• Journal of Power Electronics
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• 제17권6호
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• pp.1445-1453
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• 2017

In this study, a new zero-voltage transition (ZVT) buck converter with coupled inductor using a synchronous rectifier and a lossless clamp circuit is proposed. The regular buck converter with tapped inductor has extended duty cycle for high step-down applications. However, the leakage inductance of the coupled inductor produced considerable voltage spikes across the switch. A lossless clamp circuit is used in the proposed converter to overcome this problem. The freewheeling diode was replaced with a synchronous rectifier to reduce conduction losses in the proposed converter. ZVT conditions at turn-on and turn-off instants were provided for the main switch. The synchronous rectifier switch turned on under zero-voltage switching, and the auxiliary switch turn-on and turn-off were under zero-current condition. Experimental results of a 100 W-100 kHz prototype are provided to justify the validity of the theoretical analysis. Moreover, the conducted electromagnetic interference of the proposed converter is measured and compared with its hard-switching counterpart.

• 전력전자학회:학술대회논문집
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• 전력전자학회 2000년도 전력전자학술대회 논문집
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• pp.701-704
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• 2000

A SRG(Switched Reluctance Generator) has many advantages such as efficiency simple controllability low cost and robustness compared with outer machines. But the theories that have been adopted as SRG control methods up to the present are complicated. This paper proposes a simple control methods using PID which controls only a turn-off angle while making turn-on angle signals of SRG constant. controlling the voltage differences between the reference and the real value and calculating the proper turn-off angle of the load variations can implement to keep the output voltage constant. the control method suggested in this paper enhances the efficiency of this system and simplifies the hardware and software by using only the voltage and speed sensors. The proposed method is verified by experiment

• Journal of Power Electronics
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• 제12권3호
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• pp.377-386
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• 2012

An interleaved bridgeless buck-boost AC/DC converter is presented in this paper to achieve the characteristics of low conduction loss, a high power factor and low harmonic and ripple currents. There are only two power semiconductors in the line current path instead of the three power semiconductors in a conventional boost AC/DC converter. A buck-boost converter operated in the boundary conduction mode (BCM) is adopted to control the active switches to achieve the following characteristics: no diode reverse recovery problem, zero current switching (ZCS) turn-off of the rectifier diodes, ZCS turn-on of the power switches, and a low DC bus voltage to reduce the voltage stress of the MOSFETs in the second DC/DC converter. Interleaved pulse-width modulation (PWM) is used to control the switches such that the input and output ripple currents are reduced such that the output capacitance can be reduced. The voltage doubler topology is adopted to double the output voltage in order to extend the useable energy of the capacitor when the line voltage is off. The circuit configuration, principle operation, system analysis, and a design example are discussed and presented in detail. Finally, experiments on a 500W prototype are provided to demonstrate the performance of the proposed converter.

• Journal of Electrical Engineering and Technology
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• 제1권2호
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• pp.216-225
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• 2006

This paper presents a new circuit topology of DC busline switch and snubbing capacitor-assisted full-bridge soft-switching PWM inverter type DC-DC power converter with a high frequency link for low voltage large current applications as DC feeding systems, telecommunication power plants, automotive DC bus converters, plasma generator, electro plating plants, fuel cell interfaced power conditioner and arc welding power supplies. The proposed power converter circuit is based upon a voltage source-fed H type full-bridge high frequency PWM inverter with a high frequency transformer link. The conventional type high frequency inverter circuit is modified by adding a single power semiconductor switching device in series with DC rail and snubbing lossless capacitor in parallel with the inverter bridge legs. All the active power switches in the full-bridge inverter arms and DC busline can achieve ZVS/ZVT turn-off and ZCS turn-on commutation operation. Therefore, the total switching losses at turn-off and turn-on switching transitions of these power semiconductor devices can be reduced even in the high switching frequency bands ranging from 20 kHz to 100 kHz. The switching frequency of this DC-DC power converter using IGBT power modules is selected to be 60 kHz. It is proved experimentally by the power loss analysis that the more the switching frequency increases, the more the proposed DC-DC converter can achieve high performance, lighter in weight, lower power losses and miniaturization in size as compared to the conventional hard switching one. The principle of operation, operation modes, practical and inherent effectiveness of this novel DC-DC power converter topology is proved for a low voltage and large current DC-DC power supplies of arc welder applications in industry.

• 전력전자학회논문지
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• 제16권3호
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• pp.242-249
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• 2011

제안하는 컨버터는 부스트 하프브리지-전압 더블러를 각각 병렬-직렬로 연결하여 출력전력 및 출력전압을 증대시키므로 고승압 대전력 응용에서 소자의 선정이 용이하다. 특히 고주파변압기 턴 비를 작게 할 수 있고 DC 오프셋이 제거되어 최적의 변압기 설계가 가능하며, 3개의 코아로 전력이 분배되어 Low Profile 및 열 분산에 유리하다. 제안하는 컨버터는 전 영역(0 ∼ 1)의 듀티 사용으로 스타트업 및 추가의 클램프회로가 필요 없으며 입력전압 변동이 큰 응용에 적합하다. 또한 넓은 듀티영역에서 스위치의 ZVS 턴온과 다이오드의 ZCS 턴온 턴오프가 성취되므로 고효율을 달성할 수 있다. 제안하는 컨버터를 5 kW급 시작품으로 검증하였다.

