Design of Multi-Mode 4-Switch Buck-Boost Controller

In order to raise the utilization ratio of Lithium-Ion batteries, a multi-mode buck-boost controller IC was proposed. It could be applied to a 4-switch cascade buck-boost converter capable of outputting non-inverting step down/step up voltages. By evaluating the relative relation between input and output voltages, the converter can transfer its work state between buck and boost mode automatically. A three phase transition mode was introduced to realize the seamless transition. The system was designed and simulated in 1.5-mu m BCD technology. And the experimental results were consistent with expectations well.