• International Journal of Control, Automation, and Systems
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• 제6권2호
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• pp.180-185
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• 2008

A new method for relative error continuous and discrete time model order reduction is proposed. The reduction technique is based on two recently developed methods, namely frequency domain balanced truncation within a frequency bound and inner-outer factorization techniques. The proposed method is of interest for practical model order reduction because in this context it shows to keep the accuracy of the approximation as high as possible without sacrificing the computational efficiency. Numerical results show the accuracy and efficiency enhancement of the method.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 하계학술대회 논문집 B
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• pp.1148-1150
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• 2003

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. To improved these, a large number of soft switching topologies included a resonant circuit has been prosed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose a high power factor and high efficiency DC-DC converter using single-pulse soft switching by partial resonant switching node. The switching devices in a prosed circuit are operated with soft switching by the partial resonant method, that is, Partial Resonant Switch Mode Power Converter. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used. Some simulative results on computer results are included to confirm the validity of the analytical results.

• Journal of Power Electronics
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• 제18권1호
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• pp.23-33
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• 2018

Silicon Carbide (SiC) MOSFET belongs to the family of wide-band gap devices with inherit property of low switching and conduction losses. The stable operation of SiC MOSFET at higher operating temperatures has invoked the interest of researchers in terms of its application to high power density (HPD) power converters. This paper presents a performance study of SiC MOSFET based two-phase interleaved boost converter (IBC) for regulation of avionics bus voltage in more electric aircraft (MEA). A 450W HPD, IBC has been developed for study, which delivers 28V output voltage when supplied by 24V battery. A gate driver design for SiC MOSFET is presented which ensures the operation of converter at 250kHz switching frequency, reduces the miller current and gate signal ringing. The peak current mode control (PCMC) has been employed for load voltage regulation. The efficiency of SiC MOSFET based IBC converter is compared against Si counterpart. Experimentally obtained efficiency results are presented to show that SiC MOSFET is the device of choice under a heavy load and high switching frequency operation.

• 전력전자학회논문지
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• 제24권4호
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• pp.237-243
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• 2019

A high-efficiency and small-sized switched-mode line transformer (SMLT) is proposed in this study. The conventional structure of an adapter is composed of line transformer and rectifiers. This structure has a limit in miniaturizing due to low-frequency line transformer. Another structure is composed of power factor correction (PFC) and DC/DC converter. This structure has a limit in reducing volume due to two-stage structure. As the proposed SMLT is composed of an LLC resonant converter, a high-frequency transformer can be adopted to achieve isolation standards and size reduction. This proposed structure has different operation modes in accordance with line input voltage to overcome poor line regulation. In addition, the proposed SMLT is applied to the front of a conventional PFC converter, because the SMLT output voltage is restored to rectified sinusoidal wave by using a full-bridge rectifier in the secondary side. The design of the PFC converter is easy, because the SMLT output voltage is controlled as rectified sinusoidal wave. The validity of the proposed converter is proven through a 350 W prototype.

• Journal of the Optical Society of Korea
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• 제2권1호
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• pp.5-8
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• 1998

A high power diode-array-pumped slab Nd:YAG laser is described. The resonator consists of three mirrors in folded geometry. The laser is operated in acousto-optic Q-switching mode and intracavity frequency doubling is tried. We demonstrate that the laser exhibits frequency doubling efficiency of ∼60% with a type I LBO crystal.

• 한국컴퓨터정보학회논문지
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• 제3권3호
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• pp.73-81
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• 1998

본 논문에서는 의용영상의 병소부위 특징을 추출하여 판별 자동화할 수 있는 방안을 제안하였다. 전처리 과정으로서 의용영상의 형태정보는 입력영상을 DWT(Discrete wavelet transform)에 의해 4레벨 DWT 계수 행렬을 구하고 계수 행렬의 특징에 따라 저주파 계수 행렬로부터 저주파 특징 파라미터 32개, 수평 고주파 계수 행렬로부터 수평 고주파특징 파라미터 16개, 수직 고주파 계수 행렬로부터 수직 고주파 특징 파라미터 16개, 그리고, 대각 고주파 계수 행렬로부터 대각 고주파 특징 파라미터 32개 등 모두 96개의 특징 파라미터를 추출하였다. 본 논문에서 제안된 알고리즘을 이용하면 자동 판별 시스템을 구축할수 있고, PACS의 성능 향상에 크게 기여할 것이다.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2005년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.134-139
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• 2005

