Power: Step-Down Regulators—Part 2: Battery-Powered Applications

Oct. 18, 2004

Why do you need a voltage regulator when operating from a battery?

The battery output voltage goes down over time, so you need a regulator to maintain the required system voltage. Also, the device must provide tight output voltage regulation as battery voltage decreases.

Why would you need a step-down (buck) regulator for a battery-powered application?

IC operating voltages are decreasing relative to battery output voltages. A single Li-ion battery output can reach 4.2 V, and three new alkaline cells can produce 4.5 V. Typical required IC operating voltages are often about 3.3 V and heading lower toward 1 V, so the buck regulator is necessary.

Why use a switch-mode voltage regulator for battery-powered systems?

The switch-mode regulator can provide efficiencies of 90% or greater. In contrast, the linear low-dropout (LDO) regulator usually exhibits only 50% to 60% efficiency. Higher efficiency means longer battery run time.

What are the requirements for voltage regulators in battery-powered systems?

The voltage-regulator IC should require very few low-cost, external components. To minimize size and weight, it should be housed in a small-outline package. Also, to minimize the size and weight of its associated surface-mount capacitors and inductors, a switch-mode regulator should operate at its highest usable switching frequency.

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About the Author

Sam Davis 2

Sam Davis was the editor-in-chief of Power Electronics Technology magazine and website that is now part of Electronic Design. He has 18 years experience in electronic engineering design and management, six years in public relations and 25 years as a trade press editor. He holds a BSEE from Case-Western Reserve University, and did graduate work at the same school and UCLA. Sam was the editor for PCIM, the predecessor to Power Electronics Technology, from 1984 to 2004. His engineering experience includes circuit and system design for Litton Systems, Bunker-Ramo, Rocketdyne, and Clevite Corporation. Design tasks included analog circuits, display systems, power supplies, underwater ordnance systems, and test systems. He also served as a program manager for a Litton Systems Navy program.

Sam is the author of Computer Data Displays, a book published by Prentice-Hall in the U.S. and Japan in 1969. He also authored the book Managing Electric Vehicle Power. He is also a recipient of the Jesse Neal Award for trade press editorial excellence, and has one patent for naval ship construction that simplifies electronic system integration.

You can also check out additional articles on his other author page.