• Proceedings of the KIPE Conference
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• 2001.10a
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• pp.227-231
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• 2001

A new primary-side-assisted zero-voltage and zero-current switching (ZVZCS) three-level DC-DC converter with flying capacitor is proposed. The three-level converters are promising in high voltage applications, and ZVZCS is a very effective means for reducing switching losses. The proposed DC-DC converter uses only one auxiliary transformer and two diodes to obtain ZCS for the inner leg. It has a simple and robust structure, and offers soft-switching capability even in short-switching conditions. The proposed converter was verified by experiments in a 6KW prototype designed for communication applications and operating at 100kHz.

• The Transactions of the Korean Institute of Power Electronics
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• v.6 no.2
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• pp.209-216
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• 2001

The conventional three-level high frequency phase-shifted dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval. Due to this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved three-level Zero Voltage and Zero Current Switchig (ZVZCS) dc/dc converter using a tapped inductor, a snubber capacitor and two snubber diodes attached at the secondary side of transformer. The proposed ZVZCS converter is verified on a 7kW, 30kHz experimental prototype.

• The Transactions of the Korean Institute of Electrical Engineers B
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• v.51 no.12
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• pp.682-690
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• 2002

The conventional three-level high frequency phase-shifted dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval.. Due to this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved three-level Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor, a snubber capacitor and two snubber diodes attached at the secondary side of transformer. The proposed ZVZCS converter is verified on a 7㎾, 30KHz experimental prototype.

• Proceedings of the KIPE Conference
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• 2003.07b
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• pp.880-885
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• 2003

Using a Assistance Power Sources of the Railroad Vehicles Three-Level ZVZCS DC/DC Converter is presented in this paper. The proposed three-Level DC/DC Converter Is to achieved zero voltage and zero current switching for the two Main switches. phase shift method is used a parastic capacitance by reverse recovery characteritics in a inner diode of the switching device. Also. using a diode second part of the Transformer by the simple auxiliary circuit for the achieved zero current switching of the Auxiliary switch. For the ZVZCS movement of the all switching devices is analyzed and verified under a 5kW, in the 100kHz switching frequency.

• Proceedings of the KIPE Conference
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• 2002.11a
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• pp.121-124
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• 2002

The conventional three-level high frequency phase-shifted dc/dc converter has a disadvantage that a circulating current flows through transformer and switching devices during the freewheeling interval. Due In this circulating current and RMS current stress, conduction losses of transformer and switching devices increases. To alleviate these problems, we propose an improved three-level Zero Voltage and Zero Current Switching (ZVZCS) dc/dc converter using a tapped inductor, a snubber capacitor and two snubber diodes attached at the secondary side of transformer The proposed ZVZCS converter is verified on a 7kW, 30kHz experimental prototype.

• Proceedings of the KIEE Conference
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• 2001.04a
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• pp.320-323
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• 2001

A ZVZCS(Zero-Voltage and Zero-Current-Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The 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. A secondary auxiliary circuit, which consists of one small capacitor and two small diode, is added in the secondary to provides ZVZCS conditions to primary switches, and aids to clamp secondary rectifier voltage. The auxiliary circuit Includes neither lossy component nor addition active switch, which makes the proposed converter efficient and effective. The principle of operation, feature, and design considerations are illustrated and verified through the experiment with a 500W 50kHz prototype converter.

• Proceedings of the KIEE Conference
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• 2001.10a
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• pp.200-204
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• 2001

A ZVZCS(Zero Voltage and Zero Current Switching) Three Level DC/DC Converter is presented to secondary auxiliary circuit. The new 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. A secondary auxiliary circuit, which consists of one small capacitor two small diode and one coupled inductor is added in the secondary to provides ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages including simple circuit topology high efficiency, and low cost make the new converter attractive for high power applications. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1kW 50kHz IGBT based experimental circuit.

• 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.

• Journal of the Korean Institute of Illuminating and Electrical Installation Engineers
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• v.16 no.6
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• pp.66-73
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• 2002

This paper presents ZVZCS(Zero-Voltage and Zero-Current Switching) Three Level DC/DC Converter without primary freewheeling diodes. The new converter presented in this paper used a phase shirt control with a flying capacitor in the primary side to achieve ZVS for the outer switches. A secondary anxiliary circuit which consists of one small capacitor, two small diodes and one coupled inductor, is added in the secondary to provide ZVZCS conditions to primary switches, ZVS for outer switches and ZCS for inner switches. Many advantages include simple secondary auxiliary circuit topology, high efficiency, and low cost make the new converter attractive for high power applications. Also the circulating current flows through the circuit so that it causes the needless coduction loss to be occurred in the devices and the transformer of the circuit The new converter has no primary auxiliary diodes for freewheeling current. The principle of operation, feature and design considerations are illustrated and verified through the experiment with a 1[㎾］ 50[KHz］IGBT based experimental circuit.

• Journal of Power Electronics
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• v.18 no.2
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• pp.375-382
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• 2018

A novel active controlled primary current cutting-off zero-voltage and zero-current switching (ZVZCS) PWM three-level dc-dc converter (TLC) is proposed in this paper. The proposed converter has some attractive advantages. The OFF voltage on the primary switches is only Vin/2 due to the series connected structure. The leading-leg switches can obtain zero-voltage switching (ZVS), and the lagging-leg switches can achieve zero-current switching (ZCS) in a wide load range. Two MOSFETs, referred to as cutting-off MOSFETs, with an ultra-low on-state resistance are used as active controlled primary current cutting-off components, and the added conduction loss can be neglected. The added MOSFETs are switched ON and OFF with ZCS that is irrelevant to the load current. Thus, the auxiliary switching loss can be significantly minimized. In addition, these MOSFETs are not series connected in the circuit loop of the dc input bus bar and the primary switches, which results in a low parasitic inductance. The operation principle and some relevant analyses are provided, and a 6-kW laboratory prototype is built to verify the proposed converter.