20W, 100-425VDC, 85% Efficient, Multi-Output, Auxiliary Power Supply Reference Design
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Key Document


This 20-W multiple output, auxiliary power reference design supports AC/DC industrial power supplies with a wide input voltage range (100-425 VDC). The design achieves a peak efficiency of 85% by using discontinuous conduction mode (DCM) valley-switching of TI’s UCC28704 flyback controller with primary side regulation. The compact design uses a minimum number of components to help protect the system, including output overcurrent and output short circuit. The hardware is tested to meet Conducted Emission norm EN55022 Class A using an external EMI filter.

  • Peak power conversion efficiency of >85% at 400VDC full load
  • Designed for wide operating input voltage range from 100- to 425-V DC
  • Delivers full power of 20 W over the entire operating voltage range
  • Configurable outputs: 15V (primary referred), 5V & 15V (isolated)
  • Low stand-by power of <100mW
  • Compact form-factor to achieve high power density solutions: 40mm × 40mm

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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 (1)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
UCC28704  High-Efficiency Off-Line CV and CC Flyback Controller with Primary-Side Regulation (PSR)  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)
UCC28704 Download Download

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Technical documentation

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User guide (1)
Title Type Size (KB) Date
PDF 1165 29 Jan 2018
Design files (6)
Title Type Size (KB) Date
PDF 244 30 Jan 2018
PDF 123 30 Jan 2018
ZIP 545 30 Jan 2018
ZIP 2710 30 Jan 2018
PDF 58 30 Jan 2018
PDF 92 30 Jan 2018

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