Vehicle Lamp Lighting Circuit PWM Abnormality Detection
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Existing vehicle lamp systems using semiconductor light sources face complexity in abnormality detection due to the need for a return line and extra pins, which complicates the connection and control of PWM signals.
Innovation Solution
A lighting circuit that integrates an abnormality detection unit within the drive circuit, which asserts an abnormality detection signal when a non-input state of the PWM signal exceeds a predetermined time, eliminating the need for a return line and allowing synchronization of PWM signal supply and power supply start, enabling detection via a single signal line.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a return line is provided in the wire harness to detect PWM signal abnormalities, then abnormality detection capability is improved, but wire harness complexity and connection complexity increase
Solution Approach 1:
The patent merges the PWM signal transmission function and the abnormality detection function into a single wire harness connection. The drive circuit includes an abnormality detection unit that monitors the PWM signal on the same line used for transmission, eliminating the need for a separate return line. This combining of functions resolves the contradiction by maintaining detection capability while reducing connection complexity.
Solution Approach 2:
The single wire harness connection is made multi-functional by using it both for PWM signal transmission and for abnormality detection. The drive circuit's detection unit monitors signal characteristics on this universal line to detect disconnections or abnormalities, allowing one connection to serve multiple purposes and eliminate the need for additional dedicated detection lines.
2Reliability
If a return line with extra pins is added for PWM signal return, then abnormality detection is enabled, but ease of operation and installation deteriorate
Solution Approach 1:
The patent combines the PWM signal input and abnormality detection functions into a single pin connection on both the ECU and drive circuit sides. By integrating the detection unit within the drive circuit to monitor the PWM signal on the same line, the system eliminates the need for an additional return pin, thereby simplifying installation and improving ease of operation while maintaining detection capability.
3Measurement precision
If PWM signal transmission and abnormality detection use separate lines, then detection accuracy is improved, but device complexity increases
Solution Approach 1:
The patent implements a feedback mechanism where the drive circuit's detection unit continuously monitors the PWM signal characteristics on the transmission line and compares them against expected values. This feedback approach allows accurate detection of signal abnormalities such as disconnections or interference while using the same signal line, thereby maintaining detection precision without increasing line complexity.
Solution Approach 2:
The PWM signal line serves itself by being both the transmission medium and the detection medium. The drive circuit uses the same line it receives the PWM signal on to detect abnormalities, making the line self-diagnostic. This self-service approach eliminates the need for separate detection lines while maintaining accurate abnormality detection capability.
Data Source
AI summary
A lighting circuit which lights a semiconductor light source, the lighting circuit includes a drive circuit configured to receive a PWM signal from a controller, to generate a drive current to the semiconductor light source, and to switch the drive current according to the PWM signal. When a non-input state of the PWM signal exceeds a predetermined time, the lighting circuit is configured to assert an abnormality detection signal and to output the abnormality detection signal to the controller.