Planar coil and planar transformer

• US 6,847,284 B2
• Filed: 02/28/2002
• Issued: 01/25/2005
• Est. Priority Date: 03/05/2001
• Status: Active Grant

• Current Assignee: TDK Corporation
• Original Assignee: TDK Corporation
• Inventors: Horikami, Satoshi, Gamou, Masahiro
• Primary Examiner(s): Donovan, Lincoln
• Assistant Examiner(s): Poker, Jennifer A.
• Application Number:
  US10/297,801
• Publication Number:
  US 20030179067A1
• Time in Patent Office: 1,062 Days
• Field of Search: 336/223, 336/200, 336/192, 336/83, 336/65, 336/196, 336/232, 336/198, 296/021
• US Class Current: 336/223
• CPC Class Codes: H01F 2027/2819 Planar transformers with printed windings, e.g. surrounded by two cores and to be mounted on printed circuit
• CPC Class Codes: H01F 27/2804 Printed windings

Abstract

A planar coil includes a winding of N turns (N is an integer greater than or equal to 2). Letting r_i(n) be a radius of an inner circumference of a winding portion at the n^th turn (n is an integer greater than or equal to 1 and less than or equal to N) from the inner side; r_o(n) be a radius of an outer circumference of the same; r_min be a radius of an inner circumference of the innermost winding portion; W_total 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 r_i(n) and r_o(n) are determined so as to minimize a value of A expressed by equation (1) when the r_min, W_totla and D are given. $\begin{array}{cc}A=\sum _{n=1}^N{\left(\log \frac{r_o\left(n\right)}{r_i\left(n\right)}\right)}^{-1}& \left(1\right)\end{array}$

Claims

1. A planar coil comprising a winding formed by arranging a conductor into a flat-spiral shape, the winding including winding portions of N turns (N is an integer greater than or equal to two), wherein:

letting r_i(n) be a radius of an inner circumference of a winding portion at the n^th turn (n is an integer greater than or equal to one and less than or equal to N) from the inner side;

r_o(n) be a radius of an outer circumference of the same;

r_min be a radius of an inner circumference of the innermost winding portion;

W_total 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 r_i(n) and r_o(n) are determined so as to minimize a value of A expressed by equation (1) when the r_min, W_total and D are given;

$\begin{array}{cc}A=\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>{\left(\log <br><br>\frac{r_o<br><br>\left(n\right)}{r_i<br><br>\left(n\right)}\right)}^{-1}& \left(1\right)\end{array}$

 

where r_i(1)=r_min, r_i(n+1)−

r_o(n)=D, and r_o(N)−

r_i(1)=W_total.

2. A planar coil according to claim 1, wherein a plurality of said windings are provided, and the plurality of said windings are stacked in a direction of thickness with an insulating layer disposed between adjacent ones, and are connected in parallel or in series to each other.

3. A planar transformer comprising a plurality of windings each formed into a flat shape and stacked in a direction of thickness, and an insulating layer disposed between adjacent ones of the windings, a part of the plurality of windings serving as a primary winding and another part of the plurality of windings serving as a secondary winding, wherein:

at least one of the plurality of windings includes winding portions of N turns (N is an integer greater than or equal to two), the winding portions being formed by arranging a conductor into a flat-spiral shape, and

letting r_i(n) be a radius of an inner circumference of a winding portion at the n^th turn (n is an integer greater than or equal to one and less than or equal to N) from the inner side;

r_o(n) be a radius of an outer circumference of the same;

r_min be a radius of an inner circumference of the innermost winding portion;

W_total 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 r_i(n) and r_o(n) are determined so as to minimize a value of A expressed by equation (1) when the r_min, W_total and D are given;

$\begin{array}{cc}A=\underset{n=1}{\overset{N}{\sum <br><br>}}<br><br>{\left(\log <br><br>\frac{r_o<br><br>\left(n\right)}{r_i<br><br>\left(n\right)}\right)}^{-1}& \left(1\right)\end{array}$

 

where r_i(1)=r_min, r_i(n+1)−

r_o(n) D, and r_o(N)−

r_i(1)=W_total.

