• Proceedings of the KIPE Conference
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• 2019.07a
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• pp.317-319
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• 2019

In this paper, a three level duty cycle controlled half bridge LLC converter for EV charger application is presented. The topology and operating regions of the converter are discussed. The equations of the converter are derived in time domain. A small signal model of the converter is developed by perturbation and linearization of the steady state model about their operating point using Extended Describing function.

• Proceedings of the KIPE Conference
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• 1996.06a
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• pp.71-75
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• 1996

As the Three-level ZVS PWM DC-DC converter operates likewise full-bridge ZVS PWM DC-DC converter and the blocking voltage of each switching device is a half of the DC-link voltage, it is suitable for the high imput voltage applications. However, it has some problems as follows; The blocking voltage of each devices is unbalanced and it causes the power losses of the inner switching devices to be increased. Also, it has narrow load range so that the switching losses and the efficiency are reduced as it goes to the light load. This paper presents an nove Three-level ZVS PWM DC-DC converter, which can reduce the overvoltage of the outer switches, eliminate the unbalance of the voltage sharing between the switches at turn-off due to the stray inductances, and operate from no load to full load. The characteristics and the performances of the proposed Three-level ZVS PWM DC-DC converter are verified by simulation and experimental results

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.187-193
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• 2007

This paper presents the Efficiency Characteristic of Three-Level Converter. Three-Level DC/DC Converter Presented in this paper is used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. This converter reduces the voltage stress across the main switch to half of input voltage. This paper analyses the loss of each component and the various losses for efficiency variation. The result of the analysis are verified using 3kW prototype.

• Proceedings of the KIEE Conference
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• 2007.04c
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• pp.218-222
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• 2007

This paper present the Three-Level converter for high power application. In converter system, magnetic components are important devices used for energy storage, energy transfer, galvanic isolation and filtering. The proposed Three-Level converter is to reduce the number of magnetic components. The secondary rectification was discussed by a single core transformer winding. The result of the analysis are verified using 1kW prototype.

• Proceedings of the KIEE Conference
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• 2004.04a
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• pp.159-162
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• 2004

The paper proposes the coupled inductor rectifier of Three Level DC/DC converter CICDR-TL(Coupled Inductor Current Doubler Rectifier-Three Level) achieves Zero Voltage Switching (ZVS) for the switches in a wide load range and Zero Current Switching (ZCS) in a light load range. Advantages and disadvantages of this topology compared to the conventional Center Tapped TL Converter are discussed. Experimental evaluation results obtained on a 27V 60A DC/DC converter prototype for the 1.8kW 40kHz IGBT based experimental circuit.

• Proceedings of the KIEE Conference
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• 2002.11d
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• pp.177-182
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• 2002

This paper presents the loss analysis of Three Level Converter. Three Level DC/DC Converter presented in this paper used a phase shift control with a flying capacitor in the primary side to achieve ZVS for the outer switch. This converter reduces the voltage stress across the main switch to half of input voltage. This paper analyses the loss of each component and the various losses in the circuit assessed. The result of the analysis are verified using 2.5kW prototype.

• 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.

• Journal of Power Electronics
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• v.14 no.5
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• pp.926-936
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• 2014

A simplified and effective space vector pulse-width modulation (SVPWM) algorithm with two and three levels for three-phase voltage-source converters is proposed in this study. The proposed SVPWM algorithm only uses several linear calculations on three-phase modulated voltages without any complicated trigonometric calculations adopted by conventional SVPWM. This simplified SVPWM also avoids choosing the vector sector required by conventional SVPWM. A two-level overmodulation scheme is integrated into the proposed two-level SVPMW to generate the output voltage that increases from a linear region to a six-step state with a smoothly linear transition characteristic and a simple overmodulation process without a lookup table and complicated nonlinear functions. The three-level SVPWM with a proportional-integral controller effectively balances the neutral point potential of the neutral point clamped converter. Results from the simulation in MATLAB/Simulink and the experiment based on a digital signal processor are provided to clearly demonstrate the validity and effectiveness of the proposed strategies.

• Journal of Electrical Engineering and Technology
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• v.12 no.5
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• pp.1902-1915
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• 2017

This paper presents the evaluation of a three-phase three-level DC-DC converter which achieves the soft switching condition for all switches in the circuit and uses the phase-shift PWM strategy to adjust electric power at the output side. According to the analysis, the operation modes can be categorized into two cases: in the first case, where the phase shift angle is less than 120 degrees and in the second case, where the phase shift angle is more than 120 degrees. The outer switches of the circuit operate under ZVS condition and the inner switches operate under ZVZCS condition. It has been discovered that under ZCS condition of the inner switches, when the blocking capacitors decrease, they make the voltage across the blocking capacitor higher so the current reduce rapidly. A three-phase three-level DC-DC converter has a maximum efficiency of 93.5% when its load is of 5.7 kW. The results from the experiment have been compared to the results obtained by the $MATLAB^{(R)}$ simulator in order to confirm the validity of the proposed converter.

• The Transactions of the Korean Institute of Power Electronics
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• v.24 no.6
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• pp.406-410
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• 2019

Three-level (3L) DC-DC converters are appropriate for high-input-voltage applications. Although the voltage stress of TL converter switches can be reduced to half of the input voltage, the primary side has a large circulating current, which degrades efficiency. In this study, a dual half-bridge cascaded TL converter is presented to reduce this circulating current and thus decrease the conduction loss of the primary circuit. Moreover, the proposed converter can reduce the voltage stress of rectifier diodes, thereby reducing their conduction loss. Therefore, efficiency can be improved by reducing the conduction loss of the primary circuit and rectifier diodes.