• Journal of the Korean Society of Safety
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• v.27 no.6
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• pp.26-30
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• 2012

It is difficult to determine the junction temperature because LED lightings are manufactured using several chips with low power. This paper reports on the finite element method of the determination of junction temperature in the GaN-based LEDs. The calculated junction temperature of the LED chip using FEM was compared with the experimentally measured data. As the results of this study, the junction temperature of LED chips with via holes is lower than that of LED chips without via hole. Therefore, the research of via hole is necessary to decrease junction temperature of LED chips.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.23 no.12
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• pp.973-977
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• 2010

The temperature of junction in LED affects the life time and performance. however, the measurement of junction temperature in module is very difficult. In this paper, to measure the junction temperature in LED module, optical and electrical properties is measured in single package in temperature from 25 [$^{\circ}C$] to 85 [$^{\circ}C$], and then junction temperature can is estimated in module with measuring the average voltage of single package. As results, the junction temperature of single package is measured the temperature of 61.2 [$^{\circ}C$] in ambient temperature, also, the junction temperature of LED module is measured the temperature of 72.5 [$^{\circ}C$] in ambient temperature.

• Journal of Industrial Technology
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• v.29 no.B
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• pp.187-191
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• 2009

Recently, we have used LEDs to illumination because it has a high luminous efficiency and prolong lifespan. However the light power and lifetime is reduced by junction temperature increment of LED. So it is important to measure the junction temperature accurately. In case of using a electrical method measuring junction temperature of LED. Temperature measurement errors are spontaneously generated because of a parasitic capacitances in LED. In this paper, we proposed a method that reducing LED's parasitic capacitance effects for electrical measurement. It was demonstrated by the experimental result that is more correct than established method.

• Journal of Industrial Technology
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• v.30 no.A
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• pp.83-88
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• 2010

Recently, the LED lighting is widely used to illumination purpose due to its high luminous efficiency and the long life time. However, the light power and lifetime is reduced by junction temperature increment of LED. So it is important to measure the junction temperature accurately. In this paper, we proposed a new design and implementation method of high power LED junction temperature measurement circuit. The proposed circuit has two current sources which are a driving current source and a measurement is verified by experiment, and the result shows that the proposed circuit is appropriate to practical use.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.26 no.2
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• pp.1-7
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• 2012

LED package with 4[mm]-height mold was manufactured and the surface temperature was measured directly using both thermocouple and thermal infrared (IR) camera. FVM simulation was conducted to estimate the surface temperature of the same LED package under the same condition, by which the accuracy of the simulation was secured. Then, the effects of the height and thermal conductivity of the mold on the junction temperature of the LED package were investigated by FVM simulation. The results showed that the junction temperature decreased by 10[$^{\circ}C$] when the mold height was 3~5[mm], but the thermal conductivity of the mold didn't affect the junction temperature significantly.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.27 no.9
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• pp.594-599
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• 2014

The heat dissipation conditions of high-power 5 watt LEDs-based searchlight modules were optimized with varying LED bar'shape, materials, and ambient temperature. The LED junction temperature was estimated by using Computational Fluid Dynamics simulation. The optimal heat dissipation conditions were found as follows; LED bar' shape: L=80 mm, W=4 mm, t=10 mm, copper material, LED junction temperature of $116.6^{\circ}C$, ambient temperature of $50^{\circ}C$, total mass of 184 g, and shadowing area of $320mm^2$. The difference between the junction temperatures of our fabricated and simulated LEDs-based searchlight modules is about $3^{\circ}C$, which confirms the validity of our thermal simulation results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.25 no.12
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• pp.34-41
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• 2011

In order to understand the thermal performance of each LED chips in multi-chip LED package, a quantitative parametric analysis of the temperature evolution was investigated by thermal transient analysis. TSP (Temperature Sensitive Parameter) value was measured and the junction temperature was predicted. Thermal resistance between the p-n junction and the ambient was obtained from the structure function with the junction temperature evolution during the cooling period of LED. The results showed that, the thermal resistance of the each LED chips in 4 chip-LED package was higher than that of single chip- LED package.

• Journal of Broadcast Engineering
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• v.21 no.5
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• pp.816-823
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• 2016

This paper studies a light emitting diode(LED) overlapping method of a head-up display that consists of a digital micro device(DMD) panel and a red, green, blue LED in order to increase the brightness of display system and optical output power. This optimization overlapping method removes a quantization noise which occur due to LED overlapping too excessive and stabilizes the junction temperature of LED. In order to reduce junction temperature of LED, the a correlation between a green duty and LED overlapping ratio is studied. Throughout this study, the brightness of head-up display exhibited high increasement ratio of luminance around 33.3 percent at 39 percent overlapping method.

• Journal of the Korean Vacuum Society
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• v.20 no.4
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• pp.280-287
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• 2011

The heat temperature of a light emitting diode (LED) is investigated with the thermoelectric device (TED). The Peltier effect of the thermoelectric device is used to control the heat radiation and the junction temperature of high-power LEDs. For the typical specific current (350 mA) of high-power (1 W) LEDs, the LED temperature and the p-n junction temperature become $64.5^{\circ}C$ and $79.1^{\circ}C$, respectively. For 0.1~0.2 W driving power of TED, the LED temperature and the junction temperature are reduced to be $54.2^{\circ}C$ and $68.9^{\circ}C$, respectively. As the driving power of the TED increases over 0.2 W, the temperature of LED itself and the junction temperature are increased due to the heat reversed from the heat-sink to LED. As the difference of temperature between LED and the heat-sink is increased, the quantity of reversed heat becomes larger and it results to degrade the cooling capability of TED.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.24 no.3
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• pp.234-239
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• 2011

In this study, the heat transfer capability have been improved by using via-holes in FR4 PCB, when the LED lighting is designed to solve the thermal problem. The thermal resistance and junction temperature were measured by changing the dimension of FR4 PCB and size of via hole. As a result, when the dimension was increased initially, the thermal resistance and junction temperature was decreased rapidly, the ones was stabilized after the dimension of 200 $[mm^2]$. Also, the light output was improved up to maximum 17% by formation of via-hole and expansion of dimension in FR4 PCB. Therefore, the thermal resistance and junction temperature could be improved by expansion of PCB dimension and configuration of via-hole ability.