• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.201-203
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• 2018

최근 휴대용 어댑터의 동향은 고주파수 전력 컨버터 설계를 통한 어댑터의 고효율화 및 소형화의 중요성을 강조하고 있다. 그러나 기존 준공진형(Quasi Resonant, QR) 플라이백 컨버터는 하드 스위칭 동작으로 고주파수 구동에 한계가 있으며, 누설 인덕턴스 에너지에 의한 손실로 인해 고효율을 달성하기가 어렵다. 반면, 능동 클램프 플라이백(Active Clamp Flyback, ACF) 컨버터는 ZVS(Zero Voltage Switching) 동작을 하여 고주파수 구동에 유리하고, 누설 인덕턴스 에너지를 입력으로 회기 시킴으로써 손실을 저감할 수 있다. 또한, 경계전류모드(Boundary Conduction Mode, BCM) 동작에서의 손실분석을 기반으로, 반도체 특성이 우수하여 고주파수 동작에 유리한 GaN-FET를 적용하고 최적 설계를 진행함으로써 고효율 및 고전력밀도를 달성하였다. 따라서 본 논문에서는 GaN-FET를 기반으로 하는 고효율 및 고전력밀도 BCM ACF 컨버터의 최적 설계 방안을 제시하고 65W급 시작품의 실험결과를 통해 이를 검증한다.

• KIPE Magazine
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• v.27 no.3
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• pp.26-30
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• 2022

핸드폰, 노트북 빛 태블릿 PC와 같이 휴대할 수 있는 전자기기의 사용량이 높아질수록 대용량의 배터리를 필요로 하게 된다. 배터리 사양이 높아질수록 대용량의 배터리를 빠르게 충전시키는 어댑터 (Adapter)는 필수 요구 사항이 되었다. 고속 충전을 하기 위해선 높은 전류 공급 능력이 필요하며, 휴대성을 높이기 위해서 사이즈를 최소화하여 설계되어야 한다. 고효율 및 고밀도를 요구하는 시장에 걸맞게, 어댑터 시장 역시 Topology부터 사용 소자까지 많은 발전 중에 있다. 어댑터에 사용되는 대표적인 Topology는 절연에 용이하며 회로구조가 간단한 저비용, 고효율 Flyback Converter 회로가 기본적으로 사용된다. 하지만, 이 구조는 스위칭 주기마다 스위치 양단 전압 및 전류의 중첩에 의한 스위칭 손실이 불가피 하다는 단점이 존재한다. 그 단점을 보완하기 위해 RCD 스너버로 클램핑을 시켜줌과 동시에 변압기의 자화 인덕턴스와 스위치의 기생 커패시터의 공진 현상을 이용하여 스위치 양단 전압 V_DS가 최소화되는 지점에서 다음 스위칭 동작을 수행하는 QR(Quasi-Resonant) Flyback Converter를 사용한 어댑터가 시장에서 주로 보였다. 하지만 QR Flyback Converter 역시 기존 방식보다 유리하지만 이 또한 스위칭 주파수 증가에 따른 한계가 존재한다. 따라서 현재는 영전압 스위칭 (Zero Voltage Switching, ZVS)이 가능한 ACF(Active Clamp Flyback) Converter 회로의 연구 개발이 활발히 진행되고 있다. 이때 스위칭 특성이 우수한 GaN-FET를 적용한 어댑터가 시장에 출시되고 있다. 특히, 이 시장에서는 GaN 소자를 적용한 어댑터를 차세대 전력 반도체 적용이라는 마케팅에도 이용되는 것을 확인할 수 있다.

• The Transactions of the Korean Institute of Power Electronics
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• v.14 no.1
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• pp.23-30
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• 2009

A new high performance and low cost unified power system is proposed through investigating conventional Power-Integrated Drive(PID) system and Power-Separated Drive(PSD) system applied to LCD TV. Since the proposed system consists of two stage, namely power and inverter stage it features high efficiency and cost effectiveness. To satisfy the safety standard of the High voltage transformer, 1:1 transformer is employed between inverter and high voltage transformer. Moreover, to ensure the Zero Voltage Switching(ZVS) of all power switches and the Pulse Count Modulation(PCM) method is employed, which controls the number of pulse at the fixed frequency and fixed duty cycle. Therefore, it features high efficiency, improved heat generation, cost effectiveness and good EMI performance including no additional current balancing coil. To confirm the validity of proposed system, comparison of conventional system, verification of experimental results are presented.

