Adaptive phase-shift controlled transformerless resonant DC–DC converter with capacitive coupling and soft-switching for high-efficiency electric vehicle charging

This article presents the design, modeling, and performance analysis of a high-frequency transformerless resonant DC–DC converter specifically optimized for electric vehicle (EV) charging applications. The proposed converter employs a dual H-bridge architecture with capacitive coupling for galvanic isolation, thereby eliminating bulky magnetic components and significantly improving power density, weight, and cost efficiency. An adaptive phase-shift soft-switching control strategy is introduced to ensure zero-voltage switching (ZVS) and zero-current switching (ZCS) across a wide load range, minimizing switching stress, conduction losses, and electromagnetic interference (EMI). The self-balancing capacitive network maintains a near-zero average voltage across isolation capacitors, reducing voltage stress on semiconductor devices and enhancing long-term reliability. A comprehensive analytical model is developed to describe converter behavior under both continuous and discontinuous conduction modes (CCM and DCM). Theoretical expressions for inductor current, capacitor ripple, and power transfer are derived to optimize resonant operation and control stability. The proposed topology is simulated in MATLAB/Simulink using realistic MOSFET parameters, considering parasitic effects and gate charge characteristics. Simulation results validate that the converter achieves high-efficiency operation (88.579% %) within a 100–500 kHz switching frequency range, delivering up to 6 kW at 500 V output with minimal ripple and rapid transient response. Compared with conventional transformer-based or non-resonant topologies, the proposed system demonstrates 12% reduction in switching losses, 16 dB EMI suppression, and superior soft-switching coverage across 85% of its operational frequency range. These results confirm that the adaptive transformerless resonant converter provides an effective, compact, and reliable solution for next-generation EV charging and renewable energy integration systems.