• Journal of Power Electronics
• /
• v.18 no.4
• /
• pp.975-984
• /
• 2018

This work presents a high efficiency phase shifted full bridge (PSFB) DC-DC converter for use in the second stage of a battery charger for neighborhood electrical vehicle (EV) applications. In the design of the converter, Lithium-ion battery cells are preferred due to their high voltage and current rates, which provide a high power density. This requires wide range output voltage regulation for PSFB converter operation. In addition, the battery charger works with a light load when the battery charge voltage reaches its maximum value. The soft switching of the PSFB converter depends on the dead time optimization and load condition. As a result, the converter has to work with soft switching at a wide range output voltage and under light conditions to reach high efficiency. The operation principles of the PSFB converter for the continuous current mode (CCM) and the discontinuous current mode (DCM) are defined. The performance of the PSFB converter is analyzed in detail based on wide range output voltage and load conditions in terms of high efficiency. In order to validate performance analysis, a prototype is built with 42-54 V / 15 A output values at a 200 kHz switching frequency. The measured maximum efficiency values are obtained as 94.4% and 76.6% at full and at 2% load conditions, respectively.

• The Transactions of the Korean Institute of Electrical Engineers B
• /
• v.50 no.2
• /
• pp.79-85
• /
• 2001

In this paper, a novel Zero-Current-Transition (ZCT) technique, which provides Zero-Current-Switching (ZCS) turn-off of the main switch, the main diode and the auxiliary switch, is presented. The proposed auxiliary circuit consists of minimum elements only one auxiliary switch, resonant inductor and resonant capacitor. Also the reduced di/dt, which is obtained by resonant inductor, helps soft turn-on of the main switch. Besides, to eliminate the additional conduction loss and current stress on main switch, a topological variation was performed. The theoretical analysis and the operation principle of the new ZCT techniques are described in detail with a boost converter as an example. To verify the validity of the proposed ZCT techniques, the simulation and the experiment were performed under 1kW output power and 100kHz switching frequency.

• Proceedings of the KIPE Conference
• /
• 2020.08a
• /
• pp.160-162
• /
• 2020

A control technique for the auxiliary buck/boost converter is proposed herein to improve the load transient response of the buck converter. The proposed technique improves the system efficiency by enabling the soft switching operation of the auxiliary converter. The design guidelines for achieving capacitor charge balance for the output capacitor during the transient are also presented herein. The experimental results revealed that the output voltage undershoot and settling time during the load step-up transient were 40 mV and 14 ㎲, respectively, and the output voltage overshoot and settling time during the load step-down transient were 35 mV and 21 ㎲, respectively. The performance and effectiveness of the proposed technique were experimentally verified using a prototype buck converter with a 15-V input, 3.3-V output, and 200-kHz switching frequency.

• The Transactions of the Korean Institute of Power Electronics
• /
• v.20 no.1
• /
• pp.51-58
• /
• 2015

In order to decrease the size of a switch mode power supply, high switching frequency can be an efficient way to reduce the size of passive components in the converter. In this paper, a 500-kHz high-frequency LLC resonant converter is proposed with an accurate design method of magnetizing inductance, as well as the relationship between the switching frequency and the size of the passive components. Simulation and experimental results are presented to verify the proposed methods and equations, including the temperature data of each passive and active device of the converter. Using those results, dominant power losses in the prototype converter under 500-kHz high-frequency operation are investigated, compared with the results from a 100-kHz converter. In addition, operating waveforms and power conversion efficiency will be shown to obtain design considerations for the high switching frequency LLC resonant converter.

• Proceedings of the KIPE Conference
• /
• 2001.10a
• /
• pp.256-260
• /
• 2001

This paper presents boost and buck and buck-boost DC-DC converter circuit topologies of high-frequency soft switching transition PWM chopper type DC-DC high power converters with a single auxiliary passive resonant snubber. In the proposed boost power converter circuits operating under a principle of ZCS turn-on and ZVS turn-off commutation schemes, the capacitor and inductor in the auxiliary passive resonant circuit works as the loss less resonant snubber. In addition to this, the switching voltage and current peak stresses as well as EMI and RFI noises can be basically reduced by this single passive resonant snubber. Moreover, it is proved that converter circuit topologies with a passive resonant snubber are capable of solving some problems of the conventional hard switching PWM processing based on high-ferquency pulse modulation operation principle. The simulation results of this converter are discussed as compared with the experimental ones. The effectiveness of this power converter with a single passive resonant snubber is verified by the 5kW experimental breadboad set up.

