Multiple single-active bridge (SAB) DC-DC converters are connected in the input-parallel and outputparallel (IPOP) configuration to achieve higher power output in many applications. Module shutdown, known as phase shedding, is used to improve light-load efficiency in the IPOP modular converter. The SAB is known for its simplicity and robustness, but it is only moderately efficient; therefore, larger snubber capacitance is used to lower switching and conduction losses in the SAB and improve efficiency. However, larger snubber capacitance increases minimum power and reduces load range in the SAB, resulting in the unattainability of certain load-range segments in the IPOP converter because capacitance increases when phase shedding is used. Hence, snubber capacitances across the modules are optimized to improve average efficiency while maintaining the existing load range. As a result, snubber capacitances differ across SAB modules. With nonidentical modules, nonuniform module power distribution is used in the IPOP converter for higher light-load efficiency with selective phase shedding. This increases the average IPOP converter efficiency from 92.5% to 94.1% across the load range of 260 W to 13.6 kW. Peak efficiency is also increased from 93% to 95.5%. In this article, we present a method to optimize the modular SAB IPOP system for high efficiency over a wide load range.

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In an input-series and output-parallel (ISOP) connected modular DC-DC converter, module shutdown and reactivation are required to increase system efficiency, input voltage range and reliability. Methods are introduced to implement these capabilities in the ISOP DC-DC converter system using additional external IGBTs and existing internal IGBTs. Comparisons of the shutdown speeds and thermal stresses are made for these methods over a range of input capacitance and experimental results are obtained to verify these predicted results. Finally, conclusions are drawn on the advantages and disadvantages of each method.@en