Definition

A planar transformer implements windings as spiral traces on PCB layers rather than wound wire, with a magnetic core assembled around the PCB. Planar construction enables very low profile (often <10mm height), high power density, excellent repeatability, and integrated assembly. Multiple PCB layers connect in series or parallel for primary and secondary windings. Planar magnetics are common in DC/DC converters, with proper design achieving efficiencies over 95%. Interleaved winding structures minimize leakage inductance.