• Journal of Power Electronics
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• v.13 no.1
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• pp.20-30
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• 2013

This paper presents a soft switching DC/DC converter for high voltage application. The interleaved pulse-width modulation (PWM) scheme is used to reduce the ripple current at the output capacitor and the size of output inductors. Two converter cells are connected in series at the high voltage side to reduce the voltage stresses of the active switches. Thus, the voltage stress of each switch is clamped at one half of the input voltage. On the other hand, the output sides of two converter cells are connected in parallel to achieve the load current sharing and reduce the current stress of output inductors. In each converter cell, a half-bridge converter with the asymmetrical PWM scheme is adopted to control power switches and to regulate the output voltage at a desired voltage level. Based on the resonant behavior by the output capacitance of power switches and the transformer leakage inductance, active switches can be turned on at zero voltage switching (ZVS) during the transition interval. Thus, the switching losses of power MOSFETs are reduced. The current doubler rectifier is used at the secondary side to partially cancel ripple current. Therefore, the root-mean-square (rms) current at output capacitor is reduced. The proposed converter can be applied for high input voltage applications such as a three-phase 380V utility system. Finally, experiments based on a laboratory prototype with 960W (24V/40A) rated power are provided to demonstrate the performance of proposed converter.

• Journal of Power Electronics
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• v.12 no.4
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• pp.643-653
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• 2012

An interleaved DC/DC converter with series-connected transformers is presented to implement the features of zero voltage switching (ZVS), load current sharing and ripple current reduction. The proposed converter includes two half-bridge converter cells connected in series to reduce the voltage stress of the switches at one-half of the input voltage. The output sides of the two converter cells with interleaved pulse-width modulation are connected in parallel to reduce the ripple current at the output capacitor and to achieve load current sharing. Therefore, the size of the output chokes and the capacitor can be reduced. The output capacitances of the MOSFETs and the resonant inductances are resonant at the transition instant to achieve ZVS turn-on. In addition, the switching losses on the power switches are reduced. Finally, experiments on a laboratory prototype (24V/40A) are provided to demonstrate the performance of the proposed converter.

• The Journal of the Korea institute of electronic communication sciences
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• v.6 no.6
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• pp.865-871
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• 2011

DC-DC converter commonly used in photovoltaic systems or fuel cell systems is a boost converter. Among several types of boost converter, the interleaved boost converter with small input and output current ripples is widely used in recent years. Because of small input and output current ripples, the circuit can reduce the size of the input and output capacitors. Thus, instead of conventional electrolytic capacitor, the film capacitor with high reliability can be used and this is the life and reliability of the entire system can be improved. In this paper, the input/output current ripple formulas of the multi-stage interleaved boost converter are derived, and the characteristics in accordance with duty are found out. In order to verify the above mentioned contents, the derived results will make a comparison with the calculated values by using PSIM tool.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.55 no.1
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• pp.47-53
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• 2006

In this paper, a simple scheme compensating for the effect of dc-link ripple voltages on output voltage of two-leg and three-phase PWM inverters is proposed, where single-phase half-bridge PWM convertor and two-leg inverter are used. The voltage at neutral point of the dc-link is controlled so that the upper-half of do-link voltage is equal to the lower-half voltage in average concept. However, the effect of the do-link ripple voltage results in the inverter output voltage and current distortion. This effect can be eliminated by introducing a compensation voltage in switching time calculation. Also, the inverter dead time should be compensated for sinusoidal output waveform. The proposed scheme has been verified by experimental results which were obtained from the V/F constant operation of the induction motor fed by two-leg inverter.

