• Journal of Power Electronics
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• v.15 no.5
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• pp.1158-1167
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• 2015

In this paper, a new hybrid DC-DC converter is proposed for electric vehicle 3.3 kW on-board battery charger applications, which can be modulated in a phase-shift manner under a fixed frequency or frequency variation. By integrating a half-bridge (HB) LLC series resonant converter (SRC) into the conventional phase-shift full-bridge (PSFB) converter with a full-bridge rectifier, the proposed converter has many advantages such as a full soft-switching range without duty-cycle loss, zero-current-switching operation of the rectifier diodes, minimized circulating current, reduced filter inductor size, and better utilization of transformers than other hybrid dc-dc converters. The feasibility of the proposed converter has been verified by experimental results under an output voltage range of 250-420V dc at 3.3 kW.

• Proceedings of the KIEE Conference
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• 1993.07b
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• pp.847-849
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• 1993

Two new schemes of three-phase rectifier using softing switching methods are introduced for the input power factor correction. These three-phase rectifiers are employed the zero voltage switching for the parallel resonant and zero current switching for the series resonant AC link type rectifiers. The dynamic modeling and discontinuous integral cycle mode control technique are also presented. With the proposed circuits and control technique, the high power factor can be obtained.

• Journal of Power Electronics
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• v.14 no.1
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• pp.30-39
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• 2014

This paper studies a new three-level pulse-width modulation (PWM) resonant converter for high input voltage and high load current applications. In order to use high frequency power MOSFETs for high input voltage applications, a three-level DC converter with two clamped diodes and a flying capacitor is adopted in the proposed circuit. For high load current applications, the secondary sides of the proposed converter are connected in parallel to reduce the size of the magnetic core and copper windings and to decrease the current rating of the rectifier diodes. In order to share the load current and reduce the switch counts, three resonant converters with the same active switches are adopted in the proposed circuit. Two transformers with a series connection in the primary side and a parallel connection in the secondary side are adopted in each converter to balance the secondary side currents. To overcome the drawback of a wide range of switching frequencies in conventional series resonant converters, the duty cycle control is adopted in the proposed circuit to achieve zero current switching (ZCS) turn-off for the rectifier diodes and zero voltage switching (ZVS) turn-on for the active switches. Finally, experimental results are provided to verify the effectiveness of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.4 no.1
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• pp.66-72
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• 1999

This paper deals with the output characteristics of resonant PWM inverter type X-ray generators connected to different DC power units i.e. a single phase full bridge rectifier, a three phase full bridge rectifier and a power storage unit(PSU). The quality of X-ray beam depends on the pulsating waveforms of DC voltage supplied to the X-ray tube. In a X-ray generator, the waveform of DC output voltage can be affected from affected from harmonic distortion of DC input power. When a tube voltage waveform is distorted, the property of X-ray beam such as reproducibility, linearity and dose can be reduced. Therefore, we compared DC output waveforms and dose with three type of DC power units and show the experimental results in this paper.

• Proceedings of the KIPE Conference
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• 2010.11a
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• pp.58-59
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• 2010

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.24 no.4
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• pp.81-94
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• 2010

This paper presents a high efficiency resonant asymmetrical half-bridge flyback converter. The primary half-bridge circuit of the converter operates by a soft-switching type using the asymmetrical pulse-width modulation (PWM) method with the resonant capacitance and transformer leakage inductance. The secondary flyback circuit of the proposed converter utilizes a synchronous rectifier, which operates by a new voltage-driven method with a simple drive circuit. Thus the proposed converter improves the total efficiency. This paper explains the operational principle of the proposed converter by each mode and shows the converter design consideration and a design example for the prototype converter, respectively. After that, the proposed simple driving technique of the synchronous rectifier by a voltage-driven method is explained, briefly. The designed prototype converter has wide input voltage (AC $V_{in,rms}$=75~265[V]), 5[V] DC output voltage, and 100[W] output power. To verify the excellent performance of the proposed converter, the designed prototype is implemented and experimented. The good performance of the proposed converter is shown through the experimental results.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.27 no.4
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• pp.48-53
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• 2013

In general, the LLC resonant topology consists of three stages as; square wave generator, resonant network, and rectifier network. LLC resonant converter has the time slowly varying parameters. However, the power LEDs as the load of LLC converter can be regarded as fast time varying parameters. In this paper, the mathematical model of half-bridge resonant converter including with the power LEDs is introduced for the current controller design model. Using this controller design model, the parameter adaptive output feedback controller will be designed to control the power LEDs current. In order to show the validities of the proposed model, the parameter adaptive output feedback controller, the experimental investigation will be presented.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.5
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• pp.463-468
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• 2017

One of the most critical part for magnetron driving in microwave oven is start-up control. For this, switching frequency of resonant inverter should be carefully controlled in order to supply sufficient power to the filament of the magnetron and to prevent rectifier diode from destruction caused by the excessive voltage across them. This paper proposes a novel start-up control strategy for LLC resonant inverter for microwave oven considering the non-oscillation mode time and the magnetron voltage during the start-up process. The validity of the proposed method is verified through the experiment with 1,200W microwave oven using LLC resonant inverter.

• Journal of Power Electronics
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• v.9 no.1
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• pp.18-25
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• 2009

Conventional series-resonant pulse frequency modulation controlled DC-DC high power converters with a high-frequency transformer link which is designed for driving the high power microwave generator has the problem of hard switching commutation at turn-on and turn-off of active power switching devices. This problem is due to the influence of the magnetizing current of the high-frequency transformer. This paper presents a novel prototype for a high-frequency transformer using parasitic parameters with a lossless inductive snubber and a series resonant capacitor assisted series-resonant zero current switching pulse frequency modulated DC-DC power converter, which is designed using a high power magnetron for microwave ovens. In order to implement a complete and efficient soft switching commutation, the performance of the new converter topology is practically confirmed and evaluated in the prototype of a power microwave generator.

• Journal of Electrical Engineering and Technology
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• v.9 no.5
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• pp.1632-1642
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• 2014

This paper presents an interleaved resonant converter to reduce the voltage stress of power MOSFETs and achieve high circuit efficiency. Two half-bridge converters are connected in series at high voltage side to limit MOSFETs at $V_{in}/2$ voltage stress. Flying capacitor is used between two series half-bridge converters to balance two input capacitor voltages in each switching cycle. Variable switching frequency scheme is used to control the output voltage. The resonant circuit is operated at the inductive load. Thus, the input current of the resonant circuit is lagging to the fundamental input voltage. Power MOSFETs can be turn on under zero voltage switching. Two resonant circuits are connected in parallel to reduce the current stress of transformer windings and rectifier diodes at low voltage side. Interleaved pulse-width modulation is adopted to decrease the output ripple current. Finally, experiments are presented to demonstrate the performance of the proposed converter.