Eight Switch Buck Boost Regulator topology for high efficiency in DC voltage regulation

Improvements in the efficiency and size of DC-DC converters have resulted from advances in components, primarily semiconductors, and improved topologies. One topology, which has shown very high potential in limited applications, is the partial power processing boost technique, wherein a small DC-DC converter output is connected in series with the input bus to provide an output voltage equal to or greater than the input voltage. Since the DC-DC converter switches only a fraction of the power throughput, the overall system efficiency is very high. But this technique is limited to applications where the output is always greater than the input. The eight switch buck boost regulator (ESBBR) concept extends partial power processing boost technique to operate when the desired output voltage is higher or lower than the input voltage, and the implementation described can even operate as a conventional buck converter to operate at very low output to input voltage ratios. This paper describes the operation and performance of an ESBBR configured as a bus voltage regulator providing plusmn50% voltage regulation range, bus switching, and overload limiting, operating above 98% efficiency. The technique does not provide input-output isolation.