Power Supply Topology Selection--It's Not Just About Power

Focus:

When discussing power supply topologies, most application notes, topology charts, and articles imply that the selection of a given topology is dependent solely on the required output-power level. Unfortunately, this criterion is generally insufficient for topology selection and can lead to inadequate performance, low efficiency and unreliable power supply designs. This 16- page article addresses the additional specification factors and circuit characteristics that must be considered when trying to select the optimum power supply topology for your application. These factors include input voltage and range, output voltage/current levels, load type and characteristics, efficiency (this is where resonant converters come in), isolation criteria, and transformer volume utilization with respect to packaging density. This discussion encompasses the most-common isolated topologies focusing on the flyback and forward converters but also discusses bidirectional converters such as the half bridge and full bridge. The different configurations of these topologies and their various modes of operation are discussed. Topics such as synchronous rectification and snubber circuits/clamps are also discussed. Although there is some discussion of resonant converters, most of the article relates to hard-switching PWM converters.

What you’ll learn:

• How to select the optimum isolated power supply topology for your application

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Author & Publication:

Frank Cathell, ON Semiconductor, Phoenix, Ariz., How2Power Today, May 27 2010

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