• The Transactions of the Korean Institute of Power Electronics
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• v.19 no.1
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• pp.23-30
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• 2014

This paper proposes a single power-conversion ac-dc converter with a dc-link capacitor-less and high power factor. The proposed converter is derived by integrating a full-bridge diode rectifier and a series-resonant active-clamp dc-dc converter. To obtain a high power factor without a power factor correction circuit, this paper proposes a suitable control algorithm for the proposed converter. The proposed converter provides single power-conversion by using the proposed control algorithm for both power factor correction and output control. Also, the active-clamp circuit clamps the surge voltage of switches and recycles the energy stored in the leakage inductance of the transformer. Moreover, it provides zero-voltage turn-on switching of the switches. Also, a series-resonant circuit of the output-voltage doubler removes the reverse-recovery problem of the output diodes. The proposed converter provides maximum power factor of 0.995 and maximum efficiency of 95.1% at the full-load. The operation principle of the converter is analyzed and verified. Experimental results for a 400W ac-dc converter at a constant switching frequency of 50kHz are obtained to show the performance 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%.

• 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 Power Electronics
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• v.21 no.3
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• pp.224-230
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• 2016

In this study, a single-power-conversion series-resonant ac-dc converter with high efficiency and high power factor is proposed. The proposed ac-dc converter consists of single-ended primary-inductor converter with an active-clamp circuit and a voltage doubler with series-resonant circuit. The active-clamp circuit clamps the surge voltage and provides zero-voltage switching of the main switch. The series-resonant circuit consists of leakage inductance $L_{lk}$ of the transformer and resonant capacitors $ C_{r1}$ and $ C_{r2}$. This circuit also provides zero-current switching of output diodes $D_1$ and $D_2$. Thus, the switching loss of switches and reverse-recovery loss of output diodes are considerably reduced. The proposed ac-dc converter also achieves high power factor using the proposed control algorithm without the addition of a power factor correction circuit and a dc-link electrolytic capacitor. A detailed theoretical analysis and the experimental results for a 1kW prototype are discussed.

• The Transactions of the Korean Institute of Power Electronics
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• v.9 no.5
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• pp.405-412
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• 2004

In this paper, Non-contact power supply(NCPS) with the long primary cable longer than 20m and the large air-gap between the primary and secondary of Non-Contacting Transformer(NCT) is presented. The NCT has a large leakage inductance bigger than its magnetizing inductance because it has low coupling, and it is not efficient for NCPS to transfer the primary energy to the secondary one. In order to improve this problem, the voltage-gain characteristics of the series resonant converter, the parallel resonant converter, and the series-parallel resonant converter are analyzed respectively. In addition, the experimental results of 10kW prototype the series-parallel resonant converter is presented.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.11 no.11
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• pp.4483-4488
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• 2010

In comparison with some other light sources, LED has merits such as long lifetime, pollution free, and high energy efficiency. Lately, due to development of LED with high brightness and capacity, LED, which has been applied in display system only, has applied in the field of lighting system. Driving current of power LED has to be controlled below the designed value. In this paper, half-bridge LLC series resonant converter, which has the current limiting function, has been described. Half-bridge LLC series resonant converter allows in relatively wide input voltage and output load range when compared to the other resonant converter. Also, it is possible to reduce a magnetic component, because leakage inductance of transformer is used as a resonant inductance. It has been validated by designing and testing 200[W] half-bridge LLC converter of DC24[V] output voltage for LED lamp driver, which includes a current limiting function and power factor correction(PFC) function.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.376-379
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• 2000

This paper presents an improved ZVS partial series resonant DC/DC converter (PSRC) with low conduction losses suitable for high power and high frequency applications. The proposed PSRC have advantages of zero-voltage-swiching (ZVS) of main switches for entire load ranges and low conduction losses of main switches by decreasing current stresses Also the reduction of the effective duty cycle is not occurred during the resonant period of the main circuit because the auxiliary circuit of the proposed converter is placed out of the main power path. An improved ZVS PSRC has a so much characteristics with respect to the reduction of current stress. The operation principles of the proposed converter are explained in detail and the various simulated and experimental results show the validity of the proposed converter.

• Journal of Electrical Engineering and Technology
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• v.10 no.4
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• pp.1646-1654
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• 2015

In this paper, a single-switch ZVZCS quasi-resonant CLL isolated DC-DC converter for driving a low-power (less than 100 W) 32'' LED backlighting liquid crystal display television (LCD TV) is proposed. The proposed converter exhibits both forward and flyback operational characteristics. All semiconductors are activated and deactivated under the soft switching conditions during the switching transition without additional active devices. The switching frequency varies less than about 10 kHz for load variations, leading to minimizing the efficiency reduction under light load. Furthermore, the low di/dt and dv/dt by soft switching enhance the electromagnetic interference (EMI) performance above 1 MHz. A theoretical analysis is described in detail, and a 72-W prototype converter verifies the validity of the analysis.

• Proceedings of the KIPE Conference
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• 2004.07b
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• pp.747-751
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• 2004

In recent years power supplies for telecommunication equipment is required smaller size and higher efficiency, and low noise operation. There exists a series resonant converter in which the switching loss is reduced in order to realize a high efficiency converter. However, if a constant voltage regulation is required. The switching frequency varies widely. In this paper we study the details of resonant DC-DC converter in which the realize a high efficiency converter.

• Journal of Power Electronics
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• v.17 no.1
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• pp.11-19
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• 2017

This paper proposes a dc/dc converter for electric vehicle onboard chargers using a secondary resonant tank. To attain soft switching characteristics, such as zero voltage switching, magnetizing inductance has been used at the primary side of the transformer. The leakage inductance of the transformer is used as a resonant inductor on the secondary side to avoid the use of a separate inductor as resonance. The proposed converter is applicable for a wide load range. A 6.6KW prototype has been implemented for a wide range of load variations (250V, 330V, 360V, and 413V). A maximum efficiency of 97.4% is achieved at 413V.