Chargers have become an indispensable component with the increase adoption of electric vehicles. A charger is composed of multiple power converters and its operation has become increasingly complex. It is necessary to understand the complex behavior to ensure system stability during control design.

The transfer function of a system composed of multiple power converters can be derived using the state averaging method. However, the formulated state equation matrix has a large order making difficult to derive the transfer function. This paper proposes a method to analyze the behavior of the system using the transfer functions of the power converters that constitute the system. To facilitate the analysis, we adopted a simple two-stage configuration of a non-isolated buck converter. The circuit model and model derived using the proposed method achieved a high level of agreement, confirming the effectiveness of the proposed method.