Due to undesirable interference via unintended coupling paths, switching converters may exhibit complex intermittency, which appears as a form of bifurcation un-dergoing regular operation, subharmonics, and chaos orderly and repeatedly for a long period of time. Such intermittent operation, being an unwanted operating state, should normally be avoided in power converters. This paper expounds the mechanism and conditions for the emergence of intermittency in a common current-mode controlled Boost converter. It is found that interference at frequencies near the switching frequency or its rational multiples may induce intermittent operation. The strengths and frequencies of the interfering signals determine the type and period of intermittency. The problem is analyzed by transforming the time-bifurcation analysis to a conventional parameter-bifurcation analysis. Based on this transformation, intermittency can be investigated from the bifurcation control viewpoint. Furthermore, the critical circuit parameter conditions for the emergence of inter-mittency can be predicted and compared with those from circuit simulation.
Due to wide input fluctuation with line frequency of 50 Hz, power-factor-correction (PFC) Boost converters tend to exhibit fast-scale instability over time domain. The traditional remedy is to impose slope compensation so as to weaken or eliminate this instability. A theoretical principle on the implementation of slope compensation signal is still lacking. Empirical design will induce over compensation frequently, resulting in a large decrease of power factor. In order to tackle this issue, by constructing the discrete-time iterative map of the PFC Boost converter from the viewpoint of bifurcation control theory of nonlinear systems, consequently, the criterion of critical stability for the PFC circuit can be established. Based on this stability criterion, appropriate design of slope compensation can be achieved. Our work indicates that 3 main circuit parameters (i.e. switching cycle, output reference voltage and inductor) determine the effective amplitude design of the slope compensation signal. The results, validated by a large quantity of analytical and numerical studies, show that appropriate slope compensation can be effective in weakening (or controlling) fast-scale bifurcation while maintaining a rather high input power factor.
ZHOU YuFei HUANG JiaCheng WANG ShiBing JIANG Wei CHEN JunNing
