Miniature 12W DC-DC Flyback Converter Design Tutorial


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Reference Guide


The MAXREFDES1247 is a miniature, 12V output, isolated power supply that can deliver up to 1A of load current. The design uses the MAX17596 peak-currentmode controller in discontinuous-conduction mode (DCM) flyback topology running at 125kHz. The input voltage range of the MAX17596 is 4.5V to 36V. However, an extra bias winding from the transformer is used to power the controller. This allows the input operating voltage to go up to 60V for this design.

The transformer provides a galvanic isolation of 1500VRMS between the primary and the secondary. In addition, an optocoupler is used to provide secondary-side feedback to the controller for voltage regulation while maintaining isolation. This document also discusses a step-by-step procedure to implement this reference design and presents design equations for the calculation of all the design parameters. These equations show how to calculate the component values to allow users to modify this design for their applications.


  • Miniature Design Optimized for Small Size
  • 17V to 60V Input Range
  • Isolated Output of 12V DC at 12W
  • Cycle-by-Cycle Current Limit
  • Resistor-Programmable UVLO/OVI Threshold
  • Low-Cost DCM Flyback Design
  • Galvanic Isolation Up to 1500VRMS
  • Proven PCB Layout
  • Fully Assembled and Tested


Designed, Built, Tested

Board pictured here has been fully assembled and tested. Not available for sale.



PCB Layout

Bill of Materials

Test Results


Input Type Vin(Min) Vin(Max) Iout(Max) Single/Multiple Output Vout(V) Pout(W) Isolated/Non-Isolated Topology
DC 17 60 1 - 12 12 Isolated Flyback


Input Type DC
Vin(Min) 17
Vin(Max) 60
Iout(Max) 1
Single/Multiple Output -
Vout(V) 12
Pout(W) 12
Isolated/Non-Isolated Isolated
Topology Flyback

Maxim Devices (1)

Part Number Name Product Family Order Design kits and evaluation modules
MAX17596 Peak-Current-Mode Controllers for Flyback and Boost Regulators Isolated Power Buy Now Design Kits

Maxim Devices (1)

Part Number Product Family
Isolated Power
Peak-Current-Mode Controllers for Flyback and Boost Regulators

Design Files (4)

Title Type Size Date
maxrefdes1247-bom PDF 71KB 2021-11-17
maxrefdes1247-schematic PDF 24KB 2021-04-28
TTS MAXREFDES Test Results Template_Rev 0_0318 PDF 393KB 2021-11-17
maxrefdes1247-pcb PDF 691KB 2021-04-28
Date Type


(PDF, 71KB)



(PDF, 24KB)


TTS MAXREFDES Test Results Template_Rev 0_0318

(PDF, 393KB)



(PDF, 691KB)

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