Common-duty-ratio control of input-series connected modular DC-DC converters with active input voltage and load-current sharing

Ramesh Giri, Vijay Choudhary, Raja Ayyanar, Ned Mohan

Research output: Contribution to journalArticlepeer-review

293 Scopus citations


This paper proposes a simple control method to achieve active sharing of input voltage and load current among modular converters that are connected in series at the input and in parallel at the output. The input-series connection enables a fully modular power-system architecture, where low voltage and low power modules can be connected in any combination at the input and/or at the output, to realize any given specifications. Further, the input-series connection enables the use of low-voltage MOSFETs that are optimized for very low RDSON, thus, resulting in lower conduction losses. In the proposed scheme, the duty ratio to all the converter modules connected in input-series and output-parallel (ISOP) configuration is made common. This scheme does not require a dedicated input-voltage or load-current-share controller. It relies on the inherent self-correcting characteristic of the ISOP connection when the duty ratio of all the converters is the same. The proposed scheme is analyzed using the average model of a forward converter. The stability and performance of the scheme are verified through numerical simulation, both in frequency domain and in time domain. The proposed control method is also validated on an experimental prototype ISOP system comprising of two forward converters.

Original languageEnglish (US)
Pages (from-to)1101-1111
Number of pages11
JournalIEEE Transactions on Industry Applications
Issue number4
StatePublished - Jul 2006


  • Common duty ratio
  • Fault tolerance
  • Input series and output parallel (ISOP)
  • Input-series connection
  • Input-voltage sharing
  • Load-current sharing
  • Modular dc-dc converters

ASJC Scopus subject areas

  • Control and Systems Engineering
  • Industrial and Manufacturing Engineering
  • Electrical and Electronic Engineering


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