Output impedance modeling of a multilevel modular switched-capacitor converter to achieve continuously variable conversion ratio

The multilevel modular capacitor clamped dc-to-dc converter (MMCCC) topology is completely modular and belongs to two-phase switched capacitor converter group. The conversion ratio of an ideal MMCCC converter in step-up mode is an integer and depends on the number of modules used. For a k-module MMCCC, the maximum up-conversion ratio is (k+1), and it has already been shown in literature that different integer conversion ratios can be achieved by changing the active number of modules of an MMCCC. In this paper, different methods are proposed for MMCCC in order to achieve fractional conversion ratios (CR) in step-up mode without changing the complementary two-phase switching orientation. Fractional CRs can be obtained in several switched-capacitor circuits at the cost of significantly lower efficiency. However, MMCCC with the aid of a new pulse dropping technique can produce fractional CR while maintaining high efficiency. The variation in efficiency and equivalent resistance as a function of frequency has been analyzed in this paper. Simulation and experimental results using a reconfigurable 5-module MMCCC prototype have been used to validate the new control scheme.