65W Active clamp flyback with Si FETs reference design for a high power density 5-20V AC/DC adapter


Design files


This reference design uses the UCC28780 active clamp flyback controller to generate a 20-V/15-V/9-V/5-V adjustable output voltage. The maximum power rating is 65 W at 20-V output and up to 3 A at all other output voltage settings. This design reaches a peak efficiency of over 93% using silicon FETs, due to zero voltage switching (ZVS) and recaputuring the leakage energy.  The high efficiency enables a small form factor and a high power density.

  • Zero voltage switching (ZVS) provides high efficiency (93.5% peak value)
  • Low, no load power consumption (33 mW)
  • Supports outputs of 5V/3A, 9V/3A, 15V/3A, and 20V/3.25A
  • Conducted emissions (EMI) data provided in test report
  • Small size (48mm x 48mm x 25mm) provides high power density (18W/in^3)
Output voltage options PMP21479.1
Vin (Min) (V) 85
Vin (Max) (V) 265
Vout (Nom) (V) 20
Iout (Max) (A) 3.25
Output Power (W) 65
Isolated/Non-Isolated Isolated
Input Type AC
Topology Flyback- Active Clamp
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A fully assembled board has been developed for testing and performance validation only, and is not available for sale.

Design files & products

Design files

Download ready-to-use system files to speed your design process.

TIDT096A.PDF (12796 K)

Test results for the reference design, including efficiency graphs, test prerequisites and more


Detailed schematic diagram for design layout and components


Complete listing of design components, reference designators, and manufacturers/part numbers


Detailed overview of design layout for component placement

TIDM574.ZIP (1548 K)

Files used for 3D models or 2D drawings of IC components

TIDCFU4.ZIP (1044 K)

Design file that contains information on physical board layer of design PCB


PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

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Technical documentation

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Type Title Date
* Test report 65W Active Clamp Flyback With Si FETs Reference Design for a High Power Density (Rev. A) Apr. 29, 2020
Application note Zero-Voltage-Switching Flyback Using UCC28780 Controller and UCC5304 Isolated Sy Jul. 30, 2020

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