Zero-voltage-switching multiresonant three-level converters

This paper proposes a family of zero-voltage-switching multiresonant three-level converters (ZVS-MR-TLCs), which are derived by adding a ZVS-MR multiresonant network to the TLCs. The arrangement of a multiresonant network results in the absorption of all the major parasitic components in the resonant circuit, including the switch output capacitor, diode junction capacitor, and transformer leakage inductor. Compared with the two-level multiresonant converters (MRCs), the proposed converters achieve ZVS in a wider load range and reduce the voltage stress on the switches and diodes, and the filter can be reduced significantly. The Buck ZVS-MR-TLC is taken as the example to illustrate the operation principle, characteristics, and advantages over the two-level Buck ZVS-MRC. An interleaved control strategy and a voltage control of the flying capacitor for the new converters are presented in detail. A 1-kW high-voltage-input railway charger prototype converter is built in our lab to verify the theoretical analysis and the effectiveness of the interleaved control strategy and flying capacitor voltage control method.