Tunable White LED Lumen Variability Reduction

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Solution Overview

Problem

Existing multi-color LED systems face challenges in controlling overall output intensity while maintaining desired spectral characteristics, as adjusting power levels affects LED spectral characteristics, leading to inefficiencies and reduced performance over time.

Innovation Solution

A tunable lighting system using a combination of white LEDs and non-white LEDs, with a microcontroller and feedback sensors to adjust drive currents and maintain constant output intensity, allowing for selectable color temperatures and reduced lumen variability across the range of color temperatures.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Illumination intensity

If power levels are adjusted to control overall output intensity, then brightness control is achieved, but LED spectral characteristics change leading to lumen variability

Engineering Contradiction:

Improveoverall output intensityVSAvoidspectral characteristic consistency

Core Design Contradiction:

Illumination intensityVSManufacturing precision

Solution Approach 1:

The system employs feedback control by monitoring the actual spectral characteristics and lumen output of the LEDs, then automatically adjusting the power levels of individual LED channels to compensate for spectral shifts. This closed-loop control maintains consistent color temperature and reduces lumen variability despite changes in overall power levels.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system dynamically changes the operating parameters (power levels) of different LED types (warm white, cool white, colored LEDs) in coordinated proportions. By adjusting the relative contributions of each LED channel rather than uniformly scaling all LEDs, the system maintains spectral consistency while controlling overall intensity.

Inventive Principle:

Principle #35Parameter changes

2Adaptability or versatility

If multiple LED colors are combined to achieve tunable color temperature, then spectral flexibility is improved, but lumen variability increases across the color temperature range

Engineering Contradiction:

Improvecolor temperature selectionVSAvoidlumen output consistency

Core Design Contradiction:

Adaptability or versatilityVSManufacturing precision

Solution Approach 1:

The system uses pre-calibrated lookup tables and algorithms that define the optimal power level combinations for each desired color temperature. These parameter sets are determined during manufacturing to compensate for the different luminous efficacies of various LED types, ensuring consistent lumen output across the tunable color temperature range.

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

Feedback sensors monitor the actual lumen output and color temperature, and the control system adjusts the power distribution among different LED channels to maintain both spectral accuracy and lumen consistency across the entire color temperature range.

Inventive Principle:

Principle #23Feedback

3Duration of action of moving object

If LED power levels are reduced to extend usage lifetime, then duration of action is improved, but spectral characteristics drift and performance degrades

Engineering Contradiction:

ImproveLED usage lifetimeVSAvoidspectral characteristic stability

Core Design Contradiction:

Duration of action of moving objectVSReliability

Solution Approach 1:

The feedback control system continuously monitors spectral characteristics and compensates for drift caused by aging and thermal effects. This allows the system to maintain reliable color accuracy and spectral performance throughout the extended LED lifetime, even as individual LED components gradually degrade.

Inventive Principle:

Principle #23Feedback

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 system efficiently provides white light with selectable spectral characteristics, maintaining desired performance and energy output over time, reducing lumen variability and maximizing LED utilization.

Implementation Method 1

combining substantially white light produced by a combination of a white light source and a source of another color of light together with selected amounts of light of one or more additional different wavelengths

Methodology Applied

Scientific EffectLight mixing:

Data Source

PatentUS8928249B2Reducing lumen variability over a range of color temperatures of an output of tunable-white LED lighting devices

Publication Date: 2015.01.06 ABL IP HLDG LLC

AI summary

A system provides white light having a selectable spectral characteristic (e.g. a selectable color temperature, delta uv, and intensity) using a combination of sources (e.g. LEDs) emitting light of three, four, five, or six different characteristics, for example, one or more white LEDs, and one or more LEDs of each of three primary colors, plus cyan and royal blue. A controller maintains a desired spectral characteristic, e.g. for white light at a selected point on or within a desired range of the black body curve. In addition, the controller provides selectable adjustments for values of the spectral characteristics, while maintaining substantially constant overall output intensity for the light output of White LEDs, thereby achieving Maximum Utilization.