Sustained slow-scale oscillation in higher order current-mode controlled converter

Siu Chung Wong, Xiaoqun Wu, Chi Kong Tse

Research output: Journal article publicationJournal articleAcademic researchpeer-review

43 Citations (Scopus)


DC-DC converters under current-mode control have been known to exhibit slow-scale oscillation as a result of a Hopf-type bifurcation as one or more of the parameters of the outer voltage loop are varied. In the absence of the outer voltage loop (i.e., open loop), slow-scale oscillation was generally not observed in simple low-order dc-dc converters, i.e., buck, buck-boost, and boost converters. In this paper, slow-scale bifurcation in a higher order current-mode controlled converter is studied. It has been found experimentally that, even in the absence of a closed outer voltage loop, a current-mode controlled Ćuk converter can exhibit a slow-scale Hopf-type bifurcation. The phenomenon was observed in a commercial low-ripple dc-dc converter which has been designed using the Ćuk converter and the LM2611 controller. Such slow-scale oscillation of the inner current loop can also be observed in full-circuit SPICE simulations. An averaged model has been developed and implemented in SPICE to find the Hopf bifurcation boundaries. With this averaged model, the Hopf bifurcation can be explained conveniently using the traditional loop gain analysis. Specifically, the extra degrees of freedom in higher order dc-dc converters have opened up a new possible mode of instability which has not been found in simple low-order dc-dc converters.
Original languageEnglish
Pages (from-to)489-493
Number of pages5
JournalIEEE Transactions on Circuits and Systems II: Express Briefs
Issue number5
Publication statusPublished - 1 May 2008


  • Bifurcation
  • Ćuk converter
  • Current-mode control
  • Dc-dc converters

ASJC Scopus subject areas

  • Signal Processing
  • Electrical and Electronic Engineering


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