LED Luminance Control via Analog Amplitude Modulation
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Solution Overview
Problem
Existing lighting systems for LCDs, particularly in the aeronautical field, face challenges in achieving high luminance ranges due to limitations in PWM control signals, especially with LEDs, which do not allow for proportional light emission, and require complex digital calculations for luminance modulation, leading to certification and obsolescence issues.
Innovation Solution
An analog electronic control device generates a second control signal for the intensity of the electric current passing through LEDs, combining with a conventional PWM signal to achieve a greater luminance range, using integrator or ramp-generating circuits to enhance luminance modulation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If PWM control signal is used to control LED luminance, then the control method is simple and response time is fast, but the luminance range is limited and cannot achieve high luminance ranges required for aeronautical applications
Solution Approach 1:
The control signal is segmented into two independent components: a PWM signal that controls the temporal activation of LEDs, and a separate analog voltage signal that controls the current amplitude. This segmentation allows each signal to operate independently within its optimal range, with the PWM providing time-based modulation and the analog voltage providing amplitude-based modulation, together achieving extended luminance range without increasing overall system complexity
Solution Approach 2:
The invention adds another dimension to the control space by introducing a second control parameter (analog voltage amplitude) in addition to the traditional PWM duty cycle. This transforms the control from one-dimensional (duty cycle only) to two-dimensional (duty cycle × amplitude), enabling the system to achieve luminance ranges that cannot be obtained with PWM alone while maintaining simple circuit implementation
2Illumination intensity
If digital calculation functions are used for PWM/amplitude distribution, then high luminance ranges can be achieved, but development and certification procedures become complex and time-consuming
Solution Approach 1:
The invention replaces the digital calculation and processing system with an analog electronic control system. Instead of using microcontrollers or FPGAs to calculate and distribute PWM and amplitude signals, the system uses simple analog circuits (voltage dividers, operational amplifiers, RC filters) to generate and modulate the control signals. This substitution eliminates the need for complex software development and certification while achieving the same luminance modulation function
Solution Approach 2:
The invention changes the control parameters from digital domain to analog domain. By using continuous analog voltages to control LED current amplitude and combining it with PWM temporal modulation, the system achieves high luminance range without requiring digital calculation functions. This parameter change from digital to analog simplifies the development and certification process significantly
3Loss of energy
If LED array is used to replace fluorescent lamps, then luminous efficiency and lifetime are improved, but the ability to achieve high luminance ranges through simple PWM control is lost
Solution Approach 1:
The invention merges two control methods (PWM temporal modulation and analog amplitude modulation) into a unified control system for LEDs. By combining these two approaches, the system achieves the high luminance range capability that was previously available with fluorescent lamps while maintaining the energy efficiency and long lifetime benefits of LED technology. The merged control approach compensates for the loss of simple PWM-based luminance control when transitioning to LEDs
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 a simple, robust, and cost-effective means to achieve high luminance ranges without complex digital components, facilitating the transition from fluorescent to LED lighting without re-certification, and allows for easy adaptation to desired luminance levels.
Implementation Method 1
the analog electronic means comprise an integrator circuit, the second signal corresponds to the output signal of the said integrator circuit
Implementation Method 2
light-emitting diodes or LEDs have very low response times
Implementation Method 3
the light emitted is not proportional to the activation time but is much smaller than the latter
Data Source
AI summary
The general field of the invention is that of devices for controlling luminance of lighting devices comprising light-emitting diodes. The control device is driven by a cyclic input signal of determined period, each period comprising an activation time representative of a determined luminance level. The control device comprises analog electronic means generating a second control signal for the intensity of the electric current passing through the light-emitting diodes, the amplitude of the second control signal being an increasing function of the activation time in such a way that the combination of the cyclic input signal and of the second signal applied to the light-emitting diodes gives a greater luminance range than the range of the cyclic input signal.