Analysis of LLC Converters in ISOP-Systems with Iterative First Harmonic Approximation

Abstract:
An input-series and output-parallel connection of DC-DC converters enables the extension of voltage and power capabilities for available power semiconductors. The inherent balancing characteristic ensures equal power distribution when controlling all modules with a common control signal. However, parameter tolerances cause mismatches. To study their impact in a system consisting of LLC converters, this paper presents a new method based on iterative first harmonic approximation. The power distribution between two LLC converters within the ISOP-system is derived for estimated tolerances. A test setup consisting of two GaN-based LLC converters with an intentionally caused parameter mismatch verifies the new model.