LED String Failure Detection via Inductor Voltage Comparison
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Solution Overview
Problem
Current LED lighting systems face challenges in detecting failures, such as single LED shorts or disconnections, especially in automotive applications with multiple equal LED strings, where voltage changes are not significant enough to be measured, and require additional contacts or reference voltages.
Innovation Solution
The implementation of an LED lighting system with a failure detection circuit that measures voltage differences between inductors in series with LED strings, allowing for detection of single LED shorts and entire string disconnections without additional contacts or reference voltages, using a configuration where each string is coupled with an inductor and comparing voltage differences at specific points.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If multiple equal LED strings are connected in parallel, then the lighting system provides sufficient brightness and redundancy, but failure detection becomes difficult because voltage changes are not significant enough to be measured
Solution Approach 1:
The patent introduces inductors as intermediary elements connected in series with each LED string. These inductors serve as mediators that convert the difficult-to-detect LED string failures into easily measurable voltage differences at the inductor terminals, solving the detection problem without altering the parallel LED string configuration for reliability.
Solution Approach 2:
The patent replaces direct voltage measurement across LED strings with magnetic field-based measurement through inductors. By measuring voltage differences at the inductor terminals rather than directly across LED strings, the system uses electromagnetic principles to achieve reliable failure detection in parallel configurations.
2Difficulty of detecting and measuring
If additional contacts or reference voltages are added to enable failure detection, then detection capability improves, but device complexity and manufacturing cost increase
Solution Approach 1:
The inductors serve multiple functions: they limit current through the LED strings, provide magnetic coupling for detection, and create measurable voltage differences during failures. This multi-functionality eliminates the need for separate detection circuits, additional contacts, or reference voltage sources, maintaining simplicity while enabling reliable failure detection.
Solution Approach 2:
The LED strings themselves generate the detection signal through their normal operation. When an LED fails, the change in current through the associated inductor automatically creates a measurable voltage difference, eliminating the need for external reference voltages or additional sensing components.
3Device complexity
If LED strings are connected without series inductors, then the circuit is simpler, but failure detection based on voltage differences between inductors becomes impossible
Solution Approach 1:
The patent segments the LED lighting system by placing individual inductors in series with each LED string rather than using a single common inductor. This segmentation allows independent measurement of each string's current through its dedicated inductor, enabling precise failure detection while maintaining relative circuit simplicity.
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
This solution enables reliable failure detection in LED lighting systems, including automotive applications, by identifying voltage differences that indicate issues, allowing for timely system adjustments or shutdowns, thereby ensuring system reliability and safety.
Implementation Method 1
a first inductor and a second inductor. The first and second strings each have an equal total forward voltage
Implementation Method 2
The failure detection circuit is configured to detect a failure in the LED lighting circuit based on detection of a voltage difference between the first inductor and the second inductor
Data Source
AI summary
An LED lighting system, an automotive lighting system and a method of detecting failure in an LED lighting system are described herein. An LED lighting system includes an LED lighting circuit and a failure detection circuit. The LED lighting circuit includes a first string of a first plurality of LEDs electrically coupled in series with a first inductor and a second string of a second plurality of LEDs electrically coupled in series with a second inductor. The first and second strings each have an equal total forward voltage. The failure detection circuit is configured to detect a failure in the LED lighting circuit based on detection of a voltage difference between the first inductor and the second inductor.