Circuit oriented average modeling of switching power converters

Effective features from various modeling methods are complemented with analog simulation and series expansion practices as well as heuristic guidelines to form a systematic and versatile method to derive accurate and efficient circuit oriented large signal average models (COLSAMs) that approximate the slow dynamics manifold of the moving average values of the relevant state variables for pulse-width modulated (PWM) dc to dc and three-phase to dc power converters. These COLSAMs can cover both continuous (CCM) and discontinuous (DCM) conduction modes of operation and they are over one order of magnitude cheaper, computation wise, than the switching models. Starting with the converter´s operating waveforms and topological stages this method leads primarily to simple and effective input-output oriented models that represent transfer as well as loading characteristics of the converter. Since these models consist of time invariant continuous functions they can be linearized at an operating point in order to obtain small-signal transfer functions that approximate the dynamics of the original PWM system around an orbit. The models are primarily intended for software circuit simulators to take advantage of intrinsic features such as transient response, linearization, transfer function, harmonic distortion calculations, without having to change simulation environment. Nevertheless, any mathematics simulator for ordinary differential equations can be used with the set of equations obtained through application of Kirchoff´s laws to the COLSAMs. Furthermore, the latter provide physical insight to help with power stage and control design. A new average model to cover back and forth transitions between CCM and DCM for the zero-voltage switched full-bridge (ZVS-FB) PWM converter was developed with the above method and its high accuracy is verified with simulations from a switching behavioral model for several circuit component values