Discrete Dimming Luminance Control Circuit for Avionics
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Solution Overview
Problem
Digital avionics systems lack the capability to supply varying voltages for illuminated pushbutton switches and indicators, leading to unacceptable Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) when using pulse width modulation, and fail to effectively control illumination levels across different ambient lighting conditions.
Innovation Solution
A discrete dimming luminance control circuit that uses a combination of supply and shunt circuits with control pins to selectively apply voltages to light emitting diodes (LEDs), allowing for multiple luminance levels without generating EMI or RFI, and includes passive components to regulate voltage and temperature variations.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If pulse width modulation (PWM) is used to control illumination, then illumination levels can be varied, but Electromagnetic Interference (EMI) and Radio Frequency Interference (RFI) are generated
Solution Approach 1:
The patent divides the continuous voltage control range into discrete voltage levels (e.g., 5V, 3.3V, 1.8V, 0.9V). Instead of using rapid PWM switching, the system selects from pre-defined voltage steps, eliminating the high-frequency switching that causes EMI and RFI while still providing multiple illumination levels.
Solution Approach 2:
The patent changes the control parameter from duty cycle (PWM) to discrete voltage levels. By varying the output voltage in distinct steps rather than using pulse width modulation, the system achieves illumination control without generating electromagnetic interference.
2Device complexity
If simple voltage control is used to vary illumination, then the system is simple to implement, but the system cannot adapt to wide ranges of ambient lighting conditions
Solution Approach 1:
The patent creates a multi-functional voltage control system that can operate across diverse ambient lighting conditions (daylight, nighttime, NVG conditions) using a single discrete voltage control circuit. The circuit provides multiple voltage levels that can adapt to various lighting environments without requiring separate control circuits for each condition.
3Object-generated harmful factors
If discrete voltage levels are used instead of continuous voltage control, then EMI and RFI are reduced, but the precision of illumination control is limited
Solution Approach 1:
The patent implements dynamic selection among discrete voltage levels based on ambient lighting conditions. The system can switch between predefined voltage steps (5V, 3.3V, 1.8V, 0.9V) to adapt to changing environmental conditions, providing sufficient precision for various lighting scenarios without requiring continuous voltage control that would generate EMI.
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, multi-level illumination control with reduced EMI and RFI, maintaining high luminance consistency across varying ambient conditions and temperature changes, while being cost-effective and compliant with flight safety regulations.
Implementation Method 1
A discrete dimming luminance control circuit for light emitting diode illumination
Data Source
AI summary
A discrete dimming luminance control circuit for light emitting diode illumination includes first and second control inputs, a first supply circuit between the first control input and an output, a second supply circuit between the second control input and the output, a first shunt circuit between the second control input and the output, and a second shunt circuit between the first control input and the output. The luminance control circuit delivers a first voltage to the output when a supply voltage is applied to the first control input and the second control input is left open, a second voltage when the supply voltage is applied to the second control input and the first control input is left open, a third voltage when the supply voltage is applied to the first control input and the second control input is grounded, and a fourth voltage when the supply voltage is applied to the second control input and the first control input is grounded.