• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1963-1965
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• 1998

In this paper, a new simplified configuration for a multi-level PWM inverter is proposed. The proposed inverter consists of an auxiliary circuit with one switching device, and 3 phase full-bridge inverter. The proposed inverter, in spite of reduction of the switching devices, offers characteristics similar to the NPC(Neutral - point - clamped)- PWM inverter. Also, since the reduction of the switching devices, the control strategy is simplified. And switching loss is reduced. In addition to, it is possible that reliable DC level voltage than former multi-level inverter. And load power application is same to conventional NPC-PWM inverter. The performance of the system is verified by simulation. In this paper, show the simulation result of the single phase full bridge inverter application.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1010-1011
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• 2006

A new soft switched active snubber circuit is proposed to achieve zero voltage and zero current switching for all the switching devices in PWM DC-DC converters. The unique location of the snubber capacitor and inductor ensures low current/voltage stresses and commutation losses. With a saturable reactor, the conduction loss of the auxiliary switch could be further minimized. A boost converter adopting this technique is presented as an example, to illuminate its operation principles and derive the design procedures. Simulation and hardware implementation have been made to validate its performance. Some other basic PWM DC-DC topologies using the proposed snubber have also been given.

• Proceedings of the KIEE Conference
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• 2006.07b
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• pp.1057-1058
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• 2006

In this paper, the proposed power supply is based on a modified version of the zero-voltage switching(ZVS) full-bridge phase-shift DC-DC converter, which incorporates commutation auxiliary inductors to provide ZVS for the entire load range as well as a commutation aid circuit to clamp the output diode voltage. The control strategy is based on two control loops operating in cascade mode. The complete operating principles and simulation results in presented.

• Proceedings of the KIEE Conference
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• 2003.04a
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• pp.234-236
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• 2003

In this paper, a new control scheme of Class-E inverter for reducing the crest factor of electronic ballasts for fluorescent lamps using Pulse-Frequency-Modulation (PFM) is introduced The lifetime of the lamps is guaranteed by decreasing the lamp crest factor and voltage stress of the switch is significantly decreased by a new scheme although conventional Class-E inverter is used in this paper The proposed PFM control scheme doesn't used any auxiliary circuit. The proposed control strategy is executed by feeding back the input current. and the Zero-Voltage-Switching (ZVS) is ensured by operating beyond resonant frequency. Therefore, the control principles of proposed method are explained in detail and its validity is verified through several simulated results.

• Proceedings of the Korean Institute of IIIuminating and Electrical Installation Engineers Conference
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• 2008.10a
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• pp.69-72
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• 2008

This paper presents the transient and conventional grounding impedance behaviors of large grid grounding system associated with the injection point of impulse current The measurement methods consider two possible errors in the grounding-system impedances: (1) ground mutual resistance due to current flow through ground from the ground electrode to be measured to the current auxiliary, (2) ac mutual coupling between the current test lead and the potential test lead The test circuit was set to reduce the error factors. The transient grounding impedance depends on the rise time and injection point of impulse current It is effective that grounding conductor is connected to the center of the large grid grounding system.

• Journal of Power Electronics
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• v.3 no.3
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• pp.175-184
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• 2003

In this paper, a new control scheme of Class-E inverter for reducing the crest factor of electronic ballasts for fluorescent lamps using Pulse-Frequency-Modulation (PFM) is Introduced The lifetime of the lamps is guaranteed by decreasing the lamp crest factor and also voltage stress of the switch is significantly decreased by a new scheme although conventional Class-E Inverter is used In this paper. The proposed PFM control scheme didn't use any auxiliary circuit. The proposed control strategy is executed by feeding back the Input voltage, and the zero-voltage-switching (ZVS) is ensured by maintaining constant turn-off time of the switch Therefore, the control principles of proposed method are explained in detail and its validity is verified through several simulations and experimental results.

• Proceedings of the KIPE Conference
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• 2005.07a
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• pp.549-551
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• 2005

Bidirectional DC/DC converters allows transfer of power between two dc sources, in either direction. Due to their ability to reverse the direction of flow of power, they are being increasingly used in many applications such as battery charger/dischargers, dc uninterruptible power supplies, electrical vehicle motor drives, aerospace power systems, telecom power supplies, etc. This paper proposes a new bidirectional Sepic/zeta converter. It has low swicthing loss and low conduction loss due to auxiliary communicated circuit and synchronous rectifier operation, respectively. Because of positive and buck/boost-like DC voltage transfer function(M=D/1-D), the proposed converter is very desirable for use in distributed power system . The proposed converter also has both transformerless version and transformer one.

• Journal of Power Electronics
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• v.9 no.4
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• pp.593-603
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• 2009

This paper proposes and describes the design and operational principles of a three-phase three-level nine switch voltage source inverter. The proposed topology consists of three bi-directional switches inserted between the source and the full-bridge power switches of the classical three-phase inverter. As a result, a three-level output voltage waveform and a significant suppression of load harmonics contents are obtained at the inverter output. The harmonics content of the proposed multilevel inverter can be reduced by half compared with two-level inverters. A Fourier analysis of the output waveform is performed and the design is optimized to obtain the minimum total harmonic distortion. The full-bridge power switches of the classical three-phase inverter operate at the line frequency of 50Hz, while the auxiliary circuit switches operate at twice the line frequency. To validate the proposed topology, both simulation and analysis have been performed. In addition, a prototype has been designed, implemented and tested. Selected simulation and experimental results have been provided.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.11
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• pp.640-645
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• 1999

This paper proposes a new series-connected diode rectifier which draws sinusoidal input currents. The proposed rectifier system is configured by adding an auxiliary circuit to the conventional 12-pulse series-connected diode rectifier and employing a current injection technique. A low kVA($0.02P_{\circ}$(PU) ) active current source injects a triangular current into the interphase reactor of the diode rectifier. The current injection results in near sinusoidal input current from the utility with less than 1% THD. The resulting system is suitable for high voltage and high power applications. Experimental and simulation results are provided from a 220V, 3kVA prototype rectifier system.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.48 no.12
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• pp.686-691
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• 1999

In a switching power supply, the high frequency switching makes the passive components small, but the losses and the stresses of switches are increased by the switching frequency. Therefore, zero crossing technology using resonant is used to improve defect in high switching. In generally, zero crossing switching consists of Zero Current Switching(ZCS) and Zero Voltage Switching(ZVS). This paper proposes A Buck ZC-ZVS Converter with Reduced Conduction Losses. Comparing with a conventional Buck ZC-ZVS Converter, the proposed converter operates with the smaller rated power. This is achieved by changing the auxiliary switch position, which reduces its rating power. Simulation results using Pspice program about test circuit with rated 160W(30V, 5.3A) at 30kHz and experiment result under same condition were described in the paper.