LED Luminaire Feedback Control for Flicker Reduction
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Solution Overview
Problem
LED luminaires face health concerns due to light flickering, which can cause issues like seizures in individuals with photosensitive epilepsy, migraines, headaches, reduced visual performance, and other neurological problems, and existing solutions like ballast-compatible luminaires have high maintenance costs and inefficiencies.
Innovation Solution
An LED luminaire with a buck circuit and feedback control circuit that converts AC mains to DC voltage, modulates the voltage at a switching frequency above 30 kHz, and uses a feedback control loop to reduce low-frequency flicker, ensuring less than 6% flicker at 100 Hz or 120 Hz, thereby minimizing health risks and maintenance costs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If LED luminaires use conventional AC-driven circuits, then simplicity and low cost are achieved, but light flickering occurs causing health concerns
Solution Approach 1:
The patent applies preliminary action by converting AC power to DC power before it reaches the LED driver circuit, eliminating the root cause of flickering. The full-wave rectifier and capacitor combination pre-processes the power supply to provide stable DC voltage, preventing flicker from occurring in the first place rather than attempting to correct it later in the circuit.
Solution Approach 2:
The patent implements feedback control through an optocoupler that monitors the DC voltage and provides feedback to the switching circuit. This closed-loop feedback system detects voltage variations and adjusts the switching duty cycle accordingly, maintaining stable LED operation and eliminating flicker while keeping the overall system manageable in complexity.
2Ease of operation
If ballast-compatible luminaires are used to replace fluorescent lights, then installation is simplified, but maintenance costs and energy consumption increase
Solution Approach 1:
The patent applies the extraction principle by removing the ballast component entirely from the lighting system. Instead of using a ballast-compatible LED luminaire that requires an existing ballast, the design integrates a self-contained AC-to-DC converter directly into the LED driver circuit, eliminating the ballast's energy-wasting function while maintaining ease of installation by simply replacing the entire luminaire unit.
Solution Approach 2:
The patent implements self-service by designing an autonomous AC-driven LED driver that contains all necessary power conversion functions within the luminaire itself. The integrated rectifier, capacitor, and switching circuit automatically convert AC power to suitable DC levels without requiring external ballasts or additional components, making the system self-sufficient and energy-efficient.
3Object-affected harmful factors
If high switching frequency is used in LED driver, then light flicker is reduced, but electromagnetic interference increases
Solution Approach 1:
The patent applies the intermediary principle by introducing a full-wave rectifier and filtering capacitor as intermediate stages between the AC power source and the high-frequency switching circuit. These intermediary components smooth the input voltage and reduce electromagnetic noise before it reaches the switching stage, allowing high switching frequencies to be used for flicker reduction while minimizing EMI generation.
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 suppresses light flickering, reducing health risks and maintenance costs by providing a self-sustaining, energy-efficient LED luminaire with reduced low-frequency current ripple, ensuring stable and safe lighting.
Implementation Method 1
at least one full-wave rectifier coupled to the alternate-current (AC) mains and configured to convert a line voltage from the AC mains into a first direct-current (DC) voltage
Implementation Method 2
a buck circuit with a switching portion of a buck circuit... a first electronic switch configured to modulate the first DC voltage into a variable DC voltage at a switching frequency
Implementation Method 3
an LED driving circuit... a feedback control loop to reduce low-frequency flicker, ensuring less than 6% flicker at 100 Hz or 120 Hz
Data Source
AI summary
An LED luminaire comprising LED arrays, a buck circuit with a switching portion comprising a transformer, and an LED driving circuit comprising a feedback control circuit is used to replace a conventional luminaire with a severe temporal light artifact. The buck circuit with the switching portion is configured to generate a variable DC voltage with a low-frequency ripple associated with AC mains. The feedback control circuit is configured to feedback a mixed voltage and current control signal to the buck circuit with the switching portion to compensate the low-frequency ripple so as to regulate an LED driving voltage with a ripple-reduced LED current to drive the LED arrays with a flicker-reduced light emission that may protect users of the LED luminaire from possible health hazards such as seizures, headaches, eyestrain, reduced visual performance, migraines, etc.