• Proceedings of the KIEE Conference
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• 1988.07a
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• pp.151-154
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• 1988

Quantum converters, a subset of resonant converters operating with optimal conditions are modeled. It is shown that series resonant converter(SRC) can be modeled as buck/boost converter with an equivalent inductor and parallel resonant converter(PRC) can be modeled as Cuk converter, with an equivalent capacitor. Also new resonant circuits with boost, buck-boost and Cuk converter characteristics are proposed. From these models, the quantum converters can be designed to be controlled with closed loop feedback, having many advantages such as low device switching stress, reliable high frequency operation and low EMI.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.30 no.1
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• pp.79-86
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• 2016

In this paper, we propose a current-driven synchronous rectifier driver circuit for LLC resonant half-bridge converters. The proposed driver circuit detects a relatively low current in the primary side of the transformer although a large current is flowing in the secondary side. Due to this feature, the driver circuit has a simple circuit structure and stabilizes the switching operation with a logic-level switching voltages for the synchronous rectifier. The operation and performance of the proposed driver circuit are confirmed with a prototype of 1kW class LLC resonant half-bridge converter. The experimental results proved that the proposed synchronous rectifier driver method improves the power conversion efficiency by around 1% and reduces the internal power loss by 17W.

• Journal of Power Electronics
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• v.14 no.2
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• pp.217-225
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• 2014

This paper deals with the optimization of the driving techniques for the ZVT synchronous buck converter proposed in [1]. Two new gate drive circuits are proposed to allow this converter to operate by only one control signal as a 12V voltage regulator module (VRM). Voltage-driven method is applied for the synchronous rectifier. In addition, the control signal drives the main and auxiliary switches by one driving circuit. Both of the circuits are supplied by the input voltage. As a result, no supply voltage is required. This approach decreases both the complexity and cost in converter hardware implementation and is suitable for practical applications. In addition, the proposed SR driving scheme can also be used for many high frequency resonant converters and some high frequency discontinuous current mode PWM circuits. The ZVT synchronous buck converter with new gate drive circuits is analyzed and the presented experimental results confirm the theoretical analysis.

• Journal of Power Electronics
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• v.13 no.4
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• pp.626-635
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• 2013

An analysis of the junction capacitance in resonant rectifiers which has a significant impact on the operating point of resonance circuits is studied in this paper, where the junction capacitance of the rectifier diode is to decrease the resonant current and output voltage in the circuit when compared with that in an ideal rectifier diode. This can be represented by a simplified series resonant equivalent circuit and a voltage transfer function versus the normalized operating frequency at varied values of the resonant capacitor. A low voltage to high voltage push-pull DC/DC resonant converter was used as a design example. The design procedure is based on the principle of the half bridge class-DE resonant rectifier, which ensures more accurate results. The proposed scheme provides a more systematic and feasible solution than the conventional resonant push-pull DC/DC converter analysis methodology. To increase circuit efficiency, the main switches and the rectifier diodes can be operated under the zero-voltage and zero-current switching conditions, respectively. In order to achieve this objective, the parameters of the DC/DC converter need to be designed properly. The details of the analysis and design of this DC/DC converter's components are described. A prototype was constructed with a 62-88 kHz variable switching frequency, a 12 $V_{DC}$ input voltage, a 380 $V_{DC}$ output voltage, and a rated output power of 150 W. The validity of this approach was confirmed by simulation and experimental results.

• Journal of Power Electronics
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• v.7 no.1
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• pp.28-37
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• 2007

A new PWM-controlled quasi-resonant converter for a high efficiency PDP sustaining power module is proposed in this paper. The load regulation of the proposed converter can be achieved by controlling the ripple of the resonant voltage across the resonant capacitor with a bi-directional auxiliary circuit, while the main switches are operating at a fixed duty ratio and fixed switching frequency. Hence, the waveforms of the currents can be expected to be optimized from the view-point of conduction loss. Furthermore, the proposed converter has good ZVS capability, simple control circuits, no high voltage ringing problem of rectifier diodes, no DC offset of the magnetizing current and low voltage stresses of power switches. In this paper, operational principles, features of the proposed converter, and analysis and design considerations are presented. Experimental results demonstrate that the output voltage can be controlled well by the auxiliary circuit using the PWM method.

