Harmonic analysis of VHF resonant converter based on equivalent nonlinear controlled model

摘要

Lifting operating frequency can effectively reduce the size of energy-storage components and increase the power density of converters, thus the very high frequency (VHF) resonant converters can find wide applications in practice. In order to further study the characteristics of VHF converters, a modeling method is presented for solving the state variables. First, according to the analysis of a typical VHF converter's operating modes, a unified equivalent circuit is established, which contains nonlinear controlled current sources. Then the mathematical model of the equivalent circuit is derived and solved by using the equivalent small parameter (ESP) method. And the approximate analytical solutions of state variables can be finally obtained, which are composed of a DC component and various harmonics. It is shown that the obtained solutions are accurate enough as the results from the proposed method agree well with the simulations and experimental results. Furthermore, the approximate analytical expressions for harmonics of state variables can be used as a guide for circuit design and stability analysis of the converter.

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