Active Cross-Commutated (ACC) Buck Converter

To address the hard-switching issue of conventional buck converter and high-voltage/current stress issue of soft-switched converter like resonant cross-commutated buck converter, a new soft-switched dc–dc topology with two-phase operation is proposed in this article. The ac current generated from the floating half bridge of one phase is injected into the switching node of another phase to realize zero-voltage switching for all MOSFETs and zero-current switching for the low-side MOSFETs. This method is named as active cross-commutation (Acc). The benefits of AccBuck converter include soft switching, low-voltage stress of low-side switches, low current stress for all switches, and fixed switching frequency. The operation principles with and without parasitic output capacitance (
C
_oss
) are analyzed by using the state-plane method. Clamped diodes are added to reduce the
C
_oss
-related ringing. The analytical formula of voltage gain is derived, which is related to the duty ratio,
C
_oss
, inductance, load current, and switching frequency. A prototype was fabricated to demonstrate the proposed converter. During the fixed-duty-ratio operation, the converter achieves 97.8% peak efficiency and 1410 W/in
³
power density at 50 A output current, 54 V input, and 9 V output. The calculated load line and regulation capability are also verified experimentally.