Vehicle LED Illumination Device with PTC Current Limiting
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Solution Overview
Problem
Motor vehicle illumination devices face challenges in protecting semiconductor light sources from voltage spikes and temperature variations, particularly during load changes and battery disconnection, which can lead to damage or malfunction.
Innovation Solution
The proposed illumination device incorporates a semiconductor light source arrangement with a PTC thermistor having a temperature-dependent resistance value, along with suppressor diodes and capacitors, to regulate current and protect against voltage spikes, ensuring the light sources operate safely within the vehicle's electrical system voltage range.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If semiconductor light sources are used for illumination, then energy efficiency and lifespan are improved, but they become sensitive to voltage spikes and temperature variations causing damage
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a PTC thermistor in series with the LED before voltage spikes can cause damage. The PTC thermistor is pre-positioned in the circuit to automatically limit current during voltage transients, cushioning the LED from harmful electrical surges before they reach the sensitive semiconductor component.
Solution Approach 2:
The PTC thermistor serves as an intermediary element between the power source and the LED. It mediates the electrical current, providing temperature-dependent resistance that automatically regulates current flow. This intermediary protects the LED from direct exposure to voltage spikes while still allowing normal operation under controlled conditions.
2Reliability
If current regulation is implemented to protect LEDs, then reliability is improved, but device complexity increases due to additional components
Solution Approach 1:
The PTC thermistor implements self-service current regulation without requiring external control circuits or additional active components. The thermistor automatically adjusts its resistance based on its own temperature, which changes in response to current flow. This self-regulating mechanism provides reliable LED protection while minimizing circuit complexity, as the protection function is inherent to the thermistor's material properties rather than requiring complex control logic.
3Temperature
If PTC thermistor is used for current limiting, then temperature control is improved, but voltage drop increases reducing system efficiency
Solution Approach 1:
The system exploits parameter changes in the PTC thermistor's resistance characteristics. At normal operating temperatures, the thermistor maintains low resistance to minimize voltage drop and power loss. When temperature increases or voltage spikes occur, the resistance automatically increases to limit current and protect the LED. This dynamic parameter change allows the system to optimize between efficiency during normal operation and protection during abnormal conditions.
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 solution effectively limits current and protects light-emitting diodes from excessive voltage and temperature, ensuring reliable operation and extended lifespan by regulating current and attenuating voltage spikes, while also allowing for reduced input voltage operation and adjustable luminosity.
Implementation Method 1
at least one resistance element with a temperature-dependent resistance value
Implementation Method 2
At least one suppressor diode may be provided for protecting against voltage spikes
Data Source
AI summary
An illumination apparatus for a motor vehicle is provided. The illumination device may include at least one semiconductor light source arrangement, and means for regulating or controlling the supply current for the at least one semiconductor light source arrangement, the means having at least one resistance element with a temperature-dependent resistance value.