• 전기학회논문지
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• 제56권1호
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• pp.88-99
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• 2007

In this paper, a novel new pulse power generator based on IGBT stacks is proposed for pulse power application. Because it can generate up to 60kV pulse output voltage without any step- up transformer or pulse forming network, it has advantages of fast rising time, easiness of pulse width variation and rectangular pulse shape. Proposed scheme consists of series connected 9 power stages to generate maximum 60kV output pulse and one series resonant power inverter to charge DC capacitor voltage. Each power stages are configured as 8 series connected power cells and each power cell generates up to 850VDC pulse. Finally pulse output voltage is applied using total 72 series connected IGBTs. To reduce component for gate power supply, a simple and robust gate drive circuit is proposed. For gating signal synchronization, full bridge invertor and pulse transformer generates on-off signals of IGBT gating with gate power simultaneously and it has very good characteristics of short circuit protection.

• 전력전자학회논문지
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• 제25권4호
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• pp.261-268
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• 2020

Transformer saturation in full bridge (FB) isolated DC-DC converters is caused by uneven switching speeds and voltage drops in semiconductor devices and mismatched gate signals. In order to prevent transformer saturation, most popular and widely used approach is to insert a capacitor in series with the transformer windings. This study conducts extensive analyses on transformer saturation and the effect of DC blocking capacitors when they are placed in the primary or secondary windings of a transformer. The effect of the DC blocking capacitors is verified in voltage-fed and current-fed FB converters.

• 한국정보기술응용학회:학술대회논문집
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• 한국정보기술응용학회 2005년도 6th 2005 International Conference on Computers, Communications and System
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• pp.233-235
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• 2005

Non-contact power supply (NCPS), as a clean and safe energy supply concept has been applying wildly. Comparing with the conventional transformer the non-contact transformer has a large air gap between the long primary winding and the secondary winding. Due to it, the non-contact transformer has increased leakage inductance and reduced magnetizing inductance. So the high frequency series resonant converter has been widly used on the non-contact power supply system for transferring the primary power to the secondary one, from what a high influence voltage can be gained on the secondry coil even though the large air gap exists. However, it still has the disadvantages of the load sensitive voltage gain characteristics when load is changing. In this paper, we propose a fuzzy logic controller to adjust the frequency of the inverter to track the resonat which is changing when the load is change.

• 한국초전도ㆍ저온공학회논문지
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• 제2권2호
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• pp.37-43
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• 2000

This paper describes the construction and test results of a 10kVA single phase HTS transformer. Double pancake windings with BSCCO-2223 HTS tape and G10-FRP cryostat with room temperature bore are used in the transformer. Two double pancake windings are connected in series to provide 188 turns and other two double pancake windings are connected in parallel to conduct the secondary current of 45.4[A]. Coefficients of the constructed transformer are obtained using the fundamental teats of the transformer. According to the test results, larger leakage reactance than expected is observed due to the bulky core which surrounds the sryostat.

• 대한전기학회:학술대회논문집
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• 대한전기학회 2000년도 추계학술대회 논문집 학회본부 B
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• pp.321-323
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• 2000

This paper describes the construction and test results of a 10kVA single phase HTS transformer. Double pancake windings with BSCCO-2223 HTS tape and GFRP cryostat with room temperature bore are used in the transformer. Two double pancake windings are connected in series to provide 184 turns and two double pancake windings are connected in parallel to conduct the secondary current of 45.4A. Coefficients of the constructed transformer are obtained using the fundamental tests of the transformer. According to the test results, larger leakage reactance than expected is observed due to the bulky core which surrounded the cryostat.

• Journal of Power Electronics
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• 제13권3호
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• pp.329-338
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• 2013

In this paper, the charging characteristics of series resonant type high voltage capacitor chargers considering the transformer stray capacitance have been studied. The principles of operation for the four operational modes and the mode changes for the four different switching frequency sections are explained and analyzed in the range of switching frequency below the resonant frequency. It is confirmed that the average charging currents derived from the above analysis results have non-linear characteristics in each of the four modes. The resonant current, resonant voltage, charging current, and charging time of this capacitor charger as variations of the switching frequency, series parallel capacitance ratio ($k=C_p/C_s$), and output voltage are calculated. From the calculation results, the advantages and disadvantages arising from the parallel connection of this stray capacitance are described. Some methods to minimize charging time of this capacitor charger are suggested. In addition, the results of a comparative test using two transformers whose stray capacitances are different are described. A 1.8 kJ/s prototype capacitor charger is assembled with a TI28335 DSP controller and a 40 kJ, 7 kV capacitor. The analysis results are verified by the experiment.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2012년도 전력전자학술대회 논문집
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• pp.189-190
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• 2012

