Off-line (non-isolated) AC/DC power supply architectures reference design for grid applications
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Key Document


This reference design showcases three non-isolated AC/DC power supply topologies for line-powered applications such as residential circuit interrupters, circuit breakers, home automation equipment and appliances for < 100 mA. The three topologies are:

  • Off-line switcher using inductor
  • AC line regulator using switched capacitor (active-clamped capacitor-drop based power supply)
  • Capacitive-drop regulator (cap-drop power supply)

The trade-off between efficiency, start-up time and solution size is done across architectures for various input and output conditions. The design methodology, test data and comparison is included for system designers to quickly evaluate and customize their solution.

  • Off-line switcher using the UCC28880: High efficiency architecture using a buck converter simplifies the design covering universal input voltage – applications requiring fast startup (< 2 ms), small footprint or need to meet stringent surge requirements
  • Switching capacitor-drop power supply using the TPS7A78: Inductor-less architecture customized for a narrow input voltage range  – high efficiency solution for low current (< 30 mA) and a single chip solution with integrated active rectifier and LDO
  • Capacitor-drop (cap-drop) power supply using an LDO: Simplified solution with passive components and LDO – low-cost solution with low efficiency, high startup time and large footprint

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Schematic/Block Diagram

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Design Guide

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Design Files

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TI Devices (3)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
LP2992  250-mA, 16-V, low-dropout voltage regulator with enable  Power management  Sample & Buy View Design Kits & Evaluation Modules
TPS7A78  120-mA smart cap-drop low-dropout (LDO) linear voltage regulator  Power management  Sample & Buy View Design Kits & Evaluation Modules
UCC28880  High voltage switcher for Non-isolated AC/DC Conversion  Offline & isolated DC/DC controllers & converters  Sample & Buy View Design Kits & Evaluation Modules

CAD/CAE symbols

Part # Package | Pins CAD File (.bxl) STEP Model (.stp)
LP2992 Download Download
Download Download
TPS7A78 Download Download
UCC28880 Download Download

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Technical documentation

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User guide (1)
Title Type Size (KB) Date
PDF 2807 12 Apr 2019
Design files (6)
Title Type Size (KB) Date
ZIP 747 12 Apr 2019
ZIP 815 12 Apr 2019
PDF 1007 12 Apr 2019
PDF 196 12 Apr 2019
PDF 40 12 Apr 2019
PDF 384 12 Apr 2019

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