In this paper, a Total Loss Minimization (TLM) modulation strategy is proposed to enhance the conversion performance of the series-resonant dual-active-bridge DC-DC converters. Unlike conventional modulations, this optimal approach targets the reduction of reactive power and circulating current, which are recognized as major contributors to conduction loss. Additionally, it addresses the switching loss, which typically results from hard-switching operations. The proposed total loss minimization modulation are select triple phase-shift control and switching frequency as the focal point of investigation to minimize the reactive power and circulating current, and maintain soft-switching operation. The effectiveness of the TLM modulation is analyzed under both buck and boost modes, showcasing its versatility. A comprehensive validation has been successfully conducted through experimental testing on a 300W laboratory prototype converter. The enhancement in conversion efficiency, a key innovative outcome of this research, is further confirmed by a comparative analysis with existing literature, underscoring the advancement in technology that this study presents.