UC Berkeley

Hybrid switched-capacitor (SC) converters have seen increased use in applications that demand both high efficiency and high power density. These converters exhibit the traditional benefits of pure SC converters, such as efficient utilization of switches and the use of energy-dense capacitors, along with lossless capacitor charge transfer due to the use of one or more augmenting inductors. Increased performance can also be obtained by using more complex control schemes than the traditional two-phase control common with pure switched-capacitor converters.

Split-phase control, one such modified control scheme, is used to ensure full soft-charging of all flying capacitors in several hybrid switched-capacitor topologies belonging to the Dickson-derived class of converters. Here, capacitors are inserted into the switch-capacitor network in a staggered manner to ensure that they do not over- or under-charge in each phase, which would result in lossy hard-charging transitions. However, the time at which to insert these capacitors can change based on operating condition, component tolerance, and phase-ordering. This work will present an analysis of these effects, as well as describe specific control schemes and active-tuning methods that can ensure full soft-charging operation.

In addition, other control schemes such as multi-resonant operation, can be utilized to achieve high-performance designs. Multi-resonant hybrid switched-capacitor converters operate with multiple operating phases per switching period, and can achieve the same conversion ratio as standard two-phase hybrid switched-capacitor converters with a fewer number of switches and capacitors, allowing for higher efficiency and power density design. One such topology, the cascaded series-parallel (CaSP) converter, will be analyzed, and several high-performance hardware prototypes designed for 48 V data center dc-dc power delivery will be presented.