• ETRI Journal
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• v.39 no.2
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• pp.292-299
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• 2017

We propose pulse-mode dynamic $R_on$ measurement as a method for analyzing the effect of stress on large-scale high-power AlGaN/GaN HFETs. The measurements were carried out under the soft-switching condition (zero-voltage switching) and aimed to minimize the self-heating problem that exists with the conventional hard-switching measurement. The dynamic $R_on$ of the fabricated AlGaN/GaN MIS-HFETs was measured under different stabilization time conditions. To do so, the drain-gate bias is set to zero after applying the off-state stress. As the stabilization time increased from $ 0.1{\mu}s$ to 100 ms, the dynamic $R_on$ decreased from $160\Omega$ to $2\Omega$. This method will be useful in developing high-performance GaN power FETs suitable for use in high-efficiency converter/inverter topology design.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.4
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• pp.351-355
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• 2016

Welding machines are high-capacity systems used in a low-frequency range using IGBT. As their system is similar to a large transformer, most welding machines suffer a great loss because of hard switching and vast leakage inductance. A voltage-balancing circuit is designed to overcome these shortcomings. This circuit can reduce the transformer size by making it into a high frequency and reducing the input voltage by half and by adopting a serial structure that connects two full-bridges in a series to use a MOSFET with a good property at high frequency. In addition, a Schottky diode is used in the primary rectifier to overcome the low efficiency of most welding machines. To use the Schottky diode with a reliably relatively low withstanding voltage, an active snubber is adopted to effectively limit the ringing voltage of the diode cut-off voltage.

• Proceedings of the KIPE Conference
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• 2016.07a
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• pp.307-308
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• 2016

본 논문에서는 하나의 감극성 커플드 인덕터 보조 회로를 갖는 발전된 영전압 천이 소프트-스위칭 인버터를 제안한다. 기존에 제안된 소프트-스위칭 인버터의 큰 커패시터나 추가 회로의 필요성과 같은 구조적 단점을 극복하였다. 또한, 하나의 커플드 인덕터 보조 회로를 이용하여 풀-브리지 인버터를 구현하여 보조 회로의 소자 수를 줄여 가격과 부피에서 장점이 있다. 본 논문에서 제안된 회로의 동작 원리와 특성들을 다룰 것이며 시뮬레이션을 통하여 유효성을 검증하였다.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.73-76
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• 2003

A zero voltage soft switching inverter using active clamp is presented for induction heating application. This converter have long been attractive because of its simplicity, high efficiency, and low cost compared to other schemes. In addition to those merits, Input power factor can be improved with a variable frequency control. In this paper, it describe the control method and operational principle to improve a power factor with a single stage US converter using active clamp for induction heating application.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.788-791
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• 2005

이 논문은 부스트 하프 브릿지 1단 인버터기술을 혼합한 나아진 소프트스위칭 PWM 전력공급이 대체로 관계한다. 동작원리는 등가회로와 동작파형을 사용하여 설명하고 있다. 유효주파수 AC 동작 실행 시 1단 전력변환에 고주파 AC 전력변환 회로는 실험결과의 기초를 설명하고 평가한다. 전력변동률 대 고주파 듀티 사이클 특성과 전력변환 효율특성을 이전에 개발된 고주파와 비교하여 인버터전력소실을 나타냈다. 그것의 효과는 관찰의 실행 포인트로부터 실험 결과의 기초를 충분히 증명한다.

• Proceedings of the KIPE Conference
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• 2017.07a
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• pp.264-265
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• 2017

본 논문에서는 3상 220V/5kVA 소프트스위칭 인버터의 새로운 회로구성을 제안하고 그 동작과 성능을 분석한 내용을 기술하고 있다. 제안하는 소프트스위칭 인버터는 ARCP(Auxiliary Resonant Commutated Pole) 인버터의 회로구성과 유사한 구조이나 이와 달리 LC 공진회로와 Diode 클램프 회로로 구성되어 있다. 이론적인 분석과 실험을 통해 제안하는 인버터의 효율을 분석하고 이를 하드스위칭 인버터와 비교하여 약 1% 정도의 효율 개선이 가능함을 알 수 있었다. 제안하는 인버터는 소프트 스위칭을 위해 소프트스위칭 보조회로와 게이트 드라이버가 추가로 장착되는 점에서 비용적인 경쟁력이 떨어질 수 있다. 그러나 최근 수요가 급증하고 있는 인버터에서 1% 효율 차이는 전력수급의 효율화를 통해 비용 측면에서 경쟁력을 갖을 것으로 판단된다. 또한 소프트스위칭 회로의 컴팩트화와 하드웨어의 최적화된 물리적 배치를 통해 추가의 효율증대가 가능할 것으로 보인다.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2003.11a
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• pp.343-348
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• 2003

In this paper, a PFC(Power Factor Correction) electronic ballast with constant voltage-fed is proposed. The proposed PFC electronic ballast is combined of a High-efficiency boost converter and a conventional half bridge inverter. It is proved that the ripple of input-current and the input-current's harmonic of the proposed PFC electronic ballast are reduced using the voltage divider and soft-switching technique. It is demonstrated that simulation results for 40[W] fluorescent lamp correspond with theoretical analysis

• Transactions on Electrical and Electronic Materials
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• v.17 no.2
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• pp.79-85
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• 2016

In this study, we proposed a new single-stage small power MH lamp electronic ballast and power-factor correction circuit with improved circuit by the current of passive power factor correction. Main circuit integrates traditional DC/DC and DC/AC circuits into one-stage DC/AC inverter. Moreover, we described the working principle and control strategy of the new circuit; it's soft switching principle; and resonant element parameter design formula. An experimental prototype of HID lamp electronic ballast with output power of 70 W was built to verify the feasibility of the analysis and design. The simulation and experimental results proved that the power factor of this circuit could reach 94%, with efficiency of 90%. The input current harmonics conform to IEC 61000-3-2 standards and its cost is low. These superior performances of the new circuit indicate certain practical values.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.21 no.5
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• pp.10-24
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• 2007

In the dissertation, a power conversion system for fuel cell is composed of a PWM inverter with LC filter in order to convert fuel cell voltage to a single phase 220[V]. In addition, new insulated DC-DC converters are proposed in order that fuel cell voltage is boosted to 380[V]. In this paper, it requires smaller components than existing converters, which makes easy control. The proposed DC-DC converter controls output power by the adjustment of phase-shift width using switch $S_5\;and\;S_6$ in the secondary switch which provides 93-97[%] efficiency in the wide range of output voltage. Fuel cell simulator is implemented to show similar output characteristics to actual fuel cell. Appropriate dead time td enables soft switching to the range where the peak value of excitation current in a high frequency transformer is in accordance with current in the primary circuit. Moreover, appropriate setting to serial inductance La reduces communication loss arisen at light-load generator and serge voltage arisen at a secondary switch and serial diode. Finally, TMS320C31 board and EPLD using PWM switching technique to act a single phase full-bridge inverter which is planed to make alternating current suitable for household