• Proceedings of the KIEE Conference
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• 1999.11b
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• pp.406-408
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• 1999

In order to reduce the overall size and cost, researchers attempted to integrate the functions of power factor correction(PFC) and isolated dc-dc conversion into single power stage. However, single-stage isolated PFC converters have higher voltage stress and heavier loss when compared with a normal dc-dc converters. In this paper, we propose to add active clamping circuit to keep the switch voltage stress low and to achieve soft switching of electronic devices.

• Journal of Electrical Engineering and Technology
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• v.12 no.2
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• pp.654-664
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• 2017

This paper proposed an unified dual-phase-shift (UDPS) control for dual active bridge (DAB) converters in order to improve efficiency for a wide output power range. Different operating modes of UDPS are characterized with respect to the reactive current distribution. The proposed UDPS has the same output power capability with conventional phase-shift (CPS) method. Furthermore, its implementation is simple since only the change of the leading phase-shift direction is required for different operating power range. The proposed UDPS control can minimize both the inductor rms current and the circulating reactive current for various voltage conversion ratios and load conditions. The optimal phase-shift pairs for two bridges of DAB converter are derived with respect to the comprehensive reactive power loss model, including the reactive components delivered from the load and back to the source. Simulation and experimental results are illustrated and explained with details. The effectiveness of the proposed method is verified in terms of reactive power losses minimization and efficiency improvement.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1224-1232
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• 2014

A full-bridge secondary dual-resonant DC-DC converter using the asymmetrical pulse-width modulated (APWM) strategy is proposed in this paper. The proposed converter achieves zero-voltage switching for the power switches and zero-current switching for the rectifier diodes in the whole load range without the help of any auxiliary circuit. Given the use of the APWM strategy, a circulating current that exists in a traditional phase-shift full-bridge converter is eliminated. The voltage stress of secondary rectifier diodes in the proposed converter is also clamped to the output voltage. Thus, the existing voltage oscillation of diodes in traditional PSFB converters is eliminated. This paper presents the circuit configuration of the proposed converter and analyzes its operating principle. Experimental results of a 1 kW 385 V/48 V prototype are presented to verify the analysis results of the proposed converter.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1999.10a
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• pp.387-392
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• 1999

The micro electronic control technology with developing microcomputers make great contribution to electrohydraulic control systems. The electrohydraulic pulse control simplifies in conjunction with power electronic amplifier and high speed operated solenoid valves. It is necessary to valves to convert electronic pulse signal to hydraulic pulse flow as fast as possible. This study deals with the speed control of an oil hydraulic motor operated by two way high speed solenoid valves. The valves acts as converters of electronic-pulse signals to hydraulic power. By constructing systems in which a hydraulic motor is operated by two solenoid valves, the pulse with modulation method (PWM) has adopted as the speed control of hydraulic motor systems. The static and dynamic characteristics of the systems are investigated by the experiment. It is clarify that a hydraulic motor operated PWM show good performance as a control component, achieving accurate velocity control.

• Journal of Power Electronics
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• v.15 no.1
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• pp.18-30
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• 2015

This paper focuses on a systematical and in-depth analysis of the reactive power and soft-switching regions of Dual Active Bridge (DAB) converters with dual-phase-shift (DPS) control to achieve high efficiency in a wide operating range. The key features of the DPS operating modes are characterized and verified by analytical calculation and experimental tests. The mathematical expressions of the reactive power are derived and the reductions of the reactive power are illustrated with respect to a wide range of output power and voltage conversion ratios. The ZVS soft-switching boundary of the DPS is presented and one more leg with ZVS capability is achieved compared with the CPS control. With the selection of the optimal operating mode, the optimal phase-shift pair is determined by performance indices, which include the minimum peak or rms inductor current. All of the theoretical analysis and optimizations are verified by experimental tests. The experimental results with the DPS demonstrate the efficiency improvement for different load conditions and voltage conversion ratios.

• Proceedings of the KIEE Conference
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• 2002.04a
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• pp.147-150
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• 2002

HPSL(High Pressure Sodium lamp)have attracted much attention in recent years, because they offer high luminous efficiency and very long life. Recently, AC-DC converters have been widely as power factor improvement circuits in the power conversion equipment An application of the ZVT-PWM(Zero Voltage Transition Pulse Width Modulation) boost converter, which has great advantage on miniaturization and high power density, to the power factor improvement circuit of the HPSL inverter are described to identify the power factor correction characteristics of the inverter. In this paper the series-parallel resonant inverter(electronic ballast) for driving a HPS lamp is discussed. Finally, a power factor corrector is cascaded in front of the electronic ballast. Consequently, a high power factor above 0.99 and low THD on the line current can be achieved.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.26 no.3
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• pp.190-193
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• 2013

Power MOSFET and Power IGBT is develop in power savings, high efficiency, small size, high reliability, fast switching, low noise. Power MOSFET can be used high-speed switching transistors devices. Power MOSFET is devices the voltage-driven approach switching devices are design to handle on large power, power supplies, converters. In this paper, design the 80V MOSFET Planar Gate type, and design the Trench Gate type for realization of low on-resistance. For both structures, by comparing and analyzing the results of the simulation and characterization.

• Journal of Power Electronics
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• v.12 no.1
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• pp.145-156
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• 2012

These days, the application of electronic power transformers (EPTs) is expanding in place of ordinary power transformers. These transformers can transmit power via three or four wire converters. Their dynamic performance is extremely important, due to their complex structure. In this paper, a new method is proposed for improving the dynamic performance of distribution electronic power transformers (DEPT) by using sliding mode control (SMC). Hence, to express the dynamic characteristics of a system, different factors such as the voltage unbalance, voltage sag, voltage harmonics and voltage flicker in the system primary side are considered. The four controlling aims of the improvement in dynamic performance include: 1) maintaining the input currents so that they are in sinusoidal form and in phase with the input voltages so they have a unity power factor, 2) keeping the dc-link voltage within the reference amount, 3) keeping the output voltages at a fixed amount and 4) keeping the output voltages in sinusoidal and symmetrical forms. Simulation results indicate the potential and capability of the proposed method in improving DEPT behavior.

• Proceedings of the IEEK Conference
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• 2007.07a
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• pp.467-468
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• 2007

This paper describes characteristics of converters of auxiliary power supply for electric railway vehicles. Auxiliary power supply is called Static Inverter(SIV) which supplied lamps, air conditioning and heat equipments, control systems, etc. Simulation results shows that line No.1 cheon contains low harmonics compared with those of KTX.

• Journal of Power Electronics
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• v.15 no.3
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• pp.644-651
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• 2015

This paper introduces a novel digital one cycle control (DOCC) boost power factor correction (PFC) converter. The proposed PFC converter realizes the FPGA-based DOCC control approach for single-phase PFC rectifiers without input voltage sensing or a complicated two-loop compensation design. It can also achieve a high power factor and the operation of low harmonic input current ingredients over universal loads in continuous conduction mode. The trailing triangle modulation adopted in this approach makes the acquisition of the average input current an easy process. The controller implementation is based on a boost topology power circuit with low speed, low-resolution A/D converters, and economical FPGA development board. Experimental results demonstrate that the proposed PFC rectifier can obtain a PF value of up to 0.999 and a minimum THD of at least 1.9% using a 120W prototype.