Voltage Conversion Without Magnetic Components

July 21, 2005

What are typical charge pump applications?

Charge pumps have come far in the past decade, from unregulated single-output ICs to regulated ICs with multiple output voltages. Output power and efficiency also have improved, so the charge pump can now deliver up to 250 mA at 75% efficiency (average). Most applications are in battery-based systems like cell phones, pagers, Bluetooth systems, and portable electronics. Major applications include powering white LEDs for backlighting LCDs and powering milliwatt-range digital processors.

How does a charge pump work?

Charge pump (switched-capacitor) ICs provide dc-dc voltage conversion using a switch network to charge and discharge two or more capacitors. The basic charge pump switch network toggles between the capacitors' charge and discharge states. C1 (the "flying capacitor") shuttles charge, and C2 (the "reservoir capacitor") holds charge and filters the output voltage. Additional "flying capacitors" and switch arrays enable multiple gains.

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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.