How do I analyse a SEPIC circuit?

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Discussion Overview

The discussion focuses on the analysis of a SEPIC (Single-Ended Primary-Inductor Converter) circuit, exploring the appropriate equations and methodologies for circuit analysis involving capacitors, resistors, diodes, and inductors. Participants seek guidance on how to approach the design and analysis of such a circuit.

Discussion Character

  • Technical explanation
  • Exploratory

Main Points Raised

  • One participant inquires about the set of equations suitable for analyzing a SEPIC circuit, noting the presence of various components like capacitors, resistors, diodes, and inductors.
  • Another participant suggests that inductors can be analyzed similarly to capacitors, emphasizing the difference in impedance and the need to consider the switched nature of the circuit, which requires separate equations for the two operational phases.
  • A third participant recommends an application note from Texas Instruments as a useful resource for understanding the analysis of SEPIC circuits.

Areas of Agreement / Disagreement

Participants express differing views on the analysis approach, with no consensus on a single method or set of equations. The discussion remains open to various interpretations and methodologies.

Contextual Notes

The discussion does not resolve the specific assumptions or limitations related to the analysis of switched circuits, nor does it clarify the dependencies on component values or configurations.

Psinter
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Very simple question. The following circuit (I want to build one with my specs): https://en.wikipedia.org/wiki/Single-ended_primary-inductor_converter

How do I analyse it?

What I mean is that if a circuit has only capacitors, I use this. If it has only resistors, I use Ohm s Law, or Kirchhoff Laws. If it has capacitors and resistors I use the RC model.

Now, this one has capacitors, resistors, diodes, and inductors... what set of equations can I use to analyse it and design one to my needs?
 
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And inductor isn't that much different from a capacitor in circuit analysis equations, it just has a different impedance, sL instead of 1/sC like a capacitor.

This is a switched circuit so it doesn't have a useful DC solution. You'll have to write out the equations for the two phases (when S1 is closed and when it is open). Use the solution of S1 closed as the initial condition of the case when S1 is open.

It looks like Maxim has an app note that explains it:
http://www.maximintegrated.com/app-notes/index.mvp/id/1051
 
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Thanks guys.
 

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