With both data center power delivery and automotive powertrains tending towards a 48V distribution rail, high performance hybrid switched-capacitor (hybrid SC) converters have become an attractive power delivery solution in both spaces. However, automotive power systems present unique challenges in reliability and noise qualifications. This work investigates a regulating Dickson-based hybrid SC topology with low inherent electromagnetic interference (EMI) as well as mitigation techniques, such as an input filter and spread spectrum frequency modulation (SSFM). The proposed filter and modulation schemes enable this converter to meet automotive EMI standards. A hardware prototype combining a power stage and passive input filter is built to demonstrate the merit of hybrid SC topologies for use in 48V automotive systems.

Hybrid switched-capacitor (SC) converters have gained popularity due to their efficient switch utilization and use of energy-dense capacitors, which allows them to achieve high efficiency and power density even at large conversion ratios. The Dickson converter is one such popular hybrid SC converter, as it can achieve the theoretical minimum switch stress rating for a given operating condition. However, unlike other hybrid SC topologies that can automatically achieve full soft-charging through the addition of one or more augmenting inductors, certain Dickson variants also require the use of special switching schemes to fully soft-charge all flying capacitors. This technique, denoted as split-phase switching, inserts extra sub-phases into the control scheme so that flying capacitors are disconnected or connected at staggered times. Traditionally, split-phase timing has been calculated analytically, sometimes using imprecise models. This paper instead proposes an active control technique for detecting hard-charging events on the flying capacitors, such that the split-phase timing automatically converges on soft-charging operation. The technique is validated on an 8-to-1 resonant single-inductor Dickson hardware prototype. While this method is demonstrated on a resonant fixed-ratio converter in this work, the technique can also be applied to regulating split-phase applications, as well as used to detect hard-charging events in general.

With the rapid growth and development of high-density power converter topologies, including hybrid switched-capacitor converters, data-centers have seen a shift towards 48 V bus architectures for reduced transmission losses. In parallel, the automotive industry has similarly benefited from these advancements, with the proliferation of 48 V batteries allowing for reduced cable weight. However, the latter application space comes with additional challenges such as automotive-qualified component selection and the need to meet rigorous electro-magnetic interference (EMI) standards. This work proposes a new interleaved-input, single-inductor Dickson converter with a high conversion ratio (8:1) for 48 V automotive applications. The impacts of operating frequency on efficiency and EMI performance are explored, as well as EMI mitigation techniques such as spread-spectrum frequency modulation (SSFM). A hard-ware prototype was built to demonstrate these concepts, and was characterized with respect to the CISPR 25, Class 5 EMI standards required for many automotive applications.