[082] Sepic Converter Measurements - Part III Current-Mode Design

Measuring the Sepic converter control transfer function with current-mode control.

Introduction

This article shows the measured characteristics of Sepic converter using current-mode control, either with a coupled inductor or separate inductors. It is shown how the characteristics are much improved with current-mode, but the complex RHP zeros are still present under low line conditions.

Sepic Converter with Voltage-Mode Control

In the last article of this series, the coupled-inductor Sepic was examined. It was shown that coupling the two inductors on the same core leads to much better behaved transfer functions when voltage-mode control was used. The coupling of the inductors, whether loosely or with very little leakage, eliminated the troublesome second-resonance characteristics and complex RHP zeros. 

Figure 1 shows the schematic of the Sepic converter with voltage-mode control.  

Figure 1: Voltage-Mode Coupled-Inductor Sepic Converter Circuit