Numerical Methods for the Periodic AC Analysis of DC Power Converters

The AC analysis of periodically switching DC power converters can take many forms, often with tradeoffs. This paper reviews numerical methods for the periodic AC (PAC) analysis of DC power converters. Two analytical frequency-domain methods that rely on a single transient analysis of the unperturbed circuit in steady state are first compared: an exact method applicable to piecewise linear circuits and a harmonic balance method known as Harmonic State Space (HSS). A contribution of this paper is to show the inapplicability of the HSS method to stiff circuits. Two time-domain methods based on transient simulations of the perturbed circuit are presented next, with different speed and accuracy tradeoffs: the single and multi-tone PAC. Guidance for their successful implementation is provided. Because they do not require the circuit to be piecewise linear, these time-domain methods can be implemented with a broad class of circuit simulators, including SPICE.