Owing to the bidirectional voltage rise and fall and zero-voltage conduction characteristics of the Four Switch Buck-Boost (FSBB) converter, FSBB is extensively utilized in photovoltaic energy storage devices. However, in most of FSBB’s control methods, it employs a table-lookup approach that necessitates the prior storage of data in DSP memory, yet such data cannot precisely minimize the rms of the quadrilateral inductor current to the minimum value. This paper introduces an effective control method for FSBB converters, eliminating the need for any table-lookup, by leveraging the minimum root mean square condition of the quadrilateral inductor current. It obtains four time parameters related to quadrilateral inductor current modulation through the output solution of PI, and applies these time parameters to the converter. This method streamlines and enhances the control process by eliminating the need for any table-lookup, ensuring simplicity and reliability, and is well-suited for scenarios with wide input and output voltage ranges. Ultimately, the effectiveness of this control method was validated through Matlab simulations.