Bifurcation Phenomena and Stabilization With Compensation Ramp in Converter With Power Semiconductor Filter

A concept, named as power semiconductor filter, has been demonstrated to be an alternative to perform input harmonic filtering in switched-mode power converters. It utilizes a series pass device (SPD) to profile the wave shape of the supply current, while the voltage across the SPD is regulated at a threshold voltage between the linear and saturation regions of the SPD to minimize its power dissipation. Bulky passive components for input harmonic filtering can then be eliminated or shrunk with such active supply current control. For the sake of circuit elegancy, regulation of the SPD voltage is realized by a bang-bang (peak-voltage) controller to vary the input characteristics of the power conversion stage through adjusting some control parameters, such as duty cycle and switching frequency. Experiments reveal that the entire system might exhibit bifurcation phenomena under some supply and load conditions. This paper will derive a sampled-data model to characterize such system behaviors and to identify the onset of bifurcation and chaos. A compensation ramp will be proposed to introduce into the bang-bang controller to stabilize the system operation. Moreover, the slow-scale dynamics will be studied with small-signal models. The investigations will be exemplified on a 48 W, 40-140 V/24 V buck dc-dc converter prototype.