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 mosfet s 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.