• Journal of Power Electronics
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• v.15 no.6
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• pp.1468-1479
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• 2015

Renewable energy resources such as wind and photovoltaic power generation systems demand a high step-up DC-DC converters to convert the low voltage to commercial grid voltage. However, the high step-up converter using a transformer has limitations of high voltage stresses of switches and diodes when the transformer winding ratio increases. Accordingly, conventional studies have been applied to series-connect multioutput converters such as forward-flyback and switched-capacitor flyback to reduce the transformer winding ratio. This paper proposes new single-ended converter topologies of an isolation type and a non-isolation type to improve power efficiency, cost-effectiveness, and output ripple. The first proposal is an isolation-type charge-pump switched-capacitor flyback converter that includes an extreme-ratio isolation switched-capacitor cell with a chargepump circuit. It reduces the transformer winding number and the output ripple, and further improves power efficiency without any cost increase. The next proposal is a non-isolation charge-pump switched-capacitor-flyback tapped-inductor boost converter, which adds a charge-pump-connected flyback circuit to the conventional switched-capacitor boost converter to improve the power efficiency and to reduce the efficiency degradation from the input variation. In this paper, the operation principle of the proposed scheme is presented with the experimental results of the 100 W DC-DC converter for verification.

• The Transactions of the Korean Institute of Power Electronics
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• v.10 no.3
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• pp.274-281
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• 2005

A new resonant pulse converter for energy harvesting is proposed. The converter transfers energy from a low-voltage AC current to a battery. The low-voltage AC current source is an equivalent of the piezoelectric generator, which converts the mechanical energy to the electric energy. The converter consists of a full-bridge rectifier having four N-type MOSFETs and a boost converter haying N-type MOSFET and P-type MOSFET instead of diode. Switching of MOSFETs utilizes the capability of the $3^{rd}$ regional operation. The operational principles and switching method for the power control of the converter are investigated with the consideration of effects of the parasitic capacitances of MOSFETs. Simulation and experiment are performed to prove the analysis of the converter operation and to show the possibility of the $\mu$W energy harvesting.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.342-345
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• 1999

This paper describes a current regulated PWM boost type rectifier based on modified trapezoidal PWM. Each switch of a converter has no switching for one third period of a fundamental line current. Therefore, the switching loss of the proposed scheme is less than that of the hysteresis current controller. Operating principle is described and controller. Operating principle is described and simulations and experiments are carried out.

• The Transactions of the Korean Institute of Power Electronics
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• v.18 no.3
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• pp.247-255
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• 2013

In this paper, a soft switching DC-DC converter for AC module type photovoltaic (PV) module integrated converter is proposed. A push-pull converter is suitable for a low voltage PV AC module system because the step-up ratio of a high frequency transformer is high and the number of primary side switches is relatively small. However, the conventional push-pull converters do not have high efficiency because of high switching losses by hard switching and transformer losses (copper and iron losses) by high turns-ratio of the transformer. In the proposed converter, primary side switches are turned on at zero voltage switching (ZCS) condition and turned off at zero current switching (ZVS) condition through parallel resonance between secondary leakage inductance of the transformer and a resonant capacitor. Therefore the proposed push-pull converter decreases the switching loss using soft switching of the primary switches. Also, the turns-ratio of the transformer can be reduced by half using a voltage-doubler of secondary side. The theoretical analysis of the proposed converter is verified by simulation and experimental results.

• Proceedings of the KIPE Conference
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• 1999.07a
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• pp.472-475
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• 1999

An improved series-parallel resonant converter using auxiliary winding of resonant is presented. The conventional series-parallel resonan converter and newly developed converter are compared for high voltage application. This proposed converter gives several merits such a wide load ranges, small circulating current, low peak voltage at no load. Two experimental results for the proposed converter and conventional one are presented for conventional LCC type converter and the proposed one.

• Proceedings of the KIPE Conference
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• 2003.07a
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• pp.49-53
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• 2003

In this paper, to analyze efficiency characteristic, one of important factors in design of DC-DC converter prototype, theoretically derived power loss of individual components generating in DC-DC converter and compared theoretical results with experimental results. For evaluation of results, active clamp type Forward DC-DC converter with synchronous rectifier was composed of experimental converter. Efficiency result measured in experimental converter was compared with theoretical efficiency result derived in this paper. In comparative results, a fact that derived theoretical value and experimental value comparatively correspond have been able to verify.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.64 no.2
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• pp.260-267
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• 2015

An LCL-type isolated dc-dc converter is analyzed, using ac approximation. Analyses to express characteristics on the proposed converter are derived under steady and ideal elements conditions in this paper. The two operating modes can be identified from the analysis results representing different device conduction sequences. This converter is capable of achieving required output voltage(step up or down) operations with inductance ratio while operated at fixed frequency with constant duty ratio-50%. Experimental results show that the designed converter based on Q has zero voltage switching and constant output voltage at different load variations to verify the analysis.

• Transactions of the Korean hydrogen and new energy society
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• v.19 no.5
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• pp.417-422
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• 2008

In this paper, a novel DC/DC low-voltage high-current converter circuit is proposed to improve the efficiency of power converter used in the grid-connected fuel-cell generator system. We proposed a novel high efficiency grid-connected power conditioning system for RPG fuel cell. On the result of that, the loss of system was decreased rapidly by driving stack within the condition of maximum efficiency. The peak currents of the current-type inductor and the transformer's coil are reduced by synchronizing switching frequency of Buck-type converter is increased twice as the Push-Pull converter's switching frequency. The novel structure of DC/DC converter is able to realize ZVS-ZCS in fuel-cell system is proposed. The proposed switching component of Push-Pull converter has the ZVS and ZCS function by using the circuit of new passive clamp.

• Proceedings of the KIPE Conference
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• 2018.07a
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• pp.105-107
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• 2018

This paper presents a new hybrid multilevel converter topology, which consists of a combination of the series connected switched capacitor units with boost ability, and an H-bridge with T-type bidirectional switches. The proposed converter boosts the input voltage without any bulky inductors, and has the small number of components, which can make the size and cost of a power converter greatly reduced. The output filter size and harmonics are also reduced by the high quality multilevel output. In addition, there is no need for complicated methods to balance the capacitor voltage. Simulation and experimental results with a nine-level converter system are presented to validate the proposed topology and modulation method.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1193-1195
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• 2003

In this paper, to analyze efficiency characteristic, one of important factors in design of DC-DC converter prototype, theoretically derived power loss of individual components generating in DC-DC converter and compared theoretical results with experimental results. For evaluation of results, active clamp type Forward DC-DC converter with synchronous rectifier was composed of experimental converter. Efficiency result measured in experimental converter was compared with theoretical efficiency result derived in this paper. In comparative result, a fact that derived theoretical value and experimental value comparatively correspond have been able to verify.