Asymmetrical (n/m)X DC-DC converter for finer voltage regulation

Multilevel modular capacitor clamped DC-DC converter (MMCCC) provides the lowest power stress solution for applications desiring high voltage ratio, high efficiency (greater than 99%) and ultra-high power density, such as aerospace and other demanding applications. However, it suffers from the inability of output voltage regulation and limited step-up or -down voltage ratios. A recently proposed (n/m)X DC-DC converter can achieve variable and fractional voltage ratios, however, the voltage ratios are limited to even numbers(2, 4, 6, 8 and so on) and few odd numbers due to its symmetrical structure. This paper proposes an asymmetrical (n/m)X DC-DC converter, which is able to provide all natural number voltage ratios (2, 3, 4, 5, 6, 7, 8, and so on) with the same number of modules. Moreover, it inherits all the advantageous features of the original (n/m)X DC-DC converter. The only cost is to add one extra switch to the original (n/m)X DC-DC converter to make it asymmetrical. A 1-kW prototype has been built to verify the proposed asymmetrical (n/m)X DC-DC converter.