A Novel Ultrawide Output Range DC–DC Converter for EV Fast Charging

In this article, an ultrawide output voltage reconfigurable LLC resonant dc–dc converter is presented for electric vehicle fast charging application. The proposed LLC topology design uses six operating modes for providing a wide output voltage from 100 to 1100 V with a constant current output. The proposed circuit consists of a three-winding high-frequency transformer connected with a mosfet full bridge at the primary side and two voltage doubler diode rectifiers at the secondary side. In addition, two mosfets and two diodes switch combinations at the output side reconfigure the two diode rectifiers outputs in three ways. Hence, with full-bridge and half-bridge operations from the primary side, the proposed circuit provides a total of six operating modes. The detailed step-by-step procedure is presented for designing a continuous output voltage range using six operating modes. The proposed converter has a low operation frequency range and high magnetization to series resonating inductance ratio of the LLC tank. The closed-loop operation of the converter is validated on PLECS for a 30-A CC output. The open-loop experimental results of a 700-W laboratory prototype are also presented to validate the six operating modes for ultrawide output voltage gain.