Enhanced Control of Bidirectional Phase-Shift Full-Bridge Converters for Overshoot Elimination and Current Reduction

High efficiency and high power density bidirectional battery chargers with wide operating ranges and low current ripple have gained increasing attention in recent years. Among various topologies, the phase-shift full-bridge (PSFB) converter is widely adopted due to its wide voltage compatibility and inherently low current ripple. However, PSFB converters suffer from severe voltage overshoot during boost-type operation, resulting in excessive device stress, and generate large freewheeling currents that increase conduction losses. This article proposes an enhanced control scheme that eliminates voltage overshoot without resorting to snubber circuits, while reducing freewheeling current. A novel operating interval that naturally results in reduced overshoot voltage is modeled and analyzed. Based on this analysis, a corresponding control scheme is developed, and the overshoot voltage estimation as well as the freewheeling current behavior are examined in detail. In addition, a design guideline is provided to facilitate practical implementation, including design considerations under both high-power and low-power operating conditions, along with the associated trade-offs. Experimental results demonstrate that the proposed scheme reduces device voltage stress by 87% and decreases transformer rms current by 17%, effectively minimizing conduction losses in both the transformer and switching devices.