In this corpus, resonant converter filings (LLC converter, resonant DC-DC) are classified predominantly under H02M, power conversion circuitry, and describe DC-to-DC voltage transformation using a resonant tank to enable soft switching. Resonant inverter filings, including induction-heating inverters and class-E inverters, sit heavily in H05B, electric heating and lighting circuits, because they typically drive an AC load such as an induction coil rather than regulate a DC output. The two share circuit building blocks — switching stage, resonant tank, transformer — but patent examiners and applicants classify them by end function, which is why the IPC split in this dataset tracks application rather than pure topology.

The ranking in this dataset is led by a small group of large industrial and lighting companies with dense co-assignee relationships, most notably a Philips-related pairing linked across 16 shared families. Several other major assignees appear with related-entity filing patterns rather than single-inventor clusters, which is typical where a corporate group files jointly across regional subsidiaries. Recent-year momentum for these top assignees has dropped to zero, which reflects the general decline in new filings since the 2017 peak and the 18-month publication lag on the most recent applications, not necessarily reduced R&D activity.

The filing trend in this dataset rises to a peak of 47 in 2017, falls to a midpoint of 18 by 2022, and reaches 0 in the most recent year. Some of that recent-year drop is a publication-lag artefact — patents filed in the last 18 months typically have not published yet — but the multi-year decline visible well before the lag window suggests genuine cooling in new topology filing, consistent with a technology whose core circuit space (H02M) is already densely claimed. This pattern is common in mature power-electronics sub-fields where incremental refinement replaces foundational filing.

US20240079965A1, filed by Zerova Technologies Taiwan Limited and published 2024-03-07, claims an LLC resonant converter with transformer windings fabricated on a PCB, where primary-side windings across multiple transformers can be dynamically switched between series and parallel connection to retune the resonant tank's effective turns ratio. This is a specific implementation claim, not a claim over LLC topology generally, so it primarily constrains designs that combine PCB-fabricated windings with that particular reconfigurable coupling mechanism. Teams using PCB magnetics without the dynamic re-coupling feature, or reconfigurable windings built with conventional wound transformers, are less likely to fall within its scope, though a freedom-to-operate review of the granted claim language is the only way to confirm this for a specific design.

Relative to the 488-family H02M core, the smaller IPC clusters in this dataset — EV propulsion (B60L, 49 families), general transmission (H04B, 26) and electron/discharge tubes (H01J, 25) — show comparatively thin coverage, suggesting resonant converter and inverter designs purpose-built for those applications are less densely claimed than general power-conversion topology. PCB-integrated, reconfigurable magnetics is a concrete example of a narrower, still-open claim direction visible in the recent representative filing. Because publication lag understates the most recent 12-18 months, any white-space assessment should be paired with a fresh search rather than relying solely on the visible trend line.