• Journal of the Korean Institute of Telematics and Electronics D
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• v.35D no.11
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• pp.46-54
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• 1998

A planar Bi-Sb multijunction thermal converter, which is consisted of a linear or bifilar thin film NiCr-heater and a thin film Bi-Sb thermopile, has been fabricated, and its ac-dc transfer characteristics were examined in a frequency range from 10 Hz to 10 KHz. In order to increase the thermal sensitivity and to decrease the ac-dc transfer error of a thermal converter, the heater and the hot junctions of a thermopile were prepared on a Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$-diaphragm which acts as a thermal isolation layer, and the cold junctions on the Si$_3$N$_4$/SiO$_2$/Si$_3$N$_4$-thin film supported with the silicon rim which functions as a heat sink. The respective thermal sensitivities in air and in a vacuum of the converter with a built-in bifilar heater were about 14.0 ㎷/㎽ and 54.0 ㎷/㎽, and the ac-dc voltage and the current transfer difference ranges in air were about $\pm$0.60 ppm and $\pm$0.11 ppm, respectively, indicating that the ac-dc transfer accuracy of the converter are much higher than that of a commercial 3-dimensional multijunction thermal converter. However, the output thermoelectric voltage fluctuation of the converter was rather high.

• Journal of IKEEE
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• v.23 no.3
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• pp.1003-1014
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• 2019

In this paper, we modeled the devices used easily in PV system circuits. Simulation tools use PSPICE to enable intuitive electrical circuit simulations. Simulations were also performed on the effects of temperature and spatial radiation that are easy to overlook when using solar cells using modelled libraries. In addition, for full operation of the photovoltaic system, a complete operation system for the DC-DC buck-boost converter and the MPPT(Maximum Power Point Tracking) control system was modeled and simulated to confirm good operation. In order to verify the operation of the simulation, we constructed an actual system with the same conditions in the simulation and experimented. As a result, we proposed a single-phase 3 kW grid-connected solar power converter.

• Journal of Broadcast Engineering
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• v.16 no.5
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• pp.793-796
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• 2011

H.264/AVC compresses video data by applying DCT transform, quantization and entropy coding processes to the residual signal obtained by inter/intra prediction. This paper proposes a method enhancing an existing DC offset adjustment technology which uses information of neighboring blocks to reduce residual information for improving coding efficiency. DC offset information is not sent over bitstreams, but calculated in the same way both in the decoder and in the encoder. Experimental results show that the proposed method enhances coding efficiency by 0.25% in average BD-Rate compared to H.264/AVC and gives better or worse coding efficiency compared to the existing DC offset method depending on video sequences with coding efficiency degradation by 0.09% in average BD-Rate. This experimental results also show that further coding efficiency improvement is possible by applying the proposed method adaptively to slice or macroblock coding units.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1217-1219
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• 2003

신 발전 방식들 중 하나인 용융탄산염형 연료전지 발전시스템 개발과 관련하여, 연료전지로부터 생성된 전력을 전력계통에 안정되게 변환, 주입하기 위한 계통연계형 전력변환기를 설계하고 단위기기별 성능 시험을 수행한 결과이다. 100kW급 전력변환기의 구조 설계에 있어서는, 100kW급 용융탄산염형 연료전지 시스템의 정격 사양 및 스택의 운전 형태에 따라 새로운 시뮬레이션 결과의 검토를 통해 DC/DC 컨버터부, 정류부, 인버터부의 회로 구성을 확정하고, 각 부에 사용될 소자들을 연료전지 출력 및 운전 사양에 맞게 설계하였다.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.7 s.361
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• pp.1-8
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• 2007

The DC characteristics of GaAs Gunn diode are investigated as a preliminary study on the planar grade gap injector GaAs Gunn diode which is the transferred electron device with high output power and dc-rf conversion efficiency. The Gunn devices we fabricated were confirmed to have the DC characteristics of negative differential resistance(NDR). We discussed the nature of the NDR effect, including the electron intervalley transfer; the NDR effect was examined for six different cathode radii.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.46 no.2
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• pp.93-100
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• 2009

