Boundary conduction mode buck converter as regenerative snubber for center-tapped rectifier

This paper describes a regenerative snubber, based on an auxiliary buck converter (ABC), working in boundary conduction mode (BCM). The energy, from the leakage inductances of the main transformer in a converter, is stored to the clamp capacitor, and then transfered to the load, by the proposed snubber circuit, which is based on an ABC. The use of BCM in the snubber allows for control of the power flow and clamp voltage for the snubber. Implementing such a snubber circuit to the center-tapped rectifier of a full bridge (FB) converter, reduces the amplitude of any ringings, and the voltage stress across the rectifier diodes or transistors, allowing the use off devices with lower on-resistance. Experimental data results for the phase-shift full-bridge (PSFB) converter are presented. Practical recommendations and calculation of values for the snubber circuit elements are also shown in the work.

I. Introduction

The center-tapped rectifier is an important part of the isolated DC/DC converter, Fig. 1. The main issue connected with such a rectifier is a ringing across the active devices that is caused by the leakage inductance in the transformer. Such a ringing increases the voltage tolerance requirements and results in a reduced efficiency of the converter.