18- to 36-VDC input, 25-W DC/DC active clamp forward reference design


Design files


This active clamp forward design converts an 18-V to 36-V input to a 5-V, 25-W output. The reference design uses the UCC2897A advanced current-mode active-clamp PWM controller to simplify active clamp implementation with a P-channel auxiliary FET. The design achieves 91.7% peak efficiency at 24-V input. The active clamp topology allows for self-driving synchronous rectifier (SR) FETs, lowering cost and complexity on the secondary side. This design also uses a catalog transformer and inductor.

  • Achieves 90% efficiency from 30% to 100% load at 24-V input
  • Self-driven SR (using CSD17579Q3A MOSFETs) reduces drive complexity
  • Uses catalog magnetics for a cost-effective solution
Output voltage options PMP22509.1
Vin (Min) (V) 18
Vin (Max) (V) 36
Vout (Nom) (V) 5
Iout (Max) (A) 5
Output Power (W) 25
Isolated/Non-Isolated Isolated
Input Type DC
Topology Forward- 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.

TIDT189.PDF (2211 K)

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

TIDM625.PDF (175 K)

Detailed schematic diagram for design layout and components

TIDM626.PDF (94 K)

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

TIDM627.PDF (159 K)

Detailed overview of design layout for component placement

TIDM629.ZIP (1021 K)

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


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

TIDM628.PDF (681 K)

PCB layer plot file used for generating PCB design layout


Includes TI products in the design and potential alternatives.

PWM controllers

UCC2897A110-V active clamp current mode PWM controller with P-channel clamp FET and line OV protection

Data sheet: PDF | HTML
N-channel MOSFETs

CSD17579Q3A30-V, N channel NexFET™ power MOSFET, single SON 3 mm x 3 mm, 14.2 mOhm

Data sheet: PDF | HTML
N-channel MOSFETs

CSD19537Q3100-V, N channel NexFET™ power MOSFET, single SON 3 mm x 3 mm, 14.5 mOhm

Data sheet: PDF | HTML
Shunt voltage references

TL431LIAdjustable precision shunt regulator with optimized reference current (pin layout: KRA)

Data sheet: PDF | HTML

Technical documentation

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Type Title Date
* Test report 18- to 36-VDC Input, 25-W DC-DC Active Clamp Forward Reference Design Jun. 18, 2020

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