• Journal of Power Electronics
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• v.13 no.2
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• pp.197-205
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• 2013

In energy injection resonant AC-AC converters, due to the low frequency effect of the AC input envelope and the low energy injection losses requirement, the constant and steady control of the high frequency AC output envelope is still a problem that has not been solved very well. With the aid of system modeling, this paper analyzes the mechanism of the envelope pit on the resonant AC current. The computing methods for the critical damping point, the falling time and the bottom value of the envelope pit are presented as well. Furthermore, this paper concludes the stability precondition of the system AC output. Accordingly, an optimal control method for the AC output envelope is put forward based on the envelope prediction model. This control method can predict system responses dynamically under different series of control decisions. In addition, this control method can select best series of control decisions to make the AC output envelope stable and constant. Simulation and experimental results for a contactless power transfer system verify the control method.

• 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.27 no.6
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• pp.498-506
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• 2022

This study proposes a design methodology for bidirectional, series-resonant, dual-active bridge (SRDAB) converters. The circuit parameters of the SRDAB converters are designed by considering the output power and efficiency of the converter. The proposed method can be used to design a high-power, high-efficiency SRDAB converter. A voltage controller is employed to manipulate the output voltage of the converter, and the controller gains are selected using the transfer function and frequency response of the controller. Simulation results show that the output power of the designed SRDAB converter is 2 kW per converter module as designed. In addition, the performance of the voltage controller is evaluated using the simulation and experimental results. The output voltage follows the reference voltage within 10 ms under the step change of the reference command. The output voltage also follows the reference voltage under the step load change. The efficiency of the designed SRDAB converter is 95.6%.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.60 no.7
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• pp.1366-1371
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• 2011

The resonant converter cause the high voltage stress according to the input voltage, which increases the conduction loss in converter power switches. The topology of LLC half bridge resonant converter provides ZVS characteristic and also the stress of voltage and current is smaller than that of the general resonant converters. So we can expect the higher efficiency. In this paper, the analysis of the characteristics of the converter efficiency and the best conditions for highest efficiency were investigated. As a result, the efficiency of utilizing up to 93% is achieved.

• 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.

• The Transactions of The Korean Institute of Electrical Engineers
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• v.56 no.8
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• pp.1418-1423
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• 2007

The topology of LLC half bridge resonant converter provides ZVS characteristic. The voltage stress and current stress are smaller than that of the general resonant converters. So the LLC HB resonant converter can be considered as a optimal circuit for the notebook computer adapter. In the adapter design, we should consider the weight, the size and the overheat of the adapter. Thus the higher efficiency is an essential particular. First of all, the optimal design of transformer is the most important facts. Some parameters should be considered in order to get the highest efficiency. The adapter is designed through the considering of these parameters including the PFC circuit as the pre-regulator. It converts AC line input into about DC 390V link voltage of the LLC HB converter input and the converter has 16V/90W ratings. The efficiency measured is about up to 93%.

• Journal of Power Electronics
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• v.19 no.5
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• pp.1099-1107
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• 2019

A soft switching converter with wide voltage range operation is investigated in this paper. A series resonant converter is implemented to achieve a high circuit efficiency with soft switching characteristics on power switches and rectifier diodes. To improve the weakness of the narrow voltage range in LLC converters, an alternating current (ac) power switch is used on the primary side to select a half-bridge or full-bridge resonant circuit to implement 4:1 voltage range operation. On the secondary-side, another ac power switch is adopted to select a full-wave rectifier or voltage-doubler rectifier to achiever an additional 2:1 output voltage range. Therefore, the proposed resonant converter has the capacity for 8:1 (320V~40V) wide output voltage operation. A single-stage hybrid resonant converter is employed in the study circuit instead of a two-stage dc converter to achiever wide voltage range operation. As a result, the study converter has better converter efficiency. The theoretical analysis and circuit characteristics are verified by experiments with a prototype circuit.

• Journal of Power Electronics
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• v.19 no.2
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• pp.363-379
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• 2019

Resonant converters have attracted a lot of attention because of their high efficiency due to the soft-switching performance. An isolated high step-up converter with secondary-side resonant loops is proposed and analyzed in this paper. By placing the resonant loops on the secondary side, the current stress for the resonant capacitors is greatly reduced. The power loss caused by the equivalent series resistance of the resonant capacitor is also decreased. Clamp diodes in parallel with the resonant capacitors ensure a unique discontinuous current mode in the converter. Under this mode, the active switches can realize soft-switching during both turn-on and turn-off transitions. Meanwhile, the reverse-recovery problems of diodes are also alleviated by the leakage inductor. The converter is essentially a step-up converter. Therefore, it is helpful for decreasing the transformer turn-ratio when it is applied as a high step-up converter. The steady-state operation principle is analyzed in detail and design considerations are presented in this paper. Theoretical conclusions are verified by experimental results obtained from a 500W prototype with a 35V-42V input and a 400V output.

• Proceedings of the KIEE Conference
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• 1990.11a
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• pp.332-335
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• 1990

There are several methods in controlling resonant converters to regulate the output with low switching losses. In this paper, Pulse-width modulation method or current controlled method is applied to regulate the output with low switching losses. In digital implementation of resonant converter systems, the speed of the applied processor is very critical since the switching frequency is very high. Thus the various possible candidates of microprocessors are evaluated for the implementation of resonant converter systems. Then too design methods and techniques are desioribed when single chip processor is used to simplify hardware requirements.

• Proceedings of the KIPE Conference
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• 2011.07a
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• pp.23-24
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• 2011

In this paper, the 170W LLC half bridge DC-DC converter is designed for the lighting management system. The power conversion circuit consists of PFC and isolated LLC resonant converter. The topology of LLC half bridge resonant converter provides ZVS characteristic. And the stresses of voltage and current is smaller than that of the general resonant converters. So we can expect the higher efficiency. The optimal conditions for high efficiency were investigated through by experiment.