4. A planar coil having a winding of an odd number of turns, the winding being formed of a conductor, the planar coil comprising:

an insulating layer;

a first conductor layer including a first patterned conductor formed by arranging a conductor into a flat-spiral shape; and

a second conductor including a second patterned conductor formed by arranging a conductor into a flat-spiral shape, the second conductor layer being adjacent to the first conductor layer via the insulating layer, wherein;

each of the first patterned conductor and the second patterned conductor includes a winding portion of an innermost one turn and the remaining winding portion of N (N is an integer greater than or equal to one) turns, and

only the winding portion of the innermost one turn of the first patterned conductor and only the winding portion of the innermost one turn of the second patterned conductor are connected in parallel to each other, thereby allowing the first patterned conductor and the second patterned conductor to form the winding of 2N+1 turns.

5. A planar coil according to claim 4, wherein

in each of the first patterned conductor and the second patterned conductor, the winding portion of the innermost one turn has a width that is substantially half the width of the remaining winding portion.

6. A planar coil according to claim 4, wherein

in the first patterned conductor and the second patterned conductor, letting r_i(n) be a radius of an inner circumference of a winding portion at the n^th turn (n is an integer greater than or equal to 1 and less than or equal to N+1) from the inner side;

r_o(n) be a radius of an outer circumference of the same;

r_min be a radius of an inner circumference of the innermost winding portion;

W_total 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 r_i(n) and r_o(n) are determined so as to minimize a value of A expressed by equation (5) when the r_min, W_total and D are given;

$\begin{array}{cc}A=\underset{n=1}{\overset{N+1}{\sum <br><br>}}<br><br>K<br><br>\left(n\right)<br><br>{\left(\log <br><br>\frac{r_o<br><br>\left(n\right)}{r_i<br><br>\left(n\right)}\right)}^{-1}& \left(5\right)\end{array}$

 

where K(1)=0.5;

K(n)=2 when n≧

2;

r_i(1)=r_min;

r_i(n+1)−

r_o(n)=D; and

r_o(N+1)−

r_i(1)=W_total.

7. A planar coil according to claim 4, wherein a plurality of sets of the insulating layer, the first conductor layer and the second conductor layer are stacked in a direction of thickness, and the windings of the respective sets are connected in parallel to each other.

8. A planar transformer having a primary winding and a secondary winding, each being formed of a conductor arranged into a flat shape, wherein:

at least one of the primary winding and the secondary winding comprises;

a first conductor layer including a first patterned conductor formed by arranging a conductor into a flat-spiral shape; and

a second conductor including a second patterned conductor formed by arranging a conductor into a flat-spiral shape, the second conductor layer being adjacent to the first conductor layer via an insulating layer,

each of the first patterned conductor and the second patterned conductor includes a winding portion of an innermost one turn and the remaining winding portion of N (N is an integer greater than or equal to one) turns, and

only the winding portion of the innermost one turn of the first patterned conductor and only the winding portion of the innermost one turn of the second patterned conductor are connected in parallel to each other, thereby allowing the first patterned conductor and the second patterned conductor to form a winding of 2N+1 turns.

9. A planar transformer according to claim 8, wherein

in each of the first patterned conductor and the second patterned conductor, the winding portion of the innermost one turn has a width that is substantially half the width of the remaining winding portion.

10. A planar transformer according to claim 8, wherein

in the first patterned conductor and the second patterned conductor, letting r_i(n) be a radius of an inner circumference of a winding portion at the n^th turn (n is an integer greater than or equal to 1 and less than or equal to N+1) from the inner side;

r_o(n) be a radius of an outer circumference of the same;

r_min be a radius of an inner circumference of the innermost winding portion;

W_total 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 r_i(n) and r_o(n) are determined so as to minimize a value of A expressed by equation (5) when the r_min, W_total and D are given;

$\begin{array}{cc}A=\underset{n=1}{\overset{N+1}{\sum <br><br>}}<br><br>K<br><br>\left(n\right)<br><br>{\left(\log <br><br>\frac{r_o<br><br>\left(n\right)}{r_i<br><br>\left(n\right)}\right)}^{-1}& \left(5\right)\end{array}$

 

where K(1)=0.5;

K(n)=2 when n≧

2;

r_i(1)=r_min;

r_i(n+1)−

r_o(n)=D; and

r_o(N+1)−

r_i(1)=W_total.