DC-DC converter design
AN4070
16/53
Doc ID 022934 Rev 1
The maximum wire diameter to avoid skin effect is given by:
Equation 25
Assuming a current density J of 5 A/mm^2:
Equation 26
The primary and secondary wire selection can be done according to the following equation:
Equation 27
where A
wp
and A
ws
are the primary and secondary wire cross sectional areas.
Considering the mean turn length value reported in
Table 6
, the primary and secondary
winding length can be calculated using the following equations:
Equation 28
Knowing that copper resistivity
ρ
is equal to:
Equation 29
The primary and secondary winding resistance values are given by:
Equation 30
7.
Transformer losses calculation:
Having calculated the values of primary and secondary winding resistance the
calculation of copper losses is straightforward with the following equation:
Equation 31
mm
d
7
.
0
2
=
=
δ
2
5
mm
A
J
=
2
86
.
0
5
3
.
4
mm
J
I
A
T
in
wp
=
=
=
m
MLT
N
MLS
m
MLT
N
MLP
288
.
2
10
5
.
71
32
858
.
0
10
5
.
71
12
3
2
3
1
=
⋅
⋅
=
⋅
=
=
⋅
⋅
=
⋅
=
−
−
2
0175
.
0
mm
m
⋅
Ω
=
ρ
Ω
≅
⋅
=
⋅
=
Ω
≅
⋅
=
⋅
=
m
A
MLS
R
m
A
MLP
R
ws
s
wp
p
114
35
.
0
28
.
2
0175
.
0
25
86
.
0
858
.
0
0175
.
0
ρ
ρ
W
V
P
P
e
lm
Fe
19
.
0
10
14000
10
141
9
3
=
⋅
⋅
⋅
=
⋅
=
−
