System Board 7265

MAXREFDES1256: 49W DC-DC Flyback Converter Using MAX17597

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Input Type VIN (MIN)
Isolated/Non-Isolated Topology
DC 9 36 7 Single 7 49 Isolated Flyback

The MAXREFDES1256 is an isolated power supply capable of delivering 7V at up to 7A load current. High efficiencies are achieved by using the MAX17606 MOSFET driver on the secondary side for synchronous rectification. The input voltage range of the MAXREFDES1256 is 9V to 36V DC.

This design uses the MAX17597 peak-current-mode controller in the discontinuous-conduction mode (DCM) in a flyback topology at 100kHz.

The transformer provides a galvanic isolation of 1425VDC between the primary and secondary. Also, an optocoupler provides 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 to calculate all the design parameters. These equations show how to calculate the component values to modify this design for applications.

MAXREFDES1256 Board Enlarge+

The key features of the MAXREFDES1085 are:

  • Input voltage range of 9V to 36V
  • Synchronous rectification on the secondary side
  • Isolated output of 7V at 49W
  • Cycle-by-cycle current limit
  • Resistor programmable UVLO/OVI threshold
  • Galvanic isolation up to 1425V DC
  • Proven PCB layout
  • Fully assembled and tested


PCB Layout

Test Results


Secondary-Side Synchronous MOSFET Driver for Flyback Converters

  • Wide 4.5V to 36V Input
  • 2A/4A Peak Source/Sink Gate Drive Currents
  • Suitable for Discontinuous Conduction Mode (DCM), Border Conduction Mode (BCM)

Peak-Current-Mode Controllers for Flyback and Boost Regulators

  • Programmable Switching Frequency Allows Optimization of the Magnetic and Filter Components, Resulting in Compact, Cost-Effective, Efficient Isolated/Non-Isolated Power Supplies
  • Programmable Frequency Dithering Enables Low-EMI Spread-Spectrum Operation
  • Integrated Protection Features Enhance System Reliability