Step-by-step for an optimized flyback supply design (Pt 2 of 2)

(Note: This is the completion of a two-part feature; to read Part 1, click here.)

The control closed-loop modelling and compensation stage of an isolated flyback power supply has always been considered the most challenging part of the design, with complicated AC modelling, and obscure compensation rules. Designers tend to avoid the pure academic mathematic approach to the problem and rely more on practical lab test results, like load and line transient response, or the switching waveform of the switching node of the converter.

This article demystifies close loop modelling of a flyback design with a simple mathematic approach, guiding the designer to a well-optimized design.

The best design approach is to have a simple and intuitive model of the control circuit, select the proper compensation network, and verify the results with a more precise close loop measurement with the network analyzer. A description of a crude method that provides a good understanding of the problematic nature of the flyback close loop analysis with PWM peak current mode control, operating in continuous conduction mode.

To read Part 2 of this article, which originally appeared at EETimes-Europe, click here.

About the author

Michele Sclocchi is technical marketing for power management products. Sclocchi is based at Texas Instrument Sales office in Milan, Italy. Sclocchi joined National Semiconductor in 2000. He is a specialist in switching power supply, responsible for the new products definition in the renewable energy area. Michele Sclocchi holds a Master Degree in Electrical Engineering from the Politechnic University of Milan/Italy. He has authored over 95 publications in power electronics.

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