Isolated flyback converter (24-V to 56-V/1.25-A) reference design


Design files


This reference design utilizes a diode rectified flyback converter for a 24-V input to isolated 56-V/1.25-A output. The LM51551 PWM controller provides the control for the flyback converter, including hiccup mode short circuit protection. This reference design is ideal for when any well-regulated 56-V output is required, such as the power source for Power over Ethernet (PoE) Power Source Equipment (PSE).

  • Over 90% efficiency at full-load at 24-V input
  • Hiccup-mode short circuit protection
  • Low 82-mV peak-to-peak ripple on 54-V output
Output voltage options PMP22764.1
Vin (Min) (V) 19.2
Vin (Max) (V) 28.8
Vout (Nom) (V) 54
Iout (Max) (A) 1.25
Output Power (W) 67.5
Isolated/Non-Isolated Isolated
Input Type DC
Topology Flyback- Non Sync

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.

TIDT115.PDF (2887 K)

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

TIDM847.PDF (208 K)

Detailed schematic diagram for design layout and components

TIDM848.PDF (271 K)

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

TIDM849.PDF (191 K)

Detailed overview of design layout for component placement

TIDM851.ZIP (865 K)

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

TIDCG04.ZIP (565 K)

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

TIDM850.PDF (771 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

Boost controllers (external switch)

LM515512.2-MHz wide VIN nonsynchronous boost, flyback, & SEPIC controller with hiccup

Data sheet document-pdfAcrobat PDF open-in-new HTML
N-channel MOSFETs

CSD19531Q5A100-V, N channel NexFET™ power MOSFET, single SON 5 mm x 6 mm, 6.4 mOhm

Data sheet document-pdfAcrobat PDF open-in-new HTML
Shunt voltage references

TL431Adjustable precision shunt regulator

Data sheet document-pdfAcrobat PDF open-in-new HTML

Technical documentation

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Type Title Date
* Test report Isolated Flyback Converter (56 V/1.25 A) Reference Design Jan. 19, 2021

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