• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 추계학술대회 논문집
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• pp.159-163
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• 2001

A new and high-efficient energy-recovery circuit is proposed to drive a Plasma display panel (PDP) and compared with the conventional circuit. The Proposed circuit uses only two inductors and no auxiliary circuit to recover the energy stored in the equivalent intrinsic capacitance of Plow DP so that it feartures a very simple structure, small volume, fewer power devices. production cost and high efficiency. Besides, the light emitted from PDP is very stable and uniform. It is suitable for wall-hanging color TVs. The proposed circuit, operating at 200kHz, is verified to be applicable on a 42-inch PDP by an experiment.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 하계학술대회 논문집 Vol.7
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• pp.81-82
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• 2006

The purposes of the present study are to produce a high thermal efficient of oil-based nanofluids which can be used as ultra-high voltage transformer oil, and to investigate their thermal and physical properties under static and dynamic conditions. Three kinds of nanofluids are prepared by dispersing $Al_2O_3$ or AlN nanoparticles in transformer oil. The thermal conductivities of the nanoparticles-oil mixtures increase with temperature, particle volume concentration and thermal conductivity of solid particle itself. It was quite important to eliminate $H_2O$ as byproducts of esterification and excess oleic acid which did not form stable chemical bonds with powder surface to get high dispersion stability.

• Current Optics and Photonics
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• 제1권5호
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• pp.525-528
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• 2017

High-energy, high-power, quasi-continuous wave (QCW) operation of double-clad Yb fiber lasers incorporating an incoherent signal combiner is reported. We constructed four efficient, high-power Yb fiber lasers, each of which produced rectangular pulses at 1080 nm with a pulse energy greater than 15 J, and a pulse duration of 10 ms at a repetition rate of 10 Hz, corresponding to an average power of over 150 W and a peak power of over 1.5 kW for ~200 W of incident pump power at 915 nm. These laser outputs were combined by a homemade incoherent fiber signal combiner with low loss, yielding a maximum peak power of ~6.0 kW in a beam with $M^2{\approx}12.5$. The detailed laser characteristics and prospects for further power scaling in QCW operation are discussed.

• Journal of information and communication convergence engineering
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• 제2권4호
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• pp.243-246
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• 2004

Currently, advanced countries invest lots of efforts to develop improvement of electric power production and supply, confronting environmental problems and new energy development. They set up long term plan focusing on electric power transmission infrastructure construction technology, establishment of the customer care service network using electric technologies, improvement of economic productivity by innovative electric technology, prevention of global warming gas and clean and efficient energy use etc. Comparing to those countries, the level of technologies that we have are in behind and moreover, technological resources are limited. Therefore, Korea is required to reconsider efficient distribution of R&D investment by concentrating on limited R&D resources to important technologies which could be stepping stone to gain competitive advantage. It can be done through comparative analysis of electric technologies among advanced countries and analysis of electric technology development policy.

• ETRI Journal
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• 제35권2호
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• pp.226-233
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• 2013

This paper presents a two-stage power-efficient class-AB operational transconductance amplifier (OTA) based on an adaptive biasing circuit suited to low-power dissipation and low-voltage operation. The OTA shows significant improvements in driving capability and power dissipation owing to the novel adaptive biasing circuit. The OTA dissipates only $0.4{\mu}W$ from a supply voltage of ${\pm}0.6V$ and exhibits excellent high driving, which results in a slew rate improvement of more than 250 times that of the conventional class-AB amplifier. The design is fabricated using $0.18-{\mu}m$ CMOS technology.

• 대한전자공학회:학술대회논문집
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• 대한전자공학회 2008년도 하계종합학술대회
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• pp.519-520
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• 2008

In this paper, we design and implement the monolithic zero crossing detection power factor correction IC using a high voltage 30V BCD process. The ZCD PFC IC is designed for power applications, such as notebook, LCD monitor, etc. It includes power factor correction function and several protection circuit, regulator, high-voltage high current output drivers. And also, the designed IC has restart timer function which the output pulse is generated if the output signal of IC is not in a 200us. The simulation results show that the designed IC acts properly as power factor correction IC with efficient protective functions.

