• Journal of Power Electronics
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• v.19 no.6
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• pp.1393-1402
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• 2019

This paper proposes a new power flow control method for soft-switched, four channel, five level resonant buck dc-dc converters. These converters have two input channels, which can be supplied from sources with identical or different voltages, and four output channels with arbitrary output voltages. They are specially designed to supply multilevel inverters. The design methodology for their power flow control has been developed considering a general case when the input voltages, output voltages and loads can be asymmetrical. A special emphasize is paid to the limitations and restrictions of operation. The theoretical studies are confirmed by numerical simulations and laboratory tests carried out at various operation points. Exploiting the advantages of the newly proposed power control strategy, the converter can supply five level inverters in dc microgrids, active filters, power factor correctors and electric drives. They can also play an interfacing role in renewable energy systems.

• Journal of Power Electronics
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• v.7 no.4
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• pp.328-335
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• 2007

A conventional Single-Stage Power-Factor-Correction (PFC) AC/DC converter has a link capacitor voltage problem under high line input and low load conditions. In this paper, this problem is analyzed by using the voltage conversion ratio of the DC/DC conversion cell. By applying this analysis, a new Single-Stage PFC AC/DC converter with a boost PFC cell integrated with a Voltage-Doubler Rectified Asymmetrical Half-Bridge (VDRAHB) is proposed. The proposed converter features good power factor correction, low current harmonic distortions, tight output regulations and low voltage of the link capacitor. An 85W prototype was implemented to show that it meets harmonic requirements and standards satisfactorily with near unity power factor and high efficiency over universal input.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.119-121
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• 2006

본 논문은 중 전력, 고 입력 전압응용에서 많이 이용되는 비대칭 하프브릿지 PWM DC-DC 컨버터의 다중 출력 구성을 위한 최적의 설계 방식을 제안한다. 제안된 방식은 기본 PWM에서 부하에 따른 연속전류동작모드(CCM)의 구간을 늘여, 제어되는 전원의 부하 변동이 크더라도, 다중출력 되어지는 전원의 정상상태 동작점의 변동이 크게 발생하지 않도록 한다. 제어되는 비대칭 하프브릿지(ASHB)의 부하에 따른 시비율 변화가 작아지면 경 부하에서 변압기에 인가되는 전압의 크기가 줄어들어 다중 출력 되어지는 단의 전체적인 전압 스트레스가 감소한다. 또한 제안된 방식의 비대칭 하프브릿지 회로는 기존의 1차 측 전류 비대칭성을 보상하여 보다 넓은 부하 영역에서 영전압 스위칭이 가능하며 스위칭 손실과 이에 의한 EMI가 감소하게 된다. 제안된 방식은 기존 하드웨어와 비교하여 그 성능을 검증하였다.

• Journal of Power Electronics
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• v.3 no.1
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• pp.17-23
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• 2003

A new three-phase soft-switching active front-end inverter is presented. The topology consists of a quasi-resonant PWM boost converter with an additional resonant branch, which provides low loss at high frequency operation. This leads to a high conversion efficiency and a remarkable reduction in the siBe of the input inductor. To synchronise the PWM pattern with the resonance cycle, a modified space vector modulation with asymmetrical PWM pattern is used. A high power factor can be achieved for both power flow directions. Due to a new control strategy the converter features a low content of harmonics in the line currents even for distorted line voltages.

• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.146-150
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• 2001

A new three-phase soft-switching active front-end inverter is presented. The topology consists of a quasi-resonant PWM boost converter with an additional resonant branch, which provides low loss at high frequency operation. This leads to a high conversion efficiency and a remarkable reduction in the size of the input inductor. To synchronise the PWM pattern with the resonance cycle, a modified space vector modulation with asymmetrical PWM pattern is used. A high power factor can be achieved for both power flow directions. Due to a new control strategy the converter features a low content of harmonics in the line currents even for distorted line voltages.

• Journal of Power Electronics
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• v.12 no.2
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• pp.258-267
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• 2012

An interleaved single-stage AC/DC converter with a boost converter and an asymmetrical half-bridge topology is presented to achieve power factor correction, zero voltage switching (ZVS) and load voltage regulation. Asymmetric pulse-width modulation (PWM) is adopted to achieve ZVS turn-on for all of the switches and to increase circuit efficiency. Two ZVS half-bridge converters with interleaved PWM are connected in parallel to reduce the ripple current at input and output sides, to control the output voltage at a desired value and to achieve load current sharing. A center-tapped rectifier is adopted at the secondary side of the transformers to achieve full-wave rectification. The boost converter is operated in discontinuous conduction mode (DCM) to automatically draw a sinusoidal line current from an AC source with a high power factor and a low current distortion. Finally, a 240W converter with the proposed topology has been implemented to verify the performance and feasibility of the proposed converter.

• Journal of Power Electronics
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• v.6 no.3
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• pp.187-194
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• 2006

A new asymmetrical pulse width modulation (PWM) half bridge converter with improved ZVS performance is proposed. The ZVS operation of the proposed converter can be maintained from no load to full load conditions since the magnetizing current of the transformer contributes to the ZVS operation at light loads without considerable conduction loss of the transformer and switch. Synchronous rectification is employed to reduce the rectification loss. Operational principles, large signal modeling, ZVS analysis and design equations are presented. Experimental results demonstrate that the proposed converter can achieve a large ZVS range and significant improvement in efficiency for a 100W (5V, 20A) prototype converter.

• Journal of Power Electronics
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• v.7 no.2
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• pp.124-131
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• 2007

In this paper, a novel type of auxiliary switched capacitor assisted edge resonant soft switching PWM resonant DC-DC converter with two simple auxiliary commutation lossless inductor snubbers is presented. The operation principle of this converter is described using the switching mode equivalent circuits. This newly developed multi resonant DC-DC converter can regulate its DC output AC power under a principle of constant frequency edge-resonant soft switching commutation by an asymmetrical PWM duty cycle control scheme. The high frequency power regulation and actual power characteristics of the proposed soft switching PWM resonant DC-DC converter are evaluated and discussed. The operating performances of the newly proposed soft switching inverter are represented based on simulation results from an applications point of view.

• Proceedings of the KIPE Conference
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• 2017.11a
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• pp.111-112
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• 2017

This paper presents a novel three-port converter for the OnBoard Charger of Electric Vehicles by using an impedance control network. The proposed concept is suitable for charging a main battery and an auxiliary battery of an electric vehicle at the same time due to its power handling capability of the converter without additional switches. The power flow is managed by the phase angle (${\Theta}$) between the ports whereas voltage at each port is controlled by the asymmetric duty cycle and the phase shift (${\Phi}$) between the inverter lags controlled by the impedance control network. The proposed system has a capability of achieving zero voltage switching (ZVS) and zero current switching (ZCS) at all the switches over the wide range of input voltage, output voltage and output power. The feasibility of the proposed system is verified by the PSIM simulation.

• Journal of Power Electronics
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• v.18 no.2
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• pp.383-394
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• 2018

This paper presents an isolated power factor correction converter for general-purpose electric vehicle chargers with a wide output voltage range. The converter is based on an asymmetrical dual active bridge structure so that the voltage stress of switching devices can be eliminated by transferring the transformer leakage inductance to the circuit parameters. Harmonic and output controls are performed by secondary switches, and primary switches are only operated at a fixed frequency with a 50% duty ratio. A harmonic modulation technique is also adopted to obtain a near-unity power factor without input current monitoring. The feasibility of the proposed charger is verified with a 3.3 kW prototype.