LED Chain Short Circuit Detection via Diagnostic Voltage Comparison
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Solution Overview
Problem
Existing LED driver circuits face challenges in detecting defective LEDs, particularly those that fail as short circuits, as they only stop radiating without interrupting the current, making it difficult to identify failures in LED chains.
Innovation Solution
A semiconductor light source driver circuit with a diagnostic current source and comparison circuit that provides a diagnostic current to a resistor, allowing for comparison of the series LED voltage with a diagnostic voltage to determine if a failure condition exists in the LED chain, capable of detecting both open and short circuit conditions, including single short circuit detection.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If LEDs are connected in series to form LED chains to match supply voltages, then the system can operate with commonly used supply voltages (12V, 24V, 42V), but detecting defective LEDs becomes more difficult, especially when they fail as short circuits
Solution Approach 1:
The patent implements preliminary diagnostic testing by applying a diagnostic current to each LED before normal operation to detect potential failures. This preliminary action identifies defective LEDs (both open and short circuit conditions) before they cause chain failures, allowing the system to maintain voltage compatibility while solving the detection problem through proactive measurement.
2Productivity
If a single LED fails as a short circuit, then the current continues to flow through the LED chain, but the defective LED stops radiating and becomes difficult to detect
Solution Approach 1:
The patent introduces an intermediary diagnostic current path that allows measurement of each LED's electrical characteristics without disrupting the main current flow through the LED chain. This intermediary measurement system detects short-circuited LEDs by comparing their forward voltage characteristics, enabling failure detection while maintaining current continuity for operational LEDs.
Solution Approach 2:
The patent changes the electrical parameters applied to LEDs by switching between normal operating current and diagnostic current modes. By applying a specific diagnostic current and measuring the resulting forward voltage, the system detects parameter deviations that indicate short-circuit failures, transforming an undetectable condition into a measurable parameter change.
3Reliability
If diagnostic methods are added to detect short circuit failures in LED chains, then detection capability improves, but circuit complexity increases
Solution Approach 1:
The patent implements multi-functionality by designing the driver circuit to perform both normal LED driving and diagnostic measurement functions using shared components. The same current source and voltage measurement circuitry are used for both operation and diagnosis, reducing overall circuit complexity while maintaining high detection accuracy through intelligent control sequencing.
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
Enables effective fault detection in LED chains, including identifying single short circuit conditions, without the disadvantages of other short circuit detection methods, ensuring reliable operation of LED-based illumination systems.
Implementation Method 1
a comparison circuit that is arranged to perform a comparison to compare a series SLS voltage at the series SLS node with a diagnostic voltage at the diagnostic resistor node
Implementation Method 2
a diagnostic current source that is arranged to provide a diagnostic current to a diagnostic resistor at a diagnostic resistor node
Implementation Method 3
an SLS driver current source that is arranged to provide an SLS current to a series SLS chain at a series SLS node. The series SLS chain includes a plurality of SLSs connected in series
Data Source
AI summary
Methods and circuits are described in which an SLS driver circuit includes an SLS driver current source that may be arranged to provide an SLS current to a series SLS chain at a series SLS node. The series SLS chain may include a plurality of SLSs connected in series. The SLS driver circuit also includes a diagnostic current source that is arranged to provide a diagnostic current to a diagnostic resistor at a diagnostic resistor node. The series SLS chain also includes a comparison circuit that may be arranged to compare a series SLS voltage at the series SLS node with a diagnostic voltage at the diagnostic resistor node, and to output a status signal based on a result of the comparison such that the status signal is based, at least in part, on whether a failure condition exists in the series SLS chain.