OUT

D

OUT

D

IN

V

V

D

V

V

V

+

=

+

+

VIN

6-18V

VIN

VIN

12V, 1A

49.9

86.6k

1

1

Not Populated

TP3

SYNC

SYNC

TP2

TP5

TP4

Lb

La

TPS55340

www.ti.com

SLVSBD4B – MAY 2012 – REVISED OCTOBER 2012

DESIGN GUIDE-STEP-BY-STEP DESIGN PROCEDURE OF SEPIC CONVERTER

Figure 24. SEPIC Converter Application Schematic

The following parameters are used for a SEPIC converter design. These calculations are performed only for

CCM operation, and the use of a coupled inductor is assumed.

Table 2. Key Parameters of SEPIC Converter Example

PARAMETER

VALUE

Output Voltage

12 V

Input Voltage

6 V to 18 V, 12 V nominal

Maximum Output Current

1 A

Transient Response 50% load step (

480 mV

60 mV

SELECTING THE SWITCHING FREQUENCY (R4)

nearest standard value 95.3 k

Ω is used.

DUTY CYCLE

The duty cycle of a SEPIC converter is calculated with Equation 40. With the 6 V minimum input the duty cycle is

68% and with the 18 V maximum input voltage the duty cycle is 41%.

(40)

Copyright © 2012, Texas Instruments Incorporated

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