Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V

Generally, the DC-DC converters used in DC fast chargers must cover a wide output voltage with a fixed input voltage, and a single module needs to supply 30-50 kW of power. When designing an LLC resonant converter to cover a wide output voltage with a narrow frequency at high power, a small magnetiz...

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Main Authors: Ha-Min Park, Hyung-Woo Lee, Chan-Bae Park, Jae-Bum Lee, Jin-Chul Kim, Ju Lee
Format: Article
Language:English
Published: IEEE 2025-01-01
Series:IEEE Access
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Online Access:https://ieeexplore.ieee.org/document/10897984/
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author Ha-Min Park
Hyung-Woo Lee
Chan-Bae Park
Jae-Bum Lee
Jin-Chul Kim
Ju Lee
author_facet Ha-Min Park
Hyung-Woo Lee
Chan-Bae Park
Jae-Bum Lee
Jin-Chul Kim
Ju Lee
author_sort Ha-Min Park
collection DOAJ
description Generally, the DC-DC converters used in DC fast chargers must cover a wide output voltage with a fixed input voltage, and a single module needs to supply 30-50 kW of power. When designing an LLC resonant converter to cover a wide output voltage with a narrow frequency at high power, a small magnetizing inductance is required, resulting in increased switching turn-off losses. Additionally, a large air gap in the transformer is needed, which increases AC losses in the transformer windings owing to the fringing effect, degrading efficiency. Therefore, to cover a wide output voltage with a fixed input voltage while achieving high power and efficiency, the LLC resonant converter followed by the buck converter is proposed in this paper. Because the LLC resonant converter operates at a fixed frequency, a large magnetizing inductance can be used. This results in lower switching turn-off losses and a smaller air gap in the transformer, which decreases AC losses in the transformer windings. Additionally, by optimally selecting the frequencies of each converter and output voltage of the LLC resonant converter, which functions as the input voltage of the buck converter, high efficiency can be achieved. To confirm the validity of the proposed structure of the DC-DC converter, an 820 V input and 150-1,000 V/50 kW output prototype is built and tested.
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spelling doaj-art-184a3dc937b3473d9d68125c4db7bb1a2025-08-20T03:16:25ZengIEEEIEEE Access2169-35362025-01-0113371823719710.1109/ACCESS.2025.354427710897984Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 VHa-Min Park0https://orcid.org/0009-0005-8388-1716Hyung-Woo Lee1https://orcid.org/0000-0002-6072-8277Chan-Bae Park2https://orcid.org/0000-0003-2404-2419Jae-Bum Lee3https://orcid.org/0000-0001-9018-6221Jin-Chul Kim4Ju Lee5https://orcid.org/0000-0003-0251-6492Department of Railroad Convergence System, Korea National University of Transportation, Uiwang-si, Gyeonggi-do, Republic of KoreaDepartment of Railway Vehicle System Engineering, Korea National University of Transportation, Uiwang-si, Gyeonggi-do, Republic of KoreaDepartment of Railroad Operation Systems Engineering, Korea National University of Transportation, Uiwang-si, Gyeonggi-do, Republic of KoreaDepartment of Railroad Electrical and Information Engineering, Korea National University of Transportation, Uiwang-si, Gyeonggi-do, Republic of Korea5Department of Electrical Engineering, Hanyang University, Seongdong-gu, Seoul, Republic of Korea5Department of Electrical Engineering, Hanyang University, Seongdong-gu, Seoul, Republic of KoreaGenerally, the DC-DC converters used in DC fast chargers must cover a wide output voltage with a fixed input voltage, and a single module needs to supply 30-50 kW of power. When designing an LLC resonant converter to cover a wide output voltage with a narrow frequency at high power, a small magnetizing inductance is required, resulting in increased switching turn-off losses. Additionally, a large air gap in the transformer is needed, which increases AC losses in the transformer windings owing to the fringing effect, degrading efficiency. Therefore, to cover a wide output voltage with a fixed input voltage while achieving high power and efficiency, the LLC resonant converter followed by the buck converter is proposed in this paper. Because the LLC resonant converter operates at a fixed frequency, a large magnetizing inductance can be used. This results in lower switching turn-off losses and a smaller air gap in the transformer, which decreases AC losses in the transformer windings. Additionally, by optimally selecting the frequencies of each converter and output voltage of the LLC resonant converter, which functions as the input voltage of the buck converter, high efficiency can be achieved. To confirm the validity of the proposed structure of the DC-DC converter, an 820 V input and 150-1,000 V/50 kW output prototype is built and tested.https://ieeexplore.ieee.org/document/10897984/DC fast chargerwide output voltageLLC resonant converterbuck converterfixed frequencyhigh efficiency
spellingShingle Ha-Min Park
Hyung-Woo Lee
Chan-Bae Park
Jae-Bum Lee
Jin-Chul Kim
Ju Lee
Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V
IEEE Access
DC fast charger
wide output voltage
LLC resonant converter
buck converter
fixed frequency
high efficiency
title Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V
title_full Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V
title_fullStr Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V
title_full_unstemmed Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V
title_short Analysis and Design of a 50-kW Two Stage Converters for EV Fast Charger With High Efficiency and Wide Output Voltage of 150–1000 V
title_sort analysis and design of a 50 kw two stage converters for ev fast charger with high efficiency and wide output voltage of 150 x2013 1000 v
topic DC fast charger
wide output voltage
LLC resonant converter
buck converter
fixed frequency
high efficiency
url https://ieeexplore.ieee.org/document/10897984/
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