Resonant Converter DC-DC Patents: Leaders & Filing Trends 2026
- Filing already peaked. 2021 saw 19 filings, the high point of the decade; by 2022 activity had fallen back to 15, and the trend has not recovered since.
- H02M dominates the claim space. 123 of 148 records sit in the core power-conversion subclass, leaving thinner but real activity in motor control, engine cooling and pump-adjacent filings.
- The US is the primary filing venue. 87 records were filed at the USPTO against 15 PCT, 14 India and 13 EPO filings — a US-centred field with only modest multi-jurisdiction hedging.
What the resonant converter patent record actually shows
Resonant and LLC DC-DC converter patents cluster tightly around soft-switching topology and resonant tank design — the classic problem of moving switching losses out of the hard-switched edges. The 148 families in this dataset span 2015 through the partial 2026 year, with the bulk of activity concentrated in H02M power conversion and secondary spillover into motor control, magnetics and even engine-cooling applications where resonant DC-DC stages feed variable-speed drives.
Filing activity rose steadily through the late 2010s, peaked in 2021, and has since drifted down — a pattern more consistent with a maturing claim space than an emerging one. Publication lags filing by roughly 18 months, so the 2025 and 2026 counts in particular understate real filing activity; treat the recent-year decline as a floor, not a confirmed trend.
Filing trend and technology composition
The two views below cover the same 148 families from different angles: one tracks when the field filed, the other shows where those filings landed across IPC subclasses.
A single peak year, then decline
Filings climbed from 4 in 2017 to a peak of 19 in 2021, then eased to 15 by the 2022 midpoint and have not returned to peak levels since — consistent with a technology whose core claim space is largely staked out.
Concentrated in power conversion, with real adjacency
H02M carries 123 of 148 records, but meaningful counts also sit in H02J (power supply/grid, 20), H02K (motors/generators, 13), F01P (engine cooling, 12) and H02N (12) — signalling that resonant DC-DC art increasingly gets claimed inside application-specific systems rather than as a standalone converter.
Shares are the percentage of the 148 records in scope. A patent can carry several IPC classes, so the shares add up to more than 100%.
Go deeper on Resonant Converter DC-DC Converter with Eureka
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Try EurekaThe prior art shaping this field
LLC Resonant Converter with Windings Fabricated on PCB
An LLC resonant converter built around a switching circuit, a resonant tank and a transformer circuit whose primary and secondary windings sit directly on a PCB. The primary windings of separate transformers can be reconfigured in series or parallel to form a dynamically varied equivalent winding, letting the design fine-tune the resonant tank's turns ratio without changing the physical magnetics.Filed by Zerova Technologies Taiwan Limited, published 2024-03-07.
| # | Publication no. | Patent title | Citations |
|---|---|---|---|
| 1 | US4866367A | Multi-loop control for quasi-resonant converters | 165 |
| 2 | US20150280584A1 | System and Method for a Switched-Mode Power Supply | 90 |
| 3 | US20150016159A1 | Multiphase Power Converter Circuit and Method | 72 |
| 4 | US20140153294A1 | AC/DC Power Converter Arrangement | 71 |
| 5 | US20150008748A1 | Power Converter Circuit, Power Supply System and Method | 70 |
| 6 | WO2014070998A1 | Systems and methods for a variable frequency multiplier power converter | 61 |
| 7 | US20150162840A1 | DC-DC converter circuit using an LLC circuit in the region of voltage gain above unity | 55 |
| 8 | US20130121033A1 | DC-DC converter circuit using LLC circuit in the region of voltage gain above unity | 50 |
| 9 | US20150295497A1 | Systems and Methods for a Variable Frequency Multiplier Power Converter | 49 |
| 10 | US20150015072A1 | Power Converter Circuit and Method | 45 |
Citation counts favour older filings simply by virtue of age in the corpus; read them as markers of foundational influence, not of current filing activity.
Each row carries its publication number; clicking a row searches Eureka by that number.
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Four figures from the dataset matter most for anyone deciding where to file or partner next.
The field has already crested
From 4 filings in 2017 to a peak of 19 in 2021, then back to 15 by 2022 — the shape of a technology whose core topology claims are largely staked, with growth now happening at the edges rather than the center.
Power conversion still anchors the field
H02M alone accounts for the majority of records, but H02J, H02K, F01P and H02N each carry a double-digit share — resonant DC-DC art is migrating into motor drives, grid interfaces and thermal systems.
US-centred with light international hedging
The bulk of activity files first or only in the United States; PCT, India and EPO each carry a modest but real share, while China and Canada trail well behind.
Foundational art is old, not recent
The most-cited records date from well before the 2021 filing peak, which is typical of citation counts inside a searched corpus — they reward age and prior influence, not current relevance.
Eureka can read the same corpus for gaps instead of for coverage: under-claimed branches adjacent to resonant converter dc-dc converter, with the prior art for and against each one.
Assignees and where the claim space is thin
No single assignee dominates this dataset the way concentration patterns look in more mature fields; the strongest signal is a handful of co-filing pairs and several organisations with zero filings in the latest tracked year, suggesting programme pauses rather than sustained retreat.
One inventor cluster files repeatedly together
Wang Hongliang appears paired with three separate co-inventors — Liu Yan Fei, Li Zhanming and Fu Yue — each pairing recurring five times, the strongest co-assignment signal in a dataset of only nine tracked pairs.
