Series-Parallel Multiresonant Switched-Capacitor Converters and the Optimal Operation Region

In this article, series-parallel (SP) multiresonant switched-capacitor converters (MRSCCs) are proposed by incorporating resonant tanks into the traditional SP switched-capacitor converter (SCC) and adopting the on-time fixed frequency modulation. Compared to the traditional SP SCC with hard-switched operation, high transient current spike and inability for lossless voltage regulation, the proposed SP-MRSCC in the optimal operation region owns the merits of soft-switching operation, complete soft-charging feature, low transient current spike, as well as continuous, wide and efficient voltage-gain variation range even at light-load condition. A comprehensive analysis of operation principle, boundary conditions and component stress in four operation modes is provided to assist converter operation and design in the optimal operation region. On one hand, the upper limit of a defined loaded quality factor Q _crit is derived to avoid the appearance of a knee in the gain curve. On the other hand, the current overlapped region—that is, modes 1 and 2—is found to have better operation performance with wider voltage-gain-variation range and lower component stress. On the basis, the synchronous SP-MRSCC is proposed to reduce the conduction loss significantly in high-order circuit and step-down applications. A quantitative comparison between the proposed SP-MRSCC and other counterparts is given to outstand the aforementioned advantages. A 100W 4X SP-MRSCC prototype was designed and tested to verify the above analyses, which has the potential to be utilized for connecting 12V and 48V dc buses between traditional and future data centers.