SNVAA43 March   2023 LM5157 , LM5157-Q1 , LM51571-Q1 , LM5158 , LM5158-Q1 , LM51581 , LM51581-Q1

 

  1.   Abstract
  2.   Trademarks
  3. 1Introduction
  4. 2Application Parameters
  5. 3Calculations and Component Selection
    1. 3.1 Switching Frequency
    2. 3.2 Coupled Inductor Selection
      1. 3.2.1 Coupling Capacitor (AC Cap)
    3. 3.3 Diode Selection
    4. 3.4 MOSFET Selection
    5. 3.5 Output Capacitor Selection
    6. 3.6 Input Capacitor Selection
    7. 3.7 Output Voltage Setting
  6. 4Simplified SEPIC Schematic
  7. 5References

1 Introduction

The typical design procedures and calculations to implement a non-synchronous SEPIC power stage operating in continuous conduction mode are presented in this report. The converter in this example is based on the LM5155EVM-SEPIC and can provide a regulated output of 12 V at 1 A from an input of 4 V to 32 V. When the input voltage is between 4 V to 6 V, the output power is derated down to 6 W.

The Figure 1-1 shows the basic configuration of a SEPIC power stage.

Figure 1-1 Coupled Inductor SEPIC Power Stage