Analysis of symmetrical LLC converter for wireless charging of autonomous devices

Analysis of symmetrical LLC converter for wireless charging of autonomous devices

Boris A. Avdeev, Candidate of Engineering Sciences, Associate Professor, Head of Laboratory, Kherson Technical University, 196, Tcentralnaya ul., Genichesk, 275001, Russia, This email address is being protected from spambots. You need JavaScript enabled to view it., ORCID: 0000-0001-6902-245X

Sergei G. Chernyi, Candidate of Engineering Sciences, Research Scientist, Kherson Technical University, 196, Tcentralnaya ul., Genichesk, 275001, Russia; Assistant Professor, St. Petersburg State Marine Technical University (SMTU), 3, Lotsmanskaya ul., Saint Petersburg, 190121, Russia, This email address is being protected from spambots. You need JavaScript enabled to view it., ORCID: 0000-0001-5702-3260

Dmitry O. Kovalevsky, Researcher, Kherson Technical University, 196, Tcentralnaya ul., Genichesk, 275001, Russia, This email address is being protected from spambots. You need JavaScript enabled to view it.

UDC identifier: 621.31

EDN: KHQHFZ

Abstract. Wireless power transmission technology is becoming one of the most important elements in power supply of portable devices and autonomous devices. One of such devices for wireless power transmission is a symmetrical LLC converter. The symmetrical structure allows energy to be transmitted in both directions. The article describes the operating principle and provides control waveforms, develops a mathematical model of a wireless symmetrical LLC DC converter, and uses a numerical method based on the obtained model to construct the dependences of the power and efficiency of the system on the switching frequency and phase shift angle. The parameters that affect the efficiency of the bidirectional converter to a greater extent are determined. The active and reactive powers transmitted in both directions are determined. The obtained dependences from the mathematical model are presented in the form of graphs. Possible power losses are described when implementing the studied converter in practice. It is shown that the wireless symmetrical LLC converter works best when transmitting electricity from sources with similar voltage values, as well as the fact that the symmetrical LLC converter when operating with a large ratio of voltages on the first and second circuits can only operate at large shift angles.

Key words: symmetrical LLC converter, wireless power transmission, DC-DC converter, resonant circuit, efficiency

For citation: Avdeev, B.A., Chernyi, S.G. and Kovalevskiy, D.O. (2026), "Analysis of symmetrical LLC converter for wireless charging of autonomous devices", Robotics and Technical Cybernetics, vol. 14, no. 1, pp. 13-20,
EDN: KHQHFZ. (in Russian).

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Received 07.04.2025 
Revised 14.08.2025
Accepted 25.09.2025