Headlight Circuit for Short-Circuit Fault Detection in Series LEDs
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Solution Overview
Problem
Existing automotive illumination devices fail to detect short-circuit faults in light sources, which can lead to reduced light emission and increased risk for road users, as they only monitor for open-circuit failures.
Innovation Solution
Incorporating an auxiliary branch with transistors connected in series to each light source, using voltage drops to detect short circuits and trigger error signals or routines, and a main switch to automatically shut off the power branch if a fault is detected.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If only traditional open-circuit failure monitoring is implemented, then the device complexity is low, but the reliability of fault detection is insufficient for short-circuit faults
Solution Approach 1:
The patent introduces an auxiliary branch with transistors as an intermediary monitoring system. Each transistor is coupled to a light source such that the voltage drop across the light source controls the transistor state. In normal operation, the voltage drop keeps the transistor conductive; in short-circuit conditions, the reduced voltage drop blocks the transistor, triggering fault detection. This intermediary system enables reliable short-circuit detection without directly monitoring current in the power branch.
2Measurement precision
If an auxiliary monitoring branch with transistors is added to each light source, then the detection precision for short circuits is improved, but the device complexity increases
Solution Approach 1:
The patent segments the monitoring function by creating separate auxiliary branches, each associated with a specific light source. Each auxiliary branch contains a transistor that independently monitors its corresponding light source. This segmentation allows precise localization of short-circuit faults to individual light sources while maintaining a modular structure that simplifies the overall system design and fault isolation.
3Measurement precision
If voltage drop monitoring is used to detect short circuits, then the measurement precision of fault detection is improved, but the use of energy increases due to continuous monitoring
Solution Approach 1:
The monitoring system utilizes the existing voltage drop across the light source during normal operation as the monitoring signal. The transistor in each auxiliary branch automatically responds to changes in voltage drop without requiring additional power for active sensing. The light source itself provides the monitoring signal, and the transistor's switching action is driven by the voltage conditions, making the system self-powered and minimizing additional energy consumption.
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
Ensures reliable detection and response to short-circuit faults, preventing reduced light intensity and ensuring compliance with legal illumination requirements, thereby enhancing safety.
Implementation Method 1
each transistor is coupled to the cathode and anode of the light source in such a manner that the voltage that drops across the light source in normal operation is used to connect the transistor
Data Source
AI summary
The invention relates to a short-circuit fault detection illumination device (1) for a motor vehicle headlight, comprisinga voltage input (SE) and a terminal (ME) for connection to earth potential,a power branch (LS) supplied via the voltage input (SE), which comprises a number of light sources (2) to be monitored, wherein this number is at least two, wherein the light sources (2) are designed to emit the light of the illumination device (1) and the light sources (2) are connected to one another in series within the power branch (LS),wherein the illumination device (1) furtherhas an auxiliary branch (HS) with transistors (3) arranged therein and connected to one another in series, wherein each light source (2) of the power branch (LS) is associated with one of the transistors (3), and thus a monitoring pair (P1, P2, P3, P4), consisting of a light source (2) to be monitored and a transistor (3) assigned for monitoring, is formed, wherein each transistor (3) is coupled to the cathode and anode of the light source (2) in such a manner that the voltage that drops across the light source (2) in normal operation is used to connect the transistor (3), and in the event of a short circuit of the light source (2), the voltage drop caused by the short circuit leads to a blocking of the transistor (3) and thus of the auxiliary branch (HS), wherein the short-circuit fault detection illumination device (1) further has a fault detection device (6) coupled to the auxiliary branch (HS), which is designed to output an error signal (SF) or trigger an error routine (FR) in the event of the auxiliary branch being blocked.