AC-Driven LED Lighting with Closed-Loop Feedback Control
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Solution Overview
Problem
Current LED lighting solutions for aircraft interiors face issues with reliability, uniformity, weight, complexity, and controllability, particularly due to fluctuations in AC power, which result in flicker and reduced color accuracy, and lack effective health monitoring capabilities.
Innovation Solution
A full color LED array that operates directly on alternating current without conversion, utilizing a closed loop feedback circuit with a proportional-integral-derivative controller and health monitoring mechanisms to maintain constant power, reduce flicker, and adjust for aging, incorporating temperature and current sensors for consistent illumination.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of stationary object
If AC power is applied directly to LED string without AC to DC converter, then weight and complexity are reduced, but controllability and reliability deteriorate due to fluctuating current and voltage
Solution Approach 1:
The patent implements a closed-loop feedback control system that continuously monitors the AC input voltage and adjusts the PWM duty cycle accordingly. This feedback mechanism allows the system to maintain stable LED operation despite AC voltage fluctuations, resolving the controllability issue while keeping the AC direct-drive architecture for weight reduction.
Solution Approach 2:
The system dynamically adjusts the PWM signal parameters based on real-time AC voltage conditions. By making the control parameters adaptive rather than fixed, the system maintains optimal performance across varying AC input conditions without requiring heavy voltage regulation hardware.
2Device complexity
If AC waveform is applied directly to LED string, then device complexity is reduced, but flicker increases due to constantly fluctuating current
Solution Approach 1:
The patent employs PWM (pulse width modulation) technique that switches the LED current on and off at high frequency. This periodic switching action, controlled by variable duty cycle, converts the continuous fluctuating AC current into controlled pulsed current that eliminates visible flicker while maintaining the simplicity of AC direct-drive operation.
Solution Approach 2:
The system changes the temporal parameters of current delivery to the LEDs by using PWM with variable duty cycle. This transforms the harmful continuous fluctuation into controlled periodic pulses with adjustable width, eliminating flicker perception while maintaining device simplicity.
3Device complexity
If no closed loop feedback circuit is used, then device complexity is reduced, but color accuracy and illumination consistency deteriorate
Solution Approach 1:
The patent incorporates a closed-loop feedback circuit that monitors AC input voltage and provides real-time adjustment signals to the PWM controller. This feedback ensures that LED current remains stable despite input variations, maintaining consistent color output and illumination quality without adding excessive complexity.
Solution Approach 2:
The patent replaces heavy electrical power conversion hardware with a lightweight electronic control system using PWM and feedback. This substitution achieves precise color and intensity control through electronic modulation rather than through complex power conversion circuitry.
4Ease of operation
If AC to DC converter stage is included in each fixture, then power control is improved, but weight and cost increase
Solution Approach 1:
The patent extracts the heavy AC-to-DC power conversion stage from individual fixtures and replaces it with a simplified AC-compatible PWM control circuit. This extraction removes unnecessary weight while retaining effective power control capabilities through direct AC-driven PWM modulation.
Solution Approach 2:
The patent introduces PWM control as an intermediary mechanism between AC power and LED operation. This intermediary allows effective power control without requiring direct DC conversion, enabling the system to maintain control capabilities while avoiding the weight penalty of full power conversion hardware in each fixture.
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 provides reliable, efficient, and controllable full color LED lighting with reduced weight and complexity, minimizing flicker and ensuring consistent illumination over the lifespan of the LEDs, while enabling effective health monitoring and color adjustment.
Implementation Method 1
the closed loop feedback circuit is configured to smooth and direct the source of alternating current to the light emitting diodes, thereby maintaining a substantially constant power to the light emitting diodes by accommodating changes in voltage of the alternating current through adjustment of the current provided to the plurality of light emitting diodes
Implementation Method 2
a plurality of light emitting diodes comprising substantially equal numbers of light emitting diodes of at least three different colors
Implementation Method 3
Light Emitting Diodes (LEDs) are rapidly becoming today's leading lighting technology thanks to their ability to provide high quality light at very low power levels
Data Source
AI summary
A full color LED light for aircraft interiors is described, comprising a housing containing at least three differently colored groups of light emitting diodes, a controller for the groups of light emitting diodes and an alternating current power source. The controller distributes the alternating current to LED groups, providing a desired intensity of each differently colored group, producing a desired blended output color. At least one switching circuit receives input current from the power source, via the controller, and directs current to LED subgroups such that a near optimal voltage drop is maintained, given the varied voltage drops of the LED subgroups, regardless of the input voltage, in light of the voltage rating of the LEDs. Embodiments provide for measurement or estimation of current profiles, thermal profiles, and series resistance, allowing accurate measurement of lumen depreciation over time. Additional embodiments include a feedback circuit to temper input power fluctuations.