Solid-State LED Lighting Using Phase-Shifted Signals to Reduce Flicker
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Solution Overview
Problem
Conventional LED luminaires suffer from severe light flickering issues that can cause health risks such as headaches, eyestrain, and neurological problems, and existing solutions do not adequately address these issues while ensuring energy efficiency and compatibility with AC mains operation.
Innovation Solution
An LED luminaire design incorporating a signal generating circuit and LED driving circuit to modulate LED driving current with phase-shifted signals, using two types of LEDs with different spectral power distributions, to produce imperceptible flicker at a benign frequency, thereby reducing visual discomfort and entraining gamma oscillations in the human brain.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If conventional LED luminaires operate with simple driving circuits, then device complexity is reduced, but light flickering occurs causing health risks such as headaches and eyestrain
Solution Approach 1:
The patent applies periodic action by introducing a signal generating circuit that produces periodic modulation signals at specific frequencies (e.g., 40 Hz or 65 Hz) to drive the LED arrays. These periodic signals create controlled flicker patterns that can entrain gamma oscillations in the human brain while maintaining overall illumination. The periodic modulation is implemented through switching circuits that rhythmically adjust the LED current, transforming the harmful random flicker into beneficial periodic stimulation.
Solution Approach 2:
The patent employs parameter changes by dynamically adjusting the temporal modulation frequency and amplitude of the driving signals. The signal generating circuit varies the frequency parameter to match or exceed the critical flicker fusion frequency for human perception, thereby reducing visible flicker while maintaining physiological effects. The system also modifies the duty cycle and phase parameters of the modulation signals to optimize both health benefits and color rendering performance.
2Object-affected harmful factors
If LED driving current is modulated at high frequency to reduce visible flicker, then flicker perception is reduced, but energy efficiency may be compromised
Solution Approach 1:
The system uses periodic modulation at frequencies that balance perceptual requirements with energy efficiency. By selecting appropriate modulation frequencies (such as 40 Hz or 65 Hz) and optimizing the duty cycle, the system achieves sufficient flicker suppression for comfort while minimizing the energy overhead of the switching operations. The periodic action allows the LED current to be adjusted in a rhythmic pattern that maintains illumination quality without continuous high-power switching.
Solution Approach 2:
The patent optimizes energy efficiency by dynamically adjusting the modulation depth and frequency parameters based on operational requirements. When high flicker suppression is needed, the system increases modulation depth and frequency, accepting higher energy consumption. When comfort is the primary concern, the system reduces modulation intensity, thereby lowering energy usage. This adaptive parameter adjustment allows the system to balance energy efficiency with flicker control across different operating conditions.
3Ease of operation
If ballast-compatible LED luminaires are used to replace fluorescent fixtures, then installation is straightforward, but total cost of ownership increases due to ballast power consumption and maintenance requirements
Solution Approach 1:
The patent extracts the ballast function from the lighting system by designing self-sustaining AC mains-operable LED luminaires that do not require external ballasts. The LED driving circuit is designed to operate directly from AC mains power, eliminating the need for separate ballast components. This extraction removes the source of continuous power consumption and maintenance requirements while maintaining ease of installation through direct replacement of the fluorescent fixture.
Solution Approach 2:
The LED luminaire is designed to be self-sustaining, with the driving circuit capable of operating independently without external ballast support. The system includes integrated power factor correction and current regulation functions that enable it to draw power directly from AC mains. This self-service capability eliminates ongoing ballast power consumption and maintenance needs, reducing total cost of ownership while maintaining simple installation through direct fixture replacement.
4Device complexity
If simple LED driving circuits are used, then device complexity is reduced, but color rendering quality and spectral distribution control are insufficient
Solution Approach 1:
The patent segments the LED driving into multiple independent channels, with separate driving circuits for different LED arrays or LED types within the fixture. Each channel can be independently modulated with specific temporal patterns and spectral characteristics. This segmentation allows precise control over color rendering by adjusting the drive parameters of individual LED groups, achieving high color quality without requiring a monolithic complex circuit.
Solution Approach 2:
The patent applies local quality by providing differentiated driving characteristics to different LED arrays or LED types within the same fixture. Each LED group can receive customized modulation signals optimized for its specific spectral properties and intended function. This localized control allows optimization of color rendering for each LED type while maintaining overall system simplicity, as each local driving circuit operates independently with tailored parameters rather than requiring complex centralized control.
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 effectively reduces flicker perception, minimizing eyestrain and potential health risks while maintaining energy efficiency and compatibility with AC mains operation, and meets color rendering index requirements.
Implementation Method 1
The phase shifter circuit is configured to shift a first phase of the first set of signal into a second phase of the second set of signal
Implementation Method 2
The signal generating circuit is configured to produce a first set of signal and a second set of signal both at a predetermined temporal modulation frequency
Implementation Method 3
one or more LED arrays, a switching circuit, a signal generating circuit, and an LED driving circuit
Data Source
AI summary
A light-emitting diode (LED) luminaire comprising two types of LEDs, a switching circuit, a signal generating circuit, and an LED driving circuit is used to replace a conventional luminaire with a severe temporal light artifact. The switching circuit and the LED driving circuit are configured to reduce a low-frequency ripple associated with AC mains. The signal generating circuit is configured to produce two sets of modulation signals with a phase difference of 180 degrees between the two sets of modulation signals, which are then embedded in the LED driving current to drive the two types of LEDs, resulting in imperceptible flicker at a temporal modulation frequency as a result of color mixing of the two types of LEDs and persistence of vision, thereby drastically reducing eyestrain, visual discomfort, etc.