• Journal of Power Electronics
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• v.12 no.2
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• pp.242-248
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• 2012

Self oscillating current fed push pull resonant inverters can be controlled without using special drivers. Dc current flows through the choke coil and the power switches, although the driving signals of the power switches are sinusoidal. When the base current is near zero, the transistors cannot be operated in switching mode. Hence higher switching power losses and instantaneous peak power during off transitions are observed. In this study, an alternative design has been proposed to overcome this problem. A prototype circuit has been built which provides dc bias current to the base of the transistors. Experimental results are compared with theoretical calculations to demonstrate the validity of the design. The proposed design decreases the peak and average power losses by about 8 times, when compared to conventional designs.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.143-146
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• 2002

This paper proposes a new auxiliary resonant DC link(ARDCL)snubber circuit and deals with its power loss on the basis of actually-measured conduction loss characteristic of switching device module. Voltage-ed soft switching three-phase inverter using proposed ARDCL snubber circuit is presented along with its performance evaluations. And, the power loss analysis of three-phase hard and soft switching inverter are carried out from the point of simulation and experimental results.

• Journal of international Conference on Electrical Machines and Systems
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• v.1 no.3
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• pp.366-371
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• 2012

In this paper, we propose an electric circuit using one common-arm of H-Bridge inverters to reduce the number of switching components in the multi-level inverter combined with H-Bridge inverters and transformers. And furthermore, we suggested a new multi-level PWM inverter using PWM level to reduce THD (Total Harmonic Distortion). We use a phase-shift switching method that has the same rate of usage at each transformer. Also, we test the proposed prototype 9-level inverter to clarify the proposed electric circuit and reasonableness of the control signal for the proposed multi-level PWM inverter.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.22 no.3
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• pp.79-87
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• 2008

This paper presents a simple circuit topology of the auxiliary active quasi-resonant DC link snubber-assisted three phase voltage source soft-switching inverter for small scale PM motor drive applications. The pulse processing drive circuit interface and its soft-switching operation are discussed from an experimental point of view. Moreover, its conductive noise is measured and evaluated for electrical AC servo motor drive as compared with that of the conventional hard switching inverter.

• Journal of Power Electronics
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• v.6 no.1
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• pp.1-7
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• 2006

This paper is a record of the study on a high efficiency and high power chopper based on the new soft switching method QRAS (Quasi~resonant Regenerating Active Snubber) designed for a Fuel Cell Electric Vehicle (FCEV). This power chopper is basically proposed for 25kHz soft switching. To confirm the practicality and effectiveness of the converter, the fabrication of a prototype-model using IGBTs was completed. Additionally, a 8kW rating test, a light load test, a current discontinuous mode test and a stable operation resonance test was completed. The circuit geometry, the basic operation, and the 8kW one-tenth-prototype test results are reported with a $97.5\%$ efficiency measurement.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.49 no.10
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• pp.683-692
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• 2000

A new primary-side-assisted zero-voltage and zero-current switching full bridge DC-DC converter with transformer isolation is proposed. The auxiliary circuit adopted to assist ZCS for the leading leg is composed of only one small transformer and two diodes. It has a simple and robust structure, and load current control capability even in short circuit conditions. Possibility of magnetic saturation due to asymmetricity of circuits or transient phenomena is greatly reduced, which is a very attractive feature in DC/DC converters with transformer isolation. The power rating of the auxiliary transformer is about 10% of that of the main transformer. Operation of a 12.5KW prototype designed for welding application was verified by experiments.

• Proceedings of the KIEE Conference
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• 2002.06a
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• pp.3-5
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• 2002

This paper proposes a new prototype auxiliary resonant DC link(ARDCL)snubber circuit and deals with its power loss on the basis of actually measured conduction loss characteristic of switching device module. Voltage-type soft switching three phase inverter using proposed ARDCL snubber circuit is presented along with its performance evaluations. And, the power loss analysis of three phase hard and soft switching inverter are carried out from the point of simulation and experimental results.

• Journal of Power Electronics
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• v.10 no.6
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• pp.784-791
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• 2010

In this paper, a resonant pulse power converter (RPPC) is proposed. The proposed RPPC transfers the pulse-shape power from a DC source to a load periodically. The RPPC consists of a resonant circuit and a resonant pulse converter driven by a self-switching circuit. Depending on the magnitude difference between the input and output voltages, the operations of the RPPC are divided into 4 modes; boost mode, hybrid mode, direct mode and cut-off mode, respectively. The main switch of the RPPC turns on in the ZCS condition and off in the ZVS condition spontaneously. The operational principles of a RPPC using the self-switching technique are analyzed and verified in experiments. An example of a RPPC application is demonstrated in the area of thermoelectric energy harvesting.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.746-748
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• 1993

To overcome the problem of the diode reverse recovery in high switching frequency inverter, a new gate drive scheme is proposed for IGBT in this paper. Using this circuit, the reverse recovery current can be controlled and faster switching time can be achieved for hard switching inverter. The over-current protection method, which is suitable for the proposed gate driver, is also presented. The operation of the proposed circuit is investigated and its usefulness is verified through the experimental results.

• Proceedings of the KIEE Conference
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• 2005.07b
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• pp.1041-1043
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• 2005

It is expected to reduce stresses to components of high voltage circuit breaker and transferred switching surge from power system by applying controlled switching technique to high voltage system. This technique has already been applied to switch shunt reactor or capacitor bank in advanced countries. In this paper, operating software is installed in developed controlled switching device and HMI(Human-machine Interface) is under developing, In the future, this technique is expected to contribute to S.A(Substation Automation).