Digital Control Squeezes 40 A from Buck Converter

by Benoit Herve, Product Manager, Zilker Labs, Austin, Texas , Power Electronics Technology, Aug 01 2007

Focus:
In buck converter designs, digital loop control enables an increase in efficiency that can used to increase the amount of current delivery per phase. This article describes a single-phase buck converter based on the ZL2005 digital power controller. This converter steps down a 12-V input to 1.8-V or 1-V output at up to 40 A, rather than the 20 A to 30 A available from conventional designs. However, this is a nonstandard buck since it employs two power trains in parallel (two sets of MOSFETs and two inductors). Key to the design: a gate-drive control algorithm optimizes deadtime for max efficiency. Article reviews the various loss contributions in a buck converter, explains how the ZL2005's deadtime optimization works, and discusses frequency, inductor, capacitor and MOSFET selection; calibration of the current-sense element; temperature compensation; and setting the current limit. Efficiency results are shown and compared with existing solutions. Single-phase versus two-phase tradeoffs are discussed.

What you’ll learn:

• How to maximize efficiency and current output of a single-phase buck converter using digital control
• How to achieve 40 A from a single-phase buck converter using a digital controller and dual power trains

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