Filings are concentrated at the top: the leading assignee alone holds 11 of the 54 records in scope, and the top five combined hold 57.4% of all records. The top ten extend that to 75.9%, leaving a long tail of assignees with one or two filings each. This pattern suggests a small group has staked out the core structural claims around windings and cores, while later entrants are more likely filing narrower, defensive variations.

In this dataset, planar transformer claims centre on flat, stacked winding structures — often PCB-based — combined with a magnetic core, as opposed to the wire-wound bobbin construction of conventional transformers. Most claims here fall under IPC class H01F (77.8% of records), which covers the magnetic component itself rather than the surrounding power circuit. Claims frequently address AC winding loss, leakage inductance control, or heat dissipation path design as functional limitations layered onto the planar structure.

Based on the IPC composition, structural core and winding claims (H01F) are dense, while power-conversion integration (H02M, 24.1% of records) and semiconductor co-packaging (H01L and H10D, under 15% each) are comparatively thin. Sub-areas such as interleaved winding arrangements for leakage control, isolation-rated PCB winding stacks, and core material selection for high-frequency loss show fewer filings relative to the core structural claims. These are reasonable starting points for a freedom-to-operate search, though each needs claim-by-claim verification against the nearest prior art.