Analysis of Continuous Current Mode of an LLC Resonant DC-DC Converter at ZVS

Abstract

This paper presents a theoretical analysis of a resonant LLC DC-DC converter operating in continuous current mode with zero voltage switching (ZVS). On the base of modeling the processes in the tank circuit with differential equations, expressions for the fundamental quantities for both step-down and step-up modes are derived. The conditions for the transition to the discontinuous current mode are determined. The boundary of the ZVS operating area is defined. Output characteristics of the converter are plotted graphically for different values of circuit and control parameters.