Voltage regulator optimization using multiwinding coupled inductors and extended duty ratio mechanisms

Bradley S. Oraw, Raja Ayyanar

Research output: Contribution to journalArticlepeer-review

34 Scopus citations


This paper examines design optimization of voltage regulators (VRs) for microprocessor applications. Optimality of competing VR topologies, such as conventional (Conv) buck, coupled inductor, and extended duty ratio converters, is examined using efficiency norms and a new cost-per-watt metric to compare the amount of output capacitance (which is strongly correlated to the VR cost) to the efficiency. Coupled inductors provide a higher steady-state inductance than transient inductance. Lower transient inductance allows for smaller output capacitance. However, lower output capacitance requires a higher switching frequency and thus yields greater switching losses and lower efficiency. Extended duty ratio mechanisms reduce the switching voltage, and hence, reduce switching losses and increase efficiency. Experimental data are provided that the coupled inductor extended duty ratio converter has the same average efficiency, has higher light-load efficiency, and uses one-third of the output capacitance as the Conv multiphase buck converter. Hence, the combination of multiwinding coupled inductors and extended duty ratio mechanisms is shown to be the optimal VR configuration. The optimality concepts contributed in this paper resolve the ambiguity between VR cost and efficiency, and are essential for selecting the best solution among several competing VR designs.

Original languageEnglish (US)
Pages (from-to)1494-1505
Number of pages12
JournalIEEE Transactions on Power Electronics
Issue number6
StatePublished - 2009


  • Coupled inductors
  • Extended duty ratio mechanism
  • Optimization methods
  • Voltage regulators
  • dc-dc converters

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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