• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.11a
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• pp.294-295
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• 2006

Field sequential liquid crystal display (FSLCD) has advantages such as a high transmittance due to no use of color filter and high color reproductivity because of LED backlight for a luminance source. However, to realize FSLCD response time of the LCD must be below 5ms. In this paper, we have chosen electrically controlled birefringence (ECB) mode for this application and studied film compensation to improve the operating voltage and viewing angle and to achieve a fast response time optimizing the condition of the discotic film and TAC film, operating voltage decreases to 5V, and viewing angle range is $160^{\circ}$ at horizontal and vertical direction, respectively and $120^{\circ}$ in diagonal direction. (contrast ratio > 10:1) and optimized cell exhibits a fast response time of 4ms in most grey levels.

• 한국정보디스플레이학회:학술대회논문집
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• 2008.10a
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• pp.1529-1531
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• 2008

Since the discovery over a decade ago, carbon nanotubes (CNTs) have been attracting considerable attentions both from scientists and engineers. Because of the excellent field emission properties, such as high aspect ratio, extremely small diameter, and high emission current, CNTs become a potential candidate as field emitter for field emission display (FED) and lighting (FEL) as backlight for LCD. Due to the exceptional physical properties, such as superior thermal and electrical conductivities, as well as high stiffness and strength, the CNT-based composites can be as light-weight heat-sink or thermal spreader materials used for power electronic devices, such as power LED for general illumination. The CNTs for above applications will be reviewed, and related materials and devices will be demonstrated in this paper.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.504-507
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• 2006

현재 LCD(Liquid Crystal Display)용 광원으로서 주로 냉음극 방전램프(CCFL : Cold Cathode Fluorescent Lamp)가 사용되고 있으며, 그 외 LED를 비롯해서 외부전극 방전램프(EEFL: External Electrode Fluorescent Lamp), 면광원(FFL : Flat Fluorescent Lamp), 전계 방출램프(FEL : Field Emission Lamp)등 다른 광원에 대한 적용도 활발히 진행되고 있다. 본 논문에서는 멀티램프 구동이 유리하여 인버터 개수를 줄일 수 있는 장점을 가지고 있는 EEFL을 사용하였으며, 변압기의 자체 손실을 줄이고 소형화가 가능하며, 높은 승압 비를 갖는 압전 변압기를 병렬로 연결하여 멀티램프 구동이 가능하도록 하였다. 최적의 EEFL 구동회로를 구성하기 위해서 Push-Pull 타입의 압전 인버터를 설계하였으며, 설계된 인버터 회로에 대한 시뮬레이션 분석을 수행하고, 향후 여러 형태의 구동 방법을 적용하므로 서 압전 변압기로도 대화면 멀티 램프 구동용 인버터의 제작이 가능함을 제시하였다.

• The Transactions of the Korean Institute of Power Electronics
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• v.17 no.1
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• pp.34-40
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• 2012

In this paper, voltage clamped tapped-inductor boost converter with high voltage conversion ratio is proposed. The conventional tapped-inductor boost converter has a serious drawback such as high voltage stresses across all power semiconductors due to the high resonant voltage caused by the leakage inductor of tapped inductor. Therefore, the dissipative snubber is essential for absorbing this resonant voltage, which could degrade the overall power conversion efficiency. To overcome these drawbacks, the proposed converter employs a voltage clamping capacitor instead of the dissipative snubber. Therefore, the voltage stresses of all power semiconductors are not only clamped as the output voltage but the power conversion efficiency can also be considerably improved. Moreover, since the energy stored in the clamp capacitor is transferred to the output side together with the input energy, the proposed converter can achieve the higher voltage conversion ratio than the conventional tapped-inductor boost converter. Therefore, the proposed converter is expected to be well suited to various applications demanding the high efficiency and high voltage conversion ratio. To confirm the validity of the proposed circuit, the theoretical analysis and experimental results of the proposed converter are presented.

