Research on key application issues of smart synchronous rectifier driver IC in LLC resonant converter

In this paper, several key application issues of smart synchronous rectifier (SR) driver IC which is applied in LLC resonant converter are studied and researched. With the smart SR diver IC applied to drive the secondary-side SRs, the LLC resonant converter can further improve the efficiency and be suitable for the application which requires high power density such as brick power modules. Many smart SR driver ICs have been produced and are widely used in this application. However, with the smart SR driver IC applied in the LLC resonant converter, the reverse current problem in secondary side may occur when the converter operates at the status of light load, start up and load transient. The reverse current will low down the efficiency of circuit or even break down the converter. This paper mainly studies and analyzes the reasons of the reverse current problem caused by the utilization of smart SR driver IC in LLC resonant converter in detail and proposes some simple solutions in theory as well. The experimental results are obtained from a 400W (12V/33A) power module prototype which verifies the theoretical analysis.