• 한국기계가공학회지
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• 제15권6호
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• pp.70-76
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• 2016

Commercialization of surface lighting using Light Emitting Diodes (LED) has embraced the advance to Organic Light Emitting Diode (OLED) technology. This is necessary to achieve light-efficiency-improvement and longer component life. The range of application of LED lighting for both interior and outdoor lights has been gradually expanding. Automobiles and home appliances are now included. In the case of LED surface lighting in a domestic refrigerator, achieving high efficiency requires optimization of the number of LEDs in a pack. Optimization is also required in the design stage of development with regard to the conversion of the light source type from point light sources to the surface light type. This paper addresses these design problems. It presents a study of brightness variations for design solutions that differ from the existing technology in both the number of LED packages and use of Light Gathering Power (LGP) information. The intention is to facilitate production of high brightness LED surface lighting for domestic refrigerators.

• 한국전기전자재료학회논문지
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• 제36권3호
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• pp.255-260
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• 2023

In order to spread LED lighting, LED lighting technology directly driven by alternating current (AC) commercial power has recently been introduced. Since current does not flow at a voltage lower than the threshold voltage of the LED, a non-conductive section occurs in the current waveform, and the higher the threshold voltage of the LED, the more discontinuous current waveforms are generated. In this paper, multi-LED modules are connected in series so that the threshold voltage can be adjusted according to the number of LED modules. A small number of LED modules are driven at a low instantaneous rectified voltage, and a large number of LED modules are driven at a high instantaneous rectified voltage to lengthen the overall lighting time of AC-LED lighting, thereby minimizing the luminance deviation of AC-LED lighting. In addition, the load current flowing through the LED module is adjusted to be the same as the design current even at the maximum rectified voltage higher than the design voltage, so that the light brightness of the LED module is kept constant. Therefore, even if the rectified voltage applied to the LED module changes, the AC-LED lighting in which the light brightness is constant and the luminance deviation is minimal has been realized.

• 한국정밀공학회지
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• 제28권2호
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• pp.219-225
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• 2011

Silicone resin is recently used as encapsulant for high-power LED module due to its excellent thermal and optical properties. In the present investigation, finite element analysis of cure process was attempted to examine residual stress evolution behavior during silicone resin cure process which is composed of chemical curing and post-cooling. To model chemical curing of silicone, a cure kinetics equation was evaluated based on the measurement by differential scanning calorimeter. The evolutions of elastic modulus and chemical shrinkage during cure process were assumed as a function of the degree of cure to examine their effect on residual stress evolution. Finite element predictions showed how residual stress in cured silicone resin can be affected by elastic modulus and chemical shrinkage behavior. Finite element analysis is supposed to be utilized to select appropriate silicone resin or to design optimum cure process which brings about a minimum residual stress in encapsulant silicone resin.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2018년도 전력전자학술대회
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• pp.210-212
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• 2018

A new switching mode has been proposed to obtain high power factor and low THD in single stage AC-DC converter. The conventional voltage mode control in critical conduction mode distorts input current shape with poor THD in flyback topology. Once TRIAC dimmer is connected, visible flicker in the LED lamp is easily detected due to a lack of TRAIC holding current near the input voltage zero cross. The newly proposed method can shape the input current by providing a desired reference voltage so that low THD is obtained by ideal sinusoidal input current in case of no dimmer connection and flat input current performs good TRIAC dimmer compatibility in phase-cut dimming condition. To confirm the validity of the proposed method, theoretical analysis and experimental result from 8W dimmable LED lighting system are presented.

• Journal of Electrical Engineering and Technology
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• 제11권3호
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• pp.644-652
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• 2016

This paper presents an improved single-stage ac-dc LED-drive flyback converter using the transformer-coupled lossless (TCL) snubber. The proposed converter is derived from the integration of a full-bridge diode rectifier and a conventional flyback converter with a simple TCL snubber. The TCL snubber circuit is composed of only two diodes, a capacitor, and a transformer-coupled auxiliary winding. The TCL snubber limits the surge voltage of the switch and regenerates the energy stored in the leakage inductance of the transformer. Also, the switch of the proposed converter is turned on at a minimum voltage using a formed resonant circuit. Thus, the proposed converter achieves high efficiency. The proposed converter utilizes only one general power factor correction (PFC) control IC as its controller and performs both PFC and output power regulation, simultaneously. Therefore, the proposed converter provides a simple structure and an economic implementation and achieves a high power factor without the need for any separate PFC circuit. In this paper, the operational principle of the proposed converter is explained in detail and the design guideline of the proposed converter is briefly shown. Experimental results for a 40-W prototype are shown to validate the performance of the proposed converter.

