• 조명전기설비학회논문지
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• 제21권4호
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• pp.61-72
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• 2007

This study proposed a high efficiency DC-DC converter with a new current doubler rectifier for fuel-cell systems for use with the Nexa(310-0027) PEMFC from the Ballard Co. The proposed high efficiency DC-DC converter for the fuel-cell system generated ZVS by applying partial resonance and using a phase shift PWM control method. Constantly switching frequency, loss of switching, peak current, and peak voltage were reduced by this system. In addition to this system, two inductors were attached to a rectifier circuit allowing it to be able to provide the direct current(DC) and DC voltage safely to a load with reduced ripple components. Also, by using the newly proposed current doubler rectifier, the high frequency DC-DC converter for the fuel cell system was capable of reaching a highest efficiency of 92[%] as compared to 88.3[%] efficiency in previous results, which means that efficiency increased 3.7[%]. The overall results were confirmed by a simulation and laboratory experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2006년도 전력전자학술대회 논문집
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• pp.366-368
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• 2006

The conventional 3-Level LLC Converter using frequency-control has a disadvantage of designing magnetic components. To overcome this problem, a new constant frequency phase-shift controlled three-level LLC converter is proposed. Moreover, by employing voltage doubler type rectifier, an additional resonant capacitor is not needed. Therefore, this converter is promising for the high-power, high-voltage application with simple structure.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2003년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.276-280
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• 2003

This paper presents a zero voltage and zero current switching (ZVZCS) interleaving two-transistor forward converter for high input voltage and high power application. A phase shift has a disadvantage that a circulating current and RMS current stress, conduction losses of transformer and switching devices increases. Due to this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved interleaving two-transistor forward Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor a snubber capacitor and two snubber diodes attached at the secondary side of transformer. The proposed ZVZCS converter is verified on a 1.8kW, 5kHz experimental prototype.

• ETRI Journal
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• 제30권4호
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• pp.495-505
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• 2008

This paper presents a parallel processing searcher structure for the initial synchronization of a direct sequence ultra-wideband (DS-UWB) system, which is suitable for the digital implementation of baseband functionalities with a 1.32 Gsample/s chip rate analog-to-digital converter. An initial timing acquisition algorithm and a data demodulation method are also studied. The proposed searcher effectively acquires initial symbol and frame timing during the preamble transmission period. A hardware efficient receiver structure using 24 parallel digital correlators for binary phase-shift keying DS-UWB transmission is presented. The proposed correlator structure operating at 55 MHz is shared for correlation operations in a searcher, a channel estimator, and the demodulator of a RAKE receiver. We also present a pseudo-random noise sequence generated with a primitive polynomial, $1+x^2+x^5$, for packet detection, automatic gain control, and initial timing acquisition. Simulation results show that the performance of the proposed parallel processing searcher employing the presented pseudo-random noise sequence outperforms that employing a preamble sequence in the IEEE 802.15.3a DS-UWB proposal.

• Journal of Electrical Engineering and Technology
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• 제8권4호
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• pp.951-958
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• 2013

This paper proposes the controller design for a stability improvement of an on-board battery charger. The system is comprised of a power factor correction (PFC) circuit and phase shift full-bridge DC-DC converter. The PFC circuit performs the control of the DC-link voltage and the input power factor. The DC-DC converter regulates the voltage and the current in the battery using the DC-link voltage. This paper proposes the design method of PI controller for the PFC circuit using a small signal model. The analysis and design of a type-three controller for the DC-DC converter is also presented. A simulation and experiment has been performed on the on-board battery charger and their results are presented to verify the validity of the proposed system.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.543-547
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• 2000

Power factor and harmonics are increasingly important for high speed train auxiliary block. This paper presents experimental results of the power factor and harmonic performance of two parallel PWM circuits under various supply and load conditions. For reducing harmonics the harmonic content is eliminated by the phase shift between two converters switching phase. Experimental results show the usefulness of the proposed method and applicability to PWM converter in auxiliary block of high speed train.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2001년도 Proceedings ICPE 01 2001 International Conference on Power Electronics
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• pp.7-10
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• 2001

This paper provides a solution for the problem of efficiency decrease caused by load variation. A novel control scheme of tracking the PT's operation frequency for the maximum efficiency is proposed. As a result, a high efficiency over $80\%$ has been achieved even under the output-current decrease down to $10\%$ of the full load current.

• ETRI Journal
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• 제26권4호
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• pp.307-314
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• 2004

The application of a discrete pseudomorphic high electron mobility transistor (p-HEMT) as a grounded switch allows for the development of low cost phase shifters and phase modulators operating in a Ku band. This fills the gap in the development of phase control devices comprising p-i-n diodes and microwave monolithic integrated circuits (MMICs). This paper describes a discrete p-HEMT characterization and modeling in switching mode as well as the development of a low-cost four-bit phase shifter and direct quadrature phase shift keying (QPSK) modulator. The developed devices operate in a Ku band with parameters comparable to commercially available MMIC counterparts. Both of them are CMOS compatible and have no power consumption. The parameters of the QPSK modulator are very close to the requirements of available standards for satellite earth stations.

• Journal of Power Electronics
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• 제16권4호
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• pp.1245-1255
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• 2016

The single resonant inverter is widely employed in typical inductive power transfer (IPT) systems to generate a high-frequency current in the primary side. However, the power capacity of a single resonant inverter is limited by the constraints of power electronic devices and the relevant cost. Consequently, IPT systems fail to meet high-power application requirements, such as those in rail applications. Total harmonic distortion (THD) may also violate the standard electromagnetic interference requirements with phase shift control under light load conditions. A power regulation approach with selective harmonic elimination is proposed on the basis of a parallel multi-inverter to upgrade the power levels of IPT systems and suppress THD under light load conditions by changing the output voltage pulse width and phase shift angle among parallel multi-inverters. The validity of the proposed control approach is verified by using a 1,412.3 W prototype system, which achieves a maximum transfer efficiency of 90.602%. Output power levels can be dramatically improved with the same semiconductor capacity, and distortion can be effectively suppressed under various load conditions.

• 전자공학회논문지D
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• 제36D권1호
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• pp.15-21
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• 1999

저위상 변화 감쇄기를 이용한 RF 자동 이등 조정 증폭기 설계 방법을 제시하였다. RF 자동 이등 조정 증폭기를 사용함으로써, 증폭기의 출력 레벨을 일정하게 유지할 수 있으며 그 오차는 0.1dB 이하로 하였다. 이러한 장점 외에도, 임의의 RF 입력전력에 대하여 증폭기의 이득을 고정할 수도 있다. 만약 일정한 이득이 얻어진다면 원하는 혼변조 왜곡(IMD: Inter-modulation Distortion)을 얻는데 좀 더 신뢰성 있는 증폭기를 만들 수 있다.