• Proceedings of the KIPE Conference
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• 2015.07a
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• pp.191-192
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• 2015

본 논문은 고승압 컨버터의 고밀도화를 위해 Boundary Conduction Mode(BCM)로 동작하는 고주파 전압 클램프 탭 인덕터 부스트 컨버터를 제안한다. 제안된 회로는 모든 반도체 소자가 특정 전압에 클램프 되므로 기존 고승압 탭 인덕터 부스트 컨버터에 비해 손실 스너버가 없어 고효율에 유리하고 전압 스트레스가 낮은 장점을 갖는다. 또한 BCM 동작으로 인해 영전압 스위칭이 보장될 뿐만 아니라 전압 클램프 탭 인덕터에 의해 다이오드 역회복 문제를 해결할 수 있어 1MHz의 고주파 구동이 가능하다. 따라서 전원회로에서 큰 부피를 차지하는 리액티브 소자의 사이즈를 대폭 감소시킬 수 있어 고밀도 전원회로의 구현이 가능한 강점을 갖는다. 제안 회로의 타당성 검증을 위하여 이론적인 분석과 LED TV Backlight 구동용 20W급 시작품의 실험 결과를 제시한다.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.2
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• pp.476-484
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• 2010

Recently, as the piezoelectric transformer technology develops, piezoelectric transformer may become a variable alternative to magnetic transformers in various applications. Because it was have to favorable characteristics such as electromagnetic-noise free, compact size, higher efficiency, and superior power density, linkage flux, noiseless, etc. its resonance frequency was used to output waveform of a sine wave. In this paper, the switching mode power supply of about 87.2[KHz] is driven by the multilayer thickness vibration mode piezoelectric transformer and the DC to DC converter drive circuit using an electrical equivalent circuit is proposed. Also, it was possible to drive power source device of the high-luminance LED by propose circuits.

• Journal of the Korean Society of Clothing and Textiles
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• v.35 no.3
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• pp.292-303
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• 2011

This research suggested a draft proposal for a smart jacket design, which has applied wearable technologies to provide convenience in daily life. The smart jacket combined with a vest was the casual item for autumn and winter. The heating device was composed of the heating element, battery, controller, electric wire, connector, switch, and charger. A stable electronic conductor fiber of good heating effect with a flexible zigzag form has been selected for the heating element. The lighting device has been made in a way that attaches the LED and its power controller in the same mechanical device. As the result of the wearing test, the heating effect turned out to be effective in the order of: back, both the back and abdomen and only the abdomen. When wearing a smart jacket, the back and abdomen have been selected as favorable body parts for heating. Pockets and hems are selected as the adequate place to attach the LED lighting, and the brightness of LED lighting has turned out to be suitable and useful. Based on the test results, the first draft proposal has attached the heating element only in the back and its controller located in the inside pocket of the vest. In addition, the LED has been attached to the front pocket of the jacket. As to the second draft proposal, heating elements have been placed in the back and the abdomen. Each controller for the heating elements has been placed in the front and inside pocket of vest, and the LED lighting has been attached to the hem of the jacket. The smart jacket combined with a wearable device was assessed by functioning categories. The user showed a high satisfaction in the heating and illuminating function of a smart jacket.

• Proceedings of the Korean Institute of Information and Commucation Sciences Conference
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• 2008.05a
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• pp.713-716
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• 2008

This paper presents an automatic back-light brightness control system for mobile displays. One of the most important factors in mobile display is the power consumption due to the limited and movable power source. More than 80% of power of the LCD display is consumed by LED bark-light unit (BLU). The target brightness also becomes higher because of its moving picture and high resolution image, so there are some side effects for not only excessive power consumption but also ergonomic inconvenience in dark environment. To prevent this discomfort and reduce power consumption, this paper proposes automatic brightness control (ABC) technique in mobile displays. Developed system contains TFT-LCD panel with built-in photo sensor, driver IC capable of controlling photo sensor, and BLU. Since the photo sensor array built in panel detects automatically outdoor ambient light intensity, the power of BLU in dark environment is reduced. Developed ABC system showed reduced power consumption of 50% in dark environment. We believe that the proposed system is very useful to control power of mobile TFT-LCD.

• Journal of the Society of Naval Architects of Korea
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• v.53 no.2
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• pp.108-114
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• 2016

Recently, there has been a growing interest in marine leisure sports and high speed power boat for fishing. The prototype of 20 feet class power boat was developed and authors are joined in this government-led project. The research was performed to evaluate the optimal structure and design of the structural strength necessary to ensure the structural safety of the power boat. A new material ROCICORE fiber added to the mat and roving was adopted for high-power tenacity. ANSYS Workbench has been used to make the structural model, evaluate the strength and optimize the structural design. The response of the structure to quasi-static slamming loads according to the rules and regulations of ISO 12215-5, Lloyd’s Register of Shipping and Korean Register has been implemented and studied. An optimization study for the structural response is carried out by changing the plate thickness and section modulus of stiffeners. The power boat structure derived fuel efficiency is optimized by performing the best possible structural design to minimize the hull weight.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1513-1515
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• 2008

High efficiency phosphorescent organic light emitting devices ($PHOLED^{TM}s$) are now widely used in commercial displays. In this paper we describe some of the work behind the development of high efficiency stable green PHOLEDs capable of fulfilling display specifications.