• 전력전자학회논문지
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• 제14권5호
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• pp.397-405
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• 2009

최근 대화면 및 슬림화를 위한 LCD TV의 전원장치는 고집적화와 고효율에 대한 연구가 이슈가 되고 있고, 이를 위해 Multi-phase LLC 공진컨버터가 연구되고 있으며 본 논문에서는 제어회로를 간단화 하면서 300W Two Phase Interleaved LLC 공진컨버터를 제안 적용한 실험결과에 대하여 서술하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2003년도 춘계전력전자학술대회 논문집(1)
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• pp.227-230
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• 2003

In this paper, a full bridge edge-resonant zero voltage mode based soft-switching PWM DC-DC power converter with a high frequency center tapped transformer link stage is presented from a practical point of view. The power MOSFETS operating as synchronous rectifier devices are implemented in the rectifier center tapped stage to reduce conduction power losses and also to extend the transformer primary side power MOSFETS ZVS commutation area from the rated to zero-load without a requirement of a magnetizing current. The steady-state operation of this phase-shift PWM controlled power converter is described in comparison with a conventional ZVS phase-shift PWM DC-DC converter using the diodes rectifier. Moreover, the experimental results of the switching power losses analysis are evaluated and discussed in this paper. The practical effectiveness of the ZVS phase-shift PWM DC-DC power converter treated here is actually proved by using 2.5kW-32kHz breadboard circuit. An actual efficiency of this converter is estimated in experiment and is achieved as 97$\%$ at maximum.

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2009년 추계학술발표대회
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• pp.32-32
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• 2009

Electric Resistance Welding (ERW) process is the most efficient process to manufacture the linepipe. To develop the high performance ERW linepipe using the high strength and the high alloy steels, the modulation of input power waveform such as sinusoidal waveform is introduced because the conventional ERW technology is not sufficient enough to produce the high quality linepipe due to its strength and high alloy contents (high Ceq). In this article, the material used for the experiment was API X60 with 8.2mm thickness, and ERW simulator at POSCO was used to develop a waveform control system for the power modulation. The frequency of power modulation was varied from 50Hz to 150Hz with the fixed amplitude of ${\pm}2%$ power. The non-modulated power input and the modulated power input cases are conducted to demonstrate the variation of the narrow gap length and the arcing frequency due to power modulation. From results of the non-modulated power input case, the excessive power causes the longer narrow gap length and the low arcing frequency due to the large heat input and the strong electro magnetic force that increase the weld defect. On the contrary, the small narrow gap length and the high arcing frequency reduce the weld defect. After modulating the power input with 50Hz and 100Hz at the fixed power, the arcing frequency increases, but the narrow gap length does not change much. The high arcing frequency prevents the formation of weld defect because the sweeping frequently cleans the oxides on the narrow gap edges. As a result, the manufacturing window can be expanded by the power modulation that provides the stable ERW process for the quality improvement of the linepipe made from the high strength/high alloy steels.

• 대한전자공학회논문지TC
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• 제45권1호
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• pp.110-114
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• 2008

본 논문에서는 단일 FET를 이용하여 2.14GHz/5.2GHz 이중대역 고효율 Class F 전력증폭기를 설계 구현하였다. 전송선로를 이용하여 초기의 정합값을 적절히 이동시켜 하나의 능동소자로 2.14GHz/5.2GHz의 이중대역에서 동작되는 전력증폭기를 설계하였으며, 2.14GHz에서 32.65dBm의 출력과 11dB의 출력이득 36%의 전력효율을, 5.2GHz에서 7dB의 출력이득의 특성을 보였다. 고조파를 제어 회로를 설계하여 증폭기의 출력단에 추가 하여 Class F로 동작하는 이중대역 전력증폭기를 설계 하였다. 이중대역 Class F 전력증폭기는 2.14GHz에서 9.9dB의 출력이득과 30dBm의 출력, 55%의 전력효율을 가졌으며, 5.2GHz에서 11.7dB의 출력이득을 갖는 특성을 보였다. 고조파 제어 회로를 이용한 이중대역 Class F 전력증폭기가 전력효율을 향상시킴을 보였다.