Temperature Compensation Circuit for LED Radiant Energy Stability
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Conventional optical sensing systems using LEDs face challenges in maintaining consistent radiant energy output across a range of ambient temperatures, which affects the sensitivity of photodiodes and detection reliability.
Innovation Solution
A temperature-compensated LED-drive circuit is implemented, comprising a temperature-dependent current generator and a temperature-independent current generator, with a weighted current adder and multiplier, to produce a current that complements the LED's temperature dependence, ensuring constant radiant energy output across varying temperatures.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the input current to the LED is kept constant, then the LED structure is simple and easy to control, but the radiant energy output varies considerably with ambient temperature
Solution Approach 1:
The patent changes the electrical parameter (input current) dynamically based on temperature. Instead of keeping current constant, the system adjusts the current magnitude according to temperature conditions to compensate for LED's temperature-dependent radiant energy output variations, thereby maintaining output stability
Solution Approach 2:
The patent implements a feedback mechanism where the system monitors temperature changes and adjusts the LED drive current accordingly. The temperature-dependent current generator receives temperature information and modifies the current output to compensate for radiant energy variations, creating a closed-loop control system
2Reliability
If a temperature compensation circuit is added to maintain constant radiant energy output, then the radiant energy stability improves, but the device complexity increases
Solution Approach 1:
The patent divides the current generation function into separate modular components: a temperature-independent current generator and a temperature-dependent current generator. This segmentation allows each module to perform a specific function independently, making the overall system more manageable and potentially integrable into existing LED drive architectures
Solution Approach 2:
The patent combines two different current generation mechanisms (temperature-independent and temperature-dependent) into a composite current output. By merging these distinct functional elements, the system achieves temperature compensation while maintaining compatibility with standard LED operating requirements
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
The solution maintains the LED's radiant energy output within a few percent variation across the operational temperature range, enhancing the sensitivity and reliability of optical sensing systems.
Implementation Method 1
A temperature-dependent current generator is provided. The temperature-dependent current generator is operative to produce a current that increases or decreases in response to changes in ambient temperature
Implementation Method 2
The photodiode converts the received radiant energy to electrical current which is further processed for detecting, for example, the existence of the medium or the surface
Data Source
Figure 1
Figure 2A
Figure 2B
AI summary
Disclosed is a temperature compensation circuit for a light source (e.g., light emitting diode (LED)) whose radiant energy output decreases when ambient temperature increases. The circuit includes first means for sourcing a first current that increases proportional to an increase in ambient temperature, and second means for sourcing a second current that is first order independent of ambient temperature. The circuit further includes a weighted current adder for sourcing a third current by combining the first and second currents with first and second weights applied to the first and second currents respectively. The circuit further includes third means responsive to the third current for supplying a fourth current to the light source to maintain a radiant energy output of the light source constant independent of ambient temperature.