Accurate determination of junction temperature in a GaN-based blue light-emitting diode using nonlinear voltage-temperature relation

2021 ◽  
Vol 53 (9) ◽  
Author(s):  
Chibuzo Onwukaeme ◽  
Won-Jin Choi ◽  
Han-Youl Ryu
Keyword(s):  
Blue Light ◽  
Light Emitting Diode ◽  
Accurate Determination ◽  
Junction Temperature ◽  
Temperature Relation ◽  
Light Emitting

scholarly journals Accurate Determination of Junction Temperature in a GaN-Based Blue Light-Emitting Diode using Nonlinear Voltage-Temperature Relation

2021 ◽  
Author(s):  
Chibuzo Onwukaeme ◽  
Won-Jin Choi ◽  
Han-Youl Ryu
Keyword(s):  
Ambient Temperature ◽  
Blue Light ◽  
Accurate Determination ◽  
Quadratic Function ◽  
Junction Temperature ◽  
Nonlinear Dependence ◽  
Quadratic Model ◽  
Temperature Relation ◽  
Light Emitting

Abstract We investigate the junction temperature measurements for GaN-based blue light emitting diodes (LEDs) using nonlinear dependence of the forward voltage ( V f ) on temperature. Unlike the conventional linear model of the dependence of V f on temperature, the modeling of the temperature dependent V f with a quadratic function showed good agreements with measured data in the temperature range between 20 and 100 o C. Using the proposed quadratic model, the junction temperature and thermal resistance of the measured LED could be accurately determined as the ambient temperature varied. It was observed that the junction temperature increment remained almost unchanged as the ambient temperature increased from 20 to 80 o C, which could be attributed to the interplay between the decrease in series resistance and the increase in non-radiative recombination with increasing temperature. The presented method for accurate determination of the junction temperature is expected to be advantageously employed for the thermal management of high-power LEDs.

scholarly journals A Simple and Portable Colorimeter Using a Red-Green-Blue Light-Emitting Diode and Its Application to the On-Site Determination of Nitrite and Iron in River-water

2004 ◽  
Vol 20 (6) ◽  
pp. 975-977 ◽  
Author(s):  
Yasutada SUZUKI ◽  
Terutomi ARUGA ◽  
Hiroyuki KUWAHARA ◽  
Miki KITAMURA ◽  
Tetsuo KUWABARA ◽  
...  
Keyword(s):  
River Water ◽  
Blue Light ◽  
Light Emitting Diode ◽  
Light Emitting

scholarly journals LED Rail Signals: Full Hardware Realization of Apparatus with Independent Intensity by Temperature Changes

Electronics ◽  
2021 ◽  
Vol 10 (11) ◽  
pp. 1291
Author(s):  
Giuseppe Schirripa Schirripa Spagnolo ◽  
Fabio Leccese
Keyword(s):  
Temperature Sensor ◽  
Energy Efficient ◽  
Light Emitting Diode ◽  
Junction Temperature ◽  
Light Emitting ◽  
Temperature Changes ◽  
Wide Range ◽  
International Regulations ◽  
Long Lifetime ◽  
Set Up

Nowadays, signal lights are made using light-emitting diode arrays (LEDs). These devices are extremely energy efficient and have a very long lifetime. Unfortunately, especially for yellow/amber LEDs, the intensity of the light is closely related to the junction temperature. This makes it difficult to design signal lights to be used in naval, road, railway, and aeronautical sectors, capable of fully respecting national and international regulations. Furthermore, the limitations prescribed by the standards must be respected in a wide range of temperature variations. In other words, in the signaling apparatuses, a system that varies the light intensity emitted according to the operating temperature is useful/necessary. In this paper, we propose a simple and effective solution. In order to adjust the intensity of the light emitted by the LEDs, we use an LED identical to those used to emit light as a temperature sensor. The proposed system was created and tested in the laboratory. As the same device as the ones to be controlled is used as the temperature sensor, the system is very stable and easy to set up.

scholarly journals In vitro and in vivo Efficacy of New Blue Light Emitting Diode Phototherapy Compared to Conventional Halogen Quartz Phototherapy for Neonatal Jaundice

2005 ◽  
Vol 20 (1) ◽  
pp. 61 ◽  
Author(s):  
Yun Sil Chang ◽  
Jong Hee Hwang ◽  
Hyuk Nam Kwon ◽  
Chang Won Choi ◽  
Sun Young Ko ◽  
...  
Keyword(s):  
Blue Light ◽  
Neonatal Jaundice ◽  
Light Emitting Diode ◽  
In Vivo Efficacy ◽  
Light Emitting

scholarly journals Operando direct observation of spin-states and charge-trappings of blue light-emitting-diode materials in thin-film devices

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Fumiya Osawa ◽  
Kazuhiro Marumoto
Keyword(s):  
Blue Light ◽  
High Performance ◽  
Density Functional ◽  
Light Emitting Diode ◽  
Green Light ◽  
Spin States ◽  
Light Emitting ◽  
Full Color ◽  
Color Displays ◽  
Materials Used

Abstract Spin-states and charge-trappings in blue organic light-emitting diodes (OLEDs) are important issues for developing high-device-performance application such as full-color displays and white illumination. However, they have not yet been completely clarified because of the lack of a study from a microscopic viewpoint. Here, we report operando electron spin resonance (ESR) spectroscopy to investigate the spin-states and charge-trappings in organic semiconductor materials used for blue OLEDs such as a blue light-emitting material 1-bis(2-naphthyl)anthracene (ADN) using metal–insulator–semiconductor (MIS) diodes, hole or electron only devices, and blue OLEDs from the microscopic viewpoint. We have clarified spin-states of electrically accumulated holes and electrons and their charge-trappings in the MIS diodes at the molecular level by directly observing their electrically-induced ESR signals; the spin-states are well reproduced by density functional theory. In contrast to a green light-emitting material, the ADN radical anions largely accumulate in the film, which will cause the large degradation of the molecule and devices. The result will give deeper understanding of blue OLEDs and be useful for developing high-performance and durable devices.

Optimization and evaluation of a blue light photoinitiating system for textile inkjet printing

2018 ◽  
Vol 89 (10) ◽  
pp. 1964-1974
Author(s):  
Yi Huang ◽  
Guangdong Sun ◽  
Yating Ji ◽  
Dapeng Li ◽  
Qinguo Fan ◽  
...  
Keyword(s):  
Blue Light ◽  
Light Emitting Diode ◽  
Absorption Efficiency ◽  
Polymerization Rate ◽  
Nozzle Clogging ◽  
Light Emitting ◽  
Custom Made ◽  
Light Curing ◽  
Set Up ◽  
Pigment Ink

A blue light curing process was developed to solve the nozzle clogging challenge commonly encountered in conventional textile pigment printing, by using camphorquinone (CQ) and ethyl-4-dimethylaminobenzoate (EDMAB) as a photoinitiator combination and substituting oligomers and monomers for a polymeric binder. High light absorption efficiency was insured by closely matching the spectrum of the photoinitiator with a custom-made blue light light-emitting diode set-up. Kinetic analyses of such a CQ/EDMAB system indicated that the maximum polymerization rate of the monomer was proportional to [PI]0.5 and [I0]0.5, while excessive high photoinitiator concentration (>1 wt%) will decrease the polymerization rate because of the “filter effect.” With optimized blue light curable pigment ink formula and irradiation conditions, the photocurable pigment printed fabrics exhibited uniform and vibrant colors, clear outlines, and excellent wet and dry rubbing fastness of grades 4 and 4–5, respectively.

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