This paper presents a step up four channel DC-DC converter using charge pump voltage doubler structure. Our goal is to design and implement DC-DC converter for capacitive SP4T RF MEMS switch in front end module in wireless transceiver system. Charge pump structure is small and consume low power 3.3V input voltage is boosted by DC-DC Converter to $11.3{\pm}0.1V$, $12.4{\pm}0.1V$, $14.1{\pm}0.2V$ output voltage With 10MHz switching frequency. By using voltage level shifter structure, output of DC-DC converter is selected by 3.3V four channel selection signals and transferred to capacitive MEMS devices. External passive devices are not used for driving DC-DC converter. The total chip area is $2.8{\times}2.1mm^2$ including pads and the power consumption is 7.52mW, 7.82mW, 8.61mW.

• Journal of KIISE:Software and Applications
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• v.31 no.3
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• pp.379-386
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• 2004

Video segmentation is a fundamental task in video indexing and it includes two kinds of shot change detections such as the abrupt transition and the gradual transition. The abrupt shot boundaries are detected by computing the image-based distance between adjacent frames and comparing this distance with a pre-determined threshold value. However, the gradual shot boundaries are difficult to detect with this approach. To overcome this difficulty, we propose the method that detects gradual transition in the MPEG compressed video using the HMM (Hidden Markov Model). We take two different HMMs such as a discrete HMM and a continuous HMM with a Gaussian mixture model. As image features for HMM's observations, we use two distinct features such as the difference of histogram of DC images between two adjacent frames and the difference of each individual macroblock's deviations at the corresponding macroblock's between two adjacent frames, where deviation means an arithmetic difference of each macroblock's DC value from the mean of DC values in the given frame. Furthermore, we obtain the DC sequences of P and B frame by the first order approximation for a fast and effective computation. Experiment results show that we obtain the best detection and classification performance of gradual transitions when a continuous HMM with one Gaussian model is taken and two image features are used together.

• Proceedings of the KIPE Conference
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• 2012.07a
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• pp.333-334
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• 2012

본 논문은 LED 구동회로에서 DC/DC 컨버터회로를 분산하여 저발열, 부피저감이 가능한 새로운 구조의 LED 구동회로를 제안한다. 제안된 회로의 특징은 기존 벅컨버터에서 발열이 높고 부피가 큰 부품들을 제거하여 발열을 낮추고 부피를 줄이는 효과가 있다. 또한 전력을 분산시킴으로써 기존회로보다 소자의 전압, 전류스트레스가 감소한다. 제안한 회로를 검증하기 위해 이론적 분석결과를 통해 타당성을 검토하였고 전장용 LED 구동회로에 적용하여 실험을 통해 우수성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2015.11a
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• pp.93-94
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• 2015

본 논문에서는 전기자동차 응용을 위한 양방향 전류원 인버터를 제안한다. 본 논문에서는 회로 DQ변환에 의하여 얻어진 DC 등가회로를 바탕으로 3상 시스템의 DC 특성을 보이고 직류측 전류, 전압과 같은 변수에 대한 식을 유도한다. 본 논문에서는 시뮬레이션을 통하여 제안된 양방향 전류원 인버터가 전기자동차 응용에 적합하게 사용될 수 있음을 확인한다.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.118-120
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• 2009

본 논문에서는 직접 전력변환방식의 단상 sag/swell 보상기를 구현하였다. 제안된 보상기는 정현파 입력/ 출력 필터, 직렬연결 변압기와 dc 링크 커패시터부가 없는 단상 back-to-back PWM컨버터로 구성되어 있다. 이 보상기의 장점은 dc-link 진해 커패시터가 제거되어 전력회로부가 간단하게 구현되어 향상된 신뢰성 및 내구성을 확인 할 수 있으며 동시에 단상 전압 sag/swell을 보상하며 스위칭 손실을 줄이는 간단한 PWM 방법을 들 수 있다. 더구나, 제안된 방법은 일반적인 직접 전력변환방식에서 요구되어지는 복잡한 4-step 전류 방법이 필요 없는 간단한 전류제어방법을 채용할 수 있는 구조이며 제안된 보상기의 구조와 PWM 방법의 타당성을 프로토타입 하드웨어를 제작하여 실험결과로 보상기의 우수성을 확인하였다.