• Journal of Power Electronics
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• v.17 no.6
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• pp.1413-1421
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• 2017

In order to control the output voltage in a dual active bridge converter, this paper establishes a theoretical inductor current equation for a dual-pulse-width-modulation scheme that ensures low switching loss. It also proposes a modulation strategy that minimizes conduction loss. When compared to the conventional single-pulse-width-modulation strategy, the proposed approach can reduce the inductor current RMS and improve efficiency in the low power region, as verified through simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2001.07a
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• pp.205-210
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• 2001

A new single stage power factor corrected AC/DC converter has been proposed, that is unified with buck topology and suitable for universal input. The design example of the proposed converter lot 5V 12A application has been presented. The design considerations and simulation results for the proposed converter have been shown. The simulation results show that the line input current harmonics can meet IEC 1000-3-2 Class D requirements for the line input voltage from 90 to 260V.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.17 no.4
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• pp.20-25
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• 2003

This paper presents the PFC method for an electronic ballast using SEPIC converter. Generally, the Boost Converter Type PFC has a DC 400V and output voltage is a bigger than input rms voltage. But the SEPIC type converter has above 0.95 Power Factor and wanted output voltage. This paper employs the SEPIC(Single Ended Primary Inductance Converter) Converter for PFC and the Ring core for oscillating method. Consequently, We reduced element's size and capacity in a converter with minimum voltage for the operating lamp.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.64 no.1
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• pp.29-34
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• 2015

DC bus electrolytic capacitors are used in variety of equipments as smoothing element of the power converters because it has high capacitance for its size and low price. It is responsible for frequent breakdowns of many static converters and inverter drive systems. Therefore it is important to diagnosis monitoring the condition of an electrolytic capacitor in real-time to predict the failure of power converter. In this paper, the on-line remote diagnosis monitoring system for DC BUS electrolytic capacitors of power converter using low-cost type Zigbee communication modules is developed. To estimate the health status of the capacitor, the equivalent series resistor(ESR) of the component has to be determined. The capacitor ESR is estimated by using RMS computation using AC coupling method of DC link ripple voltage/current. The Zigbee communication-based experimental results show that the proposed remote DC capacitor diagnosis monitoring system can be applied to DC/DC converter and UPS successfully.

• Proceedings of the KIEE Conference
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• 1996.07a
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• pp.388-391
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• 1996

The conventional high frequency phase-shifted full bridge DC-DC converter has a disadavantage that a circulating current flows through transformer and switching devices during the freewheeling interval Due to this circulating current, RMS current stress, conduction losses of transformer and switching devices are increased. To alleviate this problem, this study provides a novel circulating current free type high frequency soft switching phase-shifted full bridge DC-DC converter which applies the energy recovery snubber(ERS) attached at the secondary side of transformer. The ERS adopted in this study is consisted of three fast recovery diode($Ds_1$, $Ds_2$, $Ds_3$), two resonant capacitor($Cs_1$, $Cs_2$) and a small resonant inductor [(Lr) : It can be ignored because the transformer leakage inductance(Ll) is able to use in stead of inserting the resonant inductor(Lr)]

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.400-409
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• 2001

A new phase-shifted parallel-input/series-output(PISO) dual converter for tush-power step-up applications has been proposed. Since the proposed converter shows a low switch turn-off voltage stress, switching devices with low conduction loss can be employed in order to improve the power conversion efficiency. Moreover, it features a low output capacitor root-mean-square(RMS) current stress, low input current and output voltage ripple contents, and fast control-to-output dynamics compared to its PWM counterpart. In this paper, the operation of the proposed converter is analyzed in detail and its mathematical models and steady-state solutions are presented. A comparative analysis with the conventional PWM PISO dual converter is also provided. To confirm the operation, features, and validity of the Proposed converter, experimental results from an 800W, 24-350Vdc prototype are presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.25 no.4
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• pp.319-328
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• 2020

The recent use of distributed power generation systems constructed with DC-DC converters has become extremely popular owing to the rising need for environment friendly energy generation power systems. In this study, a new single-phase five-level inverter for off-grid applications constructed with a multilevel DC-DC step-up converter is proposed to boost a low-level DC voltage (36 V-64 V) to a high-level DC bus (380 V) and invert and connect them with a single-phase 230 V rms AC load. Compared with other traditional multilevel inverters, the proposed five-level inverter has a reduced number of switching devices, can generate high-quality power with lower THD values, and has balanced voltage stress for DC capacitors. Moreover, the proposed topology does not require multiple DC sources. Finally, the performance of the proposed topology is presented through the simulation and experimental results of a 400 W hardware prototype.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.199-200
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• 2016

Multi-level Dual Active Bridge (ML-DAB) 컨버터는 높은 스위칭 패턴 자유도를 가져 인덕터 전류의 첨두치와 RMS를 효과적으로 감소시킬 수 있다. 본 논문에서 3-레벨 NPC DAB 컨버터의 동작원리를 분석하고, 비대칭적인 스위칭 패턴을 적용시켜 인덕터 전류의 첨두치를 수학적으로 분석하여 컨버터의 전력변환 효율을 높일 수 있는 동작점 설계 방법을 제안한다. 여러 동작점에 따른 전류 RMS 값을 비교하여 제안하는 동작점 설계 방법의 타당성을 검증하고자한다.

• The Transactions of the Korean Institute of Electrical Engineers P
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• v.58 no.4
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• pp.483-489
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• 2009

Electrolytic capacitors are used in variety of equipments as smoothening element of the power converters because it has high capacitance for its size and low price. Electrolytic capacitors, which is most of the time affected by aging effect, plays a very important role for the power electronics system quality and reliability. Therefore it is important to estimate the parameter of an electrolytic capacitor to predict the failure. This objective of this paper is to propose a new method to detect the rise of equivalent series resistor(ESR) in order to realize the online failure prediction of electrolytic capacitor for DC output filter of power converter. The ESR of electrolytic capacitor estimated from RMS result of filtered waveform(BPF) of the ripple capacitor voltage/current. Therefore, the preposed online failure prediction method has the merits of easy ESR computation and circuit simplicity. Simulation and experimental results are shown to verify the performance of the proposed on-line method.

• The Transactions of the Korean Institute of Power Electronics
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• v.5 no.5
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• pp.508-514
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• 2000

A single-stage power factor correction AC/DC converter with a simple link voltage suppressing circuit (LVSC) for the universal line application is proposed. Using this simple circuit, a low link voltage can be realized without deadbands at line zero-crossings. The proposed converter is analyzed and a prototype converter with 5V, 12A output is implemented to verify the performance. The experimental results show that the link voltage stress and efficiency are about 447V and 81%, respectively.