The buck converter has been known to exhibit chaotic behavior in a wide parameter range. In this paper, the resonant parametric perturbation method is applied to control chaos in a voltage-mode controlled buck converter. In particular, the effects of phase shift and frequency mismatch in the perturbing signal are studied. It is shown that the control power can be significantly reduced if the perturbation is applied with an appropriate phase shift. Moreover, when frequency mismatch is inevitable, intermittent chaos occurs, but effective control can still be accomplished at the expense of raising the control power. Analysis, simulations and experimental measurements are presented to provide theoretical and practical evidences for the proposed control method.

SUMMARYThis paper investigates the fast-scale instability in a power-factor-correction (PFC) boost converter under a conventional average current-mode control. The converter is operated in continuous mode. Computer simulations and theoretical analysis are performed to study the e ects of the time-varying input voltage under the variation of some chosen parameters on the qualitative behaviour of the system. It is found that fast-scale instability may occur during a line cycle, which can cause distortion to the line current and degrade the practical power factor. The results provide useful information for the design of PFC boost converters to avoid distortion due to fast-scale bifurcation.

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This paper studies the "intermittent" chaos and subharmonics observed in switching dc/dc converters using a simple circuit model that describes possible unintended coupling of some weak spurious signal to the converter. The study shows that the signal strength and frequency of the intruding signal are vital parameters that affect the type of intermittent behavior and the period of intermittency. Simulations and experimental results are presented.