An algorithm for automatically calculating component current ratings in switched capacitor DC-DC converters

OAPA Switched Capacitor (SC) DC-DC converters, which have traditionally been used for on-chip power supplies, are now being considered for medium to high-power applications. This paper presents a method for automatically synthesising SC converters as well as deriving the expressions for their chargemultipliers. Charge multipliers can be used to calculate important design characteristics such as converter output voltage regulation, efficiency and component current ratings, which can then be used to appraise different topologies. However, whilst a full appraisal of converters also requires component voltage ratings, this work is the first step in developing an automatic software tool that will employ a search-based algorithm to generate optimum SC topologies for a given application. The method is based on the proposition that all SC converters can be synthesised from a so-called "basic cell". The automatic derivation and solution of the charge transfer equations for a traditional Fibonacci SC converter is presented as an example of the proposed method, which is validated against existing analytic equations as well as a detailed Spice simulation. The automatic calculation of the charge-multipliers for two other well-known SC converters is also demonstrated, including a new, arbitrarily generated circuit, which again are validated against detailed Spice simulations.