• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.377-382
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• 2005

This paper presents two new circuit topologies of DC bus lineside active edge resonant snubber assisted soft-switching PWM full-bridge DC-DC converter acceptable for either utility AC 200V-rms or AC 400V-rms input voltage source. One topology of proposed DC-DC converters is composed of a typical voltage source-fed full-bridge high frequency PWM inverter using DC busline side series power semiconductor switching devices with the aid of a parallel capacitive lossless snubber. All the active power switches in the full-bridge arms and DC busline can achieve ZCS turn-on and ZVS turn-off commutations and the total turn-off switching power losses of all active switches can be reduced for high-frequency switching action. It is proved that the more the switching frequency of full-bridge soft switching inverter increases, the more soft-switching PWM DC-DC converter with a hish frequency transformer link has remarkable advantages for its efficiency and power density as compared with the conventional hard-switching PWM inverter type DC-DC converter

• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.4
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• pp.383-390
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• 2014

This paper deals with novel soft-switching method for a bidirectional DC-DC converter in battery charging and discharging system. The proposed soft-switching method provides ZVS and ZCS at turn-on, and ZVS at turn-off of the switch in both charging and discharging operation modes. The soft switching condition can be obtained in wide load range, and provide low switching loss as well as low voltage spike at turn-off of the switch. Proposed method is analyzed in charging and discharging mode. Simulation and experimental results validate the usefulness of the proposed soft-switching method.

• Journal of Power Electronics
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• v.17 no.2
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• pp.561-569
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• 2017

Power converter design requires simulation accuracy. In addition to the requirement of accurate models of power semiconductor devices, this paper highlights the role of considering a very good description of the converter circuit layout for an accurate simulation of its electrical behavior. This paper considers a simple experimental circuit including one switching cell where a MOSFET transistor controls the diode under test. The turn-off transients of the diode are captured, over which the circuit wiring has a major influence. This paper investigates the necessity for accurate modeling of the experimental test circuit wiring and the MOSFET transistor. It shows that a simple wiring inductance as the circuit wiring representation is insufficient. An adequate model and identification of the model parameters are then discussed. Results are validated through experimental and simulation results.

• Journal of Electrical Engineering and Technology
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• v.12 no.1
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• pp.198-206
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• 2017

This paper presents a novel scheme to estimate the rotor position of a single-phase hybrid switched reluctance motor (HSRM). The back-EMF generated by the permanent magnet (PM) field whose performance is motor parameter independent is adopted as an index to achieve the sensorless control. The differential value of back-EMF is calculated by hardware and processed by DSP to capture a fixed rotor position four times for every mechanical cycle. In addition, to accomplish the normal starting of HSRM, the determination method of the turn-off time position at the first electrical cycle is also proposed. In this way, a sensorless operation scheme with adjustable turn on/off angle can be achieved without substantial computation. The experimental verification using a prototype drive system is provided to demonstrate the viability of the proposed position estimation scheme.

• Proceedings of the KIPE Conference
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• 2011.11a
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• pp.257-258
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• 2011

This paper describes a new method for the seamless operation mode transfer of a PCS with minimized voltage disturbance. The proposed method provides reduced STS turn off time after line fault and smooth mode change between current and voltage control of the PCS. The usefulness of the method is verified through simulations with the consideration of the time delay in detecting a line fault and SCR turn-off time.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.263-266
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• 1990

In order to high-respone and high-reliability of devices, it depended upon how we can increase the high-frequency of the Inverter, UPS and it's application. but using high-frequency of self turn-off devices, it is important to reduce switching device loss and spike voltage of turn off. This paper proposed new methode about computer simulation of device loss also experimental results with switching device characteristic are presented.

• Proceedings of the KIEE Conference
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• 1991.07a
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• pp.596-599
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• 1991

This paper describes a novel switching algorithm of series connected power semiconductors for high voltage applications. In order to improve the reliability and efficiency of high voltage static power converters, we study on the switching characteristics of series connected power semiconductors and then propose "a servo control of snubber capacitor value" for the dynamic voltage balancing under turn-off state in series connected power semiconductors. Finally, we illustrate the validity of this algorithm by computer simulation and experimental results.

• Proceedings of the KIEE Conference
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• 2009.07a
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• pp.863_864
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• 2009

Design and drive characteristics of SR drive for hydraulic pump system using passive converter is presented in this paper. In oder to get the high performance, a simple passive circuit is added in the front-end of a conventional asymmetric converter, which consists of three diodes and one capacitor. This passive converter has the high demagnetization voltage, to reduce the demagnetization time. Futhermore optimal turn-off angle for the proposed passive converter is proposed. According to motor speed and current, an optimal turn-off angle can be achieved by look-up table to reduce torque ripple. The characteristic of proposed hydraulic pump system using passive converter is verified by simulation and experimental results.

• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.391-393
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• 2008

A modified boost converter with magnetic coupling is presented to reduce the reverse recovery loss while maintaining low conduction loss of the rectifiers. By utilizing a coupled inductor and a set of diodes, the current passing the boost rectifier is transferred to an auxiliary loop before turn-off, allowing low di/dt for reduced recovery loss. Moreover, the boost inductor is brought inside the bridge rectifier to reduce conduction loss by decreasing the number of conducting diodes during switch turn-off. Experimental results of a 500W prototype are provided to verify the increase in efficiency and validity of the proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.52 no.12
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• pp.632-640
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• 2003

In conventional Zero-Voltage-Transition(ZVT) PWM converters, zero-voltage turn-on and turn-off for main switch without increasing voltage/current stresses is achieved at a fixed frequency. The switching loss, stress, and noise, however, can't be minimized because they adopt auxiliary switches turned off under hard-switching condition. In this paper, new ZVS-PWM converters of which both active and passive switches are always operating with soft-switching condition are proposed. Therefore, the proposed ZVS-PWM converters are most suitable for avionics applications requiring high-power density. Breadboarded ZVS-PWM boost converters using power MOSFET are constructed to verify theoretical analysis.