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

Abstract

This article presents a multiple-phase (MP) flying ${C}_{\mathrm { F}}$ -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 “ ${I}_{\mathrm { L}}$ -balance” and “ ${V}_{\mathrm { CF}}$ -balance” control schemes, selecting the “ ${V}_{\mathrm { CF}}$ -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 ${C}_{\mathrm { F}}$ s are discharged by leakage currents, this topology facilitates an inactive- $C_{\mathrm { F}}$ charging scheme. This prevents overstress on inactive switches and mitigates large inrush charging currents upon reactivation of ${C}_{\mathrm { F}}$ s. 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- ${V}_{\mathrm { O}}$ , respectively. The easy scalability extends the VCR range and the load current range with high efficiency. Furthermore, it is suited for fault-tolerant schemes.