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Design and optimization of high temperature optocouplers as galvanic isolation
Abbas Sabbar1, Syam Madhusoodhanan1, Huong Tran1
1Department of Electrical Engineering, University of Arkansas, Fayetteville, AR, 72701, USA.
Scientific Reports
|February 10, 2022
Summary
This study explores the use of light-emitting diodes (LEDs) as high-temperature optocouplers. Red LEDs for display show promise for optimizing optocouplers due to their wavelength characteristics.
Area of Science:
- Optoelectronics
- Semiconductor Devices
- Materials Science
Background:
- Commercial InGaN (blue, green) and AlGaInP (red) multiple quantum well (MQW) LEDs are crucial components.
- High-temperature (HT) optocouplers are needed for galvanic isolation in power modules, replacing bulky transformers.
- Understanding LED and photodiode (PD) characteristics at elevated temperatures is essential for device integration.
Purpose of the Study:
- To investigate the light emission and detection characteristics of commercial MQW LEDs up to 800 K.
- To assess the feasibility of fabricating HT optocouplers using selected LEDs.
- To compare the performance of different colored LEDs (blue, green, red) as both light emitters and detectors (PDs) at high temperatures.
Main Methods:
- Studied commercial InGaN-based (blue, green) and AlGaInP-based (red) MQW LEDs.
- Characterized devices across a wide temperature range up to 800 K.
- Analyzed light emission and reverse-bias (photodiode) characteristics, calculating external quantum efficiency (EQE).
Main Results:
- Blue and green LEDs for display exhibited higher relative EQE and lower efficiency droop with increasing temperature compared to blue for lighting and red LEDs.
- Blue for lighting and red for display LEDs showed superior responsivity, specific detectivity (D*), and EQE when operated as PDs.
- Red LEDs for display demonstrated the highest wavelength overlap, suggesting suitability for HT optocoupler optimization.
Conclusions:
- Selected LEDs can be integrated to create functional high-temperature optocouplers for galvanic isolation.
- Red LEDs for display are identified as optimal for HT optocouplers due to superior performance and wavelength matching.
- The study validates the potential of LEDs as replacements for traditional isolation transformers in high-density power modules.
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