An LLC resonant converter uses a resonant tank of inductors and a capacitor to shape the switching waveform so that transistors switch at or near zero voltage, reducing switching losses compared to a hard-switched DC-DC converter. Patent claims in this space typically cover the specific tank topology, the transformer or winding structure, or the control method that achieves zero-voltage switching, rather than the general concept of resonant conversion. Because foundational zero-voltage-switching patents such as US4720668A and US4992919A date back decades, most current filing activity narrows in on specific implementation details like PCB-integrated windings, adaptive frequency control, or multi-transformer configurations rather than the base topology.

Filing activity in this dataset is spread across a mix of established power electronics manufacturers and semiconductor firms, with several assignees showing recent-year momentum dropping to zero, which is consistent with the overall decline in filing volume since the 2019 peak. No single assignee dominates the 1,916-family dataset outright, and the presence of co-assignee pairs such as Philips with Philips Intellectual Property & Standards, and Murata Manufacturing with Murata Power Solutions, indicates that some filings result from internal corporate restructuring rather than independent invention. Reviewing the assignee ranking table alongside filing recency is more informative than relying on cumulative counts alone, since older large filers may no longer be active.

Filing volume peaked at 135 records in 2019, held roughly steady at 107 by the 2022 midpoint, and has since declined toward 11 in the most recent, partial year. Part of that decline reflects the normal 18-month lag between filing and publication, which always understates the most recent year or two of activity. The broader pattern, though, suggests that core resonant topology and zero-voltage-switching claim space has become dense enough that fewer applicants see room for a defensible new composition claim, pushing remaining innovation toward narrower implementation details such as winding structure or control-loop integration.

The thinnest IPC branches relative to the 1,575-record H02M core are G05F (electric and magnetic variable control, 45 records), H02H (protective circuit arrangements, 58) and H03K (pulse technique and logic circuits, 63). These figures indicate that protection circuitry, adaptive control loops and pulse-logic integration layered onto a resonant converter are comparatively under-claimed next to the core switching topology. B60L (electric vehicle propulsion, 81 records) is also relatively light, suggesting vehicle-specific integration claims have not been as heavily filed as general power-conversion claims.

No. US20240079965A1 covers a specific implementation: an LLC resonant converter with multiple separated transformers whose PCB-fabricated primary windings can be reconfigured in series or parallel to hold the turns ratio while tuning the resonant tank. It does not claim the general concept of an LLC resonant converter, zero-voltage switching, or conventional wire-wound transformer designs. A design using a fixed winding configuration, a single monolithic transformer, or a different turns-ratio adjustment mechanism would generally sit outside this specific claim scope, though a freedom-to-operate review of the full claim set is the only reliable way to confirm that for a given design.