DocID024230 Rev 1

5/15

AN4250

Boost converter

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2

Boost converter

The Boost converter is generally used in the SMPS as a PFC.

Section 3 gives a complete description of the PFC block and the Boost converter.

The Boost circuit is a DC-DC converter providing a higher output voltage than input voltage.

Here below the classic Boost topology.

Figure 2. Boost converter schematic

The circuit is composed of:

–

Inductor

–

Switch (Power MOSFET)

–

Boost diode

–

Capacitor and load

The functioning of the circuit can be divided into two steps depending on the conduction

state of the switch: on-state, off-state.

On-state

During the on-state, the switch can be considered as a short-circuit, thus from the initial

topology two meshes can be derived:

Figure 3. Boost converter schematic during the Power MOSFET turn-on

V1

V

L1

L

D1

D

C1

C

R1

R

SWITCH

AM17350v1

V1

V

L1

L

C1

C

R1

R

Ton

AM17351v1

V

V

IN