• Journal of Power Electronics
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• v.11 no.4
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• pp.561-567
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• 2011

This paper presents a high-efficiency power conditioning system (PCS) for grid-connected photovoltaic (PV) modules. The proposed PCS consists of a step-up DC-DC converter and a single-phase DC-AC inverter for the grid-connected PV modules. A soft-switching step-up DC-DC converter is proposed to generate a high DC-link voltage from the low PV module voltage with a high-efficiency. A DC-link voltage controller is presented for constant DC-link voltage regulation. A half-bridge inverter is used for the single-phase DC-AC inverter for grid connection. A grid current controller is suggested to supply PV electrical power to the power grid with a unity power factor. Experimental results are obtained from a 180 W grid-connected PV module system using the proposed PCS. The proposed PCS achieves a high power efficiency of 93.0 % with an unity power factor for a 60 Hz / 120 Vrms AC power grid.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.546-548
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• 2005

This paper proposes a unity power factor ZVT PWM single-phase rectifier. The ZVT soft switching are achieved by using a simple ZVT circuit, and the reduced conduction losses are achieved by employing a single-stage converter, instead of a typical double-stage converter composed of front end diode rectifier and cascaded boost rectifier. Furthermore, thanks to good features such as simple PWM control at constant frequency, low switch stress and low VAR rating of commutation circuits, it is suitable for high power applications. The principle of operation is explained in detail, and simulation results of the new converter are also included.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2005.11a
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• pp.383-386
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• 2005

In this paper, proposed new partial resonance ZCS PWM controlled High frequency insulated Full-bridge DC-DC converter not using exciting current of high frequency transformer. It is compared with the existing principles in characteristics. It also realizes a widely stabilized ZVS operating using new ON-OFF control method at synchronized power rectification MOSFET of high frequency insulated transformer secondary. Besides, it is brought over 97[%] measurement efficiency by proposed DC-DC converter.

• Journal of IKEEE
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• v.24 no.1
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• pp.319-325
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• 2020

In this paper, a discontinuous-conduction mode (DCM) DC-DC buck converter is presented for mobile device applications. The buck converter consists of compensator for stable operations, pulse-width modulation (PWM) logic, and power switches. In order to achieve small hardware form-factor, the number of off-chip components should be kept to be minimum, which can be realized with simple and efficient frequency compensation and digital soft start-up circuits. Burst-mode operation is included for preventing the efficiency from degrading under very light load condition. The DCM DC-DC buck converter is fabricated with 0.18-um BCDMOS process. Programmable output with external resistors is typically set to be 1.8V for the input voltage between 2.8 and 5.0V. With a switching frequency of 1MHz, measured maximum efficiency is 92.6% for a load current of 100mA.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.272-277
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• 1990

A soft switched matrix converter is proposed by adopting the zero voltage switching technique being used in some resonant pole inverters. High operating frequency with safe and efficient switching improves dynamic and spectral performances and simplifies protection logics and snubber networks. Further, it can be implemented using simple analog circuits, having similar transfer characteristics to those of the modern pulse width modulated matrix converters such as, maximum voltage transfer ratio and unity input displacement factor. Analyses, design and simulation results are presented to verify the operating principle.

• 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 KIPE Conference
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• 2016.07a
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• pp.323-324
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• 2016

In this paper a high efficiency bidirectional resonant converterfor Vehicle-to-Grid applications (V2G) is proposed.The proposed converter has adopted an LC auxiliary circuit in the third winding of the transformer. With the proposed method full softswitching can be ensured in all switches over a wide range of loadsand the secondary ringing can be removed with no additional snubber or clamp circuitry.In addition, since the proposed resonant converter is able to operate at an almost constant resonant frequencyregardless of the load, CC/CV charge of the battery can be simply implemented with high efficiency. A 3.3 kW bidirectional converter for On-Board Charger of Electric Vehicle is implemented to verify the validity of the proposed method. The experimental results show the high efficiency characteristics of the proposed converter over the wide range of load in both charge and discharge mode. The maximum efficiency of the proposed system was 98.13 % at 2.3 kW during the constant voltage mode charge operation.

• Journal of Power Electronics
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• v.17 no.6
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• pp.1433-1444
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• 2017

A family of non-isolated DC-DC three-port converters (TPCs) that allows for a more flexible power flow among a renewable energy source, an energy storage device and a current-reversible DC bus is introduced. Most of the reported non-isolated topologies in this area consider only a power consuming load. However, for applications such as hybrid-electric vehicle braking systems and DC microgrids, the load power generating capability should also be considered. The proposed three-port family consists of one unidirectional port and two bi-directional ports. Hence, they are well-suited for photovoltaic (PV)-battery-DC bus systems from the power flow viewpoint. Three-port converters are derived by combining different commonly known power converters in an integrated manner while considering the voltage polarity, voltage levels among the ports and the overall voltage conversion ratio. The derived converter topologies are able to allow for seven different modes of operation among the sources and load. A three-port converter which integrates a boost converter with a buck converter is used as a design example. Extensions of these topologies by combining the soft-switching technique with the proposed design example are also presented. Experiment results are given to verify the proposed three-port converter family and its analysis.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.2
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• pp.122-129
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• 2011

In this paper, a new power factor correction circuit(PFC) based on a soft-switched boost scheme is proposed. Except for some soft-switching transition intervals, it operates exactly like the conventional boost scheme. Thus the desirable features of both high efficiency and easy control can be obtained. The design guidelines are suggested to achieve high efficiency. To verify the superior performance of the proposed circuit, experiment and simulation is carried out.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.53 no.9
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• pp.576-583
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• 2004

This paper presents a buck circuit topology of high-frequency with a single switching device. It solved the problem which arised from hard-switching in high-frequency using a resonant snubber and operating under the principle of ZCS turn-on and ZVS turn-off commutation schemes. In the existing circuit, it has the voltage stress that is almost twice of input voltage in a free-wheeling diode. In the proposed circuit, it has the voltage stress that is lower than input voltage with modifing a location of free -wheeling diode. In this paper, it expained the circuit operation of each mode and analyzed feedback-loop stabilization. Also it confirmed the waveform of each mode with simulation result. The experiment result verified the simulation waveform and compared the voltage stress of a free -wheeling diode in the exsiting circuit with the voltage stress of that in the proposed circuit. Moreover, it compares and analyzes the proposed circuit's efficiency with the hard-switching circuit's efficiency according to the change of load current.