A fast transient response flying-capacitor buck-boost converter is proposed to improve the efficiency of conventional switched-capacitor converters. The voltage boost ratio of the proposed converter is 2D, where D is the duty cycle of the switching signal waveform. Furthermore, the proposed structure utilizes pseudocurrent dynamic acceleration techniques to achieve fast transient response when load changes between heavy load and light load. The switching frequency of the proposed converter is 1 MHz for 3.3-V input and 1.0-4.5-V output range application. Experiment results show that the proposed scheme improves the transient response to within 2 μs and the total power conversion efficiency can be as high as 89.66%. The proposed converter has been realized by a 2P4M CMOS chip by 0.35-μm fabrication process with total chip size of about 1.5 mm × 1.5 mm, PADs included.