Inverse-Parallel LED Lighting System Lightning Protection
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Solution Overview
Problem
Light emitting diodes (LEDs) used in obstruction warning lights are susceptible to lightning-induced failures and have reliability issues when connected in series, as a single open-circuit failure can cause all LEDs to turn off, and existing bypass shunt devices like zener diodes and SCRs lead to heat dissipation and space concerns, as well as maintenance challenges.
Innovation Solution
An LED lighting system with LEDs arranged in an inverse-parallel configuration, utilizing a triac shunt bypass circuit that provides active protection during lightning pulses and reduces the complexity of monitoring circuitry, allowing for efficient fault detection and recovery.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If LEDs are connected in series to provide uniform brightness, then all LEDs have the same operating current, but if one LED fails open-circuit, all remaining LEDs turn off
Solution Approach 1:
The LED string is segmented into multiple parallel strings, each with its own bypass device. This segmentation isolates failures to individual strings rather than affecting the entire system, maintaining reliability while managing complexity through modular organization.
Solution Approach 2:
Bypass devices (zener diodes, SCRs, or anti-fuses) are introduced as intermediary components in parallel with each LED or LED string. These intermediaries activate only when needed to redirect current around failed LEDs, providing fault tolerance without adding continuous complexity to the operating circuit.
2Reliability
If zener diodes are used as bypass shunts to protect LEDs from open-circuit failures, then current is maintained in the LED string, but heat dissipation and space requirements increase
Solution Approach 1:
The patent compares different bypass device types (zener diodes, SCRs, anti-fuses) with varying electrical parameters. Anti-fuses are selected because they transition from high resistance to low resistance permanently, minimizing ongoing power dissipation and heat generation while maintaining the bypass function.
Solution Approach 2:
Anti-fuses are treated as disposable protective components that perform their function once during a failure event and then remain in a permanent conducting state. This single-use approach eliminates continuous energy loss associated with active bypass devices like zener diodes that must remain reverse-biased.
3Loss of energy
If anti-fuse devices are used as bypass shunts, then heat dissipation is reduced, but the resistance change is permanent preventing LED recovery
Solution Approach 1:
The patent describes a dynamic control system that monitors LED string operation and can switch between different bypass device types or configurations based on failure conditions. This allows the system to adapt between permanent anti-fuse bypasses for stable failures and reversible SCR bypasses for transient failures, maintaining both low power dissipation and recovery capability.
Solution Approach 2:
The bypass system is designed with multi-functionality to handle different failure modes. SCRs provide reversible bypass capability for transient faults, while anti-fuses provide permanent bypass for stable failures. The system can select or combine these approaches to achieve both energy efficiency and fault recovery versatility.
4Reliability
If multiple bypass devices are used in an LED string, then fault tolerance is improved, but the physical space required on the circuit board increases
Solution Approach 1:
Multiple bypass devices are merged into integrated circuits or combined into single hybrid components that provide the bypass function for multiple LEDs simultaneously. This consolidation maintains fault tolerance through redundancy while significantly reducing the physical footprint on the circuit board compared to discrete bypass devices for each LED.
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 inverse-parallel LED arrangement with triac shunt bypasses effectively protects LEDs from electrostatic discharge and lightning, reduces heat dissipation, and simplifies monitoring, enhancing fault tolerance and reliability while minimizing maintenance and component costs.
Implementation Method 1
light emitting diodes (LEDs) promise long operating life, their static-sensitive nature makes them susceptible to lightning-induced failures
Implementation Method 2
The first and second LEDs are in an inverse-parallel arrangement, the first LED acting as a reverse-voltage clamp for the second LED and the second LED acting as a reverse-voltage clamp for the first LED
Implementation Method 3
the voltage drop across its electrical terminals is much lower than the voltage drop of zener diode 16 of FIG. 1 (typically on the order of about 0.8-1.0 Volts) so there is relatively little heat dissipation
Data Source
AI summary
An LED lighting system has an LED circuit that includes a first LED having an anode and a cathode, and a second LED having an anode and a cathode. The anode of the second LED is electrically coupled to the cathode of the first LED, and the cathode of the second LED is electrically coupled to the anode of the first LED. The first and second LEDs are in an inverse-parallel arrangement, the first LED acting as a reverse-voltage clamp for the second LED and the second LED acting as a reverse-voltage clamp for the first LED.