• Journal of the Institute of Electronics Engineers of Korea SC
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• v.43 no.1 s.307
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• pp.45-52
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• 2006

In this paper, authors propose a step-up converter of pulse width modulation (PWM) and power factor correction (PFC) by using a novel loss-less snubber. The proposed converter for a discontinuous conduction mode (DCM) eliminates the complicated circuit control requirement and reduces the size of components. The input current waveform in the proposed converter is got to be a sinusoidal form of discontinuous pulse in proportion to magnitude of ac input voltage under the constant duty cycle switching. Thereupon, the input power factor is nearly unity and the control method is simple. In the general DCM converters, the switching devices are fumed-on with the zero current switching (ZCS), and the switching devices must be switched-off at a maximum reactor current. To achieve a soft switching (ZCS and ZVS) of the switching turn-off, the proposed converter is constructed by using a new loss-less snubber which is operated with a partial resonant circuit. The result is that the switching loss is very low and the efficiency of converter is high. Some simulative results on computer and experimental results are included to confirm the validity of the analytical results.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.6
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• pp.456-464
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• 2007

This paper proposes a novel three-phase current-fed active clamp DC-DC converter for fuel cells. A single common active clamp branch is used to limit transient voltage across the three-phase full bridge and to realize zero-voltage switching(ZVS) in all switches. To apply for the power generation system current-fed type has been combined with the three-phase power conversion system. The proposed approach has the following advantages: an increase (by a factor of three) of input current and output voltage chopping frequencies; lower RMS current through the inverter switches with higher power transfer capability; reduction in size of reactive later components and the power conditioning system; better transformer utilization; increase of the system reliability. Therefore, the proposed three-phase current-fed active clamp DC-DC converter is appropriate for the boost type DC-DC converter for fuel cells and also applicable for the photovoltaic and battery charge system. The paper details the analysis, simulation and hardware implementation of the proposed system. Finally, experimental results with the proposed PWM strategy demonstrate the feasibility of the proposed scheme on a 500W prototype converter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.5
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• pp.136-144
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• 2010

This paper presents the two-switch interleaved active clamp forward converter, which is mainly composed of two active clamp forward converters. Only two switches are required, and each one is the auxiliary switch for the other. So, the circuit complexity and cost are reduced and control is more simple. An additional resonant inductance is employed to achieve ZVS(Zero-Voltage-Switching) during the dead times. Interleaved output inductor currents diminish the voltage and current ripple. Accordingly, the smaller output filter and capacitors lower the converter volume. This research proposed the Two-switch interleaved Active Clamp Forward Converter characteristic. The principle of operation, feature and design considerations is illustrated and the validity of verified through the experiment with a 160[W] based experimental circuit.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.66-73
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• 2002

This paper presents ZVZCS(Zero-Voltage and Zero-Current Switching) Three Level DC/DC Converter without primary freewheeling diodes. The new converter presented in this paper used a phase shirt control with a flying capacitor in the primary side to achieve ZVS for the outer switches. A secondary anxiliary circuit which consists of one small capacitor, two small diodes and one coupled inductor, is added in the secondary to provide ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages include simple secondary auxiliary circuit topology, high efficiency, and low cost make the new converter attractive for high power applications. Also the circulating current flows through the circuit so that it causes the needless coduction loss to be occurred in the devices and the transformer of the circuit The new converter has no primary auxiliary diodes for freewheeling current. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1[㎾］ 50[KHz］IGBT based experimental circuit.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.16 no.8
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• pp.5541-5549
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• 2015

This paper introduces a safer and more power efficient heater by using induction heating, to apply to the semiconductor wafer fabrication exhaust gas cleaning system. The exhaust gas cleaning system is currently made with filament heater that generates an endothermic reaction of N2 gas for the removal of moisture. Induction theory, through the bases of theoretical optimization and electronic implementation, is applied in the design of the induction heater specifically for the semiconductor wafer exhaust system. The new induction heating design provides a solution to the issues with the current energy inefficient, unreliable, and unsafe design. A robust and calibrated design of the induction heater is used to optimize the energy consumption. Optimization is based on the calibrated ZVS induction circuit design specified by the resonant frequency of the exhaust pipe. The fail-safe energy limiter embedded in the system uses a voltage regulator through the feedback of the MOSFET control, which allows the system performance to operate within the specification of the N2 Heater unit. A specification and performance comparison from current conventional filament heater is made with the calibrated induction heater design for numerical analysis and the proof of a better design.