LED Lighting Module Temperature Control via Self-Heating
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Solution Overview
Problem
Outdoor lighting devices using series-connected semiconductor light elements face challenges in maintaining sufficient output voltage for illumination at low ambient temperatures, as the forward voltage of non-illuminated elements increases with decreasing temperature, potentially leading to insufficient drive circuit output.
Innovation Solution
A control means with a temperature-dependent element activates a heating means, such as using short-circuited semiconductor light elements as heating elements, to maintain the lighting module's temperature within a range where the forward voltage is compatible with the drive circuit's output voltage, ensuring consistent illumination across varying environmental temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ambient temperature decreases, then the forward voltage of non-illuminated semiconductor light elements increases, but the output voltage of the drive circuit becomes insufficient to start illumination
Solution Approach 1:
The heating means is activated before the illumination attempt to pre-heat the lighting module and reduce the forward voltage of non-illuminated semiconductor light elements. This preliminary heating action ensures that when illumination is attempted, the forward voltage is within the drive circuit's output voltage capability, enabling reliable startup across a wide temperature range.
Solution Approach 2:
The system changes the temperature parameter of the lighting module by activating the heating means when the temperature sensor detects low ambient temperature. This parameter change (temperature increase) directly affects the forward voltage characteristic of the semiconductor light elements, making illumination possible despite low ambient conditions.
2Temperature
If a separate heating device is added to heat the lighting module, then the temperature control capability is improved, but the device complexity and cost increase
Solution Approach 1:
The semiconductor light elements serve dual functions: they act as both the illumination sources and the heating means. When activated in a specific configuration, these same light elements generate heat to warm the lighting module. This eliminates the need for separate heating devices, reducing device complexity and cost while maintaining effective temperature control capability.
Solution Approach 2:
The lighting module uses its own light elements to generate the heat required for temperature control, rather than relying on external or separate heating systems. This self-service approach simplifies the overall system architecture by making the lighting elements multi-functional.
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 allows for reliable illumination of semiconductor light elements independent of ambient temperature, without the need for additional heating devices, by using the light elements themselves to generate heat and adjust the series connection's forward voltage within the drive circuit's capabilities.
Implementation Method 1
In a preferred embodiment the semiconductor light elements are light emitting diodes (LEDs) or organic light emitting diodes (OLEDs)
Implementation Method 2
the heating means contains one ore more semiconductor light elements... The heat produced by the at least one semiconductor light element is sufficient and used to heat the lighting module
Data Source
AI summary
The present invention refers to a lighting device (10) and a method of operating this lighting device (10). A lighting module (13) having a light element series connection (15) of several semiconductor light elements (14) is connected to the output (12) of a drive circuit (11). The control means (20) is provided which is configured to adapt a heating condition if a heating requirement is fulfilled. In the heating condition a heating means (26) is activated by the control means (20) to heat the lighting module. The heating requirement is fulfilled when the temperature (T) of the lighting module (13) drops down to a minimum temperature value (Tmin). In so doing an undesired increase of the forward voltage (Vf) of the light element series connection (15) can be avoided.