12.4W Offline Valley Switching Flyback Reference Design with Output Referenced to Input
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Key Document


The PMP30285 reference design uses the UCC28740 flyback controller to generate two outputs (5V @ 2A / 8V @ 0.3A) from an 120VAC to 437VAC input. The negative terminal of the 5V output is connected to the primary side (LINE). A transformer with a common mode cancellation winding is used to lower the EMI. The UCC28740 uses an optical coupler to regulate the output and to improve transient response. The valley-switching technique reduces switching losses and keeps the efficiency high.

  • Multiple outputs
  • Valley switching
  • Good transient response
  • Integrated 700V startup switch
  • Test report available

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Schematic/Block Diagram

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Design Guide

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Design Files

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(Output Voltage 1)
(Output Voltage 2)
Vin (Min) (V)120120
Vin (Max) (V)437437
Vout (Nom) (V)58
Iout (Max) (A)2.3
Output Power (W)102.4
Input TypeACAC
TopologyFlyback- DCMFlyback- DCM

TI Devices (2)

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Part Number Name Product Family Sample & Buy Design Kits & Evaluation Modules
ATL431  2.5-V low-IQ adjustable precision shunt regulator  Voltage references  Sample & Buy View Design Kits & Evaluation Modules
UCC28740  Constant-voltage, constant-current Flyback controller Using Opto-Coupler Feedback  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)
ATL431 Download Download
UCC28740 Download Download

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Technical documentation

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User guides (1)
Title Type Size (KB) Date
PDF 933 11 Dec 2017
Design files (6)
Title Type Size (KB) Date
ZIP 109 11 Dec 2017
ZIP 992 11 Dec 2017
PDF 165 11 Dec 2017
PDF 145 11 Dec 2017
PDF 198 11 Dec 2017
PDF 160 11 Dec 2017

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