• Journal of Electrical Engineering and Technology
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• v.12 no.4
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• pp.1529-1536
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• 2017

A digital dual-channel interleaved phase-shift full-bridge converter is investigated in this paper, and its topology and principle are analyzed. To realize current sharing and stabilize the output voltage, a controller with current sharing loop and closed voltage loop is employed. In addition, current sharing will increase the output current fluctuation and a new digital interleaved driving technology is proposed to reduce the output current ripple. To verify the analysis, simulation and experiments are carried out, which shows the effectiveness of the proposed control strategies.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.29 no.8
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• pp.55-62
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• 2015

This paper deals with a switching method to minimize the current ripple component of 3-phase interleaved bidirectional DC-DC converter for charging and discharging of the battery. The characteristics of the output current ripple in 3-phase and 2-phase operation modes according to the variation of battery voltage is analyzed and a phase conversion method for minimizing the magnitude of the current ripple is proposed. The proposed method can extend the light load range because the switching frequency is lower than that of a 3-phase operating system. Simulation and experimental results show the usefulness of the proposed method.

• The Transactions of the Korean Institute of Power Electronics
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• v.23 no.3
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• pp.208-216
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• 2018

In this paper, an LLC resonant converter employing two coupled inductors on the secondary side of the converter is proposed. The conventional LLC converter exhibits serious power loss during secondary winding of the transformer because of generation of tremendous output current ripples. To overcome this problem, an LLC resonant converter with a current doubler as a rectifying circuit was recently proposed. However, the current-doubler rectifying circuit requires coupled inductors with a high coupling ratio to retain the designed resonance characteristics. Therefore, an additional hardware filter is required at the output stage to address large output current ripples. Additional design procedures are also necessary because the inductance component of the added filter affects the designed resonant network. To solve this issue, an LLC resonant converter employing two coupled inductors is proposed in this paper. Mathematical analysis shows that the proposed secondary-side current-doubler circuit does not affect the designed resonance characteristics. The operating principles and theoretical analyses are proven through a simulation and experiments with a 54 V/28 A prototype.

• The Transactions of the Korean Institute of Power Electronics
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• v.21 no.5
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• pp.427-433
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• 2016

This paper proposes a new method for the current ripple reduction of a three-phase interleaved bidirectional DC-DC converter. Usually, the three-phase interleaved bidirectional DC-DC converter is used for battery charging and discharging to reduce battery current ripple. In V2G application, a PWM AC-DC converter is used to connect the AC power grid and three-phase interleaved bidirectional DC-DC converter for battery charging and discharging. The magnitude of DC link voltage affects the battery current ripple magnitude. Therefore, the magnitude of the battery ripple current is analyzed with variations of battery and DC link voltages. The ripple current magnitude is found to be minimized by controlling the DC link voltage. Simulation and experimental results show the usefulness of the proposed method.

• Proceedings of the KIPE Conference
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• 2000.07a
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• pp.305-308
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• 2000

A technique to suppress the low frequency ripple voltage of the DC output in three phase buck diode rectifiers is presented in this paper. The proposed pulse frequency modulation methods and duty ratio modulation methods are employed to regulate the output voltage of the buck diode rectifiers and guarantee zero-current -switching(ZCS) of the switch over the wide load range The proposed control methods used in this paper provide generally good performance such as low THD of the input line current and unity power factor. IN addition control methods can be effectively used to suppress the low frequency ripple voltage appeared in the dc output voltage. The harmonic injection technique illustrates its validity and effectiveness through the simulations.

• Journal of Industrial Technology
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• v.32 no.A
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• pp.115-118
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• 2012

Recently, there are a lot of papers in order to replace the electrolytic capacitor into the film capacitor in output of PFC(Power Factor Correction). However, the film capacitor, which has capacitance of low values, causes a large ripple voltage in output of PFC. The LED drivers are connected series in the output of PFC and affected by the magnitude of voltage ripple. In this paper, we have compared the fixed frequency method with the variable frequency for the constant-current control and propose the control method to avoid the sub-harmonic oscillation in the variable input voltage. An 80W PFC, using film capacitors instead of electrolytic capacitors, and LED driver has been built and compared the fixed frequency control method with the variable frequency control method.