Vehicle Lamp Lighting Circuit Open Fault Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Vehicle lamps with multiple light sources face issues due to open abnormalities in wire harnesses and bypass switches, leading to failure in turning off the high beam light source, as drive current flows through both light sources when an open abnormality occurs, causing operational issues.
Innovation Solution
A lighting circuit with a bypass switch and an abnormality detection circuit that uses detection voltage thresholds to differentiate between normal and abnormal conditions, allowing for the detection of open abnormalities in wire harnesses and bypass switches, ensuring proper control and operation of light sources.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If a three-wire wire harness is used to reduce the number of wires and terminals, then the device complexity is reduced, but open abnormality in the wire harness cannot be detected
Solution Approach 1:
A detection circuit is introduced as an intermediary component between the existing three-wire harness and the control system. This detection circuit monitors the voltage or current characteristics to identify open abnormalities without requiring additional wires in the main harness, thus maintaining simplicity while enabling fault detection
Solution Approach 2:
The system implements feedback by continuously monitoring the electrical characteristics through the existing three-wire configuration and providing abnormality detection signals back to the control unit, enabling real-time detection of open faults without increasing wire harness complexity
2Ease of operation
If the bypass switch is used to control the second light source, then the ease of operation is improved, but open abnormality in the bypass switch cannot be detected
Solution Approach 1:
A detection circuit is introduced as an intermediary that monitors the bypass switch status by detecting voltage or current characteristics through the existing three-wire connection, enabling abnormality detection without adding direct monitoring wires to the switch itself
Solution Approach 2:
The system provides feedback by monitoring the electrical characteristics through the three-wire harness and generating abnormality detection signals when the bypass switch fails, enabling continuous monitoring of switch health without interfering with its normal operation
3Reliability
If open abnormality occurs in the wire harness, then the drive current flows through both light sources, but the second light source cannot be turned off
Solution Approach 1:
The detection circuit provides feedback about the wire harness condition to the control system. When an open abnormality is detected, the control system can respond by turning off both light sources or activating warning indicators, preventing the harmful effect of unintended continuous light emission
Solution Approach 2:
The system takes preliminary anti-action by detecting potential open abnormalities before they cause harmful effects. The detection circuit continuously monitors the wire harness condition and triggers protective actions in advance to prevent unintended light emission and ensure safe operation
Data Source
AI summary
There is provided a lighting circuit configured to drive a light emitting unit including a first light source and a second light source connected in series. The lighting circuit includes a first pin connected to one end of the first light source, a second pin connected to a connection node of the first light source and the second light source, a third pin connected to one end of the second light source, a drive circuit configured to supply a drive current to the light emitting unit, a bypass switch provided between the second pin and the third pin, a first resistor provided in parallel with the bypass switch between the second pin and the third pin, and an abnormality detection circuit configured to detect abnormality based on a detection voltage generated between the second pin and the third pin when an ON signal is applied to the bypass switch.