LED String Fault Diagnosis via Group Voltage Ratio Analysis
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Solution Overview
Problem
Existing methods for diagnosing faulty light-emitting diodes (LEDs) are complex, unreliable, and costly, particularly due to temperature fluctuations and component tolerances, making it difficult to distinguish between faults and temperature-related changes in forward voltage.
Innovation Solution
A method and device that determine changes in measurement variables for each group of LEDs and detect defects by comparing the ratio of these changes, using a diagnostic unit connected to measuring means, which is independent of component fluctuations and environmental influences, allowing for reliable fault detection with a simple and economic approach.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the forward voltage of each individual light-emitting means is measured and compared with a nominal voltage value, then fault detection is possible, but the complexity of the circuit increases and temperature dependence causes measurement inaccuracies
Solution Approach 1:
The string of light-emitting means is divided into at least two groups, and the total forward voltage is measured for each group rather than individually for each light-emitting means. This segmentation reduces the number of measurement points while maintaining fault detection capability through ratio comparison between groups.
Solution Approach 2:
Instead of comparing absolute voltage values against nominal values, the method compares the ratio of total forward voltages between groups. This parameter transformation eliminates the need for temperature compensation while maintaining sensitivity to faults, as temperature effects affect all light-emitting means in similar ways and cancel out in the ratio.
2Measurement precision
If monitoring is performed for each individual light-emitting means, then fault detection precision is improved, but the monitoring complexity increases proportionally with the number of light-emitting means
Solution Approach 1:
The light-emitting means are grouped into at least two groups, with each group monitored as a single unit. This reduces the number of monitoring channels from N (individual monitoring) to 2 (group monitoring), while fault detection precision is maintained through ratio analysis that can identify faulty groups.
Solution Approach 2:
The measurement system is designed to measure the total forward voltage of each group, which serves multiple purposes: detecting faults within groups, monitoring overall string health, and providing temperature-independent operation. This universal approach replaces multiple individual monitoring circuits.
3Reliability
If conventional monitoring methods are used, then fault detection is possible, but the cost increases due to additional components and the system becomes dependent on temperature and component tolerances
Solution Approach 1:
The monitoring function is merged with the existing forward voltage measurement capability of the light-emitting means. By measuring the total forward voltage of groups during normal operation and comparing ratios, the system eliminates the need for separate monitoring circuits, additional components, and complex temperature compensation mechanisms.
Solution Approach 2:
The light-emitting means themselves provide the measurement signal through their forward voltage characteristics. The system uses the inherent electrical properties of the LEDs during normal operation to detect faults, without requiring external test signals, additional sensors, or specialized monitoring components.
Data Source
AI summary
A method and a device for the diagnosis of faulty light emitting diodes in a string (2) formed of at least two light emitting diodes. The light emitting diodes (3) are divided into at least two groups and an electrical measured variable is determined for each group with respective measurement units. Differences between the measured variable and a reference value are established per group and, by way of a diagnosis unit that is connected to the measurement units, a defect of a light emitting diode is identified on the basis of the ratio of the differences in the groups and signaled.