This paper presents a cost effective quasi-resonant soft-switching PWM high frequency inverter with minimum circuit components. This inverter can achieve wider soft commutation, simpler power circuit configuration, smaller volumetric size, lower cost and wider power regulation range, higher-efficiency as compared with single ended quasi-resonant ZVS-PFM inverter and active voltage clamped quasi-resonant ZVS-PWM inverter. The operation principle of the proposed inverter is described on the basis of the simulation and experimental results, together with its operating performances in steady state. The operating performances of this unique proposed high frequency inverter based on ZVS and ZCS arms-related soft commutation principle is evaluated and discussed as compared with the active voltage-clamped ZVS-PWM inverter and a conventional single-ended ZVS-PFM inverter. The practical effectiveness of a novel type quasi-resonant soft-switching PWM high frequency inverter using IGBT is actually proved for consumer induction heated appliances as rice cooker, hot water producer, steamer and super heated steamer. The extended bidirectional circuit topology of quasi-resonant PWM high frequency inverter with minimum circuit components is demonstrated, which operate as the direct frequency changer.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 전력전자학술대회 논문집
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• pp.584-588
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• 2001

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage Capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, A new pulse power supply for Microwave Oven using novel HVC embedded high frequency transformer is proposed for down-sizing, cost reduction, and efficiency emprovement of Inverter type power supply. Also, equivalent circuit model is derived by impedance measurements. And the operation of proposed pulse power supply is verified by simulations and experimental results.

• 한국정밀공학회지
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• 제15권11호
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• pp.233-243
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• 1998

The demand of high speed machining is increasing due to the high speed cutting and grinding provides high efficiency of process, short process time, improved metal removal capacity and better surface finish. Active magnetic bearings allow much high surface speed than conventional ball bearings and therefore greatly suitable for high speed cutting or grinding. This paper describes a design process of an active magnetic bearing system for a high speed grinding spindle with power 5.5kW and maximum speed 60,000rpm. Magnetic actuators are designed by the magnetic circuit theory considering static load condition, and examined with FEM analysis. Dynamic characteristics are also considered, such as bandwidth, stiffness, natural frequency and static deflection. System characteristics are simulated with a rigid rotor model.

• 조명전기설비학회논문지
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• 제14권6호
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• pp.1-5
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• 2000

최근 디지털 텔레비젼전 및 고해상도(High Definition) 텔레비전용 표시장치로 교류형 풀랴즈마 디스플레이가 각광 받고 있다. 상용화되고 있는 교류형 플라즈마 디스플레이의 구조를 보면 3전극행 면방전형(three electrodes surface discharge type)이 주류이다. 재의 효율은 11m/W의 수준으로 본격적인 상용화를 위해서는 효율의 향상이 관건이다. 효율 향상올 위해서는 패널 구조(Panel structure)의 개선도 필요하지만 주어진 구조에서 최대한의 효율을 갖도록하는 구동방법의 최적화가 선결 과제이다. 교류형 플라즈마 디스플레이의 방전 이미지는 연속되는 방전 발광에 의해 이루어 진다. 대부분의 전략 소모는 연속되논 발광을 위한 유지 방전에서 소모되기 때운에 유지방전의 파형의 최적화는 고 방전 효율을 위한 중요한 과제이다. 구동 방식으로서는 ADS(Address and Display period Separated) 구동이라는 방식이 일반적으로 널리 쓰이고 있다. 이 구동법의 평균 유지방전 주파수는 수십 [kHz]이지만 실제 주파수는 100[kHz]에서 200[kHz] 사이의 상당히 높은 값이다. 본 연구 결과에 따르면 형광체가 가시광을 방출시킬 때 형광체 재료의 특성상 감쇄시간(Decay Time)이 수 ms에 이른다. 만약 감쇄 시간이 유지방전 펄스으 주기보다 길다면 방전에서 만들어진 진공자외선(Vacuum Ultra Violet Rav)이 가시광으로 변환애 효과적으로 이용되지 못한다. 결국 발광 효율은 유지방전 주파수에 비례하여 감소한다. 결론적으로 말해 저 주파수 유지 방전으로 발광효율을 크게 개선할 수 있다.