Voltage Gain-Based Control for Four-Switch Buck-Boost Converter Exhibiting Fast Dynamic Response Over Wide Output Voltage and Load Range

The four-switch buck-boost (FSBB) converter combines zero-voltage switching (ZVS) capability with both step-up and step-down voltage conversion, making it ideal for applications that require a wide voltage range and high efficiency. However, conventional ZVS control methods rely on three mutually coupled modulation variables, which increases implementation complexity and complicates controller design. The interdependence of these variables demands careful coordination of their dynamic responses during transients to maintain optimal ZVS performance, as any mismatch can degrade transient response and stability margins. To address these challenges, this paper proposes a voltage gain-based control strategy that synchronizes the dynamic changes of the modulation variables, significantly reducing settling time and improving output voltage regulation across a wide range of output voltages and load conditions. Furthermore, the proposed method ensures ZVS operation without the need for analog circuitry, thereby enhancing both reliability and implementation simplicity. The effectiveness of the proposed strategy is validated using a 140 W, 100 kHz GaN-based prototype, with experimental results demonstrating that the converter settles within several switching cycles under varying load and voltage conditions and achieves a peak efficiency of 98.5% across the entire operating range.