Approximate Discrete-Time Modeling of DC-DC Converters With Consideration of the Effects of Pulse Width Modulation

Xin Li, Xinbo Ruan, Qian Jin, Mengke Sha, Chi Kong Tse

Research output: Journal article publicationJournal articleAcademic researchpeer-review

31 Citations (Scopus)


For dc-dc converters with pulsating output current, such as boost and buck-boost converters, the use of leading-edge or trailing-edge pulse width modulation (PWM) can result in distinctly different behavior. This phenomenon is not readily captured by the usual averaged model but can be predicted with a discrete-time model. However, the discrete-time model, which tracks the dynamics of state variables over a switching period, is usually more complex and less convenient to apply for the design of the feedback control. Based on the low-pass characteristics of dc-dc converters, an approximate discrete-time model is proposed in this paper, and upon transforming to the s-domain, the model results in transfer functions that can be conveniently used for deriving practical closed-loop parameters. With the proposed model, the loop gain, the input and output impedances are derived and analyzed. The effects of applying different types of PWM on the stability of a single dc-dc converter and a system of cascaded dc-dc converters are discussed. Finally, prototypes of a buck converter, a boost converter, and a cascaded system of buck and boost converters are constructed to verify the effectiveness of the approximate discrete-time model.
Original languageEnglish
Pages (from-to)7071-7082
Number of pages12
JournalIEEE Transactions on Power Electronics
Issue number8
Publication statusPublished - 1 Aug 2018


  • Averaged model
  • discrete-time model
  • leading edge
  • pulse width modulation (PWM)
  • stability
  • trailing edge

ASJC Scopus subject areas

  • Electrical and Electronic Engineering


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