Multiple named organisations went quiet
Infineon Technologies Austria, Horton, King Fahd University of Petroleum and Minerals, Queen's University, MIT and Tridonic all show zero filings in the most recent tracked year — a pause worth checking against their broader portfolios before assuming exit.
India is a meaningful secondary venue
India's 14 filings sit close behind the EPO's 13, ahead of Canada and China — worth noting for anyone assuming this field is purely a US/Europe contest.
| Assignee | Recent year | YoY |
|---|---|---|
| Infineon Technologies Austria AG | 0 | — |
| Horton, Inc. | 0 | — |
| King Fahd University of Petroleum and Minerals | 0 | — |
| Queen's University | 0 | — |
| Massachusetts Institute of Technology (MIT) | 0 | — |
| Tridonic GmbH & Co KG | 0 | — |
| STMicroelectronics S.r.l. (Italy) | 0 | — |
| Delta Electronics, Inc. | 0 | — |
Turning this landscape into a filing or freedom-to-operate decision
The numbers above narrow the search; the next steps depend on what you are trying to protect or clear.
Check freedom-to-operate against the most-cited art
Before drafting claims in resonant tank design or soft-switching control, run the top-cited records — several predate the 2021 peak and remain foundational — against your specific topology.
Run a citation check in EurekaWatch the quiet assignees for re-entry
Six organisations with zero recent-year filings, including MIT and Queen's University, may resume filing once publication catches up with the 18-month lag; monitoring their portfolios now avoids surprises later.
Set up assignee monitoring in EurekaExplore the under-claimed adjacency branches
PCB-integrated magnetics and motor-drive-integrated resonant stages show thinner direct coverage than core H02M topology claims — a first-claim opportunity worth scoping in detail.
Explore white space in EurekaCommon questions on resonant converter patents
The dataset does not show a single dominant assignee the way some mature power-electronics fields do; instead, activity is spread across a mix of corporate and university filers, with the strongest internal signal being a cluster of co-filing inventors (Wang Hongliang paired repeatedly with Liu Yan Fei, Li Zhanming and Fu Yue). Several well-known organisations, including Infineon Technologies Austria and MIT, appear in the dataset but show no filings in the most recent tracked year. Anyone doing competitive tracking should look at citation influence and co-filing patterns together, not just raw filing counts, since no single assignee controls a majority share.
Filings grew from 4 in 2017 to a peak of 19 in 2021, then fell back to 15 by 2022 and have not recovered to peak levels since. That pattern points to a maturing rather than an emerging technology area. Because publication lags filing by roughly 18 months, the most recent one to two years in any such trend will always look lower than the true filing rate, so the apparent decline should be treated cautiously rather than as confirmed retreat.
An LLC resonant converter is a specific resonant DC-DC topology built around an inductor-inductor-capacitor tank, chosen for its ability to achieve zero-voltage switching across a wide load range, which is why it dominates the IPC composition here under H02M. The broader category of resonant DC-DC converters includes other tank configurations and soft-switching schemes, but the patent record shows LLC-specific claims, including PCB-integrated winding designs, as the most actively filed sub-branch. Anyone drafting claims should be precise about tank topology, since that is where much of the differentiated art sits.
The United States leads by a wide margin with 87 of 148 records, followed by WIPO PCT filings at 15, India at 14, and the European Patent Office at 13; Canada and China trail with single-digit counts. This distribution suggests the field is primarily contested in the US market with meaningful but secondary interest in India and Europe. Filers targeting global coverage should note that China's low count here may reflect either genuine lower activity or corpus/search-string coverage gaps, and is worth checking separately.
The core H02M topology and control claims are dense, but adjacent application areas carry lighter direct coverage: PCB-integrated resonant tank magnetics, resonant DC-DC stages built into motor-drive front ends, and converter designs integrated with engine-cooling pump systems all show thinner claim density relative to the core. These are the branches worth scoping first for a defensible first claim, since they sit adjacent to well-established prior art rather than squarely inside it.
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Disclaimer. This page is generated from Patsnap Eureka data drawn from a limited snapshot of global patent and scientific-literature records, and is provided for general information and reference only.
Patent data carries inherent limitations: recent filings (typically the most recent 18–24 months) are under-counted due to standard publication lag; counts may be reported at either a patent-family or a patent-record basis and are not always directly comparable; classification, applicant-name, and citation data may contain errors, duplicates, or omissions; and the underlying search query defines and constrains the scope shown. As a result, the analysis may be incomplete or inaccurate and may not reflect the full technology landscape.
Nothing on this page constitutes an exhaustive prior-art, novelty, freedom-to-operate, or validity search, nor does it constitute legal, financial, investment, or professional advice, and it should not be relied upon as such. Any patent, commercial, or strategic decision should be verified independently and reviewed with qualified patent, legal, and domain professionals. Patsnap makes no warranties, express or implied, as to the accuracy, completeness, or fitness for any particular purpose of the information presented.
Machine translation. Assignee and organisation names originally recorded in Chinese, Japanese or Korean have been rendered into English by an AI translation step so that the tables stay readable. These renderings are best-effort and may not match a company’s registered English name; the original name is what the underlying patent record carries, and it is what any Eureka query launched from this page uses.