Trailer Lighting Outage Detection Circuit With PTC Fault Load
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Solution Overview
Problem
Traditional systems for detecting failed exterior lamps, particularly in vehicles with LED lighting, face challenges due to the low current drop in LED failures, which can be undetectable, and the complexity of mixed incandescent and LED setups, lacking standardization for reporting or detection.
Innovation Solution
The development of circuits with a load element, detection circuit, and power control circuit that increase power dissipation when an LED lamp fails, using a Positive Temperature Coefficient (PTC) thermistor to detect and respond to changes in current flow, enabling effective fault detection and reporting.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If traditional bulb outage detection systems are used to detect LED lamp failures, then the system can detect incandescent bulb failures with sufficient sensitivity, but the system cannot detect LED lamp failures due to the much smaller current drop
Solution Approach 1:
The patent changes the detection parameter from current drop (which is too small for LED detection) to power dissipation changes in a load element. When an LED fails, the detection circuit increases power dissipation through a PTC thermistor, creating a detectable signal that works for both LED and incandescent lamps.
Solution Approach 2:
The patent introduces a load element (PTC thermistor) as an intermediary between the LED lamp and the detection circuit. This load element translates the LED failure condition into a measurable power dissipation change, enabling detection without directly measuring the small current drop.
2Reliability
If paired electronic modules are added between the tractor and trailer to detect LED failures, then LED lamp failures can be detected, but the complexity of the lighting and harness system increases
Solution Approach 1:
The patent combines the detection circuit, power control circuit, and load element into a single integrated module that can be installed in the existing lighting socket. This eliminates the need for separate paired electronic modules between tractor and trailer, reducing overall system complexity while maintaining reliable fault detection.
Solution Approach 2:
The detection circuit is designed to work with both LED and incandescent lamps using the same detection mechanism (power dissipation changes in the load element). This universal approach eliminates the need for different detection systems for different lamp types, simplifying the overall system architecture.
3Measurement precision
If the detection circuit monitors current draw of the LED lamp, then LED lamp failures can be detected, but the small current drop in LED failures makes detection difficult
Solution Approach 1:
The detection circuit performs preliminary action by proactively increasing power dissipation in the load element when a failure is detected. This creates a larger, more easily detectable signal rather than trying to measure the small current drop that occurs naturally during LED failure.
Solution Approach 2:
The patent replaces direct electrical measurement (current monitoring) with a thermal-based detection method using a PTC thermistor. The thermistor's resistance changes in response to power dissipation, providing a more sensitive and reliable detection mechanism than direct current measurement.
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
These circuits can accurately detect LED lamp failures by increasing current draw upon failure, allowing for reliable fault indication and reducing false positives, compatible with both incandescent and LED systems without requiring specific truck configurations.
Implementation Method 1
The power control circuit can also be configured to automatically increase power dissipated by the load element when the detection circuit detects a failure in the LED lamp. The load element can optionally be a thermistor and, furthermore, a Positive Temperature Coefficient (PTC) thermistor.
Data Source
AI summary
A vehicle LED lighting outage detection circuit is disclosed for detecting a fault in the LED light and automatically increasing the power drawn from the light power supply in response to the fault. A complementary detection circuit is also disclosed for detecting the increased power draw and signaling a fault to an operator. The increased power draw can be selected to be in the form of a pulse that settles to a lower power draw state after a time to avoid excessive and wasteful power draw. The system can be mounted in a vehicle and, more particularly, to a semi-tractor truck.