A Novel Pyramid Winding for PCB Planar Inductors With Fewer Copper Layers and Lower AC Copper Loss

Relying on the advantages of small size, good controllability, and consistency, printed circuit board (PCB) inductors are being widely used. For PCB inductors, reducing copper loss is one of the key issues. Although some research works focus on fringing effect in PCB planar winding, there are few methods to reduce proximity loss for PCB inductor. Regarding the abovementioned issues, this letter first improves the Ferreira's 1-D copper loss model to accommodate the core feature of PCB winding: variable number of turns per layer. With this model, pyramid theorem is proposed that putting the layer with fewer turns into positions farther away from the air gaps can lower the total winding loss. Based on the theorem, this letter proposes a novel PCB inductor-winding structure named pyramid winding, which has fewer (or equal) turns on layers farther from air gaps. Pyramid winding has less copper loss, fewer copper layers, smaller size, and lower cost. In the experiment, inductor prototypes with the same six turns and ferrite pot cores but different PCB winding arrangements are built for a 300-kHz 2700-W LLC converter. Tests on inductor resistance and converter efficiency are done, and the pyramid theorem and the effectiveness of pyramid winding are verified.