Vehicle LED Bridge Circuit for Short-Circuit Detection
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Solution Overview
Problem
Existing vehicle lighting systems using LEDs connected in series face challenges in accurately detecting short-circuits due to increased complexity and noise interference, especially when the number of LEDs increases, making it difficult to distinguish between normal and abnormal voltage drops.
Innovation Solution
The system divides LEDs into groups and uses a bridge circuit with comparison resistors and transistors to detect short-circuits without the need for additional wiring, allowing for accurate detection and prevention of erroneous readings.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Illumination intensity
If the number of LEDs connected in series is increased to achieve required brightness, then the brightness and luminous intensity are improved, but the ability to detect short-circuit failures deteriorates due to reduced voltage drop ratio and accumulated voltage variations
Solution Approach 1:
The patent divides the series-connected LED string into multiple parallel branches, each containing a subset of LEDs. This segmentation allows the detection circuit to monitor voltage drops in smaller groups rather than the entire long series string, making it easier to detect individual LED failures without being overwhelmed by accumulated voltage variations from many LEDs.
Solution Approach 2:
The patent introduces a detection circuit that uses a transistor as an intermediary element to amplify or modulate the voltage signal from the LED branches. This intermediary mechanism enhances the detectability of small voltage changes caused by single LED failures, overcoming the limitation of small voltage drop ratios in large-series configurations.
2Ease of manufacture
If a short detecting circuit is disposed on the power supply side to reduce cost, then the manufacturing cost is reduced, but noise interference increases causing erroneous detection
Solution Approach 1:
The patent extracts the detection function from the main power supply circuit by creating separate detection branches parallel to the LED strings. This separation isolates the detection circuit from high-current switching noise and voltage fluctuations in the power supply, allowing accurate detection while keeping the detection circuit simple and cost-effective.
3Measurement precision
If additional wiring is added to connect detecting circuit to LED connecting points to improve detection accuracy, then the short-circuit detection precision is improved, but the device complexity and noise susceptibility increase
Solution Approach 1:
The patent merges the detection circuit with the existing LED branch structure by placing detection components directly within or parallel to the LED branches. This integration allows the detection circuit to access LED connecting points through existing wiring paths rather than requiring separate additional wiring, reducing complexity while maintaining detection precision.
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 configuration enhances the accuracy of short-circuit detection, reduces the impact of voltage variations, and prevents false alarms by operating transistors within the light source unit, eliminating the need for external wiring and reducing the risk of noise interference.
Implementation Method 1
a pair of comparison resistors (201, 202) connected in series, the pair of comparison resistors (201, 202) being connected to a high potential side and a low potential side of the first light-emitting element group (110) and the second light-emitting element group (120) to generate a voltage equivalent to a voltage at a connecting point between the first light-emitting element group (110) and the second light-emitting element group (120)
Implementation Method 2
a transistor (301) having a base connected to one of connecting points including: a connecting point between the first light-emitting element group (110) and the second light-emitting element group (120); and a connecting point between the pair of comparison resistors (201, 202), and having an emitter connected to another one of the connecting points
Data Source
AI summary
A bridge circuit (22) includes a first light-emitting element group (102, 110) and a second light-emitting element group (103, 120) connected in series; and a pair of comparison resistors (201, 202) connected in series and generating a voltage (Vref) equivalent to a voltage (VLED) at a connecting point between the first light-emitting element group (102, 110) and the second light-emitting element group (103, 120). A transistor (301, 302) is connected to a connecting point between the first light-emitting element group (102, 110) and the second light-emitting element group (103, 120) and a connecting point between the comparison resistors (201, 202), and operates when the first light-emitting element group (102, 110) or the second light-emitting element group (103, 120) is short-circuited.