planar magnetic - goose1987/buck-CC-CV GitHub Wiki

Optimization through iteration

iterate over discrete core geometry and material to optimize loss based on desired max output current. Increase winding results in lower flux swings but higher DC loss. AC winding losses are dependent on geometry and are accounted for later in finite element modeling.

matlab scripts : https://github.com/goose1987/buck-CC-CV/tree/master/magnetics

EPCOS/TDK cores

N87

N95

N97

N95 material gave lowest loss overall but not readily available. Go with N87 which is more common loss and volume

Assume that space is at a premium so use EQ25 + PLT, N87 material even at the higher loss

Core : EQ25 Material : N87 Turns : 5 gap : 240 um (mechanical tolerance based on vendor, Elna magnetic can hit +/- 25um) Leff : 12 uH

finite element model

15A peak at 12A RMS

15A peak current

locate winding far from gap to minimize proximity effect gap proximity