• 한국재료학회지
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• 제10권2호
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• pp.124-127
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• 2000

Si FEA로부터 tip의 표면을 Ti 금속으로 silicidation한 새로운 3극형 Ti-silicided Si FEA를 제작하고 이의 전계 방출특성을 조사하였다. 제작된 소자에서 단위 pixel(pixel area : $1000{\mu\textrm{m}}{\times}1000{$\mu\textrm{m}}$, tip array : $200{\mu\textrm{m}}{\times}200{$\mu\textrm{m}}$)을 통해 측정된 전계 방출 특성은 $10^8Torr$의 고진공 상태에서 turn-on 전압이 약 70V로, 아노드 방출전류의 크기와 current degradation이 $V_A=500V,\;V_G=150V$ 바이어스 아래에서 각각 2nA/tip와 0.3%/min로 나타났다. 3극형 Ti-silicided Si FEA의 낮은 turn-on 전압과 높은 전류안정성은 Si tip 표면에 형성된 실리사이드 박막의 열화학적 안정성과 낮은 일함수에 기인하는 것으로 판단된다.

• ETRI Journal
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• 제43권5호
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• pp.891-899
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• 2021

We propose a stray inductance extraction method on power modules of the few-kilovolts/several-hundred-amperes class using only low voltages and low currents. The method incorporates a double-pulse generator, a level shifter, a switching device, and a load inductor. The conventional approach generally requires a high voltage of more than half the power module's rated voltage and a high current of around half the rated current. In contrast, the proposed method requires a low voltage and low current environment regardless of the power module's rated voltage because the module is measured in a turn-off state. Both theoretical and experimental results are provided. A physical circuit board was fabricated, and the method was applied to three commercial power modules with EconoDUAL3 cases. The obtained stray inductance values differed from the manufacturer-provided values by less than 1.65 nH, thus demonstrating the method's accuracy. The greatest advantage of the proposed approach is that high voltages or high currents are not required.

• Journal of Electrical Engineering and Technology
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• 제9권5호
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• pp.1592-1601
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• 2014

In this study, a novel single phase soft switched power factor correction (PFC) converter is developed with active snubber cell. The active snubber cell provides boost switch both to turn on with zero voltage transition (ZVT) and to turn off with zero current transition (ZCT). As the switching losses in the proposed converter are too low, L and C size can be reduced by increasing the operating frequency. Also, all the semiconductor devices operate with soft switching. There is no additional voltage stress in the boost switch and diode. The proposed converter has a simple structure, low cost and ease of control as well. It has a simple control loop to achieve near unity power factor with the aid of the UC3854. In this study, detailed steady state analysis of the proposed converter is presented and this theoretical analysis is verified by a prototype of 100 kHz and 500 W converter. The measured power factor and efficiency are 0.99 and 97.9% at full load.

• Journal of Power Electronics
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• 제16권4호
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• pp.1256-1267
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• 2016

Distributed stray inductance exerts a significant influence on the turn-off voltages of power switching devices. Therefore, the design of low stray inductance bus bars has become an important part of the design of high-power converters. In this study, we first analyze the operational principle and switching transient of a T-type converter. Then, we obtain the commutation circuit, categorize the stray inductance of the circuit, and study the influence of the different types of stray inductance on the turn-off voltages of switching devices. According to the current distribution of the commutation circuit, as well as the conditions for realizing laminated bus bars, we laminate the bus bar of the converter by integrating the practical structure of a capacitor bank and a power module. As a result, the stray inductance of the bus bar is reduced, and the stray inductance in the commutation circuit of the converter is reduced to more than half. Finally, a 10 kVA experimental prototype of a T-type converter is built to verify the effectiveness of the designed laminated bus bar in restraining the turn-off voltage spike of the switching devices in the converter.

• 한국정보디스플레이학회:학술대회논문집
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• 한국정보디스플레이학회 2007년도 7th International Meeting on Information Display 제7권1호
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• pp.679-682
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• 2007

We have developed low voltage operating OLEDs with new electron transport layer. The device having a structure of ITO/2TNATA/HTL:Rubrene(1%)/HTL /new ETL/LiF/Al have been used. The voltage for achieving $1,000\;cd/m^2$ was 4.1 V, whereas the turn on voltage for the brightness of $1\;cd/m^2$ was 2.8 V. This high luminance at low operating voltage is caused by the high current density, resulting from high electron conduction property of the new electron transport layer.