This paper proposes a novel soft-switching control without zero-crossing detection for the cascaded buck-boost converters (CBBCs). The proposed soft-switching control consists of two parts: soft-switching modulation and closed-loop control. In the modulation, the employed PWM approach is constructed by introducing a small negative current into the conventional PWM, and the soft-switching modulation based on the negative-current-based PWM is presented by adding a new switching process controlled by a modulation variable in the CBBC. In the closed-loop control, the relationship between the models of the negative-current-based PWM and the soft-switching modulation is deduced, and by utilizing the deduced relationship, the closed-loop control is designed while the PWM is modified to achieve the softswitching. Meanwhile, to further reduce the ripple current and device losses, the parameter of the proposed control is optimized by refining the restrictive conditions. While the zero-crossing point of the inductor current is calculated with a given algorithm based on a current measurement, the circuit of zero-crossing detection is avoided. The validity and feasibility of the proposed soft-switching control approach are confirmed by the simulations and experiments on a 200-W prototype. INDEX TERMS Soft-switching control, negative-current-based PWM, zero-crossing detection, optimal design, CBBC.