• Proceedings of the KIPE Conference
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• 2008.06a
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• pp.370-372
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• 2008

A resonant converter suitable for applications of wide input variation is proposed. A half-bridge converter and a phase-shift converter are combined in primary and the secondaries of each transformer are connected in series which makes four voltage levels. Furthermore, by adopting resonant converter scheme, a resonant capacitor is connected with the secondaries of the transformers in series and an output inductor is removed. Zero voltage switching is achieved from full load to no load. The analysis of the resonant converter and experimental results of 200W prototype is presented to verify the features of the converter.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.58 no.8
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• pp.1551-1558
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• 2009

This paper proposes a new power conditioning system for the fuel cell power generation, which consists of a LLC resonant DC-DC converter and 3-phase inverter. The LLC resonant converter boosts the fuel cell voltage of 26-48V up to 400V, using the hard-switching boost converter and the high-frequency ZVS half-bridge converter. The operation of proposed power conditioning system was verified through simulations with PSCAD/EMTDC software. The feasibility of hardware implementation was verified through experimental works with a laboratory prototype, which was built with 1.2kW PEM fuel-cell stack, 1kW LLC resonant converter, and 3kW PWM inverter. The proposed system can be utilized to commercialize a real interconnection system for the fuel-cell power generation.

• Journal of Power Electronics
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• v.6 no.3
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• pp.271-278
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• 2006

A new high efficiency zero-voltage and zero-current switching (ZVZCS) bidirectional DC/DC converter is proposed in this paper. The proposed converter consists of two symmetric half-bridge cells as the input and output stages. MOSFETs of input stage are turned-on in ZVS condition, and those of output stage are turned-off in ZCS condition. In addition, MOSFETs of input and output stages have low voltage stresses clamped to input and output voltage, respectively. Therefore, the proposed converter has high efficiency and high power density. The operational principles are analyzed and the advantages of the proposed converter are described. The 300W prototype of the proposed converter is implemented for 42V hybrid electric vehicle (HEV) application in order to verify the operational principles and advantages.

• Proceedings of the KIPE Conference
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• 2018.11a
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• pp.51-53
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• 2018

The Low Voltage DC-DC converters (LDCs) of the Electric Vehicles require high power density and high efficiency operation over the wide range of load and input voltage variations. This paper introduces a novel topology which combines three 1 MHz Half-Bridge (HB) LLC resonant converters and an Inverting Buck-Boost (IBB) converter to adjust the output voltage without frequency modulation. The switching frequency of the proposed converter is fixed at 1MHz to achieve a constant frequency operation for the resonant converter. In the proposed topology GaN FETs and planar transformers are employed to optimize the converter operation at high frequency. A 1 MHz/1.8 kW prototype converter is built to verify the feasibility and the validity of the proposed LDC topology.

• 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.

• The Transactions of the Korean Institute of Power Electronics
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• v.16 no.3
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• pp.242-249
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• 2011

The proposed converter has easy device selection for high step-up and high power applications since boost half bridge and voltage doubler cells are connected, respectively, in parallel and series in order to increase output power and voltage. Especially, optimized design of high frequency transformers is possible owing to reduced turn ratio and eliminated dc offset, and distributed power through three cores is beneficial to low profile and thermal distribution. The proposed converter does not necessitate start-up circuit and additional clamp circuit due to the use of whole duty range between 0 and 1 and is suitable for applications with wide input voltage range. Also, high efficiency can be achieved since ZVS turn on of switches are achieved in wide duty cycle range and ZCS turn on and off of diodes are achieved. The proposed converter was validated through 5 kW prototype.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.505-508
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• 2000

A coreless printed circuit board(PCB) transformer is employed in a contactless energy transfer circuit that achieves an efficient power conversion at the presence of a considerable airgap between the source and the load side. A half-bridge series resonant converter is selected as the contactless energy transfer circuit in order to minimize the detrimental effects of large leakage inductance small magnetizing inductance and poor coupling coefficient of the coreless PCB transformer. The operation and performance of the proposed contactless power converter are verified on a 7 W experimental circuit that provides an 18V/0.4A output from a 210-370 V input source.

• Proceedings of the KIEE Conference
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• 1999.07f
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• pp.2562-2564
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• 1999

We have development the electronic ballast for metal halide discharge (MHD) lamp. The ballast consists of the boost pre-converter for power factor correction (PFC), a flyback a converter, half-bridge inverter and ignitor. To reject acoustic resonance phenomena, we have designed electronic ballast driving with the low frequency square wave. As results of this study, the ballast had not flicker phenomena and promoted corrected the factor (PF) highly

• Proceedings of the KIPE Conference
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• 2002.07a
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• pp.253-256
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• 2002

This paper proposes the application of coreless PCB transformer to Half-Bridge (HB), Zero-voltage-Switched (ZVS) DC/DC converter for FPL lamp with electronic ballast in vehicle. The designed 5 coreless PCB transformers for ballast driving voltage are parallel-connected in primary windings and series-connected in secondary windings. Coreless PCB transformer is designed to have spiral winding in order to transfer higher energy. The computer simulations of the proposed power circuit show coreless PCB transformer to have good performance.

• Proceedings of the KIPE Conference
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• 2006.06a
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• pp.372-374
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• 2006

This paper reported the experimental results of the 2 stage converter using a Buck converter and a soft switching dc-to-dc converter that employs two separate transformers. A 2 stage converter module is designed with the specifications of an 3.3V output voltage, 20A output current, 66W output power and 36-75V input voltage. A prototype converter module is successfully implemented within 85.2% efficiency and 3% voltage regulation for the entire input voltage range, thereby demonstrating its application potentials to future telecommunication electronics.