LED Chain Fault Detection via Intermediate Voltage Tapping
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Solution Overview
Problem
Existing fault detection methods for LED chains struggle to reliably identify short circuit defects due to variations in temperature and aging effects, leading to false positives or missed detections, especially in applications with wide temperature ranges.
Innovation Solution
A circuit arrangement with a first, second, and third circuit node is used, where a fraction of the voltage drop across the LED chain is applied between the second and third node, and an evaluation unit assesses if the potential at the third node is within a defined tolerance of the nominal value, allowing for more robust fault detection and localization of defective LEDs.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional fault detection methods are used for LED chains, then open circuit defects can be detected easily, but short circuit defects cannot be reliably detected due to temperature and aging variations
Solution Approach 1:
The LED chain is segmented into multiple sections by introducing a second circuit node that taps into the chain at an intermediate point. This segmentation allows independent monitoring of different sections, enabling precise localization of short circuit defects while maintaining reliable detection across the entire chain despite temperature and aging variations.
Solution Approach 2:
A second circuit node is introduced as an intermediary element in the LED chain monitoring system. This intermediary node provides an additional measurement point that serves as a reference for detecting voltage deviations caused by short circuit defects, improving both reliability and precision of fault detection.
2Device complexity
If a simple two-node voltage monitoring system is used, then the device complexity is low, but the ability to localize defective LEDs is insufficient
Solution Approach 1:
The circuit arrangement is segmented into multiple nodes (first, second, and third circuit nodes) along the LED chain. This segmentation enables the system to monitor different sections independently, providing sufficient information to localize defective LEDs without requiring complex additional circuitry.
Solution Approach 2:
The monitoring system applies local quality assessment by evaluating voltage drops across specific sections of the LED chain rather than treating the entire chain uniformly. This allows precise identification of defective LEDs by comparing local voltage characteristics against expected values.
Data Source
AI summary
An apparatus for detecting failures in an illumination device includes at least two light emitting diodes connected in series. The apparatus includes a first, a second, and a third circuit node for interfacing the illumination device such that the voltage drop across at least two light emitting diodes is applied between the first and the second circuit node and a fraction of the voltage drop is applied between the second and the third circuit node. An evaluation unit is coupled to the first, the second, and the third circuit node and configured to assess whether the electric potential present at the third circuit node is within a pre-defined range of tolerance about a nominal value that is defined as a pre-defined fraction of the potential difference present between the first and the second circuit node.