• 대한전기학회:학술대회논문집
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• 대한전기학회 2001년도 춘계학술대회 논문집 전기기기 및 에너지변환시스템부문
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• pp.293-296
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• 2001

A conventional power supply to drive a microwave oven has ferro-resonant transformer and high voltage capacitor(HVC). Though it is simple, transformer is bulky, heavy and has low-efficiency. To improve this defect, a high frequency inverter type power supply has been investigated and developed in recent years. But, because of additional control circuit and switching device, inverter-type power supply is more expensive than conventional one. In this study, The design procedure of a novel HVC embedded high frequency transformer is proposed for down-sizing and cost reduction of Inverter-type power supply. Also, equivalent circuit mode] is derived by FEM analysis and impedance measurements. And the operation of proposed HVC embedded transformer is verified by simulations and experimental results.

• 대한전기학회논문지:시스템및제어부문D
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• 제49권4호
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• pp.175-182
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• 2000

The back-light inverter used in the laptop computer is designed in this paper. It has been difficult for electromagnetic transformer to enhance the efficiency and compact profile of the inverter. In this paper, (1) the piezoelectric transformer (PT) is used for reducing the loss; (2) the volumes of core and winding coil are used in electromagnetic transformer, and (3) the half-bridge series parallel resonant circuit is used in the driver of the inverter. The modified PT for this paper and the equivalent circuit are supported by the simulation program. The result of the experiment shows more than 91% improvement in terms of the efficiency.

• Journal of Power Electronics
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• 제2권2호
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• pp.112-123
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• 2002

This paper presents a novel prototype of the utility AC power interfaced soft-switching sinewave pulse modulated inverter using the high-frequency flyback for the small scale distributed renewable energy power conditioner. The proposed cricuit with a high-frequency isolation link has a funtion of electrical isolation, which is more cost-effective and reliable for the small-scale distributed renwal energy utilization system from a safety point of riew. The discontinuous conduction mode(DCM) operation of the high-frequency flyback transformer is adopted to establish a simple and low-cost circuit configuration and control scheme. For the simplicity, the circuit operating principle is described on the basis of the modified conventional full bridge inverter, whitch is the typical conventional high-frequency full-bridge inverter employing the high requency flyback transformer to eanble the effictive function of the electrical isolation. Than, the new circuit topology of the unility-interfaced soft-switching sinewave pulse modulated inverter using IGBTs is proposed. The proposed cricuit topology is additionally composed of the auxiliary power regenerating snubber cricuits, which are also mathematically analyzed for the parameter desigen settings. Finally, the performance of the propose inverter is evaluated on the basis of computer-aid simulation. It is noted that the sinewave pulse modulated output current of the inverter is synchronous to the AC main voltage.

• 전기학회논문지
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• 제56권10호
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• pp.1744-1750
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• 2007

This paper addresses grid interconnection tests of a 3kW transformer-less photovoltaic (PV) inverter to verify the effectiveness of the PV inverter and promote its wide use. The 3kW transformer-less PV inverter, which was equipped with intelligent protection and control system, was manufactured. A hardware test bed was constructed for performance tests of the PV inverter. Control performance and grid protection tests were carried out using the test bed. Test results verify the performance of the power control and grid protection functions of the developed transformer-less PV inverter.

• Journal of Power Electronics
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• 제11권5호
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• pp.677-687
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• 2011

In this paper a cycloconverter-type high frequency transformer link inverter with a reduced switch count is analyzed and designed. The proposed topology consists of an H-bridge inverter at the transformer's primary side and a cycloconverter with three bidirectional switches at the secondary. All of the switches of the cycloconverter operate in non-resonant zero voltage and zero current switching modes. To overcome a high voltage surge problem resulting from the transformer leakage inductance, phase angle control based on natural commutation is employed. The effectiveness of the proposed inverter is verified by constructing s 750W prototype. Experimentally, the inverter is able to supply a near sinusoidal output voltage with a total harmonic distortion of less than 1%. For comparison, a PSpice simulation of the inverter is also carried out. It was found that the experimental results are in very close agreement with the simulation.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2007년도 하계학술대회 논문집
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• pp.512-514
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• 2007

The number of transformers and the size of transformers in inverter using 3-phase transformer could be reduced compare with a multi-level inverter using single phase transformer. but still the 3-phase transformer inverter needs many switches. In this study, we proposed the isolated multi-level inverter using 3-phase transformers and common arm. Also, the equal-area method is used to calculate conduction angle with switching frequency equal to output fundamental frequency and it can reduce harmonics component of output voltage and switching loss. Finally, We tested multi-level inverter to clarify electric circuit and reasonableness through Matlab simulation and experiment by using prototype inverter.

• 조명전기설비학회논문지
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• 제28권4호
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• pp.29-35
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• 2014

The purpose of high frequency transformer in the inverter is to reduce the voltage and current stresses of switch components when it operates at the large conversion ratio. But the loss of transformer is the major contributor in the efficiency of inverter. This paper presents the method of core design to minimize the loss of transformer. The total loss of transformer is minimized by adjusting the effective cross-sectional areas of core. The component ratio of losses are compared by using the finite-element analysis.

• 전력전자학회논문지
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• 제13권2호
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• pp.96-102
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• 2008

LCD TV의 대형화에 따라 하나의 백라이트용 냉음극 방전램프(Cold Cathode Fluorescent Lamp ; CCFL)를 이용한 백라이트는 휘도의 한계가 있어 대형 디스플레이에서는 여러 개의 램프를 사용하여 필요한 휘도를 만들고 있다. 본 논문에서는 냉음극 방전램프 4개를 동시 구동하는 인버터 트랜스포머의 설계 기준을 제시한다. 제시된 기준에 따라 각기 다른 램프의 특성에도 동일한 관전류 출력을 보장하는 인버터 트랜스포머를 설계할 수 있다. 제안된 기준에 따라 설계된 트랜스포머를 실제 42인치용 LCD-TV용 대형 백라이트에 적용하여 실험을 통해 유용성을 검증한다.

• 마이크로전자및패키징학회지
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• 제16권1호
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• pp.39-43
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• 2009

CCFL 구동용 인버터 모듈 개발을 위해, 내부전극 층수에 따른 Rosen-type 적층형 압전변압기를 제작하였으며, 내부전극 층수에 따른 출력 및 효율을 분석하였다. 압전변압기용 원료로는 PZT계 상용원료를 사용하였으며 구동회로는 Half-bridge 방식을 적용하여 압전인버터 모듈을 제작하였다 제작된 압전인버터 모듈의 입력전압은 12.5 V이고 스위칭 주파수는 104.3 KHz로서 압전인버터 구동시 약 100배의 승압비를 얻었으며, 효율은 87%이다.

• 전기학회논문지
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• 제58권12호
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• pp.2359-2369
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• 2009

The study on the multi-level inverter has been increasingly progressing to reduce the switching loss and improve the THD of output current in photovoltaic inverter. Recently, the main topics of multi-level inverter are to reduce the number of devices maintaining the power quality. Therefore, the novel topology was proposed for these problem which is composed of the isolated H-bridge multi-level inverter using the three phase low frequency transformer. The proposed multi-level inverter may not be need for a independent DC power, diode and capacitor. Specially, It has a advantage in generating high voltage source. The proposed approach is verified through simulation and experiment.