• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.1
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• pp.80-85
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• 2015

In the issues of interleaved topology which have been in limelight as high power converter, various soft-switching methods are studied to reduce switching losses in high power application. The interleaved ZCT converter has an additional filter inductor to reduce losses of diodes during reverse recovery process. However, additional current conduction modes are occurred by the inductor, we need to analyze switching losses with inductor values on each mode. In this paper, current conduction modes and boundary conditions of interleaved ZCT converter are analyzed. In the conclusion, the minimum of switching losses in converter operation modes is analyzed by calculating switching losses.

• Journal of Electrical Engineering and Technology
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• v.12 no.3
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• pp.1108-1113
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• 2017

In this paper, a bidirectional topology for quasi-Cuk dc/dc converter with capability of zero-voltage and zero-current-switching (ZVZCS) is proposed. The bidirectional quasi-Cuk (BQ-Cuk) converter has different voltage and current transfer ratio, reduced voltage stress on capacitor and capability of changing the output polarity in comparison with conventional bidirectional Cuk converter. In this paper, steady-state analysis of the quasi-Cuk converter with capability of ZVZCS in turn-on is presented. Then, critical inductances for transient from this operation to two new operations are calculated. Next, besides values designing of used elements, maximum and minimum value of their current and voltage are calculated. Finally, experimental results to verify the accuracy of the proposed converter in different operating modes are presented.

• Proceedings of the KIEE Conference
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• 1998.07f
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• pp.1860-1862
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• 1998

This Paper presents a novel resonant switching Watkins-Johnson DC-DC converters. In the proposed converters, the basic steady-state analysis of the have been presented for the ZVS type Watkins-Johnson converter. From the results, it is shown that the output voltage of the converter is independant of load resistance, and is determined only by the switching frequency. Consequently, a design procedure is presented that minimizes voltage stress to the switch while maintaining ZVS for all loads.

• 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.

• Journal of Electrical Engineering and Technology
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• v.10 no.1
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• pp.288-294
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• 2015

Recently, the module-integrated converter has shown an interest in the photovoltaic generation system. In this system, the high frequency transformer should be compact and efficient. The proposed method is based on the correlation characteristic between the copper and core loss to minimize the loss of transformer. By sizing an effective cross-sectional area and window area of core, the amount of loss is minimized. This paper presents the design and analysis of high frequency transformer by using the 3D finite element model coupled with DC-DC converter circuit for more accurate analysis by considering the nonlinear voltage and current waveforms in converter circuit. The current waveform in each winding is realized by using the ideal DC voltage source and switching component. And, the thermal analysis is performed to satisfy the electrical and thermal design criteria.

• The Transactions of the Korean Institute of Power Electronics
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• v.22 no.4
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• pp.297-304
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• 2017

The purpose of this paper is to analyze losses because of switching devices and the secondary side circuit diodes of 500 W full bridge dc-dc converter by applying gallium nitride (GaN) field-effect transistor (FET), which is one of the wide band gap devices. For the detailed device analysis, we translate the specific resistance relation caused by the GaN FET material property into algebraic expression, and investigate the influence of the GaN FET structure and characteristic on efficiency and system specifications. In addition, we mathematically compare the diode rectifier circuit loss, which is a full bridge dc-dc converter secondary side circuit, with the synchronous rectifier circuit loss using silicon metal-oxide semiconductor (Si MOSFET) or GaN FET, which produce the full bridge dc-dc converter analytical value validity to derive the final efficiency and loss. We also design the heat sink based on the mathematically derived loss value, and suggest the heat sink size by purpose and the heat divergence degree through simulation.

• Journal of Power Electronics
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• v.7 no.4
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• pp.318-327
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• 2007

The design and performance analysis of a power factor corrected (PFC), single-phase, single switch flyback buck-boost ac-dc converter is carried out for low power battery charging applications. The proposed configuration of the flyback buck-boost ac-dc converter consists of only one switch and operates in discontinuous current mode (DCM), resulting in simplicity in design and manufacturing and reduction in input current total harmonic distortion (THD). The design procedure of the flyback buck-boost ac-dc converter is presented for the battery charging application. To verify and investigate the design and performance, a simulation study of the flyback buck-boost converter in DCM is performed using the PSIM6.0 platform. A laboratory prototype of the proposed single switch flyback buck-boost ac-dc converter is developed and test results are presented to validate the design and developed model of the system.

• Journal of Power Electronics
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• v.15 no.4
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• pp.876-885
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• 2015

High frequency alternating current (HFAC) has been widely used in a wide range of power distribution systems (PDS) due to its superior performance. A high frequency AC/DC converter plays the role of converting HFAC voltage to DC voltage. In this paper, a new LCL-T resonant AC/DC converter has been proposed, and an easier control method based on input voltage comparison is presented, without the complicated calculation of the zero-crossing point. Both a low distortion and near-to-unity power factor can be achieved by the proposed resonant converter and control strategy. The operational principle and steady-state analysis are given for the proposed resonant converter. A simulation model and experimental prototype are implemented with an operation frequency of 25kHz and a rated power of 20W. The simulation and experimental results verify the accuracy of the analysis and the excellent performance of the proposed topology.

• KEPCO Journal on Electric Power and Energy
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• v.6 no.4
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• pp.473-480
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• 2020

In this paper, we proposed a high frequency equivalent circuit considering parasitic impedance components for differential noise analysis on the input stage during DC-DC buck converter switching operation. Based on the proposed equivalent circuit model, we presented a method to measure parasitic impedance parameters included in DC bus plate, IGBT, and PCB track using the gain phase method of a network analyzer. In order to verify the validity of this model, a DC-DC prototype consisting of a buck converter, a signal analyzer, and a LISN device, and then resonance frequency was measured in the frequency range between 150 kHz and 30 MHz. The validity of the parasitic impedance measurement method and the proposed equivalent model is verified by deriving that the measured resonance frequency and the resonance frequency of the proposed high frequency equivalent model are the same.

• Journal of Power Electronics
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• v.18 no.5
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• pp.1303-1314
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• 2018

To match the dynamic lower voltage of a fuel cell stack and the required constant higher voltage (400V) of a DC bus, an H-type structural Boost three-level DC-DC converter with a wide voltage-gain range (HS-BTL) is presented in this paper. When compared with the traditional flying-capacitor Boost three-level DC-DC converter, the proposed converter can obtain a higher voltage-gain and does not require a complicate control for the flying-capacitor voltage balance. Moreover, the proposed converter, which can draw a continuous and low-rippled current from an input source, has the advantages of a wide voltage-gain range and low voltage stress for power semiconductors. The operating principle, parameters design and a comparison with other converters are presented and analyzed. Experimental results are also given to verify the aforementioned characteristics and theoretical analysis. The proposed converter is suitable for application of fuel cell systems.