• Journal of Power Electronics
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• 제18권1호
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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.

• 제어로봇시스템학회:학술대회논문집
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• 제어로봇시스템학회 2005년도 ICCAS
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• pp.1132-1136
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• 2005

In this paper, adaptive equalizer receiver for a turbo code direct sequence code division multiple access (DSCDMA) by using least mean square (LMS) adaptive algorithm is presented. The proposed adaptive equalizer is using soft output of decision feedback adaptive equalizer (DFE) to examines the output of the equalizer and the Log- maximum a posteriori (Log-MAP) algorithm for the turbo decoding process of the system. The objective of the proposed equalizer is to minimize the bit error rate (BER) of the data due to the disturbances of noise and intersymbol interference (ISI)phenomenon on the channel of the DS-CDMA digital communication system. The computer program simulation results shown that the proposed soft output decision feedback adaptive equalizer provides a good BER than the others one such as conventional adaptive equalizer, infinite impulse response adaptive equalizer.

• 대한전기학회논문지:전기기기및에너지변환시스템부문B
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• 제49권12호
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• pp.813-820
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode converter is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode converter and guarantee zero-current-switching(ZCS) of the switch over the wide load range. The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. In addition, control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations and experiments.

• 한국통신학회논문지
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• 제35권7C호
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• pp.587-593
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• 2010

본 논문에서는 extrinsic information transfer (EXIT) chart를 이용하여 다중 안테나 시스템에서 irregular low-density parity-check (LDPC) code를 설계하는 방법을 기술한다. 다중 안테나 기반의 Irregular LDPC code 설계를 위하여 maximum a posteriori probability (MAP) 방식의 다중 안테나 검출 방식이 사용되었으며 수신기는 다중 안테나 검출기와 LDPC 복호기 사이에서 복호된 soft 정보를 주고 받는 turbo iterative 구조를 가정하였다. 다중 안테나 기반의 irregular LDPC code의 edge degree 분포는 EXIT chart와 linear optimization programming 기법을 사용하여 얻을 수 있으며 컴퓨터 시뮬레이션을 통하여 제안된 방법으로 설계된 irregular LDPC code의 성능을 다양한 환경에서 검증하였다.

• ETRI Journal
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• 제33권5호
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• pp.661-669
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• 2011

In this paper, we propose an efficient soft-output signal detection method for spatially multiplexed multiple-input multiple-output (MIMO) systems. The proposed method is based on the ordered successive interference cancellation (OSIC) algorithm, but it significantly improves the performance of the original OSIC algorithm by solving the error propagation problem. The proposed method combines this enhanced OSIC algorithm with a multiple-channel-ordering technique in a very efficient way. As a result, the log likelihood ratio values can be computed by using a very small set of candidate symbol vectors. The proposed method has been synthesized with a 0.13-${\mu}m$ CMOS technology for a $4{\times}4$ 16-QAM MIMO system. The simulation and implementation results show that the proposed detector provides a very good solution in terms of performance and hardware complexity.

• 전력전자학회논문지
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• 제22권2호
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• pp.140-149
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• 2017

This study proposes a new type of active-clamp forward-flyback converter with two transformers that operate in forward and flyback modes during on and off times, respectively, instead of not using an output inductor. The main switch can be turned on with zero-voltage switching (ZVS) using the leakage inductance of the transformer and the output capacitor of the main switch. The leakage inductance should be increased to ZVS. However, the ringing between the leakage inductance of the transformer and the parasitic output capacitance of the secondary side rectifier switches results in a serious voltage spike. A forward-flyback converter employing auxiliary inductor and auxiliary diode is proposed to overcome the problem. The operational principles are analyzed in detail and validated through experiments with a 385 V-to-53 V/37 A prototype.

• 한국자기학회:학술대회 개요집
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• 한국자기학회 2005년도 하계학술연구발표회 논문개요집
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• pp.42-43
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• 2005

• ETRI Journal
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• 제25권1호
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• pp.1-8
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• 2003

This paper introduces an efficient iterative decoding method for high-dimensional block turbo codes. To improve the decoding performance, we modified the soft decision Viterbi decoding algorithm, which is a trellis-based method. The iteration number can be significantly reduced in the soft output decoding process by applying multiple usage of extrinsic reliability information from all available axes and appropriately normalizing them. Our simulation results reveal that the proposed decoding process needs only about 30% of the iterations required to obtain the same performance with the conventional method at a bit error rate range of $10^{-5}\;to\;10^{-6}$.

• 전력전자학회:학술대회논문집
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• 전력전자학회 1998년도 전력전자학술대회 논문집
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• pp.401-404
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• 1998

This paper proposes a new soft switching single stage AC/DC full bridge converter with unit power factor and isolated output. This circuit shows that it is possible to combine the boost converter which is for PFC(Power Factor Correction) and full bridge converter which is for DC/DC converter. A simple auxiliary circuit which includes neither lossy components nor active switches eliminates ringing of secondary side of the transformer. The characteristics of the proposed circuit are investigated and the validity is verified by the simulation results.

• Journal of Power Electronics
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• 제2권3호
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• pp.199-205
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• 2002

This paper compares three kinds of soft-switching circuits from viewpoints of surge suppression, load characteristic, and power efficiency for a tapped-inductor buck converter with low voltage and high current. As a result, these soft-switching techniques have achieved much higher efficiency of 80 % when compared with a hard-switching buck converter for the output condition of 1V and 20A.