• 한국정보통신설비학회:학술대회논문집
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• 2007.08a
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• pp.423-426
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• 2007

An active Balun is designed for RFID reader at 2.45GHz. The Balun is integrated inside the receiver, then the LNA and mixer can be connected. The unbalanced LNA output signal is transformed to a balanced signal at the input mixer The RF mixer and LO mixer, by using this balun. The Balun provided a balanced signal with two output stage, gain mismatch is 0.116dB. The phase show a good behavior with $163.918^{\circ}$,$-16.609^{\circ}$. The phase mismatch is about $0.527^{\circ}$. The tight difference between the gain and phase on each brancd, is because of the used capacitor and integrated inductor and the other parasitic element inside the balun.

• Proceedings of the KIPE Conference
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• 2001.12a
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• pp.194-197
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• 2001

In this paper, the design method of LCL filter at the AC input side of a voltage fed active power filter is proposed. The characteristics of harmonics suppression and current control performance of active power filter are described using the analysis of the relation of these characteristics and DC voltage, switching frequency, and AC inductor values. The design examples are shown and the validity of the proposed design method is verified through the PSIM simulation.

• JSTS:Journal of Semiconductor Technology and Science
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• v.3 no.1
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• pp.42-46
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• 2003

In this paper, an MMIC broadband amplifier for wireless communication systems has been developed by using an active feedback method. This active feedback operates at much higher frequencies than a method by a spiral inductor feedback and its size is independent of the inductance value. The MMIC broadband amplifier was designed using a $0.5{\;}{\mutextrm{m}}$ MESFET library. The fabricated chip area was $1.4{\;}mm{\;}{\times}{\;}1.4{\;}mm. Measurement showed a gain of 18 dB with a gain flatness of ${\pm}3$ dB in a 1.5 GHz~3.5 GHz band. The maximum output power and the minimum noise figure were 14 dBm and 2.5 dB in the same band, respectively.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2000.06a
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• pp.1204-1209
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• 2000

Many analytical and experimental studies on the active suppression of nonlinear panel flutter by using piezoceramic patch have been carried out. However, these active control methods have a few important problems; a large amount of power is required to operate actuators, and additional apparatuses such as sensor systems and controller are needed. In this study passive suppression schemes for nonlinear flutter of composite panel, which is believed to be more robust suppression system than active control in practical operation, are proposed by using piezoelectric inductor-resistor series shunt circuit. Toward the end, a finite element equation of motion for an electromechanically coupled system is proposed using the Hamilton's principle. To achieve the best damping effect, optimal shape and location of the piezoceramic(PZT) patches are determined by using genetic algorithms. The results clearly demonstrate that the passive damping scheme by using piezoelectric shunt circuit can effectively attenuate the flutter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.57 no.2
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• pp.214-220
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• 2008

Most of converter system could obtain almost unity power factor and make input current sinusoidal waveform, but they have many problems, such as electromagnetic interference and switching losses caused by switching noise in main switch. To solve these problems in hard switching PFC converter, soft switching converter using a resonant between capacitor and inductor is invented In this paper, advantages and disadvantages of conventional ZVT(Zero-Voltage-Transition) soft switching converter using a auxiliary resonant circuit is discussed. Then Improved ZVT soft switching converter proposed. This improved ZVT converter's operation principal, specific property, design scheme of main are described. From Simulation and experiment results of conventional ZVT soft switching and improved ZVT soft switching converter with active snubber, characteristics of the converter are confirmed.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.2039-2041
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• 1998

In this paper, Operation characteristics of the active clamp(ACL) zero-voltage-switching(ZVS) forward converter(FC) and active clamp hard- switching(HS) forward converter are compared with respect to loss analysis. The losses of semiconductor (including conduction losses and switching losses), transformer(containing the core loss and copper loss) and parasitic element of passive element (capacitor, inductor) are measured and compared for each type. For an experiment we have built 50W ACL ZVS-FC and ACL HS-FC, in which the switching frequency is 200kHz, and test it. The experimental results show that both types of operation have nearly same characteristics.

• Proceedings of the KIPE Conference
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• 2004.11a
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• pp.59-63
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• 2004

In this paper, active forward converter with snubber circuit - composed of a tapped inductor, a snubber capacitor, two diodes - is proposed. By adding the snubber circuit, ZVS operation became possible even in a smaller magnetizing current conditions than the conventional converter. The operational principles and the equivalent mode analysis of the proposed converter is described and compared to conventional converter. We constructed the prototype active clamped forward converter with 300W output capacity and verified that efficiency of the proposed converter is higher than the conventional converter.

• Proceedings of the KSR Conference
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• 2004.10a
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• pp.1341-1346
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• 2004

Basic design for single-phase active power filter, which aims at railway applications provided with PWM-controlled converters, is comprehensively studided and its performance is presented in this paper, Active power filters are used to compensate railway signaling and public telecommunication interference due to the high-order harmonic currents generated in railway traction locomotives. A type of hybrid digital filter which is composed of low pass filter and high pass filter is proposed so that the desired harmonic reference current with accurate magnitude and phase shift can be extracted from catenary line current. A design criteria to determine input inductor L and output capacitor C is also described, considering voltage, current. PWM pattern, and switching frequency of the main converters, Finally, computer simulation and DSP-based experiments resulted from laboratory test are presented.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.240-241
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• 2017

멀티레벨 방식의 Dual Active Bridge 컨버터는 기존의 컨버터와 비교하여 높은 자유도의 스위칭 방식을 가진다. 본 논문에서는 멀티 레벨 방식의 DAB 컨버터의 동작원리를 분석하고, 인덕터 전류의 RMS 값과 THD를 최소화하기 위하여 기본파를 제외한 3 고조파와 5 고조파를 감쇄하는 스위칭 방식을 제안한다. 다양한 스위칭 패턴에 따른 인덕터 전류 RMS 값과 THD를 비교하여 제안하는 스위칭 방식의 타당성을 검증하고자 한다.

• Journal of Power Electronics
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• v.18 no.1
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• pp.137-146
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• 2018

This paper describes a single pulse-width modulation control strategy using the Single Pulse-Width Modulation (SPWM) method with a soft-switching technique for a wide range of output voltages from a bidirectional Dual-Active Bridge (DAB) converter. This method selects two typical inductor current waveforms for soft-switching, and proposes a rule that makes it possible to achieve soft-switching without any compensation algorithm from the waveforms. In addition, both the step-up and step-down conditions are analyzed. This paper verifies that the leakage inductance is independent from the rule, which makes it easier to apply in DAB converters. An integrated algorithm, which includes step-up and step-down techniques, is proposed. The results of experiments conducted on a 50-kW prototype are presented. The system efficiency is experimentally verified to be from 85.6% to 97.5% over the entire range.