LED Arrangement with Variable Light Emitting Surface Ratios
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Solution Overview
Problem
Tapped linear LED drivers result in varying light output intensity across different sets of LEDs due to different on times and durations, leading to non-uniform light distribution in space-constrained applications like tubular LED lamps.
Innovation Solution
A compact LED arrangement where groups of LEDs are strategically turned on and off based on input voltage thresholds, with the second group having a higher light emitting surface ratio to compensate for shorter on-duration, ensuring uniform light output density across the entire surface by adjusting current sources and LED chip sizes or packing densities.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If a tapped linear driver is used to minimize driver size in space-constrained applications, then driver space is reduced, but light output intensity becomes non-uniform across different LED sets
Solution Approach 1:
The patent applies local quality by making different LED groups have different light emitting surface ratios tailored to their specific on-times. Groups that are on for shorter durations have larger light emitting surface ratios, while groups on for longer durations have smaller ratios. This localized adjustment of surface area compensates for the temporal differences in operation, achieving uniform overall light output while maintaining the compact tapped linear driver architecture.
2Device complexity
If different LED sets are turned on at different times and durations to match input voltage levels, then driver complexity is reduced, but light distribution becomes non-uniform
Solution Approach 1:
The patent employs parameter changes by varying the light emitting surface ratio parameter across different LED groups. This physical parameter adjustment compensates for the temporal operation differences without requiring complex control circuitry. The simple approach of having different surface areas for different groups, combined with their staggered on-times, naturally balances the overall light output while keeping the driver architecture simple and compact.
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 achieves a time-average light output intensity that is substantially consistent across the LED groups, providing uniform illumination over the entire surface, thereby addressing the issue of non-uniform light distribution in tapped linear drivers.
Implementation Method 1
A LED arrangement placed over a light output surface, comprising: a first group of LEDs on the light output surface
Data Source
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AI summary
An LED arrangement uses a tapped driver driven by a rectified mains input and placed over a light output surface. There are at least first and second groups of LEDs on the light output surface. The total light output density for the LEDs of the second group (which are turned on for less of the mains cycle) per unit area of the light output surface is greater than the total light output density for the LEDs of the first group per unit area of the light output surface. A fraction of a light emitting surface of the second group (16) of LEDs to a second area (20B) of the light output surface occupied in a macro view by the second group (16) of LEDs, is larger than a fraction of a light emitting surface of the first group (14) of LEDs to a first area (20A) of the light output surface occupied in a macro view by the first group (14) of LEDs. This means the light output density when averaged over time is made more consistent between the two (or more) groups of LEDs.