Auto-appraisal of voltage rating for switched-capacitor DC-DC converters

Resonant Switched Capacitor (SC) DC-DC converters are showing potential for use in medium to high-power applications. The high-cell count in these applications means that for a given voltage conversion ratio there are theoretically a large number of alternative topologies that can be synthesised. However, each of these topologies may exhibit different competing characteristics, for example total VA rating of capacitors, total VA rating of switches, number of switches and individual switch voltage rating. Obtaining an optimum topology in terms of given design constraints is therefore important requirement. This paper builds on previous work by the authors by presenting a method for the automatic calculation of the voltage ratings of the components in a SC converter. This result along with earlier work, allows for the calculation of VA ratings, which are an important metric when comparing competing circuits. In addition, a new Canonical Cell topology is presented that extends the range of SC circuits that can be analysed using this method, to cover so-called Ladder circuits. The method is validated against detailed Spice simulations and measurements from a hardware prototype.