The dilemma between wide input range and narrow frequency band is a classic problem for the frequency modulated LLC converters. Using reconfiguring bridge can mitigate this issue effectively. However, there is a lack of systematic consideration in converter design and optimization. To address this challenge, this digest introduces a six-mode LLC converter based on a reconfigurable H5 bridge, and systematically presents its optimal design methodology in ultra-wide input range applications. A 48V, 500W laboratory prototype is designed to validate the concept. The designed prototype is adapted to an 80V~400V input range with 65 kHz~135 kHz frequency range.