LED Light Source Module Thermal Derating and Current Setting Interface
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Solution Overview
Problem
Existing LED-based lighting systems face challenges in efficiently managing the operating current and thermal derating across multiple light source modules connected in parallel, as previous interfaces require additional lines and are not suitable for correct current setting and thermal management, leading to inefficiencies and increased costs.
Innovation Solution
A three-line interface with current setting resistors and a thermal derating unit on the light source module, where the power supply unit measures the equivalence resistor to set the operating current and uses a temperature-controlled current source for thermal derating, ensuring dominant thermal protection without overheating, and employs voltage information for improved efficiency by eliminating redundant current measurement resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If the number of data lines is increased to enable precise current setting and thermal derating control, then the control precision and reliability are improved, but the device complexity and production cost increase
Solution Approach 1:
The communication line serves multiple functions: it carries both the thermal derating control signal and the current setting information simultaneously. The power supply unit measures the voltage on the communication line to determine the equivalent resistor value, which defines the LED operating current. This multi-functional approach eliminates the need for separate data lines while maintaining precise control capabilities.
Solution Approach 2:
The light source module uses its own internal equivalent resistor (formed by parallel connection of current setting resistors) to automatically define its current requirement. The module self-identifies its needs through the voltage signal on the communication line without requiring external programming or complex interface protocols, enabling self-configuring operation.
2Device complexity
If current setting resistors are connected in series to define total current requirement, then the control is simplified, but the measurement precision and adaptability to different module configurations deteriorate
Solution Approach 1:
The single current setting resistor is divided into multiple parallel-connected current setting resistors (at least two), forming an equivalent resistor network. Each resistor can be independently selected to define the current requirement for specific LED cascade configurations. This segmentation allows precise adaptation to different numbers of LEDs and module types while maintaining a simple parallel connection structure.
Solution Approach 2:
The equivalent resistor value is changed by selecting different combinations of parallel-connected resistors with specific resistance values. By changing the resistance parameter of the equivalent resistor, the system can adapt to different LED operating current requirements without changing the overall circuit topology, enabling flexible parameter adjustment for various lighting applications.
3Adaptability or versatility
If a single power supply unit is used for multiple LED-based lighting systems with differing numbers of LEDs, then the adaptability is improved, but the device complexity and programming requirements increase
Solution Approach 1:
The power supply unit automatically determines the required LED operating current by measuring the voltage signal on the communication line from the light source module. The module self-identifies its current requirement through the equivalent resistor configuration, and the power supply unit self-adjusts its output current accordingly, eliminating the need for manual programming or complex configuration for different LED counts.
Solution Approach 2:
The system implements a feedback mechanism where the light source module continuously provides voltage information on the communication line about its current requirement, and the power supply unit uses this feedback to automatically adjust and maintain the correct operating current. This closed-loop control enables the power supply unit to adapt to different LED configurations without programming changes.
4Productivity
If thermal derating control is implemented without increasing data lines, then the adaptability and efficiency are improved, but the measurement precision and control accuracy may deteriorate
Solution Approach 1:
The communication line simultaneously carries both the current setting information and the thermal derating control signal. The power supply unit measures the voltage on the communication line to determine the equivalent resistor value for current setting, while also using the same line to receive thermal derating commands from the light source module, enabling dual functionality without additional lines.
Solution Approach 2:
The voltage signal on the communication line acts as an intermediary that conveys both current requirement information and thermal derating control information between the light source module and power supply unit. This intermediary signal enables precise control of both parameters through a single communication channel, maintaining measurement precision while improving system efficiency.
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 efficient operation of multiple LED cascades with different nominal currents on a single power supply unit, reduces losses, and prevents unnatural current division, ensuring reliable and efficient lighting while maintaining thermal protection and reducing component aging.
Implementation Method 1
The thermal derating unit has a temperature coefficient of resistance and is arranged between the coupling point and the reference potential
Data Source
AI summary
A light source module may include at least one LED cascade with a plurality of LEDs, a supply line, wherein at the input side the LED cascade is coupled thereto, and a ground line. The light source module further includes a communications line for coupling to a control device for the current to be provided by the current source, a thermal derating unit coupled between a first voltage source and the communications line and including a temperature-sensitive element, wherein the thermal derating unit applies a temperature dependent current component determined depending on the temperature-sensitive element, to the communications line, at least one current measurement resistor connected in series between the LED cascade and the reference potential, wherein the conductance of the current measurement resistor is proportional to the current requirement of the LED cascade, and at least one coupling resistor coupled between the coupling point and the communications line.