"Cap Drop" Approach Implements Offline Power Supply for Light Loads

Focus:

The combination of a capacitor-dropper (cap-drop) circuit with a wide-input range buck converter can serve as a low-power ac-dc power supply in energy meters and other applications if transformer isolation is not required. The cap-drop circuit saves weight, size and cost versus the conventional ac-dc supply. This short “Ideas for Design” article describes operation of two cap-drop circuits—a full-wave version using a bridge rectifier and a half-wave version, which delivers lower current. Suitable buck converter ICs are identified and safety concerns of using a nonisolated design are discussed.

What you’ll learn:

• How to power MCUs and charge a battery in energy metering applications
• How to build a small, low-power ac-dc power supply for non-isolated applications
• How to reduce power consumption in energy metering applications

Notes:

After appearing online in September 2016, this article was published in print in ED’s April 2017 issue, pages 42-43.

View the Source

Author & Publication:

Akshay Mehta, Texas Instruments, Electronic Design, Sep 12 2016

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