• Proceedings of the Korean Society Of Semiconductor Equipment Technology
• /
• 2002.11a
• /
• pp.54-58
• /
• 2002

The present paper is to investigate the phase stability and soft magnetic properties of amorphous CoNbZr films when Pd is added as a substitution for CoNbZr alloys. The films were prepared by a RF magnetron sputtering method. The CoNbZrPd films deposited on Si wafers exhibited amorphous structures being independent upon the amount of Pd added in the films. On the addition of 4.34% Pd, the excellent soft magnetic characteristics of the films were observed with a coercive force of 0.54 Oe and an anisotropy field of 11 Oe, whereas a coercive force of 1 Oe and an anisotropy field of 3.5 Oe were shown in the film without the addition of Pd. The increased anisotropy field and low coercive force of the films may be attributed to the occupancy of Pd in the preferred sites parallel to the external magnetic field applied on the deposition process. A permeability of about 1100 was kept constant in the operation frequency ranging up to 100 MHz, which can be explained by the Landau-Lifshitz formula.

• Journal of Chest Surgery
• /
• v.7 no.1
• /
• pp.109-116
• /
• 1974

Eleven cases of peripheral arterial injuries treated at Korea University Woo Sok Hospital during these 3 years and 3 months from Feb. 1971Eleven cases of peripheral arterial injuries treated at Korea University Woo Sok Hospital during these 3 years and 3 months from Feb. 1971 to May 1974 were reviewed. Common causes of injuries were stab wound, automobile accidents and iatrogenic injuries during operation. Of the 11 arterial injuries 3 were femoral artery which` was the commonest in frequency and the next was 2 cases of brachial artery. The most frequent type of injury was transection. Laceration, contusion and spasm was also recognized. The need to operate immediately following an injury was emphasized. Operative procedures were end to end anastomosis and saphenous vein graft in 5 and 2 cases, respectively. Other cases were undergone multiple suture ligature due to staphyllococcal infection, insertion of polyethylene catheter, and lateral suture after thromboendarterectomy. Fractures and extensive soft tissue damage associated with arterial injuries with widespread destruction of the collateral circulation aggravated the situation and complicated the amputation of lower extremity in 4 cases. The factors influencing the amputation were time lag, presence of associated injuries and complications.[KTCS 1974;1:109-116] Common causes of injuries were stab wound, automobile accidents and iatrogenic injuries during operation. Of the 11 arterial injuries 3 were femoral artery which` was the commonest in frequency and the next was 2 cases of brachial artery. The most frequent type of injury was transection. Laceration, contusion and spasm was also recognized. The need to operate immediately following an injury was emphasized. Operative procedures were end to end anastomosis and saphenous vein graft in 5 and 2 cases, respectively. Other cases were undergone multiple suture ligature due to staphyllococcal infection, insertion of polyethylene catheter, and lateral suture after thromboendarterectomy. Fractures and extensive soft tissue damage associated with arterial injuries with widespread destruction of the collateral circulation aggravated the situation and complicated the amputation of lower extremity in 4 cases. The factors influencing the amputation were time lag, presence of associated injuries and complications.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
• /
• 2006.05a
• /
• pp.399-402
• /
• 2006

This paper presents a new circuit topology of dc bus line switch-assisted half-bridge soft switching PWM inverter type dc-dc converter for arc welder. The proposed power converter is composed of typical voltage source half-bridge high frequency PWM inverter with a high frequency transformer link in addition to dc bus line side power semiconductor switching devices fer PWM control scheme and capacitive lossless snubbers. All the active power switches in the half-bridge arm and dc bus lines can achieve ZCS turn-on and ZVS turn-off commutation operation and consequently the total turn-off switching losses can be significantly reduced. As a result, a high switching frequency of using IGBTs can be actually selected more than about 20 kHz. The effectiveness of this new converter topology is proved for low voltage and large current dc-dc power supplies such as arc welder from a practical point of view.

• Proceedings of the KSME Conference
• /
• 2007.05b
• /
• pp.3259-3263
• /
• 2007

This paper describes the proceedings of creating countermeasures after analysis and maintenance be able to conduct operation safely in a power plant. in order to operate the power plant in a stable and reliable way, the best condition of the govemor system can be maintained through the response characteristic analysis of the control device for the pitch blade control hydraulic actuator. The fan pitch blade control hydraulic actuator of a 500MW large-scale boiler is frequently operated under normal operation conditions. Common problems or malfunctions of the pitch blade control hydraulic actuators leads to the decline of boiler thermal efficiency and unexpected power plant trip. The inlet and outlet gas can be controlled by using the fan pitch blade control hydraulic actuator in order to regulate the internal pressure of the furnace and control the frequency in the power plant facility which utilizes soft coals as a power source.

• Proceedings of the KIEE Conference
• /
• 1998.07f
• /
• pp.1911-1913
• /
• 1998

This paper has described about a SEPP Inverter for induction heating load. It is analyzed theoretically about the Inverter operation for induction heating. According to the parameters of induction heating load, it is proposed a method of circuit analysis and operation characteristics of the Inverter. In addition, the soft switching technology known as ZVS(Zero Voltage Switching) is used to reduce turn on and off loss at switching. The Proposed inverter shows it can be practically used as power source system for high frequency induction heating appliancs.