Canonical switched capacitor converters. Comments, complements, and refinements

Switched Capacitor Converters (SCC) form useful blocks in low/medium power applications as they are suitable for integration, both as off-chip and on-chip IC realizations. However, the problem with SCC is that their voltage conversion ratio is topology-dependent. By changing the SC circuit configuration, we can gain control over voltage conversion but the available ratio remains of a discrete nature, i.e. it maps into a countable set of target voltages. Recent papers, on two-phase and multi-phase converters have attempted to solve the so-called canonical circuit realization problem. A converter circuit is canonical in the sense that (1) it can realize all theoretically attainable ratios, (2) the said realizations are not necessarily unique, (3) it contains the minimum number of circuit elements needed for such a circuit, and (4) it takes the form of expandable modular blocks. We briefly review reported SCC topologies with large numbers of ratios and critically filter out and assess the candidates for canonicity. We focus on two illustrative examples based on our previous research. Finally, we comment on open questions and theoretical peculiarities found.