• Proceedings of the KIEE Conference
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• 2003.07e
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• pp.158-161
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• 2003

A new soft switching technique that improves performance of the high power factor boost rectifier by reducing switching losses is introduced. The losses are reduced by air active snubber which consists of an inductor, a capacitor a rectifier, and an auxiliary switch. Since the boost switch turns off with zero current, this technique is well suited for implementations with insulated gate bipolar transistors. The reverse recovery related losses of the rectifier are also reduced by the snubber inductor which is connected in series with the boost switch and the boost rectifier. In addition, the auxiliary switch operates with zero voltage switching. A complete design procedure and extensive performance evaluation of the proposed active snubber using a 1.2[kW] high power factor boost rectifier operating from a $90[V_{rms}]$ input are also presented.

• Proceedings of the IEEK Conference
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• 2002.07b
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• pp.743-746
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• 2002

This paper proposes the design of a current-mode CCII-based 2$\^$nd/ _order bandpass biquad filter from a grounded series capacitor and frequency-dependent negative conductor ( C-D ) immittance function simulator using the macro model of a commercial available CCII+, AD844, from Analog Devices, Inc. The results are compared with the other results those are designed using ideal model of CCII-. The gain and phase deviations; due to the effects of passive sensitivity, active sensitivity, gain sensitivity and component variability; are considered using Monte-Carlo analysis of PSpice program.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.562-568
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• 2013

This paper presents a design of a wireless power transfer system based on magnetic resonant coupling technology with in-band wireless communication. To increase the transmission distance and compensate for the change in the effective capacitance due to the varying distance, the proposed system used a loop antenna with a selectable capacitor array. Because the increased transmission distance enables multiple charging, we added a communication protocol operated at the same frequency band to manage a network and control power circuits. In order to achieve the efficient bandwidth in both power transfer mode and communication mode, the S-parameters of the loop antennas are adjusted by switching a series resistor. Our test results showed that the loop antenna achieved a high Q factor in power transfer mode and enough passband in communication mode.

• 제어로봇시스템학회:학술대회논문집
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• 1990.10b
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• pp.1420-1423
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• 1990

DC series motor has been widely applicated in industry due to many advantageous characteristics, such as high starting torque, easy construction of its controller, and cost economy, etc.. However, by high starting current, excessive surge voltage, and so on, many problems which could make engineers relinguish to use it are induced. In this paper, various protection methods for power circuit are discussed. Particularly, a new proposed snubber circuit which consists of two diodes, one capacitor, and a resistor increases the performance with respect to the suppression of the surge voltage. Furthermore, the plugging algorithm, by checking the armature current and voltage and controlling the field coil current, is designed and implemented. Also, these methods and algorithms were applicated in electric vehicle, and we could find its stability to be considerably improved.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.34S no.6
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• pp.85-93
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• 1997

This paper analyzes the steady-state and dynamic characteristics of the watkings-johnson converter. the major contributions of this paper includ identification of the following characteristics unique to the watkins-johnson converter: (1) The output voltage of the converter is nearly constant at the continous conduction mode (CCM), and at discontinousou conduction mode (DCM) it decreses linerly as the output curretn increases. (2) The control-to-output transfer function is a second-order one with a left-half-plane (LHP) zero determined by the combination of the output capacitor and equivalent series resistor of the converter. This LHP zero signinificantly improves the stability of the converter. (3) The control-to-output transfer function reduces to a first-order one, as the converter moves from CCM to DCM. (4) The parastic resistance of the inductor does not cause any significant influence on poles and zeros of the transfer function.

• Journal of the Korean Ceramic Society
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• v.32 no.10
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• pp.1111-1116
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• 1995

To use dielectric material of high power multilayer capacitor, the composition of the commercial CaTiO3 was changed to decrease the sintering temperature, and the physical and electrical properties were investigated. Series of experiments showed that CaTiO3 with sintering additives had the highest density, the highest shrinkage, the lowest dielectric constant, the lowest loss factor, and the lowest temperature coefficient of capacitance (TCC). These properties had the constant values at sintering temperature of above 120$0^{\circ}C$.

• Proceedings of the Korea Electromagnetic Engineering Society Conference
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• 2003.11a
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• pp.380-383
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• 2003

In this paper, we analyzed the characteristics of a modified DGS(Defected Ground Ground Structure)and extracted the equivalent citcuit of that. The proposed DGS is the structure that connects two DGS units, which are composed of the defects on the metallic ground plane and the gab on the signal line. The gab on the signal line was adopted to induce series capacitor of band pass filter. Also, to confirm the validity of the proposed structure, we designed and implemented C - Band pass filter by using the modified DGS.

• Proceedings of the KIEE Conference
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• 2008.07a
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• pp.988-989
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• 2008

This paper describes a rapid pulsed power charging system for pulsed power application. It is capable of charging 35kJ/s energy up to 0.47uF 25kV within 3ms and maximum pulse repetition rate of 300 pps can be achieved. The charger is designed based on three-phase series resonant inverter followed by air cooled set-up transformers thus it has many advantages of lower weight, small size and high efficiency compared with large bulky traditional pulse charger system. Detail design procedure of resonant inverter and high voltage transformers is explained. Experimental results carried out at different condition and its results shows 90% efficiency at full load condition.

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.506-509
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• 2002

In this paper, a design method of LCL filter at the AC input side of a voltage source PWM converter is proposed. Effective method to prevent pollution of the utility caused by high frequency current ripple is to use a LCL filter instead of the L filter The C elements in the filter provide a low impedance path for the high frequency component, preventing them from entering the utility. A resistor in series with a capacitor is used for damping the resonance in the filter. The design examples are shown and the validity of the proposed design method is verified through the PSIM simulation.

• Proceedings of the KIPE Conference
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• 1998.10a
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• pp.586-591
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• 1998

This paper presents an innovative prototype of a new conceptual electromagnetic induction-based fluid heating appliance using voltage-fed series capacitor-compensated load resonant high-frequency IGBT inverter with a phase-shifted PWM and a power factor correction schemes. Its operating characteristics in steady-state and dynamic state are illustrated including unique features and evaluated on the basis of its computer simulation and experimental results of 10kw breadboard appliance developed for hot water producer and superheated steamer.