Description

High-power converters have been used for many industry applications. For three-phase AC/DC power conversion systems, three-phase 380 V (or 480 V) AC/DC converter with power factor correction is generally used in the front stage to provide a stable DC bus voltage and a DC/DC converter is adopted in the second stage to provide low output voltage and high-load current. In the front stage, the DC bus voltage may be equal or higher than 800 V. Power switches with high-voltage stress will result in high cost and poor efficiency. Thus, it is difficult to select suitable power switches in the DC/DC converter. However, two input split capacitor voltages may be unbalanced. A flying capacitor is added in the conventional three-level DC/DC converter to automatically balance two input capacitor voltages. Soft switching three-level DC/DC converters have been presented to reduce the voltage stress of power switches at half of the input voltage and to turn on the active switches under zero voltage switching (ZVS). These control schemes are based on duty cycle control to regulate output voltage. However, the ZVS condition of the power switches is related to the load condition and input voltage. In this project the system proposed an advanced hybrid LLC series resonant converter with integrated flying-capacitor cell to enable the high step-down conversion in the high input voltage applications. The inherent flying-capacitor branch in the primary side can effectively halve the primary switch voltage stress compared with the half-bridge LLC converters.