The advent of planar type magnetic components adds flexibility and advantages over conventional magnetic component design. While the geometric differences (mainly in the total height of the finished product) can be seen, planar type geometries offer several design advantages. Planar cores typically have a larger cross-section area of the center core leg. This leads to a reduced number of wire turns needed to achieve a desired magnetizing inductance. Finished planar magnetic devices are assembled using printed circuit board (PCB) windings, interleaved helical-wound or ring-stamped flat wire or key sheet style windings. Each of these forms to create wire turns in the device all but eliminate the need for a bobbin or coil former to wind wire around.
These two aspects of physical layout of the component lead to higher current capability, good heat dissipation, and low parasitic leakage due to flat wire or layered PCB trace windings and interleaving windings. Low core loss is possible due to larger center leg core geometry and choice of core material. The compact nature of planar magnetic design with efficient core self-shielding and tight coupling of windings can also have EMI advantages.
All of these design advantages result in higher volumetric power density, lower loss, higher efficiency in a low height profile component with good thermal conduction and heat dissipation properties.
Mineral Source Reporting for Transformers: CFSI_CMRT4-01