Planar coil and planar transformer

摘要

An object of the invention is to arrange a winding so as to minimize a loss in a limited space. A planar coil includes a disk-shaped insulating layer (10) and a winding (11) of N turns (N is an integer greater than or equal to 2), the winding being formed by arranging a plate-like conductor into a flat-spiral-shape on one surface of the insulating layer (10). In the winding (11), letting r1(n) be a radius of an inner circumference of a winding portion at the nturn (n is an integer greater than or equal to 1 and less than or equal to N) from the inner side; ro(n) be a radius of an outer circumference of the same; rmin be a radius of an inner circumference of the innermost winding portion; Wtotal be a difference between a radius of an outer circumference of the outermost winding portion and the radius of the inner circumference of the innermost winding portion; and D be a distance between winding portions at adjacent turns, the ri(n) and ro(n) are determined so as to minimize a value of A expressed by equation (1) when the rmin, Wtotal and D are given: 1 $\begin{array}{cc}A=\sum _{n=1}^N{\left(\log \frac{r_o\left(n\right)}{r_i\left(n\right)}\right)}^{-1}& \left(1\right)\end{array}$ where ri(1)=rmin, ri(n+1)-ro(n)=D, and ro(N)-ri(1)=Wtotal.