AN2623

Design circuit

11/25

Considering that the total instantaneous current at the primary side is

Equation 24

the magnetizing current.

The magnetizing current expression is:

Equation 25

And its peak value is:

Equation 26

Equation 27

Equation 28

The ripple current at the primary side is:

Equation 29

The rms value for the current at the primary side is:

Equation 30

Equation 31

Considering (Equation 18) and (Equation 19), the maximum allowed copper power losses in

the windings transformer can be immediately calculated. It is possible to select the diameter

i

()

i

′

() i

()

+

=

i

()

V

inmin

L

m

----------------

t

⋅

=

I

mpk

V

inmin

f

sw

⋅

L

m

D

MAX

⋅

--------------------------------

=

I

′

2pk

I

out

I

∆

0

2

--------

+

⎝⎠

⎛⎞

1

n

---

⋅

=

I

′

2min

I

out

I

∆

0

2

--------

–

⎝⎠

⎛⎞

1

n

---

⋅

=

I

1

∆

I

mpk

I

′

2pk

I

′

2min

–

+

=

I

1totRMS

D

MAX

I

′

2min

()

2

I

1

I

′

2min

1

3

---

I

2

1

∆

⋅

+

⋅

∆

+

⎝⎠

⎛⎞

⋅

=

I

1totRMS

I

RMSdiodeR

n

-----------------------------

2.75 A

=

≅