---
_id: '59805'
abstract:
- lang: eng
  text: The LLC converter achieves the highest efficiency in resonant operation. Conventionally,
    the input DC-link voltage is controlled to operate the LLC converter at resonance
    for the given operating point. However, the DC-link capacitor voltage shows a
    low-frequency voltage ripple (typically the second harmonic of grid frequency)
    in cascaded converters so that the LLC has to adapt its switching frequency within
    the grid period. Conventionally, the LLC converter operates 50% of the time above
    the resonant frequency of 40 kHz and 50% below resonance. Both operating conditions
    cause additional losses. However, experimental measurements indicate that the
    below-resonance operation causes significantly higher losses than above-resonance
    operation due to much higher primary and secondary transformer currents. It is
    better to increase the DC-link voltage by 30% of the peak-to-peak low-frequency
    voltage ripple to mostly avoid below-resonance operation (i.e., from 650 V to
    680 V in this case). With the proposed control, the LLC converter operates about
    75% of time over resonance and only 25% of time below resonance. The overall efficiency
    increases from 97.66% to 97.7% for the average operating point with an 80% load
    current. This corresponds to a 2% total loss reduction. Finally, the peak resonance
    capacitor voltage decreases from 910 V to 790 V (−13%).
article_number: '1517'
author:
- first_name: Roland
  full_name: Unruh, Roland
  id: '34289'
  last_name: Unruh
- first_name: Joachim
  full_name: Böcker, Joachim
  id: '66'
  last_name: Böcker
  orcid: 0000-0002-8480-7295
- first_name: Frank
  full_name: Schafmeister, Frank
  id: '71291'
  last_name: Schafmeister
citation:
  ama: Unruh R, Böcker J, Schafmeister F. Adaptive DC-Link Voltage Control for 22
    kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple. <i>Electronics</i>.
    2025;14(8). doi:<a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>
  apa: Unruh, R., Böcker, J., &#38; Schafmeister, F. (2025). Adaptive DC-Link Voltage
    Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage
    Ripple. <i>Electronics</i>, <i>14</i>(8), Article 1517. <a href="https://doi.org/10.3390/electronics14081517">https://doi.org/10.3390/electronics14081517</a>
  bibtex: '@article{Unruh_Böcker_Schafmeister_2025, title={Adaptive DC-Link Voltage
    Control for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage
    Ripple}, volume={14}, DOI={<a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>},
    number={81517}, journal={Electronics}, publisher={MDPI AG}, author={Unruh, Roland
    and Böcker, Joachim and Schafmeister, Frank}, year={2025} }'
  chicago: Unruh, Roland, Joachim Böcker, and Frank Schafmeister. “Adaptive DC-Link
    Voltage Control for 22 KW, 40 KHz LLC Resonant Converter Considering Low-Frequency
    Voltage Ripple.” <i>Electronics</i> 14, no. 8 (2025). <a href="https://doi.org/10.3390/electronics14081517">https://doi.org/10.3390/electronics14081517</a>.
  ieee: 'R. Unruh, J. Böcker, and F. Schafmeister, “Adaptive DC-Link Voltage Control
    for 22 kW, 40 kHz LLC Resonant Converter Considering Low-Frequency Voltage Ripple,”
    <i>Electronics</i>, vol. 14, no. 8, Art. no. 1517, 2025, doi: <a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>.'
  mla: Unruh, Roland, et al. “Adaptive DC-Link Voltage Control for 22 KW, 40 KHz LLC
    Resonant Converter Considering Low-Frequency Voltage Ripple.” <i>Electronics</i>,
    vol. 14, no. 8, 1517, MDPI AG, 2025, doi:<a href="https://doi.org/10.3390/electronics14081517">10.3390/electronics14081517</a>.
  short: R. Unruh, J. Böcker, F. Schafmeister, Electronics 14 (2025).
date_created: 2025-05-05T12:27:39Z
date_updated: 2025-05-05T12:34:00Z
department:
- _id: '52'
doi: 10.3390/electronics14081517
intvolume: '        14'
issue: '8'
keyword:
- adaptive DC-link voltage
- cascaded H-bridge
- resonant operation
- Full-Bridge Converter
- loss minimization
- LLC Resonant Converter
- peak capacitor voltage reduction
language:
- iso: eng
main_file_link:
- url: https://www.mdpi.com/2079-9292/14/8/1517
publication: Electronics
publication_identifier:
  issn:
  - 2079-9292
publication_status: published
publisher: MDPI AG
status: public
title: Adaptive DC-Link Voltage Control for 22 kW, 40 kHz LLC Resonant Converter Considering
  Low-Frequency Voltage Ripple
type: journal_article
user_id: '34289'
volume: 14
year: '2025'
...