Miniature 12W Flyback DC-DC Converter – Reference Design

March 05, 2020 by Paul Shepard

The MAXREFDES1247 from Maxim Integrated Products is a miniature, 12V output, isolated dc-dc converter that can deliver up to 1A of load current. The design uses the MAX17596 peak current-mode 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 reference design also discusses a step-by-step procedure to implement this circuit 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.

Key Features

  • Miniature Design Optimized for Small Size
  • 17V to 60V Input Range
  • Isolated Output of 12Vdc 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