• Proceedings of the KIEE Conference
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• 2003.07b
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• pp.1148-1150
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• 2003

Power conversion system must be increased switching frequency in order to achieve a small size, a light weight and a low noise. However, the switches of converter are subjected to high switching power losses and switching stresses. As a result of those, the power system brings on a low efficiency. To improved these, a large number of soft switching topologies included a resonant circuit has been prosed. But these circuits increase number of switch in circuit and complicate sequence of switching operation. In this paper, the authors propose a high power factor and high efficiency DC-DC converter using single-pulse soft switching by partial resonant switching node. The switching devices in a prosed circuit are operated with soft switching by the partial resonant method, that is, Partial Resonant Switch Mode Power Converter. The partial resonant circuit makes use of a inductor using step up and a condenser of loss-less snubber. The result is that the switching loss is very low and the efficiency of system is high. Also the proposed converter is deemed the most suitable for high power applications where the power switching devices are used. Some simulative results on computer results are included to confirm the validity of the analytical results.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.6
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• pp.515-522
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• 1999

Several power factor correction(PFC) circuits are presented to achieve high PF electronic ballast for both v voltage-fed and current-f,어 ek'Ctronic ballast. The proposed PFC circuits use valley-fil[(VF) type DClink s stages modified from the conventional VF circuit to adopt the charge pumping method for PFC operations d during the valley intervals. In voltage-fed ballast, charge pump capacitors are connected with the resonant c capaCltor In current-fed type, the charge pump capacitors are connc'Ctc'Cl with the additional second따y-side of t the power transformer. The measured PF is higher than 0.99 and THD is about 10% for all proposed PFC c circuits. The lamp current CF is also acceptable in the proposed circuits. The proposed circuit is suitable for i implementing cost longrightarroweffective electronic ballast.

• Journal of Power Electronics
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• v.13 no.2
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• pp.177-185
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• 2013

This paper studies a soft switching DC/DC converter to achieve zero voltage switching (ZVS) for all switches under a wide range of load condition and input voltage. Two three-level PWM circuits with the same power switches are adopted to reduce the voltage stress of MOSFETs at $V_{in}/2$ and achieve load current sharing. Thus, the current stress and power rating of power semiconductors at the secondary side are reduced. The series-connected transformers are adopted in each three-level circuit. Each transformer can be operated as an inductor to smooth the output current or a transformer to achieve the electric isolation and power transfer from the input side to the output side. Therefore, no output inductor is needed at the secondary side. Two center-tapped rectifiers connected in parallel are used at the secondary side to achieve load current sharing. Due to the resonant behavior by the resonant inductance and resonant capacitance at the transition interval, all switches are turned on at ZVS. Experiments based on a 1kW prototype are provided to verify the performance of proposed converter.

• The Transactions of the Korean Institute of Electrical Engineers
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• v.41 no.2
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• pp.125-134
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• 1992

This paper presents a cycloconverter with an LC resonant circuit for an induction motor drive. The cycloconverter can keep input displacement factor at 1.0 by independently controlling real and reactive power under any load conditions. Furthermore it can keep power factor at about 1.0 since input and output current waveforms are nearly sinusoidal. Since it uses high frequency resonant circuit for commutation source, it can produce an output voltage of hundreds of hertz. Since it is also possible to make a system of high capacity using the cycloconverter, it is appropriate to drive motors with high speed and high capacity as well as general purpose motors, In this paper, we describe the operating principles of the cycloconverter and power control algorithms, and analyze its waveforms and present its characteristics. Expermental results are shown for the volts/hertz control of the induction motor and the validity of the proposed model is verified.

• JSTS:Journal of Semiconductor Technology and Science
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• v.13 no.6
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• pp.562-568
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• 2013

This paper presents a design of a wireless power transfer system based on magnetic resonant coupling technology with in-band wireless communication. To increase the transmission distance and compensate for the change in the effective capacitance due to the varying distance, the proposed system used a loop antenna with a selectable capacitor array. Because the increased transmission distance enables multiple charging, we added a communication protocol operated at the same frequency band to manage a network and control power circuits. In order to achieve the efficient bandwidth in both power transfer mode and communication mode, the S-parameters of the loop antennas are adjusted by switching a series resistor. Our test results showed that the loop antenna achieved a high Q factor in power transfer mode and enough passband in communication mode.