Analysis of Steady-State Characteristics of LLC Resonant Converters

A simplified method for taking into account the magnetization branch when using a T-shaped equivalent circuit of a two-winding transformer for the analysis of a resonant dc voltage converter (DCVC) at the time interval of its linearity is proposed. The method allows us to replace the exact description of the DCVC in the interval of its linearity with two differential equations of the first order, which greatly simplifies the calculations. Calculations of the processes in the linearity interval of the DCVC using exact and simplified equations showed almost perfect matching of the results. The equation for determining the initial value of the state vector of the DCVC at the interval of its linearity in the steady-state mode is solved. Formulas for calculating the external (load) characteristics of the DCVC are given. The calculated external characteristics with the parameters of a mass-produced DCVC practically coincide with the experimental ones obtained using the Simulink model.