• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.137-140
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• 2000

This paper proposes an improved soft switching two-transistor forward converter which uses a novel lossless snubber circuit to effectively control the turn-off dv/dt rate of the main transistors. In the proposed soft switching implementation the turn-off voltage traces across the main two transistors are almost the same contributing to reduce the total capacitive turn-on loss and the snubber current is divided into the two transistors resulting in distributed thermal stresses

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.276-280
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• 2003

This paper presents a zero voltage and zero current switching (ZVZCS) interleaving two-transistor forward converter for high input voltage and high power application. A phase shift has a disadvantage that a circulating current and RMS current stress, conduction losses of transformer and switching devices increases. Due to this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved interleaving two-transistor forward Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor a snubber capacitor and two snubber diodes attached at the secondary side of transformer. The proposed ZVZCS converter is verified on a 1.8kW, 5kHz experimental prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.5
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• pp.453-459
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• 2001

In this paper, the loss analyses of two soft switching techniques for two-transistor forward converter are performed. The sums of snubber conduction and capacitive turn-on losses for two transistors are calculated to compare the losses of the two techniques. While the conventional soft switching technique shows the loss difference between two transistors, the proposed soft switching technique shows equal as well as lower losses In two transistors. Thus, it can be said that even thermal distribution and higher reliability can be obtained by the proposed soft switching technique.

• Proceedings of the KIEE Conference
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• 2005.04a
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• pp.176-179
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• 2005

This paper proposed the two-transistor forward circuit using PFC, lossless snubber and synchronous rectifier for low voltage and high current output. The principle of operation, feature and design considerations is illustrated and verified through the experiment with a 200W(5V, 40A) 100kHz MOSFET based experimental circuit.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1163-1165
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• 2003

This paper presents the TTFC(Two Transistor Forward Converter) using Synchronous Rectifier. The principle of operation, feature ana design considerations are illustrated and verified through the experiment with a 200W 100kHz MOSFET based experimental circuit.

• The Transactions of the Korean Institute of Power Electronics
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• v.12 no.1
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• pp.50-55
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• 2007

In this paper, we present an analytical method that provides fast and efficient evaluation of the conversion efficiency for Two transistor forward (TTF) DC-DC converter In the proposed method, the conduction losses are evaluated by calculating the effective values of the ideal current waveform first and incorporating them into an exact equivalent circuit model of the TTF converter that includes all the parasitic resistances of the circuit components. While the conduction losses are accurately accounted for the diode rectification, the core losses are assumed to be negligible in order to simplify the analysis. The validity and accuracy of the proposed method are verified with experiments on a prototype TTF converter An excellent correlation between the experiments and theories are obtained for the input voltages of 390V, output voltage 12V and maximum power 480W.

• Proceedings of the KIEE Conference
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• 2005.10c
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• pp.226-228
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• 2005

This paper presents the single-stage High Power Factor TTFC(Two-Transistor Forward Converter). Recently, due to growing concern about the harmonic pollution of power distribution systems and the adoption of standards such as ICE 61000-3-2 and IEEE 519, There is a need to reduce the harmonic contests of AC line currents of power supplies. This research proposed the single-stage two switch forward circuit for low voltage and high current output.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1432-1434
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• 2005

Single-stage converters are simpler and less expensive than convention two-stage converters. It can be a challenge, however, to design single-stage converters to satisfy certain key criteria such as input power factor, primary-side do bus voltage, and output voltage ripple. This is especially true for higher power single-stage AC/DC TTFC(Two-Transistor Forward Converter).

• Proceedings of the KIEE Conference
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• 2003.10b
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• pp.166-170
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• 2003

This paper presents the TTFC(Two Transistor Forward Converter) using Synchronous Rectifier of Compulsory Control-driver. The two transistor forward circuit is used to decrease voltage stress of primary side and the synchronous rectifier is used to reduce current stress of secondary side. Previous synchronous rectifier's MOSFET of TTFC have long dead time This paper presents synchronous rectifier of compulsory control-driver for minimized dead time. This paper compared with diode rectifier, self-driven synchronous rectifier and compulsory control-driver synchronous rectifier of TTFC. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 200W 100kHz MOSFET based experimental circuit.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.9
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• pp.467-475
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• 1999

This paper presents an analysis method of a forward converter, using both the finite element method considering the external circuit and a state variables equation. The converter operates at 50kHz and its one period is divided into two modes for the simplicity of the analysis. In the first mode, the switching transistor turns on and an input power is transferred into the load by the electromagnetic conversion action of a ferrite transformer. In the second mode, the switching transistor turns off and the stored energy in an inductor is delivered to the load, and the transformer core is demagnetized by the reset winding current. In this paper, time-stepping finite element method taking into account the on-state electrical circuit of the converter in used to analyze both the electrical circuit and electromagnetic field of the magnetic device during the first mode and the demagnetization period of the transformer core. Then a state variables equation for the circuit which the inductor current flows is constituted and solved during the second mode. As a result, the simulation results have been good agreement with the results obtained form experiment.