AC-Driven LED Arrays with Segmented Duty Cycles
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Solution Overview
Problem
Conventional LED lighting systems face challenges in operating directly from AC power without AC-DC conversion, leading to inefficiencies, flicker, and variations in color and intensity when using multiple LEDs, along with thermal management issues.
Innovation Solution
A solid state lighting apparatus that operates directly from an AC power source by activating and deactivating multiple sets of LEDs with different duty cycles at specific times during the AC cycle, arranged on a substrate to minimize flicker, color shifts, and intensity variations, while allowing for adjustments in color temperature and beam patterns without mechanical elements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If multiple sets of LEDs are activated at different times during AC cycle to improve efficiency, then energy conversion efficiency is improved, but flicker and intensity variations occur
Solution Approach 1:
The LED array is divided into multiple independently controllable sets or strings of LEDs. Each set can be activated or deactivated at different times during the AC cycle, allowing selective operation of different LED segments to improve overall efficiency while managing thermal and electrical characteristics.
Solution Approach 2:
Different sets of LEDs are activated during different portions of the AC cycle (e.g., positive half-cycle vs. negative half-cycle, or different quarters of the cycle). This periodic activation pattern allows the system to operate efficiently from AC power while using multiple sets to average out flicker and intensity variations that would occur with single-set operation.
2Device complexity
If LEDs are operated directly from AC power without AC-DC conversion, then device complexity is reduced, but reliability decreases due to lack of power regulation
Solution Approach 1:
The LED system is divided into multiple sets that can be independently controlled. This segmentation allows the system to operate directly from AC power by switching between different sets during different portions of the AC cycle, avoiding the need for complex AC-DC conversion circuitry while maintaining reliable operation through redundancy and load distribution.
Solution Approach 2:
The system changes operational parameters (which specific LED sets are active) based on the AC cycle phase. By dynamically adjusting which sets operate during different portions of the AC waveform, the system can directly utilize AC power without conversion while maintaining stable and reliable LED operation.
3Illumination intensity
If multiple LEDs with different peak wavelengths are used to improve color rendering, then color rendering is improved, but variations in color and intensity across the array increase
Solution Approach 1:
LEDs with different peak wavelengths (colors) are organized into separate controllable sets. This allows selective activation of different wavelength sets during different AC cycle portions, enabling color rendering improvements while managing spatial and temporal distribution to maintain color uniformity across the entire array.
4Temperature
If duty cycles are varied among LED sets to improve thermal management, then thermal management is improved, but control complexity increases
Solution Approach 1:
Different duty cycles are applied to different LED sets by activating them during different portions of the AC cycle. This periodic action provides thermal management benefits by allowing heat dissipation during non-active periods while using the inherent AC waveform to simplify control, avoiding the need for additional complex control circuitry.
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 reduces flicker and intensity/color variations, improves thermal management, and allows for flexible color temperature and beam pattern adjustments, enhancing the efficiency and reliability of LED lighting systems.
Implementation Method 1
A solid state light emitting device may include, for example, a packaged light emitting device including one or more light emitting diodes (LEDs), which may include inorganic LED chips and/or organic LED chips (OLEDs). Typically, solid state light emitting devices generate light through the recombination of electronic carriers (electrons and holes) in a light emitting layer or region of a LED chip.
Implementation Method 2
Multiple groups or sets of series-connected LEDs may be powered by different portions of an AC waveform... Still another challenge associated with utilizing multiple groups of LEDs in a light source lacking an AC-DC power converter is thermal management—including efficiently dissipating heat generated by LEDs without overheating individual LEDs
Data Source
AI summary
Solid state lighting apparatuses are adapted to operate with alternating current (AC) received directly from an AC power source. An exemplary apparatus includes a substrate and multiple sets of one or more solid state light emitters disposed over the substrate. Multiple sets of solid state light emitters are configured to be activated and/or deactivated at different times relevant to one another during portions of an AC cycle, and optionally have different duty cycles. Emitter configurations, color combinations, and/or circuit components reduce perceivable flicker, color shifts, and/or spatial variations in luminous flux. Color temperature and/or beam pattern are adjustable. Multiple emitters are arranged along non-coplanar substrate portions.