This paper introduces a tri-state modulation technique for a soft-switching bidirectional DC-DC con-verter (BDC). This method maintains the soft-switching condition and introduces a freewheeling interval that reduces the rise and fall times of the inductor current, effectively suppressing inductor current ripples. Additionally, the tri-state modulation provides an extra degree of freedom, enabling optimization for reduced operating losses. The paper details the operation principles of tri-state modulation in both buck and boost modes and discusses optimization strategies for minimizing losses. An experimental setup is developed to validate the tri-state modulation approach, where switching waveforms and efficiency are measured. The experimental results con-firm that the proposed method achieves soft-switching conditions, suppresses inductor current ripples, and provides higher efficiency compared to conventional hard-switching BDC and typical soft-switching BDC.