This thesis presents a novel Resonant Switched-Capacitor Converter with Multiple Resonant Frequencies, abbreviated as MRSCC for both high density and efficiency non-isolated large step-down Intermediate Bus Converter (IBC). Conventional Resonant Switched-Capacitor Converter (RSCC) proposed by Shoyama and its high voltage conversion ratio derivation such as Switched-Tank Converter (STC) by Jiang and li employ half sinusoidal-current charge transfer method between capacitors to achieve high efficiency and density operation by adding a small resonant inductor in series to pure switched-capacitor converter's (SCC) flying capacitor. By operating switching frequency to be the same as its resonant frequency, RSCC achieves zero-current turn off operation, however, this cause RSCC and its derivation suffer from component variation issue for high-volume adoption. Derived from RSCC, MRSCC adds additional high frequency resonant component, operates only during its dead-time, by adding small capacitor in parallel to RSCC's resonant inductor. By operating switching frequency higher than its main resonant frequency, MRSCC utilizes double chopped half-sinusoidal current charge transfer method between capacitors to further improve efficiency. In addition, operating switching frequency consistently higher than its resonant frequency, MRSCC provides high immunity towards component variation, making it and its derivation viable for high-volume adoption.