Phase-Scalable CF-Cross-Connected-Based Hybrid DC–DC Converter With Auto VCF Balancing and Inactive CF Charging

This article presents a multiple-phase (MP) flying CF-cross-connected (CCC)-based hybrid dc–dc converter for 12-V input to point-of-load (PoL) conversion. First, we illustrate the evolution of the proposed MP CCC converter from the conventional two-phase (2P) CCC converter. The proposed topology enables easy scalability in the number of active phases with the finest granularity. Second, we compare potential “IL-balance” and “VCF-balance” control schemes, selecting the “VCF-balance” one for its higher efficiency and wider voltage conversion ratio (VCR) range. Third, in light-load conditions where certain phases are disabled and their CFs are discharged by leakage currents, this topology facilitates an inactive-C_F charging scheme. This prevents overstress on inactive switches and mitigates large inrush charging currents upon reactivation of CFs. Fabricated in a 180-nm bipolar-CMOS-DMOS (BCD) process, the prototype four-phase converter achieves measured peak efficiency of 90.3% and 91.6% at 1.2-and 1.8 V-VO, respectively. The easy scalability extends the VCR range and the load current range with high efficiency. Furthermore, it is suited for fault-tolerant schemes.