• Proceedings of the Korean Vacuum Society Conference
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• 2011.02a
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• pp.147-147
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• 2011

High crystalline nonpolar a-plane (11-20) nitride light emitting diodes (LEDs) have been fabricated on r-plane (1-102) sapphire substrates by metalorganic chemical-vapor deposition (MOCVD). The multi-quantum wells (MQWs) active region is consists of 4 periods the nonpolar a-plane InGaN/GaN(a-InGaN/GaN) on a high quality a-plane GaN (a-GaN) template grown by using the multibuffer layer technique. The full widths at half maximum (FWHMs) of x-ray rocking curve (XRC) obtained from phiscan of the specimen that was grown up to nonpolar a-plane GaN LED layers with double crystal x-ray diffraction. The FWHM values were decreased down to 477 arc sec for $0^{\circ}$ and 505 arc sec for $-90^{\circ}$, respectively. After fabricating a conventional lateral LED chip which size was $300{\times}600{\mu}m^2$, we measured the optical output power by on-wafer measurements. N-electrode was made with Cr/Au contact, and ITO on p-GaN was formed with Ohmic contact using Ni/Au followed by inductively coupled plasma etching for mesa isolation. The optical output power of 1.08 mW was obtained at drive current of 20 mA with the peak emission wavelength of 502 nm.

• Korean Journal of Optics and Photonics
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• v.32 no.5
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• pp.230-234
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• 2021

Relief of thermal stress has received great attention, to improve the beam quality and stability of high-power laser diodes. In this paper, we investigate a microtrench structure engraved around a laser-diode chip-on-submount (CoS) to relieve the thermal stress on a laser-diode bar (LD-bar), using the SolidWorks® software. First, we systematically analyze the thermal stress on the LD-bar CoS with a metal heat-sink holder, and then derive an optimal design for thermal stress relief according to the change in microtrench depth. The thermal stress of the front part of the LD-bar CoS, which is the main cause of the "smile effect", is reduced to about 1/5 of that without the microtrench structure, while maintaining the thermal resistance.

• Transactions on Electrical and Electronic Materials
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• v.16 no.4
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• pp.201-205
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• 2015

This paper dealt with the condensing technology of an LED light source that uses a parabolic reflector to replace a searchlight equipped with a xenon lamp. A ray-tracing simulation was conducted to analyze the influence of the diameter of the reflector and the size of the light source on light condensing. The combination of a parabolic reflector with a diameter of 620 mm and a focal distance of 220 mm, and a 9 mm multi-chip package (MCP) with a luminous flux of 7,000 lm showed the narrowest beam angle. The luminous intensity at the center was measured at 7.7×10⁶ cd. The distance between the light source and the point where the illuminance was 1 lx was calculated to be 2.8 km. The power consumption of the system was 95 W, which is only 9.5% of that of the 1 kW xenon searchlight, and the beam angle was 1.03°. In a site experiment, it was confirmed that the light ray reflected from the LED searchlight proceeds forward without any diffusion because of the narrow beam angle.

• Korean Journal of Materials Research
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• v.23 no.3
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• pp.177-182
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• 2013

Nanosphere lithography is an inexpensive, simple, high-throughput nanofabrication process. NSL can be done in different ways, such as drop coating, spin coating or by means of tilted evaporation. Nitride-based light-emitting diodes (LEDs) are applied in different places, such as liquid crystal displays and traffic signals. The characteristics of gallium nitride (GaN)-based LEDs can be enhanced by fabricating nanopatterns on the top surface of the LEDs. In this work, we created differently sized (420, 320 and 140 nm) nanopatterns on the upper surfaces of GaN-based LEDs using a modified nanosphere lithography technique. This technique is quite different from conventional NSL. The characterization of the patterned GaN-based LEDs revealed a dependence on the size of the holes in the pattern created on the LED surface. The depths of the patterns were 80 nm as confirmed by AFM. Both the photoluminescence and electroluminescence intensities of the patterned LEDs were found to increase with an increase in the size of holes in the pattern. The light output power of the 420-nm hole-patterned LED was 1.16 times higher than that of a conventional LED. Moreover, the current-voltage characteristics were improved with the fabrication of differently sized patterns over the LED surface using the proposed nanosphere lithography method.