends axially beyond the LED array. This dimensional change allows the light guide to achieve adequate light guidance with significantly reduced thickness, improving both structural integrity and luminous efficiency.
2Strength
If a thick light guide body is used to envelop the LEDs, then the light guiding capability is improved, but thermal management of the LEDs becomes problematic
Solution Approach 1:
The invention separates the light guiding function from the thermal management function. The thin bulbous member provides sufficient light guidance without the thermal insulation effect of a thick light guide body, allowing heat from the LEDs to be efficiently managed while maintaining adequate light guiding capability.
3Device complexity
If the light guide body terminates on the printed circuit board, then the structural simplicity is improved, but the luminous distribution cannot closely resemble that of an incandescent light bulb
Solution Approach 1:
The invention extends the light guide body axially beyond the LED array and printed circuit board, creating a bulbous shape that projects forward. This dimensional extension allows the light to be distributed more uniformly in all directions, closely resembling the omnidirectional luminous distribution of an incandescent light bulb while maintaining structural simplicity.
Solution Approach 2:
The invention employs a bulbous, curved geometry for the light guide body that extends axially beyond the LED array. This spheroidal shape naturally distributes light in all directions, achieving uniform luminous distribution similar to incandescent bulbs without requiring complex internal structures.
4Illumination intensity
If additional measures are taken to produce uniform luminous distribution in SSL devices, then the luminous output uniformity is improved, but the device complexity and manufacturing cost increase
Solution Approach 1:
The invention uses a simple bulbous geometric shape for the light guide body that inherently provides uniform light distribution in all directions. This geometric solution achieves the desired luminous output uniformity without requiring complex internal structures, reflective coatings, or additional optical components, thereby maintaining device simplicity and manufacturability.
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 achieves a more uniform and efficient luminous distribution resembling incandescent bulbs, improves thermal management, and allows for cost-effective manufacturing while meeting energy efficiency standards.
Implementation Method 1
with a reflective coating on the inner surface to enhance homogeneity
Implementation Method 2
a heat sink having an annular surface portion carrying a plurality of SSL elements
Data Source
AI summary
Disclosed is a lighting device (10) comprising a heat sink (30) having an annular portion (31) including an annular surface portion (33) delimiting a central aperture (37), said annular surface portion (33) carrying a plurality of SSL elements (50); and a bulbous member (20) cooperating with the heat sink (30), said bulbous member (20) having a first surface portion (21) opposite said SSL elements (50) and a second surface portion (22) extending from said first surface portion (21) through said central aperture (37); wherein the bulbous member (20) is used as a light guide member for light emitted by the plurality of SSL elements (50). A luminaire including such a lighting device (10) is also disclosed.