최근 전기 자동차가 현실화 되면서 자동차 내부의 Li-Ion 배터리와 전장 부품들 및 납축전지 간의 에너지를 변환하는 회로에 대한 요구가 커지고 있다. 이 회로는 높은 전압을 갖는 Li-Ion 배터리와 낮은 구동 전압을 갖는 다른 전장 부품들로 인해 출력 단이 대 전류를 취한다는 특징을 갖고 있는데 이로 인하여 출력 단의 도통 손실을 줄이기 위한 연구들이 계속되고 있다. 본 논문은 기존의 2 Transformer 형식의 브릿지 컨버터를 Parallel-Series로 연결시킨 회로를 제안하고 이 회로의 동작을 분석하였다. 제안한 회로는 2차 측에 인덕터가 존재하지 않는 Current-Fed방식으로 구동 되며, 이를 통해 도통 손실을 감소 시켰으며, 2차 측을 Series 형태로 쌓아 배터리 연계 시스템에서 문제가 되었던 Wide Range 입. 출력 시스템에서의 동작 문제를 해결하였다.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.505-508
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• 2000

A coreless printed circuit board(PCB) transformer is employed in a contactless energy transfer circuit that achieves an efficient power conversion at the presence of a considerable airgap between the source and the load side. A half-bridge series resonant converter is selected as the contactless energy transfer circuit in order to minimize the detrimental effects of large leakage inductance small magnetizing inductance and poor coupling coefficient of the coreless PCB transformer. The operation and performance of the proposed contactless power converter are verified on a 7 W experimental circuit that provides an 18V/0.4A output from a 210-370 V input source.

• Journal of Power Electronics
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• 제14권5호
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• pp.882-889
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• 2014

This paper presents a zero voltage switching (ZVS) converter with three resonant tanks. The main advantages of the proposed converter are its ability to reduce the switching losses on the power semiconductors, decrease the current stress of the passive components at the primary side, and reduce the transformer secondary windings. Three resonant converters with the same power switches are adopted at the low voltage side to reduce the current rating on the transformer windings. Using a series-connection of the transformer secondary windings, the primary side currents of the three resonant circuits are balanced to share the load power. As a result, the size of both the transformer core and the bobbin are reduced. Based on the circuit characteristics of the resonant converter, the power switches are turned on at ZVS. The rectifier diodes can be turned off at zero current switching (ZCS) if the switching frequency is less than the series resonant frequency. Therefore, the reverse recovery losses on the rectifier diodes are overcome. Experiments with a 1.6kW prototype are presented to verify the effectiveness of the proposed converter.

• 전력전자학회논문지
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• 제4권3호
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• pp.231-239
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• 1999

변압기로써 결합된 직렬공진 부하를 가진 전압원-인버터(Voltage-Source Inverter)가 공진주파수로 작동되는 경우에 출력 전류를 제어하는 기법으로서, 개선된 전류조절형 델타변조(Current-Regulated Delta Modulator; CRDM)방식을 제안한다. 일반적인 CRDM은, 전류편차가 상당한 크기로 나타난다는 문제가 있으며, 특히 유도가열장치와 같이 부하가 변압기를 통하여 연결되는 경우에는 변압기의 자속포화 문제가 발생하므로 실제 사용에 한계가 있다. 이러한 문제를 해결하기 위하여, 자속포화 현상을 분석하고 이를 방지하기 위한 간단한 방법을 제안하며, 전류편차를 제거하기 위한 적분형 CRDM을 적용한다. 그리고 슬라이딩 모드 제어의 개념을 이용하여, 안정된 동작을 보장하는 적분기 이득의 상한치를 회로특성치로부터 구하는 방법을 제안하고, 제안된 기법의 효용성을 시뮬레이션과 실험으로써 확인한다.