The right-half-plane (RHP) zero can be eliminated in the proposed buck-boost (BB) converter to achieve fast transients for Internet-of-Thing (IoT) applications. The pseudo-boost mode in the BB converter eliminates one power switch in the current path and ensures that the continuous inductor current is half of the conventional design value to achieve 97.46% peak efficiency. Besides, the output voltage ripple is reduced to 7mV. By inserting an additional phase, a smooth transition between the buck and pseudo-boost modes ensures a voltage drop less than 15mV. The slope-based transient enhancement (SBTE) circuit accelerates transient response in 9 $\mu$S with a load variation of 400 mA.