### Abstract

Resonant converters rely on a precise knowledge of leakage inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary leakage inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the leakage inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the leakage energy storage originated from the secondary winding, and hence maximize the secondary leakage inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere's law and Dowell's model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.

Original language | English |
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Title of host publication | 34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019 |

Publisher | Institute of Electrical and Electronics Engineers Inc. |

Pages | 1408-1414 |

Number of pages | 7 |

ISBN (Electronic) | 9781538683309 |

DOIs | |

Publication status | Published - May 24 2019 |

Event | 34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019 - Anaheim, United States Duration: Mar 17 2019 → Mar 21 2019 |

### Publication series

Name | Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC |
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Volume | 2019-March |

### Conference

Conference | 34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019 |
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Country | United States |

City | Anaheim |

Period | 3/17/19 → 3/21/19 |

### Fingerprint

### Keywords

- Dc/dc converter
- Leakage inductance
- LLC resonant converter
- Magnetic cores
- Soft switching converters
- Transformer

### ASJC Scopus subject areas

- Electrical and Electronic Engineering

### Cite this

*34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019*(pp. 1408-1414). [8722190] (Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC; Vol. 2019-March). Institute of Electrical and Electronics Engineers Inc.. https://doi.org/10.1109/APEC.2019.8722190

**Effects of secondary leakage inductance on the LLC resonant converter - Part II : Frequency control bandwidth with respect to load variation.** / Noah, Mostafa; Shirakawa, Tomohide; Umetani, Kazuhiro; Imaoka, Jun; Yamamoto, Masayoshi; Hiraki, Eiji.

Research output: Chapter in Book/Report/Conference proceeding › Conference contribution

*34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019.*, 8722190, Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC, vol. 2019-March, Institute of Electrical and Electronics Engineers Inc., pp. 1408-1414, 34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019, Anaheim, United States, 3/17/19. https://doi.org/10.1109/APEC.2019.8722190

}

TY - GEN

T1 - Effects of secondary leakage inductance on the LLC resonant converter - Part II

T2 - Frequency control bandwidth with respect to load variation

AU - Noah, Mostafa

AU - Shirakawa, Tomohide

AU - Umetani, Kazuhiro

AU - Imaoka, Jun

AU - Yamamoto, Masayoshi

AU - Hiraki, Eiji

PY - 2019/5/24

Y1 - 2019/5/24

N2 - Resonant converters rely on a precise knowledge of leakage inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary leakage inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the leakage inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the leakage energy storage originated from the secondary winding, and hence maximize the secondary leakage inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere's law and Dowell's model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.

AB - Resonant converters rely on a precise knowledge of leakage inductance of the equipped transformers. Resonant circuit topologies such as LLC usually utilize the transformer leakage as an inductive component in the resonant tank, allowing for a drastic reduction in the converter weight, size and volume. The existence of the secondary leakage inductance affects the whole operation of the LLC resonant converter. This paper reveals that placing the secondary winding near the air gap would increase the resonant tank input impedance, vertically shrink the voltage-gain curve of the converter, and consequently minimize the frequency range (i.e frequency bandwidth with respect to load variation). On contrary, placing the secondary winding in a close contact with the magnetic core would decrease the resonant tank input impedance, vertically stretches the voltage-gain curve of the converter, and widen the frequency variation range. It has been reported that the winding location with respect to the air gap has an impact on the leakage inductance value. In other words, placing the secondary winding in a close contact with the magnetic core (zero mmf position) would maximize the leakage energy storage originated from the secondary winding, and hence maximize the secondary leakage inductance and vice versa. The theoretical discussion is presented which is merely based on Ampere's law and Dowell's model. Furthermore, transformer prototypes had been constructed and tested in a 390V/12V-220W LLC converter prototype to evaluate the proposed analysis.

KW - Dc/dc converter

KW - Leakage inductance

KW - LLC resonant converter

KW - Magnetic cores

KW - Soft switching converters

KW - Transformer

UR - http://www.scopus.com/inward/record.url?scp=85067090778&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=85067090778&partnerID=8YFLogxK

U2 - 10.1109/APEC.2019.8722190

DO - 10.1109/APEC.2019.8722190

M3 - Conference contribution

AN - SCOPUS:85067090778

T3 - Conference Proceedings - IEEE Applied Power Electronics Conference and Exposition - APEC

SP - 1408

EP - 1414

BT - 34th Annual IEEE Applied Power Electronics Conference and Exposition, APEC 2019

PB - Institute of Electrical and Electronics Engineers Inc.

ER -