LED Heating Control Using Junction Temperature Feedback
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Solution Overview
Problem
Existing heating devices using LEDs for temperature control in semiconductor testing face issues with thermal runaway due to unregulated current supply, leading to reduced luminous efficiency and premature degradation of LEDs.
Innovation Solution
A heating device with an LED controller that adjusts power supply to LEDs within an allowable current range, incorporating a correction unit to estimate junction temperature and adjust the allowable current based on measured voltage, preventing thermal runaway and maximizing LED performance over time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the LED current is increased to improve heating efficiency, then the heating performance is improved, but the LED junction temperature increases causing thermal runaway and reduced reliability
Solution Approach 1:
The patent implements a feedback control mechanism where the LED controller continuously monitors the LED voltage and compares it against a reference voltage. When the voltage exceeds the reference, indicating overheating, the controller reduces the drive current. This closed-loop feedback prevents thermal runaway while maximizing heating efficiency within safe operating limits.
Solution Approach 2:
The patent dynamically adjusts the LED drive current parameter based on real-time voltage measurements and temperature conditions. The controller modifies the current supplied to the LED according to the measured voltage levels, transitioning between different current ranges to optimize both heating performance and thermal management.
2Productivity
If the LED operates at high current for extended periods to improve productivity, then the heating efficiency is improved, but the LED degradation accelerates reducing duration of action
Solution Approach 1:
The patent employs periodic monitoring and adjustment of LED operating conditions. The controller periodically measures LED voltage and adjusts current accordingly, allowing the LED to operate at high current for heating tasks while taking periodic breaks or reducing intensity when temperature thresholds are approached, thereby extending overall operational lifespan.
Solution Approach 2:
The patent performs preliminary characterization of the LED's current-light output properties and establishes safe operating limits before actual heating operations. The controller uses pre-acquired data about the LED's thermal and electrical characteristics to predict temperature rise and prevent degradation before it occurs, enabling extended high-productivity operation.
3Reliability
If the allowable current is fixed to prevent thermal runaway, then the LED reliability is improved, but the luminous efficiency and heating performance are reduced
Solution Approach 1:
The patent transitions from a static, fixed allowable current approach to a dynamic current control system. The LED controller continuously adjusts the drive current based on real-time voltage measurements and environmental conditions, allowing the system to operate at optimal efficiency points while preventing thermal runaway through adaptive rather than rigid current limiting.
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 ensures efficient and prolonged utilization of LEDs by preventing thermal runaway, maintaining optimal temperature control, and extending the lifespan of the LEDs in heating applications.
Implementation Method 1
a heater which includes an LED and heats a heating target with light emitted from the LED
Implementation Method 2
heats a heating target with light emitted from the LED
Data Source
AI summary
A heating device using an LED is provided. The heating device includes a heater for heating a target with LED light, an LED controller for controlling power supplied to the LED such that a temperature of the target is adjusted with the power being in the range where a current thereof does not exceed an allowable current Imax, a correction unit for correcting Imax, and a voltage measurement unit for measuring a voltage of the LED. The correction unit estimates a junction temperature Tjm of the LED when Imax is supplied based on a measurement result by the voltage measurement unit when an estimation current Ie is supplied after Imax is supplied to the LED for correction. When Tjm of the LED when Imax is supplied exceeds Tmax corresponding to Imax, the correction unit corrects Imax.