• The Transactions of the Korean Institute of Electrical Engineers B
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• v.50 no.8
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• pp.392-401
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• 2001

This paper presents the single-stage high power factor AC to DC converter operated in active-clamp mode. The proposed converter is added active-clamping circuit to boost-flyback single-stage power factor corrected power supply. The active-clamping circuit limits voltage spikes, recycles the energy trapped in the leakage inductance, and provides a mechanism for achieving soft switching of the electronic switches to reduce the switching loss. The auxiliary switch of active-clamping circuit uses the same control and driver circuit as the main switch to reduce the additional cost and size. To verify the performance of the proposed converter, a 100W converter has been designed. The proposed converter gives good power factor correction, low line current harmonic distortions, and tight output voltage regulation, as used unity power factor.

• Proceedings of the KIEE Conference
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• 2005.07c
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• pp.2143-2145
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• 2005

Power semicondcutor인 IGBT MOSFET, GTO, SI-Thyristor등은 높은 스위치 신뢰성과 life time, 그리고 fast repetition rate 등을 지니고 있기 때문에 medium/High voltage영역에서 스위치 사용이 대두되어 왔으나, Thyratron이나 Trigatron(Gap switch)와 비교하여 낮은 전압/전류를 스위칭하기 때문에 전통적으로 직렬연결을 통해 high voltage 영역의 스위치로 사용되어 왔다. 하지만, 직렬연결되어 있는 각각의 power semiconductor와 gate driving circuit의 on/off synchronization이 맞지 않기 때문에 부하의 급격한 변화에 따른 전압의 balance에 문제가 가장 심각하게 대두되어 왔다. 이러한 문제를 해결하기 위해서 gate driving circuit에서 제어를 해주는 방법과 power semiconductor에서 제어를 해주는 방법이 있으나 두 방식 모두 문제점이 있다. 본 논문에서는 기존의 zener clamping방식에서 벗어나 새로운 active clamping방식의 직렬연결을 제안했으며 시뮬레이션과 실험을 통해 나타난 이 결과들은 on/off transient 시 symmetry를 유지하는데 효과적이라는 것을 보여주고 있다.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.520-522
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• 2008

A novel two-switch active clamp forward converter suitable for high input voltage applications is proposed. The main advantage of the proposed converter, compared to the conventional active forward converters, is that circuit complexity is reduced and the voltage stress of the main switches is effectively clamped to either the input voltage or the clamping capacitor voltage by two clamping diodes without limiting the maximum duty ratio. Also, the clamping circuit does not include additional active switches, so a low cost can be achieved without degrading the efficiency. Therefore, the proposed converter can feature high efficiency and low cost for high input voltage applications. The operational principles, features, and design considerations of the proposed converter are presented in this paper. The validity of this study is confirmed by the experimental results from a prototype with 200W, 375V input, and 12V output.

• Journal of Power Electronics
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• v.9 no.5
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• pp.772-780
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• 2009

A novel soft-switching two-switch flyback converter is proposed in this paper. This converter is composed of two active power switches, a flyback transformer, a blocking diode, and two passive regenerative clamping circuits. The proposed converter has the advantages of a low cost circuit configuration, a simple control scheme, a high efficiency, and a wide operating range. The circuit topology, analysis, design considerations, and experimental results of the new flyback converter are presented.

• Proceedings of the KIEE Conference
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• 2009.04b
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• pp.156-160
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• 2009

This paper presents the interleaved active-clamping ZVS(Zero Voltage Switching) forward converter, which is mainly composed of two active-clamping forward converters. Only two switches are required, and each one is the auxiliary switch for the other. The circuit complexity and cost are thus reduced. The leakage inductance of the transformer or an additional resonant inductance is employed to achieve ZVS during the dead times. The duty cycles are not limited to be equal and within 50%. The complementary switching and the resulted interleaved output inductor currents diminish the current ripple in output capacitors. Accordingly, the smaller output chokes and capacitors lower the converter volume and increase the power density. Detailed analysis and design of this new interleaved active-clamping forward converter are described.

• Journal of Power Electronics
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• v.11 no.4
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• pp.499-506
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• 2011

This paper presents an interleaved active-clamping zero-voltage-switching (ZVS) forward-flyback converter without an output choke. The presented topology has two active-clamping circuits with two separated transformers. Because of the interleaved operation of the converter, the output current ripple will be reduced. The proposed converter can approximately share the total load current between the two secondaries. Therefore, the transformer copper loss and the rectifier diodes conduction loss can be decreased. The output capacitor is made of two series capacitors which reduces the peak reverse voltage of the rectifier diodes. The circuit has no output inductor and few semiconductor elements, such that the adopted circuit has a simpler structure, a lower cost and is suitable for high power density applications. A detailed analysis and the design of this new converter are described. A prototype converter has been implemented and experimental results have been recorded with an ac input voltage of 85-135Vrms, an output voltage of 12V and an output current of 16A.

• The Transactions of the Korean Institute of Power Electronics
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• v.3 no.4
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• pp.426-436
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• 1998

Identification of fault current during the operation of a power semiconductor switch and activation of suitable remedial actions are important for reliable operation of power converters. A short circuit is a basic and severe fault situation in a circuit structure such as voltage source converters. This paper presents a new active protection circuit for fast and precise clamping and safe shutdown of fault currents of the IGBTs. This circuit allows operation of the IGBTs with a higher on-state gate voltage, which can thereby reduce the conduction loss in the device without compromising the short circuit protection characteristics. The operation of the circuit is studied under various conditions, considering variation of temperature, rising rate of fault current, gate voltage value, and protection circuit parameters. An evaluation of the operation of the circuit is made using IGBTs from different to confirm the effectiveness of the protection circuit.

• Journal of Power Electronics
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• v.10 no.3
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• pp.235-244
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• 2010

This paper presents a new isolated soft-switching bidirectional buck-boost inverter for fuel cell applications. The buck-boost inverter combines an isolated DC-DC converter with a conventional inverter to implement buck-boost DC-DC and DC-AC conversion. The main switches achieve zero voltage switching and zero current switching by using a novel synchronous switching SVPWM and the volume of the transformer in the forward and fly-back mode is also minimized. This inverter is suitable for wide input voltage applications due to its high efficiency under all conditions. An active clamping circuit reduces the switch's spike voltage and regenerates the energy stored in the leakage inductance of the transformer; therefore, the overall efficiency is improved. This paper presents the operating principle, a theoretical analysis and design guidelines. Simulation and experimental results have validated the characteristics of the buck-boost inverter.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.489-490
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• 2010

A novel soft-switching two-switch flyback converter is proposed in this paper. This converter is composed of two active power switches, a flyback transformer, and two passive regenerative clamping circuits.The proposed converter has the advantages of a low cost circuit configuration, a simple control scheme, a high efficiency, and a wide operating range. The circuit topology and experimental results of the new flyback converter are presented.

• Proceedings of the KIPE Conference
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• 2010.07a
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• pp.142-143
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• 2010

An active-clamped current-fed half-bridge converter for the high step-up application is proposed in this paper. The proposed converter is composed of active clamping snubber circuits and a voltage doubler rectifier. The operational principle, theoretical analysis, and design considerations are presented. To confirm the operation, features, and validity of the proposed circuit, the experimental result for a 200W, 24V input and 400V output prototype are presented.