A High-Switching-Frequency Multi-Mode Four-Switch Buck-Boost Converter Empowered by a 400-MHz Bandwidth Two-Stage Operational Amplifier

This paper introduces the utilization of a high-bandwidth rail-to-rail operational amplifier in switching converters, which opens the door to advancing switching converters towards higher switching frequencies. As the switching frequency increases, the signal within switching converters also rises, frequently surpassing the switching frequency itself. Consequently, a high-bandwidth amplifier becomes imperative. The proposed operational amplifier is fabricated using the 0.18-μm BCD process and integrated into the voltage-seconds balance circuit of a multi-mode four-switch buck-boost (FSBB) converter for validation purposes. Post-layout simulation results demonstrate that the amplifier achieves a bandwidth of 400 MHz with a quiescent current of 140 μA. Furthermore, the amplifier is applied in a high-frequency four-switch buck-boost converter to meet the demands of high switching frequencies. The input voltage for the four-switch buck-boost ranges from 150 V to 420 V, while the output voltage is maintained at 28 V. The excitation inductance value is only 5 μH. Simulation results demonstrate that the switching frequency can be enhanced to 2 MHz with the use of the high-bandwidth operational amplifier.