Control method for four-switch buck-boost converter

A control method for a four-switch buck-boost converter, comprising:

• when a real-time load current of the four-switch buck-boost converter reaches a critical load at a current input voltage, adjusting a duration of a powering mode and a duration of a reset mode based on a principle of minimizing a soft-switching time of each transistor switch in the four-switch buck-boost converter, calculating a duration of a direct power path mode according to an energy formula, and adjusting a duration of an freewheeling mode to be zero;
• when the real-time load current of the four-switch buck-boost converter does not reach the critical load at the current input voltage, linearly increasing operating frequency with the real-time load current, keeping the duration of the powering mode, the duration of the direct power path mode and the duration of the reset mode at values corresponding to the critical load, and reducing the duration of the freewheeling mode;
• and
• when the real-time load current of the four-switch buck-boost converter exceeds the critical load at the current input voltage, quadratically decreasing the operating frequency with the real-time load, and determining linear growth coefficients of the duration of the powering mode, the duration of the direct power path mode and the duration of the reset mode in each working cycle based on a real-time input voltage.