AC LED Light Engine Spectral Shift Control
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Solution Overview
Problem
LED lighting systems face challenges in achieving improved power factor and reduced harmonic distortion due to the phase difference between voltage and current, which leads to increased harmonic energy content and reduced energy at the fundamental frequency, especially in non-linear loads like rectifier loads.
Innovation Solution
A solid state light engine with selective current diversion technology that shifts the relative intensities of LED wavelengths as a function of electrical excitation, allowing current diversion away from LEDs in a series circuit until a predetermined threshold is reached, thereby improving power factor and reducing harmonic distortion using simple, low-cost circuitry.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional LED lighting systems operate with standard rectifier circuits, then the lighting function is achieved, but power factor is degraded and harmonic distortion increases
Solution Approach 1:
The LED string is divided into multiple segments (first LED string and second LED string) that can be independently controlled. The first LED string operates at a first current level while the second LED string operates at a second current level, allowing selective current diversion to improve power factor and reduce harmonic distortion without compromising overall lighting output.
Solution Approach 2:
The system dynamically adjusts the current distribution between different LED strings based on operating conditions. By varying the current levels in different LED segments, the system can adapt to different lighting requirements while maintaining improved power factor and reduced harmonic distortion throughout the operating range.
2Reliability
If current is diverted away from LEDs in a series circuit to improve power factor, then harmonic distortion is reduced, but light output may be affected
Solution Approach 1:
The LED load is segmented into multiple independent strings that can be differentially controlled. By diverting current from only specific segments while maintaining operation in others, the system improves power factor without significantly impacting overall light output, as the remaining LED segments continue to contribute to illumination.
Solution Approach 2:
The system changes the current parameters of different LED strings independently. By adjusting the current level in each segment according to its specific characteristics and operational requirements, the system optimizes both power factor and light output, ensuring that current diversion does not result in unacceptable loss of illumination.
3Device complexity
If simple circuitry is used for current diversion to reduce costs, then device complexity is reduced, but control precision may be limited
Solution Approach 1:
The system employs self-regulating characteristics of LED circuits and simple feedback mechanisms to achieve current diversion without requiring complex external control circuitry. The inherent electrical characteristics of the LED strings and simple protective circuits enable automatic current management, reducing overall device complexity while maintaining adequate control precision for power factor correction.
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 significantly reduces harmonic distortion and improves power factor in AC LED lighting systems, achieving high power quality with minimal additional circuitry, including the integration of harmonic improvement circuitry on the same die as the LEDs, and allows for controlled color temperature changes in response to dimming.
Implementation Method 1
Forward current flow through an LED may cause photons to recombine with holes to release energy in the form of light
Implementation Method 2
current may be selectively and automatically diverted substantially away from at least one of a number of LEDs arranged in a series circuit
Data Source
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AI summary
Apparatus and associated methods involve operation of an LED light engine in which a relative intensities of selected wavelengths shift as a function of electrical excitation. In an illustrative example, current may be selectively and automatically diverted substantially away from at least one of a number of LEDs arranged in a series circuit until the current or its associated periodic excitation voltage reaches a predetermined threshold level. The diversion current may be smoothly reduced in transition as the excitation current or voltage rises substantially above the predetermined threshold level. A color temperature of the light output may be substantially changed as a predetermined function of the excitation voltage. For example, some embodiments may substantially increase or decrease a color temperature output by a solid state light engine in response to dimming the AC voltage excitation (e.g., by phase-cutting or amplitude modulation).