Reconfigurable Bidirectional Stacked Half-Bridge Resonant DC-DC Converter for Extended Voltage Conversion Range

This article proposes a reconfigurable bidirectional stacked half-bridge resonant dc/dc converter that can operate under wide ranges of forward voltage conversion ratio Mf and backward voltage conversion ratio Mb. In the forward direction, the proposed converter operates as a full-wave resonant buck converter (when Mf < 1), as a half-wave resonant boost converter with three-level voltage vcd (when 1 ≤ Mf < 2), and as a halfwave resonant boost converter with two-level vcd (when Mf ≥ 2). In the backward direction, the proposed converter operates as a full-wave resonant boost converter (when Mb ≥ 1), as a half-wave resonant buck converter with three-level vcd (when 0:5 ≤ Mb < 1), and as a half-wave resonant buck converter with two-level vcd (when Mb < 0:5). When it operates with threelevel voltage vcd, alternative asymmetric pulsewidth modulation (PWM) alternately charges and discharges the secondary-side half-bridge capacitors, thus inherently balancing their voltages. We obtain the accurate voltage conversion ratio of the proposed converter operating with three-level voltage vcd, which is continuous at the operating boundaries. We provide detailed design guidelines for the proposed converter, considering three operating modes in each power-flow direction. The proposed bidirectional converter and its modulation scheme are experimentally validated using a 200-1000-V, 1-kW hardware prototype powered from a 125-V input.