• Journal of the Korean institute of surface engineering
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• v.47 no.5
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• pp.233-238
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• 2014

In this paper, in order to achieve slim and light liquid crystal display, we examine the optical conditions that can obtain uniform light with higher optical efficiency over whole light guide plate (LGP) through simulation. Furthermore, to overcome the issues of hot spot in front of red, green, and blue light emitting diodes (RGB LEDs) source and non-uniform color mixing, we propose four shaped color mixing bars tied up with the LGP and check the optical characteristics of the LGP with them by simulation. Consequently, we could know the optical conditions of improving optical efficiency and optical uniformity in the LGP through the optical design. Also we confirmed that the issues of the hot spot and non-uniform color mixing in edge type LED could be solved by using the ${\bigwedge}$-shaped window color mixing bar.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.28 no.5
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• pp.344-349
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• 2015

A new information society of late has arrived by the rapid development of various information & communications technologies. Accordingly, mobile devices which are light and thin, easy and convenient to carry on the market. Also, the requirements for the larger television sets such as fast response speed, low-cost electric power, wider visual angle display are sufficiently satisfied. The currently most widely studied display material, the Organic Light-emitting Diodes(OLEDs) overwhelms the Liquid Crystal Display(LCD), the main occupier of the market. This new material features a response speed of more than a thousand times faster, no need of backlight, a low driving voltage, and no limit of view angle. And the OLEDs has high luminance efficiency and excellent durability and environment resistance, quite different from the inorganic LED light source. The OLEDs with simple device structure and easy produce can be manufactured in various shapes such as a point light source, a linear light source, a surface light source. This will surely dominate the market for the next generation lighting and display device. The new display utilizes not the glass substrate but the plastic one, resulting in the thin and flexible substrate that can be curved and flattened out as needed. In this paper, OLEDs device was produced by changing thickness of Teflon-AF of hole injection material layer. And as for the electrical properties, the four layer device of ITO/TPD/$Alq_3$/BCP/LiF/Al and the five layer device of ITO/Teflon AF/TPD/$Alq_3$/BCP/Lif/Al were studied experimentally.

• Proceedings of the Korean Vacuum Society Conference
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• 2013.02a
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• pp.312-312
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• 2013

GaN based light emitting diodes (LEDs) are important devices that are being used extensively in our daily life. For example, these devices are used in traffic light lamps, outdoor full-color displays and backlight of liquid crystal display panels. To realize high-brightness GaN based LEDs for solid-state lighting applications, the development of p-type ohmic electrodes that have low contact resistivity, high optical transmittance and high refractive index is essential. To this effect, indiumtin oxide (ITO) have been investigated for LEDs. Among the transparent electrodes for LEDs, ITO has been one of the promising electrodes on p-GaN layers owing to its excellent properties in optical, electrical conductivity, substrate adhesion, hardness, and chemical inertness. Sputtering and e-beam evaporation techniques are the most commonly used deposition methods. Commonly, ITO films on p-GaN by sputtering have better transmittance and resistivity than ITO films on p-GaN by e-bam evaporation. However, ITO films on p-GaN by sputtering have higher specific contact resistance, it has been demonstrated that this is due to possible plasma damage on the p-GaN in the sputtering process. In this paper, we have investigated the advanced sputtering using plasma damage-free p-electrode. Prepared the ITO films on the GaN based LEDs by e-beam evaporation, normal sputtering and advanced sputtering. The ITO films on GaN based LEDs by sputtering showed better transmittance and sheets resistance than ITO films on the GaN based LEDs by e-beam evaporation. Finally, fabricated of GaN based LEDs by using advanced sputtering. And compared the electrical properties (measurement by using C-TLM) and structural properties (HR-TEM and FE-SEM) of ITO films on GaN based LEDs produced by e-beam evaporation, normal sputtering and advanced sputtering. As a result, It is expected to form plasma damage free-electrode, and better light output power and break down voltage than LEDs by e-beam evaporation and normal sputter.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.22 no.2
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• pp.263-267
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• 2013

The continuing demand for increasingly slimmer and brighter liquid crystal display (LCD) panels has led to an increased focus on the role of light guide panels (LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit (BLU). The most basic process in the production of such BLU components is the micromachining of V-shaped grooves. Thus, given the current trend, micromachining of V-shaped grooves is expected to play increasingly important roles in today's manufacturing technology. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with V-shaped grooves. High-aspect-ratio patterns are required to reduce the number of sheets and enhance light efficiency, but there is a limit to the aspect ratio achievable for a given material and cutting tool. Therefore, this study comprised a series of experimental evaluations conducted to determine the machining limit in microcutting V-shaped grooves on electroless nickel plated die materials when using single-crystal diamond tools with point angles of $20^{\circ}-80^{\circ}$. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools. The experimental results are that V-shaped patterns with angles of $80^{\circ}$ or up can be realized regardless of the machining conditions and equipment. Moreover, the feed rate has little effect on machinability, and it is thought that the fly-cut method is more efficient for shallow patterns.