Synchronous Zeta Converter Outperforms The SEPIC

Focus:

The SEPIC converter has become increasingly popular because of its ability to regulate an output voltage by bucking or boosting equally well. The functionally similar Zeta converter has seen much less usage due to issues such as limited output current (3 A to 4 A max) and limited documentation. But as this article explains, the ZETA’s usefulness can be extended by converting it to fully synchronous operation. As a result, the Zeta’s efficiency and flexibility can be significantly improved beyond that of a traditional SEPIC converter. The article begins by briefly comparing the structure of the conventional Zeta with the SEPIC and the synchronous Zeta. It then explains synchronous zeta operation, compares component stresses in the Zeta versus those in the SEPIC, and then discusses an example sync Zeta design including controller selection. The latter point is important since this topology allows use of a sync buck controller (of which are there are many on the market.) The article concludes by comparing experimental results for a sync Zeta with those of a comparable SEPIC.

What you’ll learn:

• How to design a synchronous Zeta converter as a higher-performance alternative to the SEPIC
• How to understand the differences between SEPIC and Zeta converters

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Author & Publication:

John Betten, Texas Instruments, Dallas, Texas, How2Power Today, May 15 2014

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