AN2435

Sepic topology for PFC converter

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The current through diode D1 is the sum of the currents running through inductor L1 and

negative and inversely proportional to inductor L1 and inductor L2 respectively.

Figure 4 shows the theoretical waveforms of the inductors’ currents. Equation 1 and

Equation 1

Equation 2

Equation 3

Equation 4

Figure 1.

Basic circuit of the sepic converter

Figure 2.

Sepic converter when the main switch is on

I

()

I

L10

V

IN

L

1

---------

t

•

+

=

I

()

I

L20

V

IN

L

2

---------

t

•

+

=

I

()

I

L10

V

IN

L

1

---------

T

ON

•

V

out

L

1

-----------

t

•

–

+

=

I

()

I

L20

V

IN

L

1

---------

T

ON

•

V

out

L

2

-----------

t

•

–

+

=

+

-

+

-

+

-