• 한국전자통신학회논문지
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• 제11권11호
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• pp.1093-1100
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• 2016

본 연구는 슈퍼캐패시티 EDLC(:Electric double layer capacitor)를 적용한 가로등용 태양광-풍력 하이브리드 발전시스템 성능의 우수함과 안정성을 입증하고자 한다. 독립전원용 태양광-풍력 하이브리드 발전시스템의 부하로 LED 광원을 이용한 조명장치를 적용하고 고출력 발전시스템을 통한 가로등 시스템 장치의 개발을 목표로 하고 있다. 발전된 전력을 배터리에 저장하는데 있어서 보조장치로 적용될 EDLC는 기존의 컨트롤러와는 달리 배터리의 고출력과 긴 수명을 보장할 수 있어 기존장치에 비해 유지보수가 적게 들고 우수한 성능을 확보할 수 있다.

• 전기학회논문지
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• 제65권4호
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• pp.601-610
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• 2016

The light-emitting diode (LED) has been used in a variety of industrial fields and for general 0lighting purposes on account of its high efficiency, low power consumption and long lifespan. The LED is driven by direct current; therefore, an AC/DC converter is typically required for its use. An electrolytic capacitor is generally used for stabilizing DC voltage during use of the AC/DC converter. However, this capacitor has a short lifespan, which makes it a limiting factor in LED lighting. Furthermore, LED lighting requires a dimmable control to enable energy savings and fulfil a growing consumer demand. In this paper, the dimmable single-stage power factor correction (PFC) continuous conduction mode (CCM) flyback converter that employs no electrolytic capacitor is presented. The LC resonant filter is alternatively applied to reduce the 120[Hz] ripple on the output. And the optimum value of the LC resonant filter parameters considering both efficient and performance is analysed. Simulation and experimental results verify the satisfactory operation of the converter.

• 대한설비공학회:학술대회논문집
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• 대한설비공학회 2008년도 하계학술발표대회 논문집
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• pp.1167-1171
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• 2008

The flow and thermal performance of the skiving and louver fin type heat sinks for the cooling system of the small LED projector were experimentally evaluated. A small fan tester based on AMCA standards was used to control and measure the air flow rate into the heat sink. Three heat blocks were used to simulate the heat and light sources(red, green and blue) of the small LED projector. We measured the pressure drop, temperatures and input power at the specific air flow rate and discussed those results. As a result, it is found that the louver fin type heat sink has higher pressure drop and lower thermal resistance than the skiving type. From the comparison of the temperature of the heat block between skiving and louver fin type, the louver fin type heat sink was found to be more suitable for cooling the high power heat source than skiving type. The thermal performance of the fan-sink(louver fin type) system was discussed with the picture taken by a thermal video.

• Journal of Advanced Marine Engineering and Technology
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• 제38권6호
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• pp.737-743
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• 2014

본 논문에서는 기존 1kW 할로겐 탐조등을 대체하기 위한 고출력 LED 탐조등에 관하여 기술하였다. 설계사양은 KDS 6230-1046-1과 KS V 8469를 기준으로 하였으며, 요구 광도 800,000cd를 만족시키기 위하여 지향각 $6^{\circ}$의 렌즈를 사용하였다. 시제작 LED 탐조등의 방열은 공랭식으로써 팬이나 히트파이프를 사용하지 않았다. 시험결과, 시제작 LED 탐조등의 소비전력은 148W로 1kW 할로겐 탐조등에 비해 85% 절감되었으며, 중심광도는 945,000cd로써 KS V 8469를 만족하였다. 광효율은 기존 탐조등보다 4.7배 향상되었으며, 지향각, 색온도 및 연색성은 각각 $5.4^{\circ}$, 5,500K, 70이었다. LED 탐조등의 외함 온도는 $60^{\circ}C$ 이하이고, SMPS 주변 온도는 $50^{\circ}C$ 이하로 IEC 60092-306을 만족하였다.

• 해양환경안전학회지
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• 제19권6호
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• pp.681-687
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• 2013

본 연구에서는 240 W급 고출력 LED 집어등의 특성을 기존 메탈 집어등과 비교하여 배광 패턴의 특성 및 광효율을 분석하고, 파장 대역의 특성을 해양 투과 특성 및 시감도를 고려하여 집어등 광원으로써 적정성을 분석하였다. 색온도 6500 K, white LED 패키지를 적용한 240 W LED 집어등의 특성을 보면 배광각은 ${\pm}45^{\circ}$, 조도 변화률이 0.8로 개선되었으며, 광효율은 98.8 lm/W로 향상되었다. LED 집어등의 해수의 투과율과 인간의 암순응시 시감도를 1,500 W 메탈등 1개와 4개의 240 W LED 집어등에 적용하여 비교한 결과, 방사출력이 수심 50 m에 이르면 거의 동등하였으며, 암순응시 시감도만을 적용한 경우에도 LED 집어등이 약 5 % 정도 높은 광속을 나타내었으며, 수심 50 m의 방사출력에 암순응시 시감도를 적용한 경우 LED 집어등의 광속이 14 % 높게 나타나 메탈등의 대체 가능성을 확인할 수 있었다.