Steady-State Analysis of Resonant Cross-Commutated Buck Converter Under Continuous Voltage Mode

Resonant current generated in one phase of two interleaved buck converters is injected into the switched node of the other phase to turn on the active switch at zero voltage over wide load range, and to turn off the synchronous switch at near-zero current at rated load. This idea was introduced in a recent letter and applied to an interleaved two-phase buck converter with output voltage regulated by extended duty ratio. This paper focuses on modeling its steady state when capacitor voltages are continuous. Closed-form formulas of inductor current and capacitor voltage were derived during each switched stage. The complex fourth-order circuit mode was solved by decomposing it to two second-order modes. The current to discharge the parasitic capacitor of mosfet was calculated by using state-plane trajectory. The method of state-space representation was employed to calculate inductor RMS current, mosfet turn-off current, and voltage stresses. The expectations were validated by three resonant cross-commutated (rcc) converters switched at 2 MHz with 12-V input, 3.3 V at 20-A output, and peak efficiencies of 93.6%, 93.6%, and 93.3%. The discrepancy between measured and modeled instantaneous state variables was less than 2%.