<p>LLC converters for electric vehicle charging are required to support a wide output voltage range. Conventional approaches achieve a wide output voltage range by reconfiguring the output capacitors of two LLC converters in series or parallel. However, these methods inevitably require a large number of components, including two resonant tanks, semiconductor devices for two LLC converters, and three relays for series/parallel reconfiguration. To minimize the component counts, this paper presents an LLC resonant converter that achieves a wide output voltage using only a single LLC converter with one bidirectional switch. The proposed converter employs a single resonant tank and a three-winding transformer consisting of one primary winding and two secondary windings. The two secondary windings are reconfigured in series or parallel by a bidirectional switch, achieving a wide output voltage range. The impact of leakage inductance difference in a tree-winding transformer on load current unbalance was quantitatively analyzed, and a transformer winding arrangement is proposed to minimize the current unbalance in parallel mode. The proposed converter is validated with a prototype with 800 V input and 150–1000 V, 11 A, and 